Letteratura scientifica selezionata sul tema "Field crops – Zimbabwe"

The effects of one- and two-year maize-cover crop rotations on weed seed bank density and species composition were evaluated in fields at the University of Zimbabwe (UZ) and the International Maize and Wheat Improvement Center (CIMMYT, Harare) between 2014 and 2017. Nine cover crops were rotated, and maize and weed seed bank analyses were done using the seedling emergence method. Maize was used as the control. The results indicated that weed seed density was not significantly (p > 0.05) affected by cover crop mulch type across the seasons. There was a significant (p < 0.05) decline in weed density in the second maize phase of the rotation in UZ Field A. Bidens pilosa, Galinsoga parviflora, Amaranthus hybridus and Eleusine indica were the dominant weeds. B. pilosa density significantly decreased in the second season in UZ Field A but did not vary significantly among cover crops. Significant changes in weed species richness, evenness, and diversity were observed only in the second phase of the rotation in UZ Field A. The results suggest that maize-cover crop rotations could be effective in reducing seed bank size in the short term but have no short-term effect on weed species community composition.

Tobacco crop area and yield forecasts are important in stabilizing tobacco prices at the auction floors. Tobacco yield estimation in Zimbabwe is currently based on statistical surveys and ground-based field reports. These methods are costly, time consuming, and are prone to large errors. Remote sensing can provide timely information on crop spectral characteristics which can be used to estimate crop yields. Remote sensing application on agriculture in Zimbabwe is still very limited. Research should focus on identifying suitable reflectance indices that are related to tobacco growth and yield. Varietal yield response to fertiliser and planting dates as well as suitable temporal windows for spectral data collection should be identified. The challenges of the different tobacco land sizes have to be overcome by identifying suitable satellite platform, with sufficient spectral resolution to separate the tobacco crop from the adjacent competing crops and noncrop vegetative surfaces. The identified suitable index should be strongly correlated with tobacco in season dry mass and yield. The suitable vegetative indices can be employed in establishing tobacco cropped area and then apply the long-term area yield relationship from government and nongovernmental statistical departments to estimate yield from remote sensing derived cropped area.

In a field experiment on legume-maize cropping sequence, the effect of nitrogen and phosphate fertiliser application on nutrient budgeting after a two year cropping cycle was studied. The results of this work showed that partial nutrient balances can give an indication about the sustainability of a system unless a full stock of all the nutrients is known. It is also clear from these results that there would unlikely be a carryover of N to the next season, probably due to leaching of N from the top soil. Positive partial P balances would, on the other hand, be of residual value. However, it should be noted that the positive partial P balances were only observed where maize yield was low. The long-term perspectives of a crop production system cannot be assessed solely on the basis of partial nutrient balances. The nutrient stock: balance ratio may be a better indicator of sustainability, giving a more accurate indication of how long farming can continue in the same way, given the available nutrients. These points towards taking a fresh look at the existing recommended application rates for maize crops.

Improving iron (Fe) concentration in staple grain crops could help reduce Fe-deficiency anaemia in communities dependent on plant-based diets. Co-application of nitrogen (N) and zinc (Zn) fertilizers has been reported to improve both yield and grain Zn concentration of crops in smallholder farming systems. This study was conducted to determine if similar effects are observed for grain Fe concentration. Field experiments were conducted in two years, in two contrasting agro-ecologies in Zimbabwe, on maize (Zea mays L.), cowpea (Vigna unguiculata [L.] Walp) and two finger millet (Eleusine coracana (L.) Gaertn.) “seed pools”. The two finger millet “seed pools” were collected during previous farmer surveys to represent “high” and “low” Fe concentrations. All plots received foliar Fe-ethylene diamine tetra-acetic acid (EDTA) fertilizer and one of seven N treatments, representing mineral or organic N sources, and combinations thereof. Higher grain yields were observed in larger N treatments. Grain Fe concentration increased according to species: maize < finger millet < cowpea but varied widely according to treatment. Significant effects of N-form on grain Fe concentration were observed in the low finger millet “seed pool”, for which mineral N fertilizer application increased grain Fe concentration to a greater extent than other N forms, but not for the other species. Whilst good soil fertility management is essential for yield and grain quality, effects on grain Fe concentration are less consistent than reported previously for Zn.

