Dissertations / Theses on the topic 'Inorganic fertilizer'

Two sets of continuous deep soil cores were removed from a 4 hectare field during the third year of crop treatment. Samples were removed once following sludge addition and once 6 weeks later following inorganic fertilizer application and a 30 cm pre-planting irrigation. A total of 504 soil samples were analyzed for soil texture, gravimetric moisture content, electrolytical conductivity, and pH, as well as concentrations of NO₃ , Cl⁻ , NO₂, and organic C. After three annual sludge applications, soil beneath plots amended with sludge, had higher average water-extractable NO3 concentration than plots amended with inorganic fertilizer. From one sampling date to the next, the field-averaged concentration of NO₃ increased from 282 mg 1⁻¹ to 335 mg 1⁻¹ . Results suggest a trend of increasing NO₃ in the vadose zone.

Thesis (MSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Inorganic fertilizer applications are common practice in commercial agriculture, yet not much is known regarding their interaction with organic matter and soil biota. Much research has been done on the effect of inorganic N on forest litter decomposition, yet very little research has focused on the effect of inorganic fertilizers on crop litters and, to our knowledge, none on composted organic matter. Furthermore none of the research has been done in South Africa. The main aim of this research project was to determine the effect of inorganic fertilizer applications on the decomposition of selected organic matter sources commonly used in South African agriculture and forestry. Two decomposition studies were conducted over a 3-month period, one on composts and the other on plant litters, using a local, sandy soil. In the first experiment a lower quality compost, compost A (C:N ratio, 17.67), and higher quality compost, compost B (C:N ratio, 4.92) was treated with three commercially used fertilizer treatments. Two were typical blends used for vegetable (tomato and cabbage) production: tomato fertilizer (10:2:15) (100 kg N, 20 kg P, 150 kg K per ha) and cabbage fertilizer (5:2:4) (250 kg N, 100 kg P, 200 kg K per ha). The third fertilizer blend, an equivalent mass application of N and P applied at 150 kg of each element per ha, is more commonly used in pastures. In the second experiment, five commonly encountered crop and forestry litters, namely kikuyu grass, lucerne residues, pine needles, sugar cane trash and wheat straw, were selected to represent the labile organic matter sources. The litters were treated with the tomato and cabbage fertilizer applications rates. Both decomposition experiments were conducted under ambient laboratory conditions at field water capacity. Decomposition rates were monitored by determining CO2 emissions, DOC production, β-glucosidase and polyphenol oxidase activity (PPO). At the start and end of decomposition study, loss on ignition was performed to assess the total loss of OM. Based on the results obtained from these two experiments, it was concluded that the addition of high N containing inorganic fertilizers enhanced the decomposition of both composted and labile organic matter. For both compost and plant litters, DOC production was greatly enhanced with the addition of inorganic fertilizers regardless of the organic matter quality. The conclusion can be made that inherent N in organic matter played a role in the response of decomposition to inorganic fertilizer application with organic matter low in inherent N showing greater responses in decomposition changes. For labile organic matter polyphenol and cellulose content also played a role in the responses observed from inorganic fertilizer applications.
AFRIKAANSE OPSOMMING: Anorganiese kunsmis toedieningss is algemene praktyk in die kommersiële landbou sektor,maar nog min is bekend oor hul interaksie met organiese materiaal en grond biota. Baie navorsing is reeds oor die uitwerking van anorganiese N op woud en plantasiereste se ontbinding gedoen. Baie min navorsing het gefokus op die uitwerking van anorganiese kunsmis op die gewasreste en tot ons kennis, is daar geen navorsing gedoen op die invloed van anorganiese kunsmis op gekomposteer organiese material nie. Verder is geeneen van die navorsing studies is in Suid-Afrika gedoen nie. Die hoofdoel van hierdie navorsingsprojek was om die effek van anorganiese kunsmis toedienings op die ontbinding van geselekteerde organiese materiaal bronne, wat algemeen gebruik word in die Suid-Afrikaanse landbou en bosbou, te bepaal. Twee ontbinding studies is gedoen oor 'n 3-maande-tydperk, een op kompos en die ander op die plantreste, met die gebruik van 'n plaaslike, sanderige grond. In die eerste eksperiment is ‘n laer gehalte kompos, kompos A (C: N verhouding, 17.67), en 'n hoër gehalte kompos, kompos B (C: N verhouding, 4.92) met drie kommersieel anorganiese bemesting behandelings behandel. Twee was tipiese versnitte gebruik vir die groente (tamatie en kool) produksie: tamatie kunsmis (10: 2:15) (100 kg N, 20 kg P, 150 kg K per ha) en kool kunsmis (5: 2: 4) (250 kg N, 100 kg P, 200 kg K per ha). Die derde kunsmis versnit was 'n ekwivalente massa toepassing van N en P van 150 kg van elke element per ha, wat meer algemeen gebruik word in weiding. In die tweede eksperiment was vyf algemeen gewas en bosbou reste, naamlik kikoejoegras, lusern reste, dennenaalde, suikerriet reste en koring strooi, gekies om die labiele organiese materiaal bronne te verteenwoordig. Die reste is met die tamatie en kool kunsmis toedienings behandel. Beide ontbinding eksperimente is uitgevoer onder normale laboratorium toestande by veldwaterkapasiteit. Ontbinding tempo is deur die bepaling van die CO2-vrystellings, opgelosde organiese koolstof (OOK) produksie, β-glukosidase en polifenol oksidase aktiwiteit (PPO) gemonitor. Aan die begin en einde van ontbinding studie, is verlies op ontbranding uitgevoer om die totale verlies van OM te evalueer. Gebaseer op die resultate van hierdie twee eksperimente, was die gevolgtrekking dat die toevoeging van hoë N bevattende anorganiese bemestingstowwe die ontbinding van beide komposte en plant reste verhoog. Vir beide kompos en plantreste word OOK produksie verhoog met die toevoeging van anorganiese bemesting, ongeag van die organiese materiaal gehalte. Die gevolgtrekking kan gemaak word dat die inherente N in organiese materiaal 'n rol gespeel het in die reaksie van ontbinding op anorganiese bemesting toedienings met die grootste reaksie in organiese material laag in inherente N. Vir labiele organiese material het polifenol en sellulose inhoud ook 'n rol gespeel in die reaksie waargeneeming op anorganiese bemesting.

The effects of poultry manure versus inorganic fertilizer use on copper, zinc and manganese concentrations and the sustainability of metal contents under raspberry cultivation was investigated on two aeolian soils in the Lower Fraser Valley, British Columbia. Total elemental analysis by a teflon bomb procedure using reverse aqua regia and hydrofluoric acid was done on soils sampled at three depths (0-15 cm, 15-30 cm and +40 cm) and results were compared to metal contents extracted by the Mehlich III method. High variability of some of the soil data was attributed to mixing of the loess capping with the underlying glacio-fluvial outwash material, differences in site conditions of the test fields, variations in sampling depth, and inadequate analytical reproducibility at the low concentrations found in some of the soils. For the variables tested, differences between sites most often occurred in the first 30 cm and never at the +40 cm depth. Higher contents in the 0-30 cm depth than in the lower depths indicated an enrichment of the surface layers either by anthropogenic inputs or by bioaccumulation. Poultry manure applications had a significant effect on organic matter content, total and available manganese, and total and available zinc in both soils studied. The comparison of the manured versus the inorganically fertilized site indicated that zinc was the metal most effected by the manure application. The other metals were not significantly increased by poultry manure amendments. The comparison of the site that had been under long-term raspberry cultivation against the site that had been only recently converted to raspberries from long-term pasture cover, showed that long-term raspberry cultivation reduced metal and organic matter contents in the 0-15 cm depth and increased these variables in the 15-30 cm depth. It was hypothesised that this was in direct response to differing biocycling patterns under different land uses. Total and available manganese and zinc were strongly interconnected and their correlation to the organic matter content appeared most interesting in terms of fluxes between the various soil components. inorganically fertilized site indicated that zinc was the metal most effected by the manure application. The other metals were not significantly increased by poultry manure amendments. The comparison of the site that had been under long-term raspberry cultivation against the site that had been only recently converted to raspberries from long-term pasture cover, showed that long-term raspberry cultivation reduced metal and organic matter contents in the 0-15 cm depth and increased these variables in the 15-30 cm depth. It was hypothesised that this was in direct response to differing biocycling patterns under different land uses. Total and available manganese and zinc were strongly interconnected and their correlation to the organic matter content appeared most interesting in terms of fluxes between the various soil components.
Land and Food Systems, Faculty of
Graduate

