Capacity of soils to buffer impact of climate variability and value of seasonal forecasts

Soil provides a buffer to store water for use by plants between rainfall (or irrigation) events. This paper presents. a study on how the plant available water holding capacity (PAWC) of soil interacts with rainfall variability and nitrogen input level to determine wheat yield, water use and the potential value of seasonal forecasting in nitrogen (N) management in southeast Australia. An agricultural production systems model was used to simulate those interactions. Results show that optimising N management towards maximum economic return led to increased production risk. Wheat yield, gross margin and crop water use increased, while deep drainage decreased with increasing soil PAWC. In high rainfall areas where the risk of crop loss was generally small, increased soil PAWC reduced the variability in gross margin, leading to higher yield, less water loss by deep drainage, and reduced potential value of seasonal forecasts. in low rainfall areas, the increase in wheat yield, gross margin and crop water use with increase in soil PAWC was much smaller due to limited rainfall. in those dry the potential value of seasonal climate forecasts was simulated to increase with regions, increased soil PAWC. Soils with higher PAWC enabled more rainfall to be used by crops, but did not change the seasonal crop water use efficiency in terms of kg grain produced per unit water consumed by evapotranspiration. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.