ABSTRACT
Soil water plays a crucial role in regulating farm ‘eld water balance (FWB) and soil-plantatmosphere continuum (SPAC), in which precipitation, surface water, groundwater, irrigation, soil evaporation, and plant transpiration are received and converted by soils of farm ‘elds and exert interactive in¥uences on one another (Heilig et al. 2000; Li et al. 2000). The ultimate goal of soil water management is to increase the ef‘ciency of output for per unit of water, that is, economic output produced by depleting unit volume of soil water. All the water that is consumed by crop growth and development occurs through the uptake of soil water by plant rooting systems, which in turn exert considerable in¥uences on the changes and conversion of soil water. Soil water is thus affected by precipitation, irrigation, percolation, and groundwater. Conversely, soil moisture determines both the intensity and the dif‘culty of crops’ uptake, thereby affecting crop growth and development and eventually the economic output of crops. Hence, soil water is a key to converting all water components involved in both FWB and SPAC.
