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United States Department of Agriculture

Agricultural Research Service

Research Project: WATER MANAGEMENT TO IMPROVE PRODUCTIVITY AND PROTECT WATER QUALITY Title: In-Situ Use of Ground Water By Alfalfa

Authors
item Ayars, James
item Shouse, Peter

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: April 15, 2007
Publication Date: June 17, 2007
Citation: Ayars, J.E., Shouse, P.J. 2007. In-Situ Use of Ground Water By Alfalfa. ASABE Annual International Meeting.Paper #072186, 2007 ASABE Annual Meeting

Interpretive Summary: Disposal of saline drainage water is a significant problem for irrigated agriculture. One proposal is to recycle drainage water on salt tolerant crops until the volume has been reduced sufficiently to enable final disposal by evaporation. Part of this concept will require crop water reuse from shallow groundwater; and data are needed to quantify the potential use of this groundwater by alternative crops. A column lysimeter study was initiated to determine the potential crop water use from shallow groundwater by alfalfa as a function of ground water quality and depth to ground water. The results demonstrated that up to 50% of the crop water use could be met from shallow groundwater with an electrical conductivity less than 4 dS/m, and that the potential crop water use from deeper ground water increased over the years. The columns with high salinity in the shallow groundwater experienced increased salinity in the soil profile with time, which resulted in reduced crop water use from shallow groundwater. Crop water use from shallow groundwater improved the water use efficiency of the crop.

Technical Abstract: A replicated column lysimeter study was conducted over a 4 year period to determine the effect of groundwater salinity and depth to ground water on the in-situ use of groundwater by a salt tolerant alfalfa crop. The treatments included a control with no groundwater, and ground water with electrical conductivities of 0.3, 2, 4, 6, and 8 dS/m at depths of 1.2m, and 2 and 4 dS/m at a depth of 2 m. There were a total of 4 replications for each treatment. Low salinity irrigation water was applied one to 2 times per week based on the computed contributions from ground water. The results demonstrated that in excess of 50% of the crop water requirement can be obtained from ground water with an electrical conductivity less than 4 dS/m. The multiple year study demonstrated that ground water contribution increased with time in the deep ground water columns until comparable levels of crop water use were achieved from shallow and deep ground water with the same salinity. There was accumulation of salinity in the lower parts of the root zone by the end of the study which would require leaching in a field setting. The total yield of alfalfa was improved in the shallow ground water lysimeters with good quality (< 4dS/m) ground water compared to the control with no ground water. The overall water use efficiency (WUE) of the alfalfa was improved with the columns with low salinity ground water (< 4dS/m) compared to the control. There was an improvement of WUE with time in each of the treatments. In areas with drainage water disposal problems in-situ use of ground water by crops will be a significant management tool.

Last Modified: 12/22/2014
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