Academic literature on the topic 'Soils – Aluminum content – New South Wales'

This study, in southern New South Wales (NSW), examined the chemical properties of ~4700 surface soils in agricultural paddocks and recorded lime and gypsum inputs. The area was bounded approximately by Cootamundra in the north, the NSW/Victorian border in the south, extending to Tumbarumba in the east and to near Berrigan in the west. The long-term average annual rainfall ranged from ~420 mm in the west to a maximum of 1175 mm in the east. The data, collected between 1997 and 2003, were for the surface 20 cm of soil, in two 10-cm layers. The data were generated from a soil testing program conducted with farmers in the region. We grouped the soils into three zones based on a GPS location taken at the time of sampling. These zones were 1 (lower rainfall mixed farming), 2 (higher rainfall mixed farming) and 3 (long-term pasture). Acidic soils occurred across all three zones; however, the soils in zone 1 appeared to be less acidic than soils in the other two zones. We found that surface soils (0–10 cm) with soil pH in 1 : 5 soil : 0.01 mol/L calcium chloride (pHCa) ≤4.5 represented 27%, 57% and 54% for zones 1, 2 and 3, respectively. In addition, zone 1 had 74% of surface soils with a pHCa ≤ 5.0, and this was more acidic than previously reported. However, the surface soils in zone 1 had relatively low exchangeable aluminium (Alex) and had less acidic subsurface soils (10–20 cm), so that responses to lime application by pastures and crops may be less frequent or smaller than the surface soil pHCa alone may indicate. There was a higher frequency of acidic soils (pHCa ≤ 4.5) in the subsurface soils than in the surface soils in zones 2 (62 cf. 57%) and 3 (64 cf. 54%), suggesting that the acidity problem at this depth was a major problem. Low pHCa in the subsurface soil is known to be a constraint on crop yield. We found no evidence of the amendment of this soil depth when lime was applied and incorporated into the 0–10 cm depth, and economic amendment of acidity in the 10–20 cm depth remains unresolved. Increased adoption of liming occurred in the late 1990s, and by 1997 the percentage of paddocks limed was 14.3%, 21.3% and 13.6% in zones 1 to 3, respectively. Soil pH buffering and long-term pHCa decline after liming were similar to rates reported in field experiments. The total quantities of lime applied were insufficient for soil amendment and maintenance of soil pHCa, particularly in the long-term pasture areas. The rate of soil acidification in the 0–20 cm depth in the average annual rainfall range of 525–625 mm was estimated to be 1.52 kmol H+/ha.year. This would require 76 kg lime/ha.year to neutralise. Sodic and saline soils occurred mainly in the lower rainfall cropping areas, and were more frequent in an area around the township of Lockhart. Half the gypsum applications were at low rates (≤0.5 t/ha), and were probably for sulfur application to canola. Some of the sodic soils were acidic (34% ≤ pHCa 4.5) so that the application of lime/gypsum mixes could be appropriate in the amendment of these soils. Soils in the pasture system had mean organic carbon content (OC%) of 2.42, compared to the cropping zones at 1.65 and 1.75%. OC% was related to annual average rainfall; the increase in OC% was 0.19% and 0.08% for each 100 mm of average annual rainfall for the surface and subsurface soil, respectively. A group of soils in the cropping areas had surface OC% ≤ 1.25% OC (zone 1, 12%; zone 2, 20%) and this could be the result of intensive cropping. Most soils (55–63%) were of moderate P status (P(Colwell), 21–60 µg/g). However, there was still a substantial group of soils (31–43%) of low P status (P ≤ 20 µg/g). Most surface soils in all zones (72–80%) were low to marginal in sulfur status (KCl 40, ≤10 mg S/kg). Sulfur deficiency has been identified in canola, and current practice in the cropping areas is for inputs of gypsum at low rates.

