RUNOFF, EROSION, AND POLYMER APPLICATION IN MOVING-SPRINKLER IRRIGATION

Irrigation strategies must be designed to maximize or optimize product ion while conserving water, minimizing irrigation cost, and avoiding p ollution of the environment. Self-propelled moving sprinkler irrigatio n systems (MSIS) have become increasingly popular in recent years. Run off and erosion during irrigation with MSIS can be high under some con ditions. The objective of this review was to address three aspects rel ated to runoff and erosion with irrigation by MSIS: (i) factors that l ead to an increase in runoff and erosion during irrigation, (ii) effec t of runoff on crop production, and (iii) evaluation of the beneficial effect of polymer application by reducing runoff and erosion and incr easing crop yield. Surface runoff from 3-m2 fallow plots in a slit loa m loess and a clay vertisol under irrigation with linear MSIS at an av erage application rate of 100 mm h-1 was 53% and 39%, respectively. Th e high runoff levels were caused mainly by seal formation at the soil surface. Prevention of surface runoff movement along the slope in a fi eld increased the available water distribution uniformity in the soil and increased the average pod peanut yield by 882 kg ha-1. Application of 20 kg ha-1 polyacrylamide (PAM) and 40 kg ha-1 polysaccharide (PS) on the soil surface prior to the irrigation season reduced runoff and erosion levels significantly, and increased the cotton and potato yie ld under irrigation with MSIS. The application of PS in the field was more convenient than PAM application because of the higher dissolution rate in water and lower viscosity of PS.