Improving iron (Fe) concentration in staple grain crops could help reduce Fe-deficiency anaemia in communities dependent on plant-based diets. Co-application of nitrogen (N) and zinc (Zn) fertilizers has been reported to improve both yield and grain Zn concentration of crops in smallholder farming systems. This study was conducted to determine if similar effects are observed for grain Fe concentration. Field experiments were conducted in two years, in two contrasting agro-ecologies in Zimbabwe, on maize (Zea mays L.), cowpea (Vigna unguiculata [L.] Walp) and two finger millet (Eleusine coracana (L.) Gaertn.) “seed pools”. The two finger millet “seed pools” were collected during previous farmer surveys to represent “high” and “low” Fe concentrations. All plots received foliar Fe-ethylene diamine tetra-acetic acid (EDTA) fertilizer and one of seven N treatments, representing mineral or organic N sources, and combinations thereof. Higher grain yields were observed in larger N treatments. Grain Fe concentration increased according to species: maize < finger millet < cowpea but varied widely according to treatment. Significant effects of N-form on grain Fe concentration were observed in the low finger millet “seed pool”, for which mineral N fertilizer application increased grain Fe concentration to a greater extent than other N forms, but not for the other species. Whilst good soil fertility management is essential for yield and grain quality, effects on grain Fe concentration are less consistent than reported previously for Zn.

The effects of on-farm seed priming (i.e. seed soaking) on the emergence, growth and yield of cotton and maize were studied in the field in the south-eastern lowveld of Zimbabwe. Experiments were conducted on both crops in the 1999/2000 and 2000/2001 seasons and, in the 2001 winter season, on maize only. The interaction of priming with tillage (ox-drawn ploughing or hand-hoeing) and simulated sowing rainfall regimes (irrigations of 15 mm, 30 mm or 45 mm at planting) was studied. Priming usually increased the rate of emergence in maize, but always decreased final percent emergence in cotton. In the 2000/2001 season, there was an interaction between priming and simulated sowing rainfall regimes such that the 15 mm treatment gave a smaller adverse effect of priming in cotton than the 30 and 45 mm treatments. In maize, however, the 15 mm treatment gave an adverse rather than a positive effect of priming on emergence. There was little effect of tillage on emergence or growth. Priming did not affect the relative growth rate of cotton or maize, although plants grown from primed maize seed were consistently larger at any given date throughout the 2001 winter season. Plants from primed seed also flowered and matured earlier in the winter 2001 season. There were no significant effects of priming on yield, except in the 1999/2000 season, where priming decreased yield in cotton. It was concluded that the effect of priming can depend on crop species.

Soil erosion which manifests itself in the form of gullies, rills and sheet wash is animmensely complicated process involving the interaction of many biological, social,economic, environmental and political factors. It varies in its occurrence bothspatially and temporally. The ultimate result of soil erosion is that it reduces cropyields and ruins agriculture, though the exact extent of soil erosion and landdegradation is not known.The study was carried out in Masvingo Province, ZakaDistrict, Ward 5 with 4502 households using the questionnaire survey, interviewand field observations as research methods. The study established that populationpressure ( people and livestock), as evidenced by, cultivation of steep slopes,stream bank cultivation, deforestation and overstocking are major problems .Fromthe results, it emerged that people continue to compound the problem by settlingand extending farmlands on steep slopes, stream banks, grazing land and dambos/veils. Therefore, there is need to educate people on conservation, proper tillage,proper or correct stocking rates, develop a proper land tenure system and avoidingland degradation. There are patches of abandoned land on account of failure tosupport crops or grazing. This means that there is need for soil conservationmeasures to be instituted so as to save the soil from further deterioration. This isnot to say nothing has been done before, rather it is the enormity of the problemthat dictates that form and decisive action needs be taken sooner rather than latter.Measures which have been implemented are fragmented and seem to have metwith very limited, if at all any, success so there might be need to revisit both theapproach ,methods, techniques and strategies which have been tried hitherto witha view to blend them with the yet untried and untested methods.