On some of the lighter textured soils in the wheatbelt of central-western New South Wales near Dubbo, soil acidity is a major problem, and lucerne (Medicago sativa) often establishes and grows poorly. We selected a site with a surface soil pHCa of 4.4 and an exchangeable aluminium of 0.4 cmol(+)/kg, which was also acidic down the soil profile. Experimental plots of 4 application rates of lime (nil, 1, 2 and 3 t/ha) in 4 replications were established. The site was limed in 1990 and lucerne sown in May 1991. Over the next 6 years the trial was periodically grazed with sheep, and lucerne regrowth and stand density were monitored. In October 1997, the lucerne was removed and 3 crops of varying acid tolerance (wheat, barley and canola) were sown as split plots in both 1998 and 1999. Lucerne density was higher in the limed plots compared with the unlimed treatment, and this difference persisted for 6 years. Dry matter production of lucerne was increased by lime applied at rates up to 2 t/ha. All 3 crops sown after the lucerne phase responded to lime applied 8 and/or 9 years earlier. The responses were attributed to the strong residual effect of the lime in the 0–10 cm soil layer, to smaller improvements in the 10–20 cm zone (possibly due to the movement of lime down the soil profile over the 7 years before the date of measurement) and to carry over effects of nitrogen fixation by the lucerne into the cropping phase. The protein content of the wheat grain was increased concurrently with grain yield due to the previous liming and resultant legume nitrogen effects. The results support the application of lime to improve the productivity of lucerne and subsequent crops, even when the soil is acidic to depths below the cultivation layer.

Subterranean clover responds poorly to superphosphate application on some acid soils of the Southern Tablelands of New South Wales. A field experiment was undertaken, for two years, to examine the effects of incorporating large additional amounts of superphosphate or rock phosphate in the soil, with and without lime, on the growth of subterranean clover, lucerne and phalaris sown with recommended rates of lime superphosphate. Dry matter responses of subterranean clover and lucerne to superphosphate topdressing in the second year were also recorded. In the first year, subterranean clover growth was increased by the additional lime and by lime plus superphosphate. Lucerne growth was increased by additional lime. In the second year, the growth of subterranean clover was increased by the lime treatments and the superphosphate treatments applied in the previous year and by the deep incorporation into the soil of lime and superphosphate together. Subterranean clover growth also responded to the application of rock phosphate without lime. Lucerne dry matter production in the second year was increased by the lime, superphosphate and rock phosphate treatments applied in the first year. Lime application increased the yield responses of subterranean clover and lucerne to superphosphate topdressed in the second year. Lime application had no effect on the nitrogen content of the clover but increased that of lucerne. Lime application reduced the aluminium levels in the tops of all three species. The data suggest that the responsiveness of pastures to superphosphate on these soils is increased by the application of lime and rock phosphate and is related to low nitrogen fixation and high aluminium levels in the plant.

Different fertiliser products are commonly promoted for use on pastures in order to improve pasture productivity and support a more ‘healthy’ soil microbial environment. However, minimal field research has been conducted to validate such claims. A 6-year study (2009–14) was conducted on phosphorus (P)-deficient soils at three sites near Yass, New South Wales, to investigate the effect of topdressing perennial native-based pastures with a range of alternative fertilisers compared with single superphosphate and an unfertilised control treatment. The alternative fertiliser products included manures, composts, crushed rock, rock-phosphate-derived products, concentrated ash and microbial products. Annual measurements were made of soil chemical properties, botanical composition and pasture yield during spring and/or winter + spring, as well as the relative effectiveness of products per unit of pasture grown. Soil microbial community structure under each fertiliser treatment was also analysed in the sixth year of the study. Fertiliser products with substantial quantities of P increased extractable soil P and resulted in significantly higher pasture growth and clover content compared with the unfertilised control. Superphosphate was found to be the most P-effective fertiliser for increasing pasture growth, along with a range of other products that showed differential responses. However, the cost and P-effectiveness of the products in relation to pasture growth varied considerably and was a function of rate and frequency of application as well as amount and solubility of the P applied. Despite large differences in pasture growth across the various fertiliser treatments, there was no significant effect of the alternative fertiliser products on microbial community structure compared with either the superphosphate or unfertilised control treatments. The observed variation in bacterial, fungal and archaeal community structures across all fertiliser treatments was best explained by soil pH or aluminium (Al) concentration, which was influenced differentially by the fertiliser products. Fungal community structure was also correlated with pasture-productivity parameters (i.e. spring pasture yield, clover content and soil-available P). Our findings reveal a highly resilient soil microbial community that was influenced minimally by use of the alternative fertiliser products, thus highlighting that on-farm management decisions regarding fertiliser product choice should primarily focus on pasture response and cost-effectiveness.

