MODEL OF INTEGRATED EFFECTS OF BORON, INERT SALT, AND WATER-FLOW ON CROP YIELD

High boron concentration in the soil causes yield reduction. Recently, a piecewise linear response curve was applied to describe yield response to B in near steady-state conditions. However, application of similar curves to field situations where water, B, and other ion contents are transient and nonhomogeneous is limited. The objective of this study was to develop a model for simulation of the integrated effects of B, inert salt, and water on crop yield under field conditions. The model computes water flow in response to irrigation, rain, or evapotranspiration processes and subsequently computes inert salt and B transport. Crop yield is related to soil matric and osmotic potentials and B toxicity. Effects of B toxicity are considered by adapting the steady-state approach to the transient situation. Field experiments with barley (Hordeum vulgare L.) and corn (Zea mays L.) were conducted on the Utah Power & Light Co. research farm (Huntington, UT). Soil was Penoyer loam [coarse-silty, mixed (calcareous), mesic Typic Torriorthent]. Line source irrigation was used to obtain different irrigation levels. The effects of B, Salt (mixture of Na, Ca, Cl, and SO4), and B + Salt on yield were studied in barley. The effect of B + Salt was studied also in corn. Measurements and simulations were in close agreement for both crops. Barley yield ranked B + Salt < B < Salt < control. Corn yield ranked B + Salt < control. The B adsorption properties result in less leaching than do those of an inert ion like Cl. The effects of initial and boundary conditions together with the B adsorption characteristics on B concentration in the soil solution and the subsequent yield reduction are presented. This model can serve for an analysis of the long-term effects of high B and help in understanding the relative effects of available water, inert salt, and B on yields.