Application of deficit irrigation management to variable rate irrigation for winter wheat in sub-arid climates

Abstract.

To evaluate the potential advantages of Variable Rate Irrigation (VRI) in increasing crop yield and water productivity (WP) in sub-arid climates, the deficit irrigation managements were applied with VRI system, and the responses of cumulative water use, yield, and WP to deficit irrigation were compared among the management zones during one growing season of winter wheat in the alluvial flood plain of the North China Plain. The field was delineated into three management zones with available soil water holding capacity (AWC) and each zone was equally divided into four sub-zones to represent the three treatments of irrigation trigger points at 55%, 65%, and 75% of field capacity and the rain-fed treatment. The rain-fed treatment received the least irrigation amount (46 mm) for seedling emergence and aiding fertilization, and produced lower yield and WP than the treatments irrigated. In the irrigation treatments, the seasonal irrigation amount differed among the management zones and was substantially higher in zone 3 (380 to 396 mm) than in zone 1 (300 to 380 mm) and zone 2 (226 to 356 mm). Consequently, the values of yield had a small variation rang among irrigation treatments (6370 to 6714 kg ha^-1) in zone 1, while greater variations were found in zone 2 (5508 to 7092 kg ha^-1) and zone 3 (6083 to 7004 kg ha^-1). The WP had a similar variation as yield. To obtain the maximum yield and WP of winter wheat simultaneously, the irrigation trigger point of 55%, 75%, and 65% of field capacity was recommended for zone 1, 2, and 3, respectively. Our results suggested that different deficit irrigation levels should be used in the management zones having different AWC values in sub-arid climates when the goal is to maximize yield and WP.