Soil carbon is an important component of the global carbon cycle with an estimated pool of soil organic carbon of about 1500 Gt. There are few estimates of the pool of inorganic carbon, but it is thought to be approximately 50% of the organic carbon pool. There is no detailed study on the estimation of the soil carbon pool for Australian soils.In order to quantify the carbon pools and to determine the extent of spatial variability in the organic and inorganic carbon pools, 120 soil cores were taken down to a depth of 0.90 m from a typical cotton field in northern NSW. Three cores were also taken from nearby virgin bushland and these samples were used as paired samples. Each soil core was separated into 4 samples, i.e. 0–0.15, 0.15–0.30, 0.30–0.60, and 0.60–0.90 m. Soil organic carbon was determined by wet oxidation and inorganic carbon content was determined using the difference between total carbon and organic carbon, and confirmed by the acid dissolution method. Total carbon was measured using a LECO CHN analyser. Soil organic carbon of the field constituted 62% (0–0.15 m), 58% (0.15–0.30 m), 60% (0.30–0.60 m), and 67% (0.60–0.90 m) of the total soil carbon. The proportion of inorganic carbon in total carbon is higher than the global average of 32%. Organic carbon content was relatively higher in the deeper layers (>0.30�m) of the studied soils (Vertosols) compared with other soil types of Australia. The carbon content varied across the field, however, there was little correlation between the soil types (grey, red, or intergrade colour) and carbon content. The total soil carbon pool of the studied field was estimated to be about 78 t/ha for 0–0.90 m layer, which was approximately 58% of the total soil carbon in the soil under nearby remnant bushland (136 t/ha). The total pool of carbon in the cotton soils of NSW was estimated to be 44.8 Mt C, where organic carbon and inorganic carbon constitute 34.9 Mt C and 9.9 Mt C, respectively. Based on the results of a limited number of paired sites under remnant vegetation, it was estimated that about 18.9 Mt of C has been lost from Vertosols by cotton cropping in NSW. With more sustainable management practices such as conservation tillage and green manuring, some of the lost carbon can be resequestered, which will help to mitigate the greenhouse effect, improve soil quality and may increase crop yield.

Eight surface soils (0–15 cm) including 1 Ferrosol, 2 Tenosols, 2 Kurosols, 1 Sodosol, 1 Chromosol, and 1 Kandosol were collected from mainly pasture sites in New South Wales. The soils had different physico-chemical properties and there were some differences between the sites in climatic conditions. Soil microbial biomass carbon (MBC) was estimated by the chloroform-fumigation extraction method, and substrate utilisation patterns determined by the Biolog method were used to assess the amount, functional diversity, substrate richness and evenness, and community structure of the microorganisms in these soils. The amount of MBC (585 µg C/g) and the microbial diversity (H´ = 3.24) were high in soils that had high clay (33%), organic C (5.96%), total N (0.45%), free iron (7.06%), moisture content (50%), and cation exchange capacitiy (133.5 mmolc/kg). These soil properties, e.g. soil moisture (r2 = 0.72), organic C (r2 = 0.58), total N (r2 = 0.63), free iron (r2 = 0.44), and EC (r2 = 0.53), were positively correlated with MBC and microbial diversity index, whereas pH and sand and silt content showed negative correlations. The climatic factors (temperature and rainfall) had no significant influence on either MBC or diversity.

Accurate data on the distribution of the various types of sodic soils in New South Wales are not available. However, general observations suggest that large areas are affected by structural instability as a result of sodicity, particularly on grey clays and red-brown earths of the Murray-Darling Basin. There is a strong need for new sodicity surveys because the production of crops and pasture often is well below potential on these lands. Exchangeable sodium data on their own do not adequately describe sodic soil behaviour, so information is also required about related factors such as electrical conductivity, exchangeable magnesium, clay mineralogy, pH, calcium carbonate content, degree of remoulding, and the frequency of continuous stable macropores. Critical limits for sodicity that are used by soil management advisory services need to be redefined. Considerable research into the reclamation and management of sodic soils has occurred in the irrigation areas and rainfed cropping districts of the Murray-Darling Basin in New South Wales. Mined and by-product gypsum, and to a lesser extent lime, have been shown to greatly improve the physical condition and profitability of production from soils with a dispersive surface. However, the responses to these treatments are less likely to be economical when sodicity is confined to the subsoil. Adequate supplies of gypsum and lime are available in New South Wales, but further research is required to determine economically optimal and environmentally acceptable rates and frequencies of application, particle sizes and chemical compositions for different farming systems that utilize the various types of sodic soil.

