The amount of water in the soil that is available for plants to use depends on many factors: Precipitation amount and intensity, soil hydraulic properties that affect runoff and drainage, plant shoot and root distribution, soil surface sealing and crusting properties, slope characteristics, and land management practices. These various factors may have spatial and temporal distributions that result in complex patterns of plant-available water. All these factors are incorporated in a Precision Agricultural-Landscape Modeling System (PALMS), which can be used to study plant-available water on small watersheds from tens to hundreds of hectares in size with grid resolutions of 5 to 20 m.  

Results/Conclusions

The spatial variability of saturated hydraulic conductivity influences the partitioning of rainfall between infiltration and runoff and thus affects the spatial distribution of plant-available water. PALMS simulations for several typical agricultural fields are presented to demonstrate effects of surface sealing, variable hydraulic conductivity, and macropores on the spatial distribution of plant-available water.