IRRIGATION MANAGEMENT IN ARID AREAS AFFECTED BY SURFACE CRUST

The effects of supplemental irrigation and irrigation practices on soi l water storage and barley crop yield were studied for a crust-forming soil at the University of Jordan Research Station near Al-Muwaqqar vi llage during the 1996/97 growing season. An amount of 0.0, 48.9, 73.3, 122.2 and 167 mm supplemental irrigation water were applied. The 48.9 , 73.3 and 122.2 mm applications were applied through surface irrigati on into furrows with blocked ends, and the 0.0 and 167 mm applications via sprinkler irrigation. The greatest water infiltration and subsequ ent soil storage was achieved with the 122.2 mm application followed b y the 73.3 mm irrigation, both surface applied. Application efficiency (the fraction of applied water that infiltrated into the soil and sto red in the 600 mm soil profile) and soil water storage associated with supplemental blocked furrow irrigation was significantly greater than with supplemental sprinkler irrigation. For arid zone soil, which has little or no structural stability, application of supplemental irriga tion water via short, blocked-end furrows prevents runoff and increase s the opportunity time for infiltration, thereby increasing the amount of applied water that is infiltrated into the soil and stored in the soil profile. Supplemental irrigation, applied by a low-rate sprinkler system, was not as effective because of the low infiltration rates th at resulted from the development of a surface throttle due to dispersi on of soil aggregates at the soil surface. The differences in stored w ater had a significant effect on grain and straw yields of barley. Wit hout supplemental irrigation, barley grain and straw yields were zero in natural rainfall cultivation with a total rainfall of 136.5 mm. Bar ley yields in the control treatment, with a 167 mm supplemental sprink ler irrigation were low being 0.19 and 1.09 ton/ha of barley grain and straw, respectively. Supplemental irrigation through blocked-end furr ows increased barley grain and straw yields significantly compared wit h supplemental sprinkler irrigation to a maximum of 0.59 and 1.8 ton/h a, respectively. The improvement coming from the increased water stora ge associated with furrows. Since irrigation water is very limited if available, farmers are encouraged to form such furrows for reducing ru noff from rainfall thereby increasing the amount of water available fo r forage and field crop production. (C) 1998 Elsevier Science B.V. All rights reserved.