BORDER STRIP FERTIGATION: EFFECT OF INJECTION STRATEGIES ON THE DISTRIBUTION OF BROMIDE

Abstract

Fertigation using surface irrigation is a cost-effective and simple method of applying fertilizer across the field. The primary objective of this study was to compare different strategies for timing injection of bromide and its fate when injected into the irrigation water, as a surrogate for nitrate, during the irrigation of narrow sloping border strips. A fertigation experiment was conducted on sloping borders strips in the Coachella Valley Water District, California, on a Coachella fine sand, (sandy, mixed hyperthermic Typic Torrifluvents) and the crop was date palms (Phoenix dactylifera L.). Four treatments were used: bromide injection during the first half, the last half, and the middle half of the irrigation and during the entire irrigation (100%). The average low quarter distribution uniformity (DUlq) for water application was 0.73. For bromide, DUlq values ranged from 0.21 for the last half injection strategies to 0.64 for the 100% treatment. Use of one-dimensional models (EVALUE and SRFR) predicted satisfactory water but not bromide distributions. This is mainly because the models do not account for the flow through the furrows adjacent to the border dikes. The results of this study support the general finding that unless the soil is extremely sandy, injection during the entire irrigation produced the best distribution uniformity of added bromide. In this study, injection during the first half of the irrigation was not statistically different from injection during 100% of the irrigation.