Using the energy integral of soil water retention curve to evaluate the Soil water availability

The Soil water availability (SWA) reflects the degree of difficulty that plant absorbs and utilizes soil moisture. However, these SWA indexes including static criterions and dynamic indexes are inconsistent and difficult to use practically. In this paper, we thought SWA actually reflected consumption energy value of uptake water by plant, and the consumption energy value could be determined a definite integral from permanent wilting point to field capacity about soil water retention curve. The energy integral of soil water retention curve per soil volume water content change is used and tested on different soil types in the Loess Plateau of China. The results indicated that the method provides clearly theory-based water-uptake energy consumption by plants, and achieved the same results as those by productivity index and root water-uptake rate.