Disposal of spent mushroom substrate (SMS) generated after mushroom cultivation is a subject of great concern. Unplanned disposal causes land, water, and air pollution together with the nuisance in the surroundings. During recent years, environmental legislation has forced mushroom growers to think about more amicable ways of SMS disposal. Hence, farmers in different corners of the country are using SMS as manure for various field crops and horticulture but without any support of the recommended rates from scientific data and therefore may not be getting the optimum benefits. This study sought to evaluate the effects of spent mushroom substrate on the yield and quality of baby spinach. The experiment was conducted in Mazowe, Zimbabwe, with 5 treatments (10 t ha−1, 20 t ha−1, 30 t ha−1 of SMS, and two controls) arranged in a CRBD and replicated 3 times. Biomass production (fresh mass, dry mass, root length, fresh root mass, and dry root mass) and sensory evaluation were determined 35 days after planting. Results showed that increasing rates of spent mushroom substrate significantly ( p < 0.05) increased the fresh yield and quality of baby spinach. Application of spent mushroom substrate beyond 30 t ha−1, however, increased the bitterness of baby spinach. The results of the study present the potential of the spent mushroom substrate as an organic fertilizer for the production of quality baby spinach.

Alectra vogelii Benth. (Family: Scrophulariaceae) is a vascular hemiparasite of various leguminous crops in Africa, including peanut (Arachis hypogaea), bambara groundnut (Vigna subterranea), cowpea (Vigna unguiculata), common bean (Phaseolus vulgaris), soybean (Glycine max), and mung bean (Vigna radiata) (1). It is a common parasite of peanut in Angola, Burkina Faso, Malawi, Mozambique, Nigeria, Swaziland, Zambia, and Zimbabwe (2). During April and May 2000, A. vogelii was observed parasitizing several wild Arachis species in a field at the Chitedze Agricultural Research Station near Lilongwe, Malawi. These species were part of a germ plasm enhancement program that included A. appressipila (ICRISAT Groundnut Accession number [ICG] 8127), A. batizocoi (ICG 8124), A. benensis (ICG 13215), A. cardenasii (ICG 13164 and 13166), A. correntina (ICG 8918), A. duranensis (ICG 13200), A. helodes (ICG 8955 and 14917), A. hoehnei (ICG 13228), A. magna (ICG 8960), A. pintoi (ICG 13222 and 14914), A. stenosperma (ICG 13172 and 13223), and A. valida (ICG 13230). In addition, A. vogelii was observed on four unidentified Arachis species (ICG 13231, 14875, 14888, and 14907). Parasitized plants were less vigorous and connections between A. vogelii and host plants could be observed by carefully removing the soil in the root zone. Mature A. vogelii plants were 0.3 to 0.5 m and had multiple stems branching at the base. Subsoil plant parts were a deep orange color. Flowers were prominent lemon yellow with horseshoe-shaped stigmata and leaves were light green. This is the first report of A. vogelii parasitizing wild Arachis species. References: (1) C. Parker. Crop Prot. 10:6–22, 1991. (2) P. Subrahmanyam. 1997. Parasitic flowering plants. Pages 70–71 in: Compendium of Peanut Diseases, 2nd Ed. N. Kokalis-Burelle, D. M. Porter, R. Rodriguez-Kabana, D. H. Smith, and P. Subrahmanyam, eds. American Phytopathological Society, St. Paul, MN.

