Optimization of irrigation water use in alfalfa sown in clay soils in the Imperial Valley, California, USA

Since the economical point of view, and for the seeded surface at Imperial Valley, California, USA, alfalfa (Medicago sativa) becomes the most important in the region. During period 1977 to 2001, the alfalfa average seeded surface were 71,592 ha, using an annual irrigation water volume of 1.41x10(9) m(3), where approximately, 15% to 20% of the total amount of applied water, represents lost water as surface runoff. The objective of this study is to show that using an improved irrigation method, the alfalfa crop can be irrigated under commercial conditions with a reduction of the surface runoff without affecting final yield. This study was realized during period November 2000, to August 2003, in a 32 ha parcel with alfalfa, in a clay soil at Imperial Valley, California. The experimental plot was divided into two sections of 16 ha each. In one section were used an Improved Irrigation Method (IIM), and in the other section, were used the Common Irrigation Method (CIM). During the study, were obtained a total of 22 alfalfa cuts, in which there was no difference in hay alfalfa yield. With the use of both irrigation methods, the average yield for the IIM was 2.21 ton ha(-1), and 2.35 ton ha(-1) for CIM. The total amount of applied water, in the 32 irrigations was different (P = 0.01). For the IIM were applied 404 cm, and for the CIM were 529 cm, which represents 22.2% less water than CIM. Surface runoff for the IIM was 5.89%, while in CIM was 17.3%.