Phosphate and ammonium removal from waste water by adsorption using inorganic natural sorbents has been identified as a promising technology. The advantages of this methodology are associated with its availability and effective low cost. Some natural and synthetic zeolite materials have been used for the individual phosphate and ammonium removal from aqueous solutions. The zeolites revealed high affinity for ammonium removal. However, some modifications stages are indispensable to enhance their oxyanionic sorption capacity to achieve high phosphate removal ratios. So, it is highly desirable to obtain a single sorbent for both cation and anion removal capacity from aqueous solutions. For this purpose, a natural zeolite with clinoptilolite as major mineral phase, was impregnated with metallic oxyhydroxides after conversion to the sodium form. As a result, hydrated metal oxides (HMO) of Al, Fe and Mn were immobilized on the zeolite surface structure. The efficiency of aluminium, iron and manganese hydrated metal oxides was individually evaluated for the simultaneous phosphate and ammonium removal from aqueous solutions through batch and continuous mode assays using a granular natural zeolite sample. High selectivity was developed by modified zeolites towards these species in the presence of competing ions commonly present in urban and industrial waste waters. The regeneration assays demonstrated the limited use of modified zeolites in operational cycles as losses of the hydrated metal oxide along within the operation cycles will require re-impregnation stages. Then, an alternative option for final valorization of ammonium and phosphate is the use of the loaded zeolites as soil amendment for agricultural and forestry purposes or for environmental rehabilitation of degraded soils. Therefore, a second approach could be to use the impregnated zeolites as nutrients carriers, improving their fertilizing properties by including potassium. For this purpose, powder samples of the natural zeolite in the potassium form were impregnated with the metallic oxyhydroxides and were enriched on nutrients (N,P,K) by using treated waters from the secondary effluent from "El Prat" Waste Water Treatment Plant using batch mode assays. The N-P-K release rates of the enriched zeolite samples were determined by column test using mixtures with three different types of agricultural soils.
La recuperación de fosfato y amonio de agua residual mediante adsorción usando adsorbentes inorgánicos naturales ha sido identificado como una tecnología muy prometedora. Las ventajas de esta metodología se asocian a la amplia disponibilidad de adsorbentes de este tipo y su bajo costo. Algunos materiales zeolíticos naturales y sintéticos han sido usados para la adsorción individual de fosfato y amonio de soluciones acuosas. Las zeolitas revelan alta afinidad para la adsorción de amonio. Sin embargo, algunas etapas de modificación son indispensables para incrementar la capacidad de adsorción oxianiónica y conseguir altas tasas de adsorción de fosfato. Entonces, resulta conveniente obtener un solo adsorbente para la adsorción simultánea de cationes y aniones de soluciones acuosas. Con este propósito, una zeolita natural que contiene clinoptilolita como mayor fase mineralógica, se impregnó con hidróxidos metálicos después de su conversión a la forma sódica. Como resultado, los óxidos metálicos hidratados (HMO) de Al, Fe and Mn fueron inmovilizados en la superficie de la estructura zeolítica. La eficiencia de los óxidos metálicos hidratados de aluminio, hierro y manganeso fue evaluada individualmente para la adsorción simultánea de fosfatos y amonio de soluciones acuosas mediante ensayos por lotes y en continuo usando una zeolita en forma granular. Una alta selectividad fue demostrada por parte de las zeolitas modificadas respecto a la adsorción de estas especies en presencial de iones competidores comúnmente existentes en aguas residuales urbanas e industriales. Los ensayos de regeneración demostraron el uso limitado de las zeolitas modificadas en continuo así como también la pérdida de los óxidos metálicos hidratados con cada ciclo de operación puesto que requiere de una nueva impregnación en cada etapa. Entonces, una opción alternativa para la final valorización de fosfato y amonio es el uso de las zeolitas saturadas como material de mejoramiento de suelos con propósitos agrícolas o también para la rehabilitación de suelos degradados. Es así que se evidencia una oportunidad en el uso de zeolitas impregnadas como transportadores de nutrientes, de tal forma que mejoren las propiedades fertilizantes mediante la inclusión de potasio. Para cumplir con este objetivo, la zeolita natural en polvo se impregnaron con oxihidróxidos metálicos que fueron enriquecidos con nutrientes esenciales (N, P, K) usándolas para tratar aguas residuales provenientes de efluentes secundarios, específicamente de la Planta de Tratamiento de Agua Residual "El Prat" usando ensayos por lotes. Las tasas de liberación de N-P-K de las zeolitas enriquecidas se determinaron mediante pruebas en columna usándolas como aditivos en tres tipos diferentes de suelos agrícolas.

Experiments were conducted at the University of Aberdeen under controlled laboratory conditions to examine the interactive effect of combining crop residues barley (Hordeum vulgare), clover (Trifolium pretense), cowpea (Vigna unguiculata), Leucaena (Leucena leucocephala) and Mucuna (Mucuna pruriens) and inorganic N fertiliser on N₂O emission and mineral N dynamics. Emissions of N₂O increased following sole application of the residues dependent on their utility or chemical composition. In general emissions were significantly higher from soils amended with low C:N ratio clover, cowpea, Leucena and Mucuna residues compared to the high C:N ratio barley species. N₂O emission was further increased following combined application of crop residues and inorganic N fertiliser but the magnitude of emission was influenced by the proportional ratios at which the residue-N and the fertiliser-N were combined, and the C:N ratio, lignin and polyphenols contents of the residues, with the low lignin and low polyphenols cowpea treatment emitting higher N₂O over 30 days compared to the high lignin Mucuna and the  high polyphenols Leucena treatments. Results from experiments demonstrated that whilst there is the potential for N₂O emission to be controlled through varying ratios of residue:fertiliser input, the magnitude and direction of interactions between these N sources varies between different species as a result of their differing qualities. Based on our applications of Leucaena, Mucuna and cowpea residues, the 75:25 residue: fertiliser ratio at 100 mg N kg^-1 soil is recommended from this study as offering the best compromise between release of N for crop uptake and management of N₂O emission, but this requires further investigation at field scale.

Non-point source pollution of surface waters with phosphorous (P) transported from agricultural soils has emerged as a major environmental issue in the last decade. Regulations limiting P accumulation in surface soils have been established to protect surface water quality. Yet, little information is available on the quantities of P that may leach through soils and the factors influencing P leaching in agricultural soils. One important factor may be the type of fertilizer P applied, since it is known that P solubility varies among fertilizer sources. The purpose of this thesis was to quantify P leaching in soils amended with inorganic and organic fertilizers.
In a field study, we found that the fertilizer P source (triple superphosphate, composted cattle manure, or a mixture of the two) did not affect soil test P concentration, the degree of soil P saturation, or P leaching in a sandy-loam soil. The soil test P level in the 0--15-cm depth (146 mg P kg -1) exceeded the critical limit of 66-mg kg-1 established in Quebec, and ortho-P and DOP concentrations in leachates collected from piezometers were generally higher than the provincial water quality standard of 0.03 mg P L-1. If transported from our study site, P leached through this coarse-textured soil could pose a threat to groundwater and surface water quality.
These findings were verified in the laboratory with two coarse-textured soils. We found that more NO3-N and DON were leached from soils receiving inorganic N and P fertilizers than composted cattle manure, but the amounts of ortho-P and DOP leached were not affected by fertilizer sources. In coarse-textured soils, the quantities of P leached can be substantial, but depends more on soil characteristics than the fertilizer P source.

L’objectif de la présente étude est de développer un système agroforestier dans lequel l'arbre fixateur de N2 est utilisé, via les émondes, comme alternative à l'engrais pour la fertilisation du maïs. La démarche scientifique met en œuvre la méthodologie azote-15 et comprend trois phases: (ii) une phase de diagnostic en milieu réel de la fixation de N2 (ii) une phase de caractérisation, en milieux contrôlé, des émondes et de quantification de leur contribution à la nutrition azotée du maïs (iii) une phase de quantification, en milieu réel, des contributions du sol, des émondes et de l'engrais à l'alimentation azotée du maïs. Nous mettons en évidence un seuil de pluviométrie au-dessous duquel la fixation réelle de N2 (FRN) est faible, et montrons que l'inoculation de bradyrhizobium permettrait de lever cette contrainte. Deux caractéristiques des émondes: l'une de capacité (N biodegradable) et l'autre de cinétique (demi-vie) sont mesurées au laboratoire et validées au champ ; elles permettent de déboucher sur un modèle de prévision de l'offre en N. Par la suite, nous développons un modèle d'optimisation des dates de semis du maïs et d'émondage de l'arbre qui permet d'ajuster l'offre à la demande. Les contributions de l'engrais, du sol et des émondes à la nutrition azotée de la céréale sont déterminées. Parmi celles-ci, la contribution de la FRN, via les émondes, rend compte du rôle de la FRN dans la durabilité du système agroforestier. L’indice de surface équivalente (ISE) de la culture en couloir est 0,90 et 1,60, respectivement, dans le cas d'une culture pure de mais avec engrais et dans celui de la culture pure de maïs sans engrais. Le système agroforestier proposé est performant et exige peu d'intrants couteux. Dans la pratique, il reste à franchir une étape essentielle: la mise en œuvre de ce système en fonction de la diversité des exploitations et des contraintes socio-économique