The effects of pasture improvement on soil pH, total nitrogen, organic carbon and extractable phosphorus (P) were determined by analysing adjacent soils from improved and unimproved pastures at 67 sites on the Northern Tablelands of New South Wales. Pasture improved sites contained at least 1 clover species, predominantly white clover, and had received at least 125 kg P/ha over periods of 15-45 years. The majority of pasture improved sites contained more soil nitrogen, carbon and phosphorus and were of lower soil pH than adjacent unimproved sites. However, the decreases in pH were not statistically significant and not usually related to the magnitude of the increases in other soil fertility parameters nor to the amounts of superphosphate applied or duration of fertiliser history. The largest decline in soil pH and largest increase in organic carbon were on granitic soils which had received more than 250 kg P/ha. The relatively small decreases in soil pH and lack of relationship with fertiliser history, compared with soils from southern New South Wales, were attributed to: (i) re-cycling of legume-fixed nitrogen by summer-growing grasses; (ii) the naturally lower pH, higher nitrogen content and higher buffering capacity of many northern soils. Soil acidification therefore seems to be much slower and less frequent in the perennial pasture systems of the Northern Tablelands of New South Wales.

The effect of dry aggregation levels >0.85 mm and the percentage clay content of 9 soils from south-western New South Wales on erosion rate is evaluated using a portable field wind tunnel. Standard soil preparations and wind velocities are used based on conventions established in the North American wind erosion literature. For the prediction of erosion rate on both cultivated and uncultivated soils, 2 highly significant empirical relationships for percentage soil clay content and percentage mass dry aggregation >0.85 mm are presented. These spatial and temporal variations in erosion rates have significance for our understanding of soil erodibility. The concept of erodibility continuum is introduced.

This study was concerned with determining the effect upon soil structure when the drainage scheme evaporation pond product "high magnesium bitterns" was applied to soils from the Wakool-Tullakool irrigation district, N.S.W, Australia. Two soils were chosen covering the extremes of soil types found in the district. They were; 1. Burraboi Sandy Loam (Gn 2.63) a Calcic Aqiuc Haplustult and, 2. Moulmein Clay (Ug5.24) a Typic Chromoxerert. Laboratory tests were carried out to determine the basic physical and chemical properties of the two soils. Clay mineralogy for the two soils was determined using X- ray diffractometry. Both Na/Ca and Na/Mg cation exchange isotherms were constructed from data obtained using a sequential dialysis equilibration on the clay fraction of both soils. The final solution concentration was set at 0.006 mmol(+)L-1 thus approximating the actual soil solution at field capacity. Both soil clays showed exchange preference for the divalent cations over the monovalent cation Na. The values of K(VAN) show that Na selectivity at very low values of ENa decreases rapidly with increasing ENa to a minimum value after which Na selectivity increases. The values of Kex, the thermodynamic exchange constant, for Burraboi Sandy Loam were 0.746 for the Na/Ca system and 1.193 for the Na/Mg system. Thus the Ca system shows a decrease in Na selectivity relative to the Mg system. There was no significant difference in between the values of Kex for the Na/Ca and Na/Mg systems in Moulmein Clay. The calculated values of the rational activity coefficients /Na and /M2+ were not equal to unity over the range of Na saturation, and Kex did not remain constant, Thus non-ideal exchange occurred. It was also evident that some heterogeneity of exchange sites existed. An infiltration trial using diluted bitterns was carried out on Moulmein clay to assess its effect on the infiltration characteristic of the soil. No significant difference between treatments could be detected and it is thought that soil variability masked any treatment effect. A separate experiment on the same site where the infiltered soil was sampled for moisture content in a vertical grid pattern, showed that the downward movement of infiltering solute, when the soil is at the peak of its drying cycle, is governed by vertical movement through conducting macropores. Little lateral movement was seen and the solute did not penetrate the soil matrix to any great extent until redistribution occurred. Upon wetting soil swelling occurred and infiltration effectively ceased. Laboratory examination of samples taken from the infiltration trial also showed no detectable treatment differences. The total concentration of the immiscibly displaced soil solution increased with depth in all treatments as inferred by electrical conductivity measurements. It is thought that the infiltering solution moved rapidly down the profile carrying salts dissolved from the macropore periphery stopping when the pores became constricted in a region of increased soil moisture and subsequent soil swelling. Emerson structural stability tests carried out on the infiltration samples showed that the soils treated with the diluted bitterns (0.1 M and 0.01M) had slightly improved structural stability moving from class 1 and 2 to class 3, as defined by Emerson. This could be due to displacement of the Na by Mg or due to an increase in ionic strength in the soil solution.

