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0000-0001-9811-4679
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Publisher: CSIRO Publishing
Date: 19-04-2022
DOI: 10.1071/CP21723
Abstract: Context Farmers and consultants are faced with selecting from amongst competing liming materials. Aim We sought to establish guidelines for the efficient use of competing liming materials. Method The effectiveness of 12 commercial liming materials from around Australia in increasing soil pH, their rate of movement below the depth of incorporation and their residual value to grain yield were measured in our field study. Key results Chemical composition (equivalent CaCO3 content) was a major determinant of effectiveness over the longer term. There appeared to be no value to grain yield in the provision of additional Mg above what was already in the soil at this site. Finer commercial products were more effective in the short term and no less effective in the longer term, indicating that fineness also remains a major determinant of effectiveness. The effect of the source of the liming product was a minor determinant of effectiveness. As previously found, there was a tardiness in the reaction rate of dolomites and a slight advantage in the reaction rate of softer limestones but as with fineness, the data for different sources tended to converge over 6–7 years. Conclusion All liming materials provided a benefit to grain yield over the 7 years and that benefit was proportional to the material’s chemical purity and fineness. Implication Growers and advisers can select the best value for cost amongst the commercially available products at a given geographical location. The quantitative assessment of chemical composition and particle size remains the best means of assessment over both the short and longer terms.
Publisher: CSIRO Publishing
Date: 2023
DOI: 10.1071/CP23009
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP20334
Abstract: Strategic tillage describes the occasional use of tillage in an otherwise no-till system. The practice can provide a pragmatic solution to emerging agronomic issues in no-till systems but raises concerns about prolonged or irreversible soil damage. We investigated the impact of a single tillage event at a long-term no-till experiment under treatments with retained or annually autumn-burned crop residues. One half of each residue-treatment plot received a single pass of a rotary hoe (ST) 4 weeks before sowing in 2011, the first year of the experiment the other half of each plot remained unchanged (NT). Soil physical, chemical and biological fertility in the surface layers (0–20 cm), as well as crop growth and yield were monitored for 5 years (2011–15). Following the ST treatment, soil bulk density and strength were initially reduced to the depth of cultivation (~15 cm) irrespective of residue treatment. Water-stable macroaggregates in the surface 0–5 cm were also reduced but recovered to pre-tillage levels within 1–2 years after ST treatment. Soil pH, total carbon (C), total nitrogen (N), and fine-fraction C and N were all initially stratified in the surface layer (0–5 cm) of the NT treatment but were redistributed more evenly throughout the 0–10 cm layer of the ST treatment and remained so throughout the 5-year period. With ST, there was an initial loss in total C stocks in the 0–10 cm layer of 2.2 t/ha, which recovered within 2 years however, total C stocks remained lower in plots with stubble retained than with stubble burnt after 5 years. Soil Colwell P levels were not stratified and not influenced by tillage treatment, presumably because of the annual additions in the starter fertiliser at sowing. ST had no impact on crop establishment or grain yield in any year but increased the early biomass of wheat at Z30 compared with NT in the first 2 years. Annual stubble retention reduced the early growth of crops in all years, and yield of wheat in the first 3 years, consistent with long-term effects of retained stubble at the site, but there was no interaction between stubble retention and tillage treatments on soil conditions or crop growth. Crop yields of long-term, annually cultivated treatments were also similar to those of ST and NT treatments during the 5 years of the experiment. Overall, the minor short-term negative impacts on soil physical conditions, the persistent and arguably beneficial effects on soil chemistry and biology, and absence of impacts on crop production suggest that strategic tillage can be a valuable agronomic tool in sustainable production in this region.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP20045
Abstract: Grain yield is frequently constrained by soil acidity in southern Australia yet limestone crushing plants are few and distant, making the use of limestone costly. The efficient technology of agricultural liming is therefore critical to the continuation of the practice following its adoption during the 1980s. We hypothesise that finer particles are the most effective materials for ameliorating soil acidity even over the longer term, when the residual value of coarser particles might be expected to be greater. Finer particle sizes of limestone, particularly & .075 mm, initially gave the largest increases in soil pH per tonne of limestone applied. Despite the rapid and large increase in soil pH with finer particles, there was no less residual value in surface soil pH after 7 years or in grain yield in the 7th and 8th growing seasons compared with coarser particles. Most particle size fractions of limestone converged to a similar soil pHca at 0–10 cm depth after about 6 years but the coarsest particle size fraction (2–5 mm) lagged the other five. Finer particles also resulted in better movement of alkali and Ca into the subsurface soil layers below the depth of incorporation (0–10 cm). The measurement of unreacted limestone in the soil showed that the dissolution of limestone took up to 3 years (1807 mm of rainfall) for the 2.5 t/ha rate and up to 6 years (3592 mm) for the 5 t/ha rate. The rapid increase in soil pH in Year 1, the slow ongoing reaction of limestone over 3–6 years as measured by unreacted limestone, the slow but measurable improvement in subsurface acidity, and the sustained residual value to grain yield over in excess of eight seasons, indicate that the use of finer liming materials should remain a viable practice for growers.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP19375