Fertilizantes de liberação controlada como a ureia revestida com polímeros podem propiciar melhor sincronia entre a disponibilidade de nitrogênio (N) no solo e as exigências do nutriente pela cultura de milho (Zea mays L.). Para avaliar o efeito de diferentes estratégias de uso da ureia revestida com polímeros na disponibilização de nitrogênio inorgânico, nitrato (NO3-) e amônio (NH4+) no solo durante o ciclo da cultura de milho, e na produtividade final de grãos, foram conduzidos experimentos na safra 2012/2013, em duas condições edafoclimáticas no município de Piracicaba, Estado de São Paulo. Os solos dos experimentos foram: Latossolo Vermelho Distrófico (LVd) e Latossolo Vermelho Amarelo Distrófico (LVAd). O delineamento experimental foi de blocos completos ao acaso com quatro repetições e os tratamentos constaram da aplicação da dose de 180 kg ha-1 de N, utilizando-se duas fontes de N, ureia revestida com polímeros e ureia convencional, aplicadas, respectivamente, nas proporções de 100:0, 90:10, 80:20, 70:30, 60:40, 50:50 e 0:100%, além de um tratamento com ureia em manejo convencional com aplicação parcelada (20% na semeadura e 80% em cobertura entre os estádios V4-V6), e o controle sem aplicação de N. Foi semeado híbrido de milho com elevado potencial de produtividade. Os fertilizantes aplicados na semeadura foram incorporados a 5 cm de profundidade e 10 cm ao lado da linha de milho. Para determinar o teor de nitrogênio inorgânico no solo, nas camadas de 0-0,1, 0,1-0,2, 0,2-0,4 e 0,4-0,6 m, foram realizadas amostragens na semeadura e em V4, V12 e R3 no LVd e na semeadura e em V6, V14 e R4 no LVAd. Produtividade de grãos, massa seca da parte aérea, acúmulo de N na parte aérea, exportação de N nos grãos, e a eficiência de utilização interna de nitrogênio foram avaliados na maturidade fisiológica da cultura. Os resultados foram submetidos à análise de variância e quando observado efeito significativo de tratamentos, foram realizadas análises de contraste de médias (p<=0,1). A produtividade máxima nos dois experimentos foi da ordem de 10 Mg ha-1 de grãos de milho. Nos dois experimentos a ureia revestida com polímeros disponibilizou nitrogênio mineral no solo ao longo de todo o ciclo da cultura de milho, o que resultou no LVAd em produtividade de grãos mais elevada em relação à utilização de ureia convencional, diferentemente do ocorrido no LVd, onde não foram observados efeitos de tratamentos. A utilização de misturas de URP e U na adubação da cultura do milho, com proporções variando de 100% a 50% da fonte de liberação controlada, mostrou-se eficiente e pode ser considerada uma estratégia que fornece N conforme a exigência da cultura, o que resulta em maior produtividade de grãos em condições edafoclimáticas favoráveis.
Controlled release fertilizers such polymer coated urea can provide better synchrony between nitrogen (N) availability in the soil and its requirements by maize (Zea mays L.). To evaluate the effect of different use strategies of polymer coated urea on the availability of inorganic nitrogen, nitrate (NO3-) and ammonium (NH4+) throughout the crop cycle, and the grain yield, field experiments were carried out in the 2012-2013 growing season, in two soil-climatic conditions, in Piracicaba, São Paulo State. The soils were a clayey and a sandy Oxisol. The experimental design was randomized blocks with four replications, and the treatments consisted of 180 kg N ha-1, using two sources of N, polymer coated urea and conventional urea, respectively, in proportions of 100:0, 90:10, 80:20, 70:30, 60:40, 50:50% and 0:100%, besides a treatment with urea in conventional management, split-applied (20% at seeding and 80% side-dressed in V4-V6 corn growth stage) and a control (without N). Maize hybrid with high productivity potential was used. The fertilizers applied at seeding were placed in bands 5 cm depth and 10 cm aside the corn row. To determine the inorganic nitrogen content in the soil at 0-0.1, 0.1-0.2, 0.2-0.4 and 0.4-0.6 m soil layers, samples were collected at seeding, V4, V12 and R3 corn growth stage in the clayey Oxisol, and at sedding, V6, V14 and R4 in the sandy Oxisol. Grain yield, aerial biomass, nitrogen uptake by the aerial biomass, grain nitrogen uptake and internal utilization efficiency of nitrogen were evaluated. Data were analyzed using analysis of variance and when differences were detected, means where separated using contrast test (p<=0.1). The maximum maize grain yield in the experiments was approximately 10 Mg ha-1. In the two experiments, polymer coated urea led to a greater inorganic nitrogen availability throughout the maize cycle, which resulted in higher yield comparing to the use of conventional urea in the sandy Oxisol, not thus in the clayey Oxisol, where no effects of treatments in grain yield were observed. The use of blends of polymer coated urea and conventional urea in maize fertilization, with ratios ranging from 100 to 50% of the controlled release source, was efficient and can be considered a strategy that supplies N as the crop demands it, and thus lead to a greater maize grain yield under agro-climatic favorable conditions.

The majority of small-scale farmers in the Eastern Cape apply inadequate quantities of manure, inorganic (NPK) fertilizer and Gromor as lone fertilizers or tend to mix manure or Gromor with chemical fertilizers for crops, without any scientific basis (Mkile, 2001). Hence this study – aimed at achieving effective and efficient use of chemical fertilizers, manure and Gromor, either as lone fertilizers or mixed with one another, in maize production – was established. A three-year dry land field experiment, arranged in a RCBD with 3 replicates where cattle manure, chemical fertilizer and Gromor were mixed at different ratios – as treatments FM1 (10 percent fertilizer + 90 percent manure); FM2 (25 percent fertilizer + 75 percent manure); FM3 (50 percent fertilizer + 50 percent manure); MAP (100 percent fertilizer); M (100 percent cattle manure); FG1 (10 percent fertilizer + 90 percent Gromor); FG2 (25 percent fertilizer + 75 percent Gromor); FG3 (50 percent fertilizer + 50 percent Gromor); G (100 percent Gromor) and a control (with nothing applied) – was conducted at the Nolukhanyo agricultural project at Bathurst in the Ndlambe Local Municipality. Maize cultivars PAN 6480 and Sahara were used as test crops. Manure, Gromor and soil were analyzed for their nutrient composition. Data recorded involving number of kernels per cob-1, grain and dry matter (DM) yields for the 2010-11, 2011-12 and 2012-13 seasons, and leaf area index (LAI) – were subjected to Genstat Version 14.1 for statistical analysis. Grain yields of PAN 6480 and Sahara recorded in seasons 2010-11, 2011-12 and 2012-13 were significantly higher (p≤0.05) than those of the controls. In 2012-13, PAN 6480 on treatments FG3 and FG1 produced the highest grain yields (5 327 and 5 107kg ha-1) respectively, while in 2010-11 the highest yield was 3 780kg ha-1. In the 2012-13 season, Sahara on F treatment was the highest with 4 553kg ha-1 whilst there were no significant differences in F and M treatments. Dry matter yields of Sahara were higher than those of PAN 6480 in all seasons. The highest Sahara LAI obtained on FM2 was 5.85 in the 2012-13 season, whereas PAN 6480 had LAI of 4.77 on F treatment, followed by FG3 with 4.72 LAI. PAN 6480 number of leaves for 6 plants in m2 and LAI in week 8 of the 2012-13 season had a positive correlation, r2=0.84. PAN 6480 number of kernels and cob length in the same area correlated quite well (r2 =0.91). Chemical fertilizer corrects the imbalances of nutrients inherent in organic manures and increases both maize grain yields and dry matter yields, and also influences number of leaves and LAI. Treatments FG1, FG3 and FM1 of PAN 6480 resulted in high maize grain yields when planted 13 in late November of the 2012-13 growing season and when water in the soil profile was conserved as a result of good rains received prior to planting. Treatments FG1 (10 percent fertilizer + 90 percent Gromor), FG3 (50 percent fertilizer + 50 percent Gromor) of PAN 6480 produced the highest grain yields (5 107kg ha-1 and 5 327kg ha-1 respectively) in the 2012-13 season, whilst FM1 (10 percent fertilizer + 90 percent manure) gave the highest grain yield (of 4 277kg ha-1) for the same cultivar in the 2010-11 season.

Many producers in North America are finding it profitable to make the transition from conventional farming to organic agriculture. Organic fertilisers may affect crop production and soil quality differently than inorganic fertilisers. The objectives of this study conducted in Ste.-Anne-de-Bellevue. Quebec were to examine crop yield, grain quality, soil fertility and microbial community parameters in wheat and corn agroecosystems receiving poultry manure or inorganic fertiliser. Wheat grain yield declined and corn grain yield did not increase with higher N rates, suggesting that increased N supply did not encourage grain production. Soil analyses demonstrated high inherent soil fertility at the study site, and fertilisation led to an environmentally undesirable increase in residual soil NO3 concentrations. Microbial biomass and respiration in corn agroecosystems were greater with poultry manure amendments than inorganic fertiliser, but not in wheat agroecosystems due to significant variation among field replicates. Phospholipid fatty acid analysis revealed significant differences between wheat and corn soil microbial community composition, but differences due to fertilisation were less evident. Further work is needed to uncover the relationships among N fertilisation, crop nutrition and soil microbiology in organic agroecosystems.