A significant proportion of Australia's sugarcane crop is grown on east-coast estuarine floodplains underlain by pyritic gel-clay subsoils. At the current study site these agricultural acid sulfate soils are typically characterised by a topsoil horizon of river alluvium, a subsoil of oxidised actual acid sulfate soil (AASS), a zone of partially oxidised AASS and a deep sulfidic horizon of pyritic potential acid sulfate soil (PASS). Addition of nitrogenous fertiliser at key points in the sugarcane cropping cycle can create soil nitrogen levels in excess of immediate soil flora/fauna and crop requirements. In high rainfall tropical and sub-tropical regions conditions are thus suitable for nitrate, a strong oxidising agent, to leach down to the sulfidic soil layers with the consequent risk of pyrite oxidation. Little information is available on the fate of nitrogenous fertilisers in these pyritic subsoils. The purpose of this field and laboratory study was to evaluate the potential for nitrate reduction to occur in the presence of pyrite in sugarcane soils in the Tweed River valley, northern NSW, Australia. The study focus was on examining the soil profile hydrology including leaching mechanisms and nitrate concentrations down the profile to the AASS/PASS interface, as well as evaluating the potential for nitrate to increase the rate of pyrite oxidation in this generally anoxic soil zone. Following an investigative nitrogen field trial to gather initial data, a second replicated urea fertiliser treatment trial with a nil-treatment control plot and three nitrogen (N) treatments was set up on a plant-cane-block in collaboration with a Tweed region cane grower, Robert Quirk. Installed loggers recorded rainfall, air and soil temperature, soil moisture and watertable data. Separate surveys and analytical work characterised selected soil physical, morphological and geochemical aspects. Soil profile sampling on four occasions over the twelve month crop cycle was analysed for N-species, NH{u2084}{u207A} and N0{u2083}{u207B}. Hydraulic data analysis showed the watertable generally varying between 0.2 and 1.4 m below ground level with observed strong and rapid responses to rainfall events greater than approximately 15 mm per day. This and associated data supports the postulate that soil nitrate could move down the profile under even moderate precipitation events in these soils. Temperature, pH, redox potential and biological substrate soil data demonstrated the biogeochemical suitability of these subsoil zones to support nitrate reduction. Soil-N analysis revealed significant differences between N-trial treatments using urea fertiliser and also significant nitrogen transformation and movement within the soil profile. Over a period of weeks, the urea fertiliser was rapidly transformed and appeared in the upper profile as elevated levels of ammonium and nitrate ions. The initial high ammonium levels quickly declined to be replaced almost completely by nitrate in the upper layers of the cane soil. Subsequently, increasing soil nitrate concentrations were evident deeper in the soil profile on higher nitrogen treatment plots during the middle phase of the crop cycle. In no instances were significant levels of nitrate detected below the soil redoxcline (the oxic-anoxic boundary) at around 1.0 m depth, nor was nitrate pooling evident anywhere in the AASS transition zone. Laboratory experimental work was undertaken to evaluate nitrate reduction coupled with pyrite oxidation under the biogeochemical conditions existing in the AASS transition zone. Results indicated that nitrate reduction associated with pyrite oxidation does take place in pyritic gel clay from the field site.