APSoil plant available water capacity (PAWC) characterisation of select Liverpool Plain soils and their landscape context

[摘要] Knowledge of the plant available water capacity (PAWC) of soils on their farm can help growers and advisors improve the quality of yield forecasts (consisting of rules of thumb or assisted by tools like Yield Prophet®) used to inform management decisions such as timing of sowing (and associated crop type and variety choice) and the input level of resources such as nitrogen fertiliser. Past investments by GRDC and CSIRO have helped deliver a database (‘APSoil’) of 1000+ PAWC characterisations across the country. Between 2014 and 2017 GRDC funded project ‘Measuring and managing soil water in Australian agriculture’ (CSP00170) contributed a further 250 APSoil PAWC characterisations, ten of which were located in the Liverpool Plains. These were carried out in collaboration with local LLS staff (Gunnedah office) and consultants.This report documents the results from these characterisations (Part IIa) as well as a number of other new characterisations from other projects (Part IIb) for the benefit of local growers and advisors. It also describes the methodology used to measure PAWC in the field and how to access the existing PAWC data in the APSoil database (Part I). As PAWC characterisations are costly and labour intensive, growers and advisors are often not in the position to do a local field characterisation and will instead rely on the existing APSoil characterisations in the APSoil database to estimate the PAWC of their soils. This comes down to finding a soil with similar properties. Given that the nearest APSoil characterisation may be for a completely different soil, this is not an easy task and one that still challenges researchers as well. The report provides some general guidance for this, but also examines to what extent we can extrapolate or generalise from the combined PAWC characterisations in the Liverpool Plains drawing on available soil-landscape information (Part III). This is still research in progress and the preliminary results reported here are included to provide directions for future research and development.The fifteen new PAWC characterisations have enhanced the coverage of soil types within the Liverpool Plains considerably. Most of the soil-landscape units (SLUs) used for dryland cropping now have at least one PAWC characterisation, although as noted in Part III it is still difficult to determine to what extent this characterisation represents most of the soils (relevant to cropping) in the SLUs and how to predict the variability within them. Subsoil constraints, primarily due to salinity, were found to have a larger effect on variability in PAWC than soil texture or geology differences, although the latter were relevant in explaining the PAWC of soils in some of the SLUs. The fact that in the Liverpool Plains most cropping occurs on vertosols contributes to this finding and it may not extend to other regions. While the use of SLU mapping for selection of characterisation sites and interpretation of results proved worthwhile, more research needs to be carried out to develop methods and tools to capture the within SLU variability in PAWC. This could include terrain analysis and Electromagnetic Induction (EM). The value of the digital mapping contained in the new Soil and Landscape Grid of Australia should also be explored. The increasing availability of regional, state and national soil information on-line opens the way to more soil specific management and digital agriculture, although further research, development and extension is required to make it easily accessible and interpretable by growers and advisors.

[发布日期] 2017-07-27 [发布机构] CSIRO

[学科分类] 地球科学(综合)