The aim of the study was to examine the effect of combined use of organic residue with inorganic fertiliser-P on organic residue decomposition, P transformations and utilisation by upland rice. Five agroforestry tree prunings (organic residues) were incubated without and with inorganic fertiliser-P for 56 days using soil as inoculum only. Decomposition and P release were in the same order i.e. Gliricidia sepium > Senna siamea > Leucaena leucocephela > Paraserienthus falcataria > Acacia mangium. The lignin, polyphenol and cellulose contents and their ratios to the P content of the residue influenced decomposition and hence P release. Added inorganic fertiUser-P had no effect on decomposition. A greater proportion of inorganic fertiliser-P was recovered when applied with low quality residue and less with high quality residue. Gliricidia sepium and Acacia mangium prunings were incubated without and with morganic fertiliser-P for 56 days in high and low P status soils. Gross mineralisation was estimated by isotopic dilution. Unlike Acacia, Gliricidia increased gross mineralisation in the low P status soil with weaker P sorbing capacity although net mineralisation was not attained. Inorganic fertiliser-P had no effect on gross mineralisation. Organic residue influenced both the inorganic and organic labile soil P fractions while inorganic fertiliser-P influenced only the labile inorganic P fractions. Upland rice (ROK 16) grown on the two soil types treated without and with Gliricidia and inorganic fertiliser-P indicated increased dry shoot weight and total P uptake in the low P soil and not the high P soil. With a double isotopic labelling technique, it was observed that in the low P status soil, Gliricidia P-accounted for over 50% of the total rice P uptake followed by organic-P (25%). Over 80% of the total P uptake in the high P status soil was soil-P. Organic residue increased the quantity of inorganic fertiliser-P utilised but not the native soil P.

Tesis Presentada como Requisito Parcial para Obtener el Titulo de Ingeniero Agronomo, Escuela Superior Politecnica de Chimborazo, Facultad de Recursos Naturales, Ecscuela de Ingenieria Agronomica.
Abstract in Spanish and English.

In our country the necessity to offer new alternatives for the agricultural sector is high-priority especially for the lucern cultivation that every day is surface cultivated especially in the Chimborazo province increases; for what is of our interest to establish the answer from the cultivation to the inorganic fertilization and liming for the floor’s pH correction, for this way to obtain better yields and for consequence to improve the economic conditions of the farmers. With the result that the titled investigation: “Efficiency of the Inorganic Fertilization in the Alfalfa Cultivation (Medicago sativa L) and Liming for the Correction of the pH of the Floor” had the following objectives: to determine inorganic fertilization efficiency in the lucern cultivation and liming for the correction of the pH of the floor; to evaluate the production of the lucern cultivation; to carry out an economic analysis.

The purpose of this study was to investigate the results of two long-term fertilization experiments on soil organic C, total N, and mineralizable N in the Jiangsu Province of People's Republic of China. The soil samples that received manure over the years contained more soil organic C, and total N than the inorganic fertilized samples. Soil organic C was closely correlated with total N and there were correlations between crop yields and soil organic C contents and between crop yields and soil total N contents. Plant-available N was estimated using biological and chemical tests. Mineralized N formed under anaerobic incubation was low except for those soil samples that received manure. Microbial biomass C and N were estimated using the chloroform fumigation-incubation method (CFIM) and fumigation-extraction procedures. Biomass measurements by CFIM were more precise and reliable than values obtained by fumigation-extraction. Treatment differences in biomass were not significant. Estimates of biomass C and N were influenced by the choice of the control soil and the period of incubation used by the CFIM. Unfumigated (10-20 d) control soils were found to be the best control for samples. Extraction of mineralized N using O.5M NaHCO$ sb3$ after incubation overestimated biomass N since this extraction was found to extract non-biomass N.

Soil P fractionation was used to examine changes in soil inorganic and organic P under grazed irrigated pasture in a long-term field trial at Winchmore in Mid-Canterbury. The soil P fractionation scheme used involved sequential extractions of soil with O.5M NaHCO₃ @ pH 8.5 (NaHCO₃ P), 0.1M NaOH (NaOH I P), 1M HCl (HCl P) and 0.1M NaOH (NaOH II P). The Winchmore trial comprised 5 treatments: control (no P since 1952), 376R (376 kg superphosphate ha⁻¹ yr⁻¹ 1952-1957, none since), 564R (564 kg superphosphate ha⁻¹ yr⁻¹ 1952-1957, none since) 188PA (188 kg superphosphate ha⁻¹ yr⁻¹ since 1952) and 376PA (376 kg superphosphate ha⁻¹ yr⁻¹ since 1952: Topsoil (0-7.5cm) samples taken from the different treatments in 1958, 1961, 1965, 1968, 1971, 1974 and 1977 were used in this study. Changes in soil P with time showed that significant increases in soil inorganic P occurred in the annually fertilised treatments (l88PA, 376PA). As expected, the overall increase in total soil inorganic P between 1958 and 1977 was greater in the 376PA treatment (159 µg P g⁻¹) than that in the 188PA treatment (37 µg P g⁻¹). However, the chemical forms of inorganic P which accumulated in the annually fertilised treatments changed with time. Between 1958 and 1971 most of the increases in soil inorganic P in these treatments occurred in the NaHCO₃ and NaOH I P fractions. On the other hand, increases in soil inorganic P in the annually fertilised treatments between 1971 and 1977 were found mainly in the HCl and NaOH II P fractions. These changes in soil P forms were attributed to the combined effects of lime addition in 1972 and increased amounts of sparingly soluble apatite P and iron-aluminium P in the single superphosphate applied during the 1970's. In the residual fertiliser treatments (376R, 564R) significant decreases in all of the soil inorganic P fractions (i.e. NaHCO₃ P, NaOH I P, HCl P, NaOH II p) occurred between 1958 and 1977 following the cessation of P fertiliser inputs in 1957. This was attributed to continued plant uptake of P accumulated in the soil from earlier P fertiliser additions. However, levels of inorganic P in the different soil P fractions in the residual fertiliser treatments did not decline to those in the control which indicated that some of the inorganic P accumulated in the soil from P fertiliser applied between 1952 and 1957 was present in very stable forms. In all treatments, significant increases in soil organic P occurred between 1958 and 1971. The overall increases in total soil organic P were greater in the annually fertilised treatments (70-86 µg P g⁻¹) than those in the residual fertiliser (55-64 µg P g⁻¹) and control (34 µg P g⁻¹) treatments which reflected the respective levels of pasture production in the different treatments. These increases in soil organic P were attributed to the biological conversion of native and fertiliser inorganic P to organic P in the soil via plant, animal and microbial residues. The results also showed that annual rates of soil organic P accumulation between 1958 and 1971 decreased with time which indicated that steady-state conditions with regard to net 'organic P accumulation were being reached. In the residual fertiliser treatments, soil organic P continued to increase between 1958 and 1971 while levels of soil inorganic P and pasture production declined. This indicated that organic P which accumulated in soil from P fertiliser additions was more stable and less available to plants than inorganic forms of soil P. Between 1971 and 1974 small (10-38 µg P g⁻¹) but significant decreases in total soil organic P occurred in all treatments. This was attributed to increased mineralisation of soil organic P as a result of lime (4 t ha⁻¹) applied to the trial in 1972 and also to the observed cessation of further net soil organic P accumulation after 1971. Liming also appeared to affect the chemical nature of soil organic P as shown by the large decreases in NaOH I organic P(78-88 µg P g⁻¹) and concomitant smaller increases in NaOH II organic P (53-65 µg P g⁻¹) which occurred in all treatments between 1971 and 1974. The chemical nature of soil organic P in the Winchmore long-term trial was also investigated using 31p nuclear magnetic resonance (NMR) spectroscopy and gel filtration chromatography. This involved quantitative extraction of organic P from the soil by sequential extraction with 0.1M NaOH, 0.2M aqueous acetylacetone (pH 8.3) and 0.5M NaOH following which the extracts were concentrated by ultrafiltration. Soils (0-7.5cm) taken from the control and 376PA annually fertilised treatments in 1958, 1971 and 1983 were used in this study. 31p NMR analysis showed that most (88-94%) of the organic P in the Winchmore soils was present as orthophosphate monoester P while the remainder was found as orthophosphate diester and pyrophosphate P. Orthophosphate monoester P also made up almost all of the soil organic P which accumulated in the 376PA treatment between 1958 and 1971. This indicated that soil organic P in the 376PA and control treatments was very stable. The gel filtration studies using Sephadex G-100 showed that most (61-83%) of the soil organic P in the control and 376PA treatments was present in the low molecular weight forms (<100,000 MW), although the proportion of soil organic P in high molecular weight forms (>100,000 MW) increased from 17-19% in 1958 to 38-39% in 1983. The latter was attributed to the microbial humification of organic P and indicated a shift toward more complex and possibly more stable forms of organic P in the soil with time. Assuming that the difference in soil organic P between the control and 376PA soils sampled in 1971 and 1983 represented the organic P derived from P fertiliser additions, results showed that this soil organic P was evenly distributed between the high and low molecular weight fractions. An exhaustive pot trial was used to examine the relative availability to plants of different forms of soil inorganic and organic P in long-term fertilised pasture soils. This involved growing 3 successive crops of perennial ryegrass (Lolium perenne) in 3 Lismore silt loam (Udic Ustochrept) soils which had received different amounts of P fertiliser for many years. Two of the soils were taken from the annually fertilised treatments in the Winchmore long term trial (188PA, 376PA) and the third (Fairton) was taken from a pasture which had been irrigated with meatworks effluent for over 80 years (65 kg P ha⁻¹ yr⁻¹). Each soil was subjected to 3 treatments, namely control (no nutrients added), N100 and N200. The latter treatments involved adding complete nutrient solutions with different quantities of N at rates of 100kg N ha⁻¹ (N100) and 200kg N ha⁻¹ (N200) on an area basis. The soil P fractionation scheme used was the same as that used in the Winchmore long-term trial study (i.e. NaHCO₃ P, NaOH I P, HCl P, NaOH II p). Results obtained showed that the availability to plants of different extracted inorganic P fractions, as measured by decreases in P fractions before and after 3 successive crops, followed the order: NaHCO₃ P > NaOH I P > HCl P = NaOH II P. Overall decreases in the NaHCO₃ and NaOH I inorganic P fractions were 34% and 16% respectively, while corresponding decreases in the HCl and NaOH II inorganic P fractions were small «10%) and not significant. However, a significant decrease in HCl P (16%) was observed in one soil (Fairton-N200 treatment) which was attributed to the significant decrease in soil pH (from 6.2 to 5.1) which occurred after successive cropping. Successive cropping had little or no effect on the levels of P in the different soil organic P fractions. This indicated that net soil organic P mineralisation did not contribute significantly to plant P uptake over the short-term. A short-term field experiment was also conducted to examine the effects of different soil management practices on the availability of different forms of P to plants in the long-term fertilised pasture soils. The trial was sited on selected plots of the existing annually fertilised treatments in the Winchmore long-term trial (188PA, 376PA) and comprised 5 treatments: control, 2 rates of lime (2 and 4 t ha⁻¹ ) , urea fertiliser (400kg N ha⁻¹ ) and mechanical cultivation. The above ground herbage in the uncultivated treatments was harvested on 11 occasions over a 2 year period and at each harvest topsoil (0-7.5 cm) samples were taken from all of the treatments for P analysis. The soil P fractionation scheme used in this particular trial involved sequential extractions with 0.5M NaHCO₃ @ pH 8.5 (NaHCO₃ P), 0.1M NaOH (NaOH P), ultrasonification with 0.1M NaOH (sonicate-NaOH p) and 1M HCl (HCl P). In addition, amounts of microbial P in the soils were determined. The results showed that liming resulted in small (10-21 µg P g⁻¹) though significant decreases in the NaOH soil organic P fraction in the 188PA and 376PA plots. Levels of soil microbial P were also found to be greater in the limed treatments compared with those in the controls. These results indicated that liming increased the microbial mineralisation of soil organic P in the Winchmore soils. However, pasture dry matter yields and P uptake were not significantly affected. Although urea significantly increased dry matter yields and P uptake, it did not appear to significantly affect amounts of P in the different soil P fractions. Mechanical cultivation and the subsequent fallow period (18 months) resulted in significant increases in amounts of P in the NaHCO₃ and NaOH inorganic P fractions. This was attributed to P released from the microbial decomposition of plant residues, although the absence of plants significantly reduced levels of microbial P in the cultivated soils. Practical implications of the results obtained in the present study were presented and discussed.