Abstract: Critical ranges for soil tests are based on results that inevitably involve some broad variance around the fitted relationship. Some of the variation is related to field-based factors affecting crop response to nutrients in the soil and some to the efficiency of the soil-test extractant itself. Most attempts to improve soil tests focus on the extractant, whereas here, we explore the variation that could be accounted for by field-based factors in the soil-test calibration relationship between Colwell phosphorus (P) and wheat yield, using the Australian Better Fertiliser Decisions for Crops database—the biggest dataset available for this relationship. Calibrations developed from this dataset have been criticised, and so we aimed to explore factors accounting for more of the variation in the relationships for the dryland, winter-dominant rainfall region of southern New South Wales. As reported previously, soil type was shown to influence the critical range and r-value for the Colwell P soil-test calibration for P responses by wheat. We also identified a tendency for dry conditions, at sowing or during the season, to lower relative yields for a given soil-test value, indicating increased reliance on fertiliser P over soil P. A similar trend was evident for later sowing date, again suggesting an increased probability of crop P requirements being met from the fertiliser P. However, additional records need to be generated to establish definitively that early sowing or subsurface P reserves minimise response to fertiliser P. In general, factors that influence crop access to soil P will have an impact on response to fertiliser P. Although this analysis shows that it is possible to ‘tighten’ the response curve for Colwell P and wheat by restricting the data for a given soil type to ideal management and seasonal conditions, the ‘outliers’ that are excluded frequently reflect an important subset of environmental conditions encountered by wheat crops in dryland agriculture.
Publisher: Elsevier BV
Date: 10-2019
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CP20280
Abstract: Soil testing guidelines for sulfur (S) under dryland cropping in south-eastern Australia are not well developed. Our objective was to assess the value of soil and tissue tests for S and nitrogen (N), because the two minerals frequently interact), in predicting S-deficient sites and hence increasing the probability of response to application of S (and N). Here, we report three proximal experiments in 2014–16 for barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) on a sandy soil in a semi-arid environment near Merriwagga in western New South Wales. The trials contained a factorial combination of four rates of each of applied N as urea and S as high-grade gypsum. Responses to S were obtained for dry matter (DM) quantity and nutrient content at flowering in 2014, but no grain-yield response was obtained in any year. DM response to applied S was obtained when the concentration of S in the DM was increased from 0.08% in barley and 0.09% in wheat without S application to 0.10–0.11% in both crops with S applied as gypsum. Because we obtained no grain-yield responses to applied S, the 0.10% S in grain was likely to have been adequate for both crops in these experiments. A pool of subsoil S was accessed during each season and this compensated for any DM deficiencies of S by the time of grainfill. Shallow soil tests (0–10 cm) for S can therefore indicate sufficiency but not necessarily deficiency therefore, in grain-cropping areas, we recommend soil S tests on the same s les as used for deep N testing (to 60 cm) and that an S-budgeting approach be used following the soil tests. Furthermore, for marginal nutritional circumstances such as occurred in this study, the supporting use of N:S ratio is recommended, with values & in DM or grain likely to indicate S deficiency for both barley and wheat.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/SR20120
Abstract: This study aimed to ascertain whether application of sheep urine led to the development of acidic subsurface layers of a pasture soil. Deionised water or simulated urine solution delivering urea-nitrogen (N) at 44.8 g m–2 and potassium at 25 g m–2 was applied to soil in either winter or spring. Treatments were applied to the soil surface within 10.3 cm internal diameter PVC tubes inserted 20 cm into the soil either under ryegrass or kept bare. Main s ling times corresponded to the completion of various soil N transformations as determined by periodic s ling. Main s lings involved the collection of above ground plant material and soil s ling in 2 cm depth increments in 0–10 cm and 5 cm intervals in 10–20 cm depths. Following treatment application, urea and ammonium-N moved to a depth no greater than 20 cm but the extent of movement was greater in winter than spring due to the influence of initial soil moisture. Following urea hydrolysis, soil pH increased in the 0–15 cm depth. Subsequent nitrification significantly acidified soil under pasture by 0.8–1.0 pH units in the 2–8 and 2–6 cm depths in winter and spring respectively. This created a net acidic subsurface layer of 0.2–0.4 pH units compared with soil at the beginning of the experiment. Subsurface acidification was 0.5–0.7 pH units greater in bare soil compared with the presence of pasture. Transformations of N resulting from application of simulated urine solution formed acidic subsurface layers in the field regardless of the season of application.
No related grants have been discovered for mark Conyers.