Taking The E Out Of ET

Droughts are frequent in the High Plains. Nebraska records show 21 drought periods of 5 or more years in length in the years from 1220 to 1952. Today Nebraska is facing a drought and a depleting Ogallala aquifer that is forcing farmers to find more water efficient ways to produce crops. Some land that is now irrigated may have to return to rainfed or limited irrigation. Also, a large number of cropland acres in the High Plains will always be rainfed. The winter wheat fallow system was developed to compensate for the low precipitation in the high plains. Fallowing with tillage that buried most crop residues was replaced with tillage which left residues on the soil surface. Residue on the soil surface helps protect the soil from wind and water erosion. This stubble mulch let more rain and snow soak into the soil to increase the soil water thus increasing efficiency. The crop residue also reduced soil temperatures to reduce evaporation of water from the soil. Crop Water Use (Evapotranspiration - ET) for irrigated corn in the High Plains ranges from 60 to 70 cm for fully watered corn. Up to 35% of this water use is from evaporation. Research has shown that the evaporation in fully irrigated corn can be reduced to as low as 15% of the ET with crop residues. This saving in E in ET plus saving 2.5 to 5.0 cm of soil water with the elimination of tillage reduces the irrigation water needs as much as 16 cm. Cropping practices for rainfed such as ecofallow and skip-row increase the success of crops grown using these systems. This paper will discuss how to be successful with these water saving systems.