Soil bottles and soil slurry experiments were conducted to investigate the effect of some additives on the aerobic and anaerobic biodegradation of chlorinated aliphatic hydrocarbons; tetrachloroethylene (PCE), trichloroethylene (TCE) and dichloroethylene (DCE) in a contaminated soil from Startvätten AB Linköping Sweden. For the aerobic degradation study the soil sample was divided into two groups, one was fertilised. The two groups of soil in the experimental bottles were treated to varying amount of methane in pairs. DCE and TCE were added to all samples while PCE was found in the contaminated soil. Both aerobic and anaerobic experiments were conducted. For aerobic study air was added to all bottles to serve as electron acceptor (oxygen). It was observed that all the samples showed a very small amount of methane consumption while the fertilised soil samples showed more oxygen consumption. For the chlorinated compounds the expected degradation could not be ascertained since the control and experimental set up were more or less the same.

For the anaerobic biodegradation study soil slurry was made with different media i.e. basic mineral medium (BM), BM and an organic compound (lactate), water and sulphide, phosphate buffer and sulphide and phosphate buffer, sulphide and ammonia. To assure anaerobic conditions, the headspace in the experimental bottles was changed to N2/CO2. As for the aerobic study all the samples were added DCE and TCE while PCE was found in the contaminated soil. The sample without the soil i.e. the control was also given PCE. It was observed that there was no clear decrease in the GC peak area of the pollutants in the different media. The decrease in GC peak area of the pollutants could not be seen, this may be so because more susceptible microorganisms are required, stringent addition of nutrients and to lower the risk of the high concentration of PCE and petroleum products in the soil from Startvätten AB.

Un phenomene de deperissement du sapin (abies alba m. ) se developpe depuis plusieurs annees dans le luchonnais. Apres un inventaire des symptomes et une cartographie des secteurs forestiers atteints, des travaux ont ete menes dans differents domaines afin d'expliciter ce phenomene. Il ressort que le deperissement semble du a une synergie de facteurs contribuant a affaiblir progressivement la sapiniere en provoquant directement (pollutions acides, faible fertilite des sols) ou indirectement (secheresse, competition) des troubles nutritionnels

Concern over excess phosphorus (P) input and loading in some soils of the Canadian prairie region has led to a need for a better understanding of the fate of added manure and fertilizer P. Information on the effects of manure application over long term (i.e., years) and short term (i.e., weeks, months) as related to management practices and manure form is still lacking. Knowledge of the P forms and species present in soil following application of manure and inorganic P fertilizers, and linking this to potential P availability and mobility is needed to make sound P management recommendations. The objective of this thesis project was to assess the speciation of soil P in different manures and inorganic fertilizer-amended Saskatchewan soils as affected by time, presence and absence of plants, landscape position, soil type, and management practices including rate and placement. Three studies were conducted (growth chamber and field-based experiments) to study P behavior in soils. These studies closely followed a time scale, beginning with speciation and fate followed over the very short-term (i.e., days to weeks) to a short-term period (i.e., months to a year) following amendment application, and finally the effects of repeated annual manure additions made over the long term (i.e., 11 years). Soils used in this study were loamy textured Brown and Black Chernozems. Solid cattle manure (SCM) and liquid hog manure (LHM) were applied at low and high rates in the very short-term and long-term studies. The low rate of SCM and LHM application was 7.6 T ha-1 yr-1 (dry weight) and 37,000 L ha-1 yr-1, respectively which was equivalent to approximately 100 kg total N ha-1 yr-1 application (agronomic N rate). The high rate was four times this amount. Inorganic fertilizer (mono-ammonium phosphate blended with urea) at rate of 54 kg N ha-1 and 12 kg P ha-1 and SCM at rate of 60 T ha-1 were applied in the short-term study. A sequential chemical extraction procedure was used to fractionate P in very short-term and short-term studies and different soil test phosphorus (STP) methods were used to determine effects on the labile P in the long-term study. Changes in P speciation with time and their relative proportions in fertilizered soils were also assessed using the synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy in all studies. This study has revealed that manure, especially SCM elevates labile P over all time frames examined. Over the very short-term (i.e., weeks to a month), P was added as manure tends to remain in labile forms like brushite and adsorbed P that is accessible to plants for uptake. In the manure band (months to a year), manure P was relatively unchanged over a period of months while in the mono-ammonium phosphate (MAP) fertilizer band, adsorbed and Ca-P was readily formed from fertilizer P. Aging over several years (one to eleven years), along with high soil pH and high Ca:P ratio enhanced formation of more stable Ca-P minerals like apatite, especially in SCM amended soil. Overall, the unique combined use of wet chemical analysis and synchrotron-based techniques in this thesis research has improved our understanding of fate and transformation of P added to prairie soils. It is suggested that future studies of fate of applied P in soil also utilize a combination of wet chemical and spectroscopic techniques, as this was shown to be a rewarding approach.

