Farm Table says:
The take home messages from this GRDC funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.
- Plant available water (PAW) is a key determinant of potential yield in dryland agriculture. Obtaining a measurement or estimate of PAW can, therefore, inform crop management decisions relating to time of sowing, crop type or the level of fertiliser inputs
- Estimating PAW, whether through soil coring, use of a soil water monitoring device or a push probe, requires knowledge of the plant available water capacity (PAWC) of a soil. PAWC characterisations for 26 soils in the Liverpool Plains are publicly available in the APSoil database, which can be viewed in Google Earth and in the ‘SoilMapp’ application for iPad and Android
- Variation in the observed PAWC is linked to parent material, texture and subsoil constraints. Similarity in soil properties is therefore key, when choosing an appropriate PAWC data for your soil
- Recognising how soils are distributed across the landscape, helped by understanding how the soils have been formed, assists with assessing similarity in soil properties. The nearest characterisation is not necessarily the most appropriate one
- Relationships between soil properties, parent material and position in the landscape are reflected in soil-landscape, soil and land resources and land resource area mapping and described in accompanying reports available online through eSPADE (NSW)
- Digital soil maps (DSMs) provide predictions of soil properties at 90 or 100 m resolution and are available through eSPADE for NSW, and the Soil and Landscape Grid of Australia (SLGA), for all of Australia
- The project is currently testing a 5-step PAWC estimation approach at sites across the Liverpool Plains involving: 1) identification of soil-landscape unit., 2) observations on position within the soil-landscape units, 3) comparison with APSoil PAWC characterisations in the same or similar soil-landscape unit, 4) use of digital soil mapping products to compare properties and identify risk of salinity subsoil constraints, 5) adjustment of PAWC based on local conditions.
Figure 5. APSoil 1306, APSoil 1307, APSoil 1308 (left to right respectively)