The land reform that has unfolded in Zimbabwe since 1980 used different models and had diverse consequences. Since the implementation of the fast tract land reform programme in 2000, Zimbabwe experienced heavy reduction in yield and output at farm level that led to a 70% shortfall in production to meet annual food requirements (Richardson, 2005). The economic crisis in Zimbabwe has been characterized by worsening food insecurity especially in the rural areas where harvests continue to be poor. In the beef sector, Zimbabwe has failed to meet its export quota to the EU. The shortfall in production to meet annual food requirements shows a very grim situation but do not tell us about the performance of resettled farmers who now occupy much of the productive land. The broad objective of the study was to determine and compare the production efficiency of resettled farmers in Zimbabwe across land reform models. In addition, the study determined land use intensity. The study was conducted in the Mashonaland Central Province of Zimbabwe mainly because a wide variety of field crops were grown by resettled farmers. The respondents were stratified into three groups. These were: beneficiaries of land reform before 2000 (resettle scheme), fast track A1 model and fast track A2 model. The three models differ on how they were implemented and supported and this might result in different efficiencies of the models. A total of 245 copies structured questionnaire were administered on the resettled farmers from June to September 2010. Descriptive statistics was applied to the basic characteristics of the sampled households. The effect of model of land reform, gender of the household head, marital status, age of the household head, education, household size, religion, dependence ratio, whether the farmer was fulltime or part-time in farming, experience of the farmers in farming at that environment, total land size owned by the farmers and soil type on revenue per hectare and land use rate were determined using the GLM procedure of SAS (2003). Significance differences between least-square group means were compared using the PDIFF test of SAS (2003). The relationship between Revenue and land utilization was examined using the Pearson‟s correlations analysis. Dependance between response variables that had an effect on either revenue per hectare or land utilization with all the other response variables was tested using the Chi-square test for dependance. To find the effect of arable land used and herd size on revenue per hectare and land use the RSREG Procedure of SAS (2003) was used. Input oriented DEA model under the assumption of constant return to scale was used to estimate efficiency in this study. To identify factors that influence efficiency, a Tobit model censored at zero was selected. The mean land use rate varied significantly (p<0.05) with the land reform model with A2 having highest land use rate of 67%. The A1 and old resettlement households had land use rates of 53% and 46%, respectively. Sex, marital status, age of the household head, education and household size significantly affected land use (P<0.05). Revenue per hectare was not affected by any the factors that were inputted in the model. Results from the DEA approach showed that A2 farmers (large land owners) had an average technical efficiency score of 0.839, while the lowest ranking model (A1) had an average score of 0.618. Small land holders (A1 and the old resettled farmers) are on average less cost-efficient than large land owners, with a score of 0.29 for the former compared with 0.45 for the latter. From the factors that were entered in the Tobit model, age of household head, excellent production knowledge and farmer status affected technical efficiency whereas allocative efficiency was only affected by good production knowledge, farm size, arable land owned and area under cultivation. Factors which affected economic efficiency of the resettled farmers are secondary education, household size, farm size, cultivated area and arable land owned. None of the included socio-economic variables has significant effects on the allocative and economic efficiency of the resettled farmers. Thus, the allocative and economic inefficiencies of the farmers might be accounted for by other natural and environmental factors which were not captured in the model.

AbstractClimate change and variability is already reducing agricultural productivity and opportunities for employment, pushing up food prices and affecting food availability and production of formerly adapted crop types. Such is the case in cotton production in Zimbabwe, where it was the only viable commercial crop in marginal areas. As a form of adaptation, there is need for African farmers to have a range of agricultural techniques as coping strategies and tactics to enable sustainable production of crops and deal with extreme events. Such techniques include water conservation and introduction of new adapted crop genetics to cope with the new environment. The emerging trends in climate change will force farmers to adopt new crops and varieties and forms of agricultural production technologies. The objective of this study is to determine the contribution of combining in-field water harvesting and early maturing cotton varieties in curbing drought in cotton in semiarid Zimbabwe. The results show that both water harvesting in form of planting basins significantly (P <0.05) increased boll number and branch number of cotton across all varieties. The varieties M577 and M567 out-performed the conventional varieties in early growth, branch number, and boll number. Tied contour ridges gave a significantly (P <0.05) higher moisture content in 0–5 cm and the 6–10 cm depth compared to conventional tillage. The new varieties displayed early phenological development. Despite the existence of rainfall gaps, the in-field water harvesting techniques captured enough moisture and prevented moisture losses through runoff which resulted successful flowering and fruiting in the short varieties compared to conventional tillage on conventional varieties. In this regard, water harvesting and early maturing varieties offer considerable hope for increasing crop production in arid and semiarid areas of Zimbabwe.