MSCAGR (Soil Sciece)
Department of Soil Science
In most parts of Limpopo Province of South Africa, crop yields are low and continue to decrease due to decline in soil fertility, which has been identified as a major constraint to crop production. Therefore, there is a pressing need for soil amendments such as the application of biochar, which has the potential to improve soil fertility due to its physical and chemical properties. Biochar is the product of incomplete combustion of biomass in the absence of oxygen. The overall objective of the study was to determine the effects of biochar and NPK fertilizer on maize performance and selected soil nutrient levels. A 3x2 factorial experiment was conducted at the School of Agriculture Experimental Farm for two consecutive seasons (2015/16 and 2016/17 seasons). Treatments consisted of biochar applied at three levels, viz. 0, 10 and 20 t/ha and NPK inorganic fertilizer applied at two rates viz. NPK0 (zero NPK fertilizer) and NPK1 {N (150 kg/ha) P (50 kg/ha) K (20 kg/ha)}. The treatments were laid out in a randomized complete block design (RCBD) and replicated three times. Maize cultivar (DKC 2147) was used as the test crop. Maize growth and yield measurements assessed included: plant height (cm), stem diameter (cm), number of leaves, leaf area, dry biomass (kg/ha), nutrient uptake, cob yield, grain yield and harvest index. Soil samples were collected from 0-10 cm and 10-20 cm soil depths at the end of each season to determine total N, P, K nutrient levels in the soil. Data collected was subjected to two-way analysis of variance using the general linear model (GLM) procedure of Genstat software version 17. Comparison of means was done using the Standard Error of Deviation (SED) method at 5% level of significance (p<0.05). Biochar and NPK fertilizer had no effect on total N and exchangeable K at all soil depths in 2015/16 and 2016/17 seasons. Biochar had no effect on phosphorus at all soil depths in 2015/16 and at 0-10 cm soil depth in 2016/17 season. The effect of biochar and NPK fertilizer was highly significant (p<0,001) on available P at 10-20 cm soil depth in 2016/17 season. Significant interactive effect of biochar and NPK fertilizer on soil total N at 10-20 cm (in 2015/16 season), available P and exchangeable K at 10-20 cm soil depth in 2016/17 season was also observed. Plant growth parameters increased with biochar addition at 20 t/ha and NPK1 (150 kg N/ha, 50 kg P/ha, 20 kg K/ha) fertilizer. The results of this study showed that biochar application at the rate of 10 and 20 t/ha has the potential to influence selected soil nutrient levels, maize growth, yield and yield components with and without NPK fertilizer application. Since this study was conducted over two seasons and biochar properties changes over a long-term period, more research is needed to evaluate the effect of biochar on soil nutrient levels and maize growth, nutrient uptake and yield over a long period of time.
NRF

碩士
國立臺灣大學
園藝學研究所
84
This study was to investigate effects of temeparature and light on the growth and flowering of Phal. equestris var. alba and Dori -taenopsis plants which are hybrids of Phalaenopsis and Doritis. The results shows the best temerature for the growth in Phal. equestris var. alba is 20~30C, 25~35C in Dtps. Purple Gem, and 25 ~30C in Dtps. Coral Gleam x Phal. Pinlong Lady and Dtps. Pinlong Princess '' Ruby Queen ''.The temperature treatment in 1994 had no effects on the time of flowering in Phal. equestris var. alba, while the 20~30c treatment promoted the flowering in 1995, specu -lating the flowering is mainly controlled by the nutrition sta -tus of the plants. The flowering of Dtps. Coral Gleam x Phal. Pinlong Lady an be induced in 15~20C and 15~25C in Dtps. Pinlong Princess '' Ruby Queen ''. Neverthless the temperature and day -length respectively failed to induce the flowering of Dtps. Purple Gem, expect the flowering of the plants grown in 30C above all year round were inhibited. The temperature shift of 35/30C to 25/20C with 16 hours lighting can somewhat promote the flowering in Dtps. Purple Gem. The light intensity largely influences the growth anfd flowering in Phal. equestris var. alba, however the high phosphate fertilizer not. Under the moderate light intensi -ty, the different fertilizers have no significant effects on the inflorescence emergence time and numbers in Phal. equestris var. alba.

Cereal rye (CR), the most common and effective nitrogen (N) scavenging cover crop option in the Midwest, is often utilized in cropping systems to reduce nitrate loss for environmental benefits. To increase environmental efficiency in Midwest corn cropping systems, we must increase the overall adoption of CR. However, due to the yield reduction potential (6%) for corn planted after CR termination, CR is primarily recommended before soybean. To increase CR adoption, we must develop adaptive fertilizer management practices that achieve competitive grain yields relative to cropping systems where CR is not adopted. Therefore, the objectives of this study are to determine (1) the effect of CR and starter nitrogen rate on corn growth and nitrogen content. (2) the optimum starter nitrogen rate to achieve agronomic optimum corn yield following CR. (3) the impact of phosphorus (P) at starter on plant growth, nitrogen content, and yield with the inclusion of CR. For our study, five starter N rates were applied in a 5x5 cm band to both CR and non-CR plots, concentrations ranged from 0-84 kg N ha^-1 in 28 kg N ha^-1 intervals. Total N applied was the same for each treatment, relative to its location, and was split between starter N at planting and sidedress applied at growth stage V6 relatively. Although CR termination took place at least two weeks before planting, CR decreased corn grain yield at one of three locations by an average of 8%, nitrogen recovery efficiency (NRE) by 27%, and R6 total N content by 23%, relative to the conventional control (non-CR 0N), when no starter N was applied. At one of three locations, starter N rates of 56 kg N ha^-1, 56 kg N ha^-1 plus 17 kg P ha^-1, and 84 kg N ha^-1 increased corn grain yield, in CR plots, and 56 kg N ha^-1 plus 17 kg P ha^-1 increased corn grain yield in non-CR plots. Phosphorus increased corn grain N content at growth stage R6 in one of three locations and did not impact corn grain yield at all locations. We conclude that the inclusion of starter N at planting has the potential to increase agronomic productivity in CR corn cropping systems in soil environments with a high capacity to mineralize soil N. However, further research is required to refine our starter N results to find an optimum starter N rate to apply before planting corn following CR.

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2019
Tomato (Solanum lycopersicum L.) is one of the most popular and widely consumed vegetable crops all over the world. They play a vital role in human diet and good sources of vitamins and minerals. However, low soil fertility is a major challenge to vegetable crops production for growers in Africa. Soils in the arid and semi-arid regions like South Africa have little nutrient and mineral contents, which adversely affect plant growth and quality. Therefore, the objectives of the study were to determine the effects of sole and combined applications of Effective Microorganisms enriched compost, broiler manure and inorganic (NPK) fertiliser applications, on growth and yield of three tomato varieties and to assess the influence of the applied fertiliser on nutritional composition of three tomato varieties. Field experiments were conducted at Horticultural skill centre, University of Limpopo (Mankweng), and at Mphebatho farm, Apel, Limpopo province, South Africa. The experiment was laid out in a 7 x 3 split-plot design. Recommended amount of organic and inorganic fertilisers was used. The treatments were: control (without fertiliser application), NPK (2:3:4(30) at a rate of 200 N ha-1, 260 P ha-1 and 257 K ha-1, applied as N from Urea, P from superphosphate and K from potassium chloride (KCl), mineralised broiler manure (10 000 kg ha-1), ½ NPK + ½ broiler manure rates, EM enriched compost (14 m3 ha-1), ½ EM compost + ½ NPK rates, and ½ EM compost + ½ broiler manure rates. Three tomato varieties (Floradade, Roma and Moneymaker) seedlings were transplanted using standard spacing of 30 x 60 cm. Chlorophyll contents of leaves, biomass production, plant height, fruit number, stem diameter and branch number were determined after six weeks of transplanting and fortnightly thereafter. The interactions between tomato varieties and fertiliser materials with regard to plant height were not significant (P ≤ 0.05) at both sites (Apel and Mankweng). Average plant height (63.75 cm) obtained in Moneymaker grown in EM compost treatment was significantly highest at Apel, for Floradade (42.25 cm) in broiler manure treatment while that of Roma variety (39.63 cm) was found in ½ EM compost + ½ NPK treatment at 8 WAT. Similar trend was also recorded at 10 WAT. For Mankweng the significantly (P ≤ 0.05) highest average plant height at 8 WAT (66.63 cm) was obtained in Moneymaker grown in ½ broiler manure + ½ NPK treatment for Floradade (45.63 cm) obtained in broiler manure treatment, and 44.50 cm recorded for Roma in broiler manure treatment. Similar trend was also followed at 10 WAT. At vi Apel, significantly highest average number of tomato fruits at 8, 10 and 12 WAT were recorded in treatment with ½ EM + ½ NPK while the least values were found in control. Whereas at Mankweng the variation in number of tomato fruits under different fertiliser treatments were not significant. Similar, non-significant interactions (V x F) for tomato shoot nutritional composition were found in tomato grown at both sites (Apel and Mankweng) in relation to fertiliser treatments. At Apel however, comparing the fertiliser treatments, tomato grown in soil treated with ½ broiler manure + ½ NPK had the significantly highest average (3.01 %) K content while the least value (2.65 %) was obtained in the control. Similarly, significantly highest mean (44.33 mg kg-1) Zn was found in crops grown in the same treatment, but the lowest significant value (36.50 mg kg-1) was obtained in ½ EM + ½ NPK treatment. For Mn and Fe contents in tomato significantly highest mean values (150.17 mg kg-1 and 2381 mg kg-1) for Mn and Fe respectively were found in sole broiler manure treatment while the least values 114.83 mg kg-1 and 1357.6 mg kg-1 for Mn and Fe respectively were found in ½ EM + ½ NPK and sole NPK treatments respectively. It may be concluded that in tomato production, combined application of organic and inorganic sources of nutrients can be more beneficial and can be adopted by smallholder farmers with limited resources.
DAFF Zero hunger

