Factors Which Affect Furrow Intake Rates

To apply irrigation water efficiently, the water must be absorbed evenly across the field. In surface irrigation systems, this requires either that the water be spread quickly across the soil surface so that each portion of the field has a nearly equal time to absorb water, and that all portions of the field absorb water at the same rate; or that water intake rate varies across the field to compensate for differences in intake opportunity time. Water distribution in surface irrigation systems is determined by: 1) the water application system capabilities and management, and 2) the infiltration characteristics of the field soils. Improved application systems and design procedures for surface irrigation are being developed. But unless soil infiltration rates can be managed to achieve uniform water intake at desireable rates, high surface irrigation application efficiencies cannot be achieved. Although the problem of nonuniform soil water intake can be solved by applying the water through sprinkler or trickle systems at rates lower than the lowest intake rates, with the present high energy costs, this option is often not economical. The objective of this study is to evaluate several farmer manageable factors which can affect water intake rates into irrigated furrows. The long term research goal is to quantify the effects of farmer practices which decrease intake uniformity, practices he can apply to improve uniformity, and practices which can change intake rates. Intake rate modification can be useful to accelerate advance (thus decreasing variations in intake opportunity times), counteract the effects of variations in intake opportunity times, or better - adapt a field to a fixed or desireable water application system or schedule. The manageable factors which will be discussed are: 1) wheel compaction of furrows 2) surface soil water content 3) flow rates, and 4) intermittent application, such as "surge" irrigation