PREPLANT IRRIGATION IN THE CENTRAL AND SOUTHERN HIGH PLAINS - A REVIEW

Abstract

ABSTRACT Preplant irrigation has been widely practiced in the semi-arid High Plains since the early expansion of pump irrigation from the Ogallala Aquifer in the late 1930s. As groundwater storage continues to decline, the common practice of heavy water application to fully wet the root zone of graded furrow fields prior to planting is being questioned. Under some conditions, preplant irrigation is an essential practice for timely stand establishment and high yields. However, in many situations, the large application depths required for surface irrigation result in inefficient soil water storage and low yield response. With center pivot sprinkler systems, smaller and more precise preplant irrigation application amounts are possible resulting in more efficient preseason storage. We conclude that the benefits of preplant irrigation are likely to be greatest (1) when the soil profile is dry before planting; (2) when seasonal irrigations are not applied to drought-tolerant crops or are reduced in amount; (3) when early planting limits soil wetting by precipitation by the desired date; and (4) when preplant irrigation plus seasonal precipitation on deep, high water storage soils can result in moderately high irrigated yields without seasonal irrigation. The benefits are likely to be low (1) when soil profiles are moderately wet at time of irrigation; (2) when planting dates are flexible and can follow precipitation events for stand establishment; and (3) when seasonal irrigation provides adequate water to meet plant requirements. As groundwater decline continues and precipitation becomes more important for supplying crop water requirements, the use of preplant irrigation as an irrigation water management practice will likely decline in importance in the High Plains.