Over 10% of the world’s land is salt affected. Salt accumulation is a major soil constraint for agricultural sustainability in arable or newly cultivated soils. As a result of salinity, soil chemical, physical and biological properties deteriorate, plant uptake of water and nutrients, particularly P, decreases and plant growth declines. Application of plant residues can enhance the activity of soil microorganisms, the availability of nutrients, including P and the plant uptake of P and growth. Such a practice can also be economically viable as it can reduce the use of P from inorganic sources, maintaining the world’s reserve of P rocks and reducing the price of fertilizers and the environmental pollution often associated with the excessive application of inorganic N and P fertilizers. Little is known about how P, with N in proper form, added from inorganic and/or residue sources can affect wheat growth in the salt affected soils with no confounding pH or sodium adsorption ratio (SAR). Increasing microbial activity, N and P availability and wheat uptake of P by application of N and P from organic and inorganic sources may improve wheat growth and hence productivity under saline conditions. The overall aim of this study was to determine ways for enhancing the activity of microorganisms and increasing the availability of N and P, the uptake of nutrients, particularly P and the growth of wheat by management of fertilization from inorganic and organic sources in saline soils. This study therefore was conducted with the following aims: 1) to investigate the relationship between salinity and P availability; 2) to assess wheat response to combined application of N and P fertilizers under saline conditions; 3) to evaluate the effect of plant residue addition on N and P availability and microbial activity in salt affected soils; 4) to determine microbial response to addition of inorganic N rate and form, and how this will affect N and P availability in a saline soil, and 5) to determine the effect of P added from inorganic fertilizer and plant residue, compared to inorganic P fertilization, on microbial biomass and wheat nutrient composition and growth in a saline soil. In saline soils, P availability can be affected by the salt type and concentration and soil texture. Three experiments were conducted to study the relationship between P availability, soil texture and salinity. The results of the first experiment in which soil was shaken with different concentrations of NaCl or CaCl2 or Na2SO4, indicated that P solubility decreased with increasing concentration of Ca2+, but was not affected by Na+ salts. In the second experiment, P availability (after 24h shaking) decreased with increasing salt concentration up to EC1:5 3.1 dS m-1, increased with increasing P addition (0, 100, 200, 400, 600, 1200, 2500 and 5000 µg P g-1 soil), and was generally higher in sandy soil than in sandy loam soil. In the third experiment (15 days incubation), it was found that P availability significantly decreased one day after P addition which was followed by a further decrease to day 5, but then remained unchanged until day 15. It can be concluded that P availability is reduced in presence of clay, and decreases with increasing concentration of salts, particularly Ca2+, and that the availability of P stabilizes in sandy and sandy loam soils within 2 weeks after addition of P from inorganic source. Increasing N or P fertilization enhanced wheat growth in salt affected soils. Therefore combined application of N and P may enhance wheat growth in saline-non sodic soils with neutral pH. Three glasshouse experiments were carried out with the aim to determine the salinity range to be used in the subsequent experiments and to test the hypothesis that combined addition of N and P fertilizers can enhance wheat growth in a sandy loam soil with low SAR and neutral pH. The first two experiments were conducted in a sandy loam salinized to EC1:5 of 0.18, 1.36, 2.00 and 2.67 dS m-1 using NaCl and CaCl2. The wheat varieties Janz and Krichauff died in all soils to which salt was added showing that these EC levels were too high. The third experiment was conducted with Krichauff in the sandy loam soil with EC1:5 0.19, 0.32, 0.49, 0.67 and 0.86 dS m-1, equivalent to ECe 2.2, 4.4, 6.7, 9.2 and 11.8 dS m-1, respectively, and with 0, 30 and 60 mg P kg-1 soil and 50, 100 and 200 mg N kg-1 soil. Salinity reduced plant dry matter at all N and P application rates. Increasing N application rates decreased growth at low and high salinity, whereas increasing P addition improved growth at all salinity levels. The highest shoot and root dry weights were obtained with 50 mg N and 60 mg P kg-1 soil. Nitrogen and P fertilization did not increase wheat growth in soil with greater than EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Plants are known to respond differently to N form. A glasshouse experiment was carried out to assess the effect of N form (NH4 +, NO3 - or NH4NO3) added at 50, 100 and 200 mg kg-1 soil, in addition to the control (no N), on nutrient composition and growth of Krichauff in a sandy loam soil with EC1:5 0.21, 0.48 and 0.86 dS m-1, equivalent to ECe 2.8, 6.6 and 11.8 dS m-1. Increasing soil salinity decreased shoot and root dry weights and shoot macro- and micronutrient concentrations with all forms of N. At every N addition rate and with increasing N addition from N50 to N200, compared to NH4 +, the salinity of soil solution was far higher with NO3 - and lowest with NH4NO3. Shoot and root dry weights were highest with addition of 50 mg NO3-N or 100 mg NH4-N or as NH4NO3 at all salinity treatments. Concentrations of shoot P, Fe, Mn and Zn concentrations were greater with NH4 + and NH4NO3 compared to NO3 -, but concentrations of shoot K and Ca were higher with NO3 - than with NH4 + nutrition at all salinity treatments. At a given N rate, shoot and root dry weights were greatest with NH4NO3 in the saline sandy loam soil with up to EC1:5 0.67 dS m-1. Two experiments were conducted to evaluate the effect of plant residue addition on microbial activity and biomass, and N and P availability in salt affected soils. Although the same amounts of Na+ and Ca2+ salts, EC1:5 differed between tested soils due to differences between soils in clay content and water holding capacity. The first experiment aimed to assess the salinity range for microbial activity over 2 weeks in saline soils with different texture amended with glucose/nitrate (C/N ratio 16:1). The EC1:5 were 0.2, 1.26, 1.83, 2.28 and 2.99 dS m-1 in the silty loam, 0.16, 1.10, 1.98, 2.33 and 3.18 dS m-1 in the sand and 0.19, 0.82, 1.75, 2.03 and 2.79 dS m-1 in the sandy loam. Soil respiration significantly decreased with increasing salinity in the glucose/nitrate amended soils, but was not completely inhibited even at highest salinity treatment. Cumulative CO2-C increased over 2 weeks and was highest in the silty loam soil and decreased in the following order: silty loam soil < sandy loam soil < sandy soil. The second experiment was conducted to determine the effect of three different plant residues added at 2% (w/w) on microbial biomass and N and P availability over time (70 days) in saline sandy and sandy loam soils with low SAR and neutral pH. The EC1:5 was 0.21, 1.08, 1.90, 2.63 and 2.89 dS m-1 in the sand and 0.19, 0.87, 1.63, 2.32 and 2.49 dS m-1 in the sandy loam. Microbial biomass C, N and P decreased with increasing soil salinity and were highest on day 10. With residue addition, microbial biomass C and P were significantly higher in the sandy than in the sandy loam soil, whereas no significant differences were found between soils for microbial biomass P at all salinity treatments. Under all salinity treatments, compared to other residues, highest biomass N was found in canola-amended sandy loam and in lupin-amended sandy soils. With increasing soil salinity, highest microbial P was found in the sandy soil amended with lupin residue. Nitrogen availability was generally higher in the sandy soil than in the sandy loam soil, whereas the opposite was found for P availability. Compared to canola and lucerne, N and P availability were highest in lupin amended sandy and sandy loam soil. Two experiments were conducted to assess whether N addition (rate and form) can affect the microbial activity in presence of residues in a saline sandy loam soil. The first experiment aimed to evaluate the effect of N rate (0, 25, 50 and 100 mg N kg-1 soil) added as NO3 - on soil respiration over 2 weeks under non-saline conditions in presence of 2% lupin residues. The second was to determine the effect of N added at 50 mg N kg-1 soil as NH4 + or NO3 - and lupin residue added at 2 and 4% (w/w) on microbial activity and biomass and N and P availability over 45 days in a sandy loam soil with EC1:5 0.21, 0.51 and 0.85 dS m-1, equivalent to ECe 2.8, 7.0 and 11.7 dS m-1. Soil respiration and cumulative respiration were not significantly affected by N application rate over 2-week-incubation under non-saline conditions. Microbial biomass and N and P availability decreased with increasing salinity and were highest at 4% lupin residue. Soil respiration rate and cumulative CO2-C and microbial biomass C, N and P were greater with addition of 50 mg N kg-1 soil as NO3-N compared to NH4-N at every addition rate of lupin residues under saline conditions. Soil microbial biomass C, N and P were highest on day 15 and decreased over time, whereas N and P availability were lowest on day 15 and increased over time. Since addition of inorganic N and P fertilizers improved the growth of wheat (cv Krichauff) in the saline sandy loam soil at SAR 1 and neutral pH, two glasshouse experiments were conducted to determine the effects of plant residue addition on the nutrition of wheat. The first experiment was conducted under non-saline condition to determine the effect of lupin residue rate (2% and 4% w/w) on wheat growth. The second experiment was conducted under saline conditions to determine the effect of P added as lupin residue (2%) and/or KH2PO4 (0, 20 and 40 mg P kg-1 soil) with and without 50 mg N kg-1 soil added as (NH4)2.SO4 on microbial biomass, N and P availability, plant growth and nutrient composition in the saline sandy loam soil. The EC1:5 were 0.23, 0.35 and 0.51 dS m-1, equivalent to ECe 3.1, 4.8 and 7.0 dS m-1, respectively. In the first experiment under non-saline conditions, shoot dry weight was lower with addition of 4% than with 2% lupin residue with and without inorganic N. In the second experiment under saline conditions, microbial biomass C and N increased with increasing application of inorganic P, but was not as much as in presence of lupin residues. In presence of lupin residue, wheat growth increased with increasing addition of inorganic P under saline conditions. Compared to the soil with P from inorganic fertilizer and residues, inorganic P increased shoot and root dry weights and shoot P, K, Mn and Zn concentrations, but not N concentration. Addition of 50 mg inorganic N in presence of lupin residues significantly increased N and P availability and microbial biomass, but had no significant effect on wheat growth in a saline sandy loam soil. The results showed that optimal application of N and P organic and inorganic fertilizers can improve N and P availability, microbial activity and wheat growth in salt affected soils. Highest wheat dry weight was achieved by application of 60 mg P kg-1 soil in a sandy loam soil with EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Wheat growth was also improved with application of N-NH4 + or as NH4NO3 at 100 mg N kg-1 soil. These N and P fertilization rates can potentially enhance wheat growth in the sandy loam soil with up to EC1:5 0.67 dS m-1, but with SAR 1 at neutral pH. Plant residues increased microbial activity and N and P availability in the saline soils. In the soils used here, with residue addition wheat growth was P limited due to competition with microorganisms for available P. Therefore application of residues with inorganic P is necessary to satisfy wheat requirements of N and P in the saline sandy loam soil. In the saline sandy loam soil at SAR 1 and neutral pH, application of 2% lupin residues and 40 mg KH2PO4-P kg-1 soil achieved highest microbial biomass, nutrient availability and wheat growth. However, wheat growth with these rates is not as high as with inorganic P at similar rate due to micronutrient deficiency in the saline soil with lupin residues.
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Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Management-induced degradation of soil chemical and microbial quality is one of the most pressing concerns and a considerable threat to the sustainability of agroecosystems. However, information on this important issue is limited and largely based on short-term studies. A long-term experiment initiated in 1939 at the University of Pretoria provided a unique opportunity to assess the direct and residual effects of manure and inorganic fertilizers on soil chemical properties, microbial components and maize yield in rotation with field pea. Long-term addition of manure resulted in increased total organic C (TOC), total N and available P levels in the soil. Seasonally, these nutrients exhibited variations that appeared to be related to influences of crop rotation. Soil N content in an adjacent native site remained relatively constant but tended to increase in the control and manured plots. Soil microbial biomass C, N and P and microbial populations were affected by previous manure application as well as by crop rotation. Microbial biomass and numbers were generally higher in the manured plots. Manure application also had substantial residual effects and resulted in maize grain yields higher than in the control. Long-term NPK application resulted in decreased TOC and basic cation contents, and lowering of soil pH. The decrease in TOC was greater in single fertilizer treatments whereas basic cation contents and pH declined more in the balanced fertilizer treatments. Soil microbial biomass and numbers were influenced by, and exhibited qualitative changes in response to, long-term fertilization. Crop rotation also exerted effects on chemical and microbial properties of the soil. Maize grain yield showed significant increases in response to balanced fertilizer treatments. Response of maize to simple fertilizer applications was not beneficial in terms of yield returns. These results suggest that judicious use of inorganic fertilizers may, in the long-term, maintain soil quality and productive capacity. A comparison of the effects of residual manure and NPK fertilizers on the content of selected nutrients, microbial properties, C and N inputs, tissue nutrient concentration and crop yield showed differences due to treatments. TOC, total N and available P levels were increased due to residual manure alone or in combination with NPK fertilizers. C and N inputs and tissue P concentration were also generally higher in manured than in the NPK treatment. However, the higher increase in nutrient contents of manured plots was not reflected in microbial properties of the soil. Despite lower nutrient levels, the NPK treatment resulted in relatively greater increases in microbial properties of the soil. The differential responses were largely due to differences in quality and decomposability of organic material. Organic material in the NPK treatment appeared to have a higher decomposition and turnover rate than in other treatments, suggesting that C limitation in soils of low C but good nutrient supply may be compensated by high turnover rates of the available organic materials. The beneficial effect of residual manure on microbial properties and crop yield was decreased by application of supplemental N fertilizer but remained unaffected by application of supplemental K fertilizer. The depressive effect of excess soil P levels on soil microbial properties and crop yield was exacerbated by supplemental N fertilizer and mitigated by supplemental manure and K fertilizer applied to residual P. The decrease in available P levels due to supplemental K application implies that this may serve as a viable alternative to ameliorate soils with excess P levels.
Thesis (PhD (Plant Production and Soil Science))--University of Pretoria, 2003.
Plant Production and Soil Science
unrestricted

