A model and its numerical solution were developed to predict water content profiles, evapotranspiration, water flow from or to the water table, root extraction, and root water potential under transient field conditions. Soil properties needed are hydraulic conductivity and soil water potential as functions of water content. Plant properties needed are rooting depth and limiting root water potential. Climatic properties needed are potential evaporation and potential transpiration.The model predicted significant changes in root extraction, evapotranspiration, and drainage due to the variations in pressure head‐water content relations and root depth. Variations in the limiting root water potential had a small influence on estimated evapotranspiration, drainage, and root extraction.

Recent attention has been focused on the use of synthetic soil conditioners in the modification of soil water relationships especially in arid regions. Soils of extremes in texture—either sands or clays—present problems in this regard. In this laboratory study, Hygromull (a urea formaldehyde) and Agrosil LR and Agrosil S (amorphous sodium hydrosilicates) were evaluated on soils of different textures. Available water content was increased by Hygromull and Agrosil LR. Saturated hydraulic conductivity of the clay soils was improved by Hygromull, while that of the sandy soil was reduced by Agrosil LR. Hygromull increased porosity of all soils but, unlike Agrosil LR, had no effect on aggregation. In contrast, Agrosil S had no effect on any property studied. Notwithstanding the attributes of these conditioners, their acceptance in commercial farming in dry regions will depend on the outcome of field trials and economic considerations.

No abstract

No abstract

A mathematical model was developed to predict water content profiles, evapotranspiration, water flow from or to the water table, root extraction, and root water potential at the surface under transient conditions.The model was field tested in 1970 and 1971. With alfalfa (Medicago sativa L.) as the crop, predicted and computed water content‐depth profiles show best agreement 48 hours after any water addition. The poorest agreement for all crops tested was right after irrigation.The computed cumulative upward water flow from the water table was 4.80 cm as compared to 0.0 cm measured for the whole 1971 season of 116 days.