Location: Water Management ResearchTitle: Protecting groundwater quality with high frequency subsurface drip irrigation Author
|Ayars, James - Jim|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/2/2014
Publication Date: 3/4/2014
Citation: Ayars, J.E., Phene, C.J. 2014. Protecting groundwater quality with high frequency subsurface drip irrigation. U.S. Committee on Irrigation and Drainage, USCID, March 4-7, 2014 in Sacramento, California. p. 151-161. Interpretive Summary:
Technical Abstract: Nitrate pollution from agriculture is a significant problem in the groundwater of the San Joaquin Valley of California (SJV). Nitrate is very mobile in water and transport is directly related to both water and fertilizer management on a crop. Surface irrigation is the principal method used in the SJV and it typically has low values of efficiency and uniformity that result in deep percolation losses. Cropping in the San Joaquin Valley includes field crops, processing tomato, corn and alfalfa, and extensive permanent plantings, grapes, stone fruit, and citrus. These crops have been surface irrigated in the past. However there is a shift to using drip irrigation on the permanent plantings and some field crops. Drip irrigation is a technology that has been available for many years but is only now being implemented on a wide variety of annual and perennial crops. One feature of surface drip irrigation (DI) and subsurface drip irrigation (SDI) is the ability to manage high frequency irrigation and fertigation. This combination allows for excellent control of both water and nitrogen. SDI and DI are being used in a replicated study to determine the nitrogen requirements of a developing pomegranate orchard. High frequency irrigation maintained the soil matric potential at nearly constant levels and prevented any deep percolation and transport of nitrate below a depth of 5 feet. Prime fruit yields were higher in the SDI treatments compared to the DI (5.78 t/ac vs 4.98 t/ac). Total yield of prime plus juice fruit (10.3 t/ac in the SDI and 9.4 t/ac in the DI) were significantly higher than commercial yields of 4 to 5 t/ac for marketable fruit. The water use efficiency for the prime fruit was statistically higher for the SDI than the DI systems. The nitrogen use efficiency (NUE) decreased as the applied nitrogen increased. There were no differences in the NUE between systems. Crop evapotranspiration (ETc) has increased at the plant size developed as would be expected. The ETc in 2012 was 19.7 inches and a similar or larger value is expected for 2013.