Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2001
Publication Date: N/A
Interpretive Summary: Farmers are being asked to change management practices to improve irrigation efficiency and reduce deep percolation losses of nitrate that can contaminate groundwater. In this study, we monitored a field of cotton for four years. After the first two years, the data showed that 21 percent of the applied water ran off the field. The farmer made simple changes by narrowing the row spacing and irrigating every other row. This change resulted in reducing the runoff to 14 percent or a savings of 7 inches of water. While the changes resulted in water savings, the increased time required to irrigate the field resulted in less uniform application and infiltration of the water. The top portion of the field received more water, resulting in greater deep percolation losses. This information will be useful to engineers in the design of irrigation systems. Extension personnel would find this information useful when consulting with farmers on improving irrigation management on the farm.
Technical Abstract: Developing best management practices for irrigated agriculture requires an understanding of water and nitrate movement through the soil in order to minimize nitrate contamination of the groundwater. Irrigation efficiency plays an important role in deep percolation losses of nitrate, so farmers are being encouraged to improve management practices and implement new practices. In this study, irrigation efficiency and deep percolation of water and nitrate were studied for a production field under surface irrigation. The field was studied two years before and after management practices were changed. Runoff losses from the fields were decreased from 21 percent to 14 percent by changing the row spacing from 1 m to .8 m and irrigating every other row. Irrigation efficiency was slightly decreased by the changes, but the overall water use was less because of the decreased runoff. Irrigation uniformity was not as good with the alternate row irrigation. More deep percolation appeared to occur at the upper end of th field.