Ben-Hur, M., Institute of Soils and Water, Agricultural Research Organization, The Volvani Center, Bet Dagan, 50250, Israel

A water management technique utilizing runoff water is beneficial for the success of agricultural development in arid regions. The objectives of this study were to (i) study the effect of sodium polymetaphosphate (NaPMP), sodium tripolyphosphate (STP), phosphogypsum (PG) and slope length on seal formation, infiltration rate (IR) and runoff amount; and (ii) determine the efficiency of use of PG, STP and NaPMP in runoff farming for wheat production, whereby the PG spread over the collector area is used to diminish runoff, and STP and NaPMP spread over the contributing area is geared to increase runoff. Field experiments were conducted in the northern Negev, Israel, where the average annual precipitation is 209 mm. Runoff from Calcic Haploxeralf was measured by small plots (<100 m2) under conditions of simulated and natural rainfall. In the stabilization of soil surface structure, and prevention of a sharp drop in the IR, 5 t ha-1 PG was found effective. The NaPMP and STP increased clay dispersion, and enhanced seal formation and runoff. This effect increased as the amount of the dispersant agents approached 150 kg ha-1. The NaPMP was more efficient than STP in increasing the runoff amount. The NaPMP and STP weakened the stability of soil aggregates, and increased clay dispersion, and enhanced seal formation. An increase in plot length decreased the runoff depth (amount area). However, plot rolling—which decreased surface storage—eliminated this reduction in runoff depth. The wheat yields for the seeded area in the runoff farming system which was treated with STP and PG, were significantly higher than with the ordinary system. © 1991, CSIRO. All rights reserved.