An infiltration model for managing furrow irrigation with limited water supplies

This study was conducted to determine whether the irrigation of a furrowed field when water supplies are limited could be managed to increase field corn yield (Zea mays L) while conserving water. Strategies of delaying the first irrigation of the season, multiple irrigations, and dryland farming techniques were evaluated for their effects on total water use and field corn yield through use of simulation. To model deficit irrigation it was necessary to develop and verify a two dimensional infiltration model that considered the effect of surface sealing and soil cracking. The infiltration model was verified with field data taken at Mead, NE for a silty clay loam soil. It was found that the output from the developed model better matched field data when cracks were considered in the simulations than when they were not. The irrigation simulations consisted of combining three models: an infiltration model, a surface irrigation model and a crop model CERES-MAIZE. The crop model simulated the water extraction from the soil by the roots. The drying produced cracking of the soil, which was considered by the infiltration model. The surface irrigation model simulated the water distribution along a single furrow. The crop model predicted yield across the irrigated field. A case study for a Cozad silt loam soil located in western Nebraska was used to evaluate the simulation of these strategies. For the year 1986, which represents an average rainfall year, it was found that it was better to start irrigation when the soil deficit was 50%, to irrigate two times, to encourage runoff and to use a reuse pit. It was concluded for this case study that when water is limited the best irrigation strategy is to irrigate the whole field and allow runoff because the last irrigation of the season can then be avoided. A reuse pit is necessary to contain runoff and conserve water