Management-induced degradation of soil chemical and microbial quality is one of the most pressing concerns and a considerable threat to the sustainability of agroecosystems. However, information on this important issue is limited and largely based on short-term studies. A long-term experiment initiated in 1939 at the University of Pretoria provided a unique opportunity to assess the direct and residual effects of manure and inorganic fertilizers on soil chemical properties, microbial components and maize yield in rotation with field pea. Long-term addition of manure resulted in increased total organic C (TO C), total Nand available P levels in the soil. Seasonally, these nutrients exhibited variations that appeared to be related to influences of crop rotation. Soil N content in an adjacent native site remained relatively constant but tended to increase in the control and manured plots. Soil microbial biomass C, Nand P and microbial populations were affected by previous manure application as well as by crop rotation. Microbial biomass and numbers were generally higher in the manured plots. Manure application also had substantial residual effects and resulted in maize grain yields higher than in the control. Long-term NPK application resulted in decreased TOC and basic cation contents, and lowering of soil pH. The decrease in TOC was greater in single fertilizer treatments whereas basic cation contents and pH declined more in the balanced fertilizer treatments. Soil microbial biomass and numbers were influenced by, and exhibited qualitative changes in response to, long-term fertilization. Crop rotation also exerted effects on chemical and microbial properties of the soil. Maize grain yield showed significant increases in response to balanced fertilizer treatments. Response of maize to simple fertilizer applications was not beneficial in terms of yield returns. These results suggest that judicious use of inorganic fertilizers may, in the long-term, maintain soil quality and productive capacity. A comparison of the effects of residual manure and NPK fertilizers on the content of selected nutrients, microbial properties, C and N inputs, tissue nutrient concentration and crop yield showed differences due to treatments. TOC, total N and available P levels were increased due to residual manure alone or in combination with NPK fertilizers. C and N inputs and tissue P concentration were also generally higher in manured than in the NPK treatment. However, the higher increase in nutrient contents of manured plots was not reflected in microbial properties of the soil. Despite lower nutrient levels, the NPK treatment resulted in relatively greater increases in microbial properties of the soil. The differential responses were largely due to differences in quality and decomposability of organic material. Organic material in the NPK treatment appeared to have a higher decomposition and turnover rate than in other treatments, suggesting that C limitation in soils of low C but good nutrient supply may be compensated by high turnover rates of the available organic materials. The beneficial effect of residual manure on microbial properties and crop yield was decreased by application of supplemental N fertilizer but remained unaffected by application of supplemental K fertilizer. The depressive effect of excess soil P levels on soil microbial properties and crop yield was exacerbated by supplemental N fertilizer and mitigated by supplemental manure and K fertilizer applied to residual P. The decrease in available P levels due to supplemental K application implies that this may serve as a viable alternative to ameliorate soils with excess P levels.
Thesis (PhD)--University of Pretoria, 2010.
Plant Production and Soil Science
unrestricted

The continuity of the menace of mercury (Hg) is due to the continuous production and use of Hg and Hg containing products. Toxicity is just an outfall of use and exposure. Anthropogenic activities such as coal combustion and artisanal and small-scale gold mining have led to increasing Hg contamination and is the major source of Hg pollution into the environment that needs to be remediated. This study aimed to assess the phytoextraction capability of sweet sorghum (Sorghum bicolor) under different fertiliser treatments in Hg-contaminated soil. The potted experiment in a controlled environment included control S. bicolor and three phytoremediation treatments, i.e., Hg only; the addition of 4:1 green compost and; the addition of 0.2% NPK fertiliser. There were conspicuous signs of Hg phytotoxicity in plants with Hg only, namely wilting, senescent, inhibition of growth, and photosynthesis. There was stunted growth, but healthy plants observed in the treatment with the addition of green compost towards the end (day 60) of exposure. However, S. bicolor grew well until the last day of exposure in the treatment with the addition of 0.2% NPK fertiliser. Thus, this treatment showed the most effective phytoextraction potential of S. bicolor in Hg-contaminated soil. The effectiveness of S. bicolor in reducing the level of mercury was best assessed in the Hg bioavailable concentration in the spiked soil in which the Hg + NPK treatment has the lowest (0.77 mg kg−1). That resulted in the highest uptake (84.31%) percentage of Hg concentration recorded in the treatment with the addition of 0.2% NPK fertiliser compared to the other two treatments. The results suggest that the proportion of phosphate in the NPK fertiliser used, plays a huge role in the phytoextraction of Hg in the contaminated soil by S. bicolor. The Translocation Factor (TF) and Bioconcentration Factor (BCF), although higher within Days 20 and 40, was greater than 1 at the end of the exposure period suggesting a high probability that Hg was significantly transferred to the aerial parts of the plants. This is regarded as typical hyperaccumulator plant species. While S. bicolor was able to reduce the level of Hg in all three treatments, Hg + NPK treatment gave overall best results in physiological growth, the uptake, and reducing the level of Hg bioavailable in the spiked soil in terms of the effectiveness of phytoremediation method.
Environmental Sciences
M. Sc. (Environmental Science)