Development of Improved Water Application and Management Techniques for MovingIrrigation Systems

摘要

The effect of high frequency irrigation and sprinkler application packages on thewater and nitrogen use for corn irrigated with center pivot irrigation systems was investigated. High frequency (daily) irrigation did not increase corn yields in Nebraska. High frequency irrigation can reduce runoff if the soil is allowed to dry before initiating irrigation. The sprinkler package affects the water use efficiency of center pivots. Results show that evaporation of water droplets while in the air is very small (1-2% of the application). Evaporation from the wetted canopy and soil surfaces can be substantial and increases with the frequency of irrigation. High frequency irrigation with center pivots seems to be best suited to sprinkler packages that apply water below the crop canopy and that only wet part of the soil surface. However, the water application rate for these packages can be very high and may induce runoff if inter-row tillage is not used. Irrigation and fertilizer management are needed to abate the buildup of nitrate in groundwater. Frequent irrigation reduces nitrate leaching if watering is delayed until the soil dries to a point that minimizes deep percolation while avoiding crop water stress. However, slight water stress reduced both crop yield and nitrogen uptake. Plots on a silty clay loam soil that were not fertilized for four years yielded nearly the same as plots fertilizer at the recommended rate, indicating that improved nitrogen management depends on better predicting the mineralization of organic nitrogen. Leaching of chemicals applied with the irrigation water increases if preferential flow paths are available in the soil. If preferential flow does not occur chemicals already in the soil leach before chemicals in the irrigation water. Transfer function models were developed to predict preferential flow, but the input function for these models is unique to the way the chemical is applied and for the rate of water application, limiting the utility of the transfer function model.