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Title: Onion Response to Nitrogen and Irrigation Type Following Soybean in 2006

Author
item Halvorson, Ardell
item BARTOLO, MICHAEL - CO ST U, ROCKY FORD, CO
item Reule, Curtis
item BERRADA, ABDEL - CO ST U, ROCKY FORD, CO

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 10/17/2007
Publication Date: 12/16/2008
Citation: Halvorson, A.D., Bartolo, M., Reule, C.A., Berrada, A. 2008. Onion Response to Nitrogen and Irrigation Type Following Soybean in 2006. Agricultural Experiment Station Technical Report TR08-16, Colorado State University, Fort Collins, CO. p. 19-22.

Interpretive Summary: Onion is a high cash value crop with a very shallow root system that requires frequent irrigation and is frequently fertilized with N rates exceeding 200 lb N/a to maximize yield. In 2006, we established six N treatments (0, 40, 80, 120, 160, and 200 lb N/a) in an area cropped to soybean in 2005 to determine N fertilization requirements to optimize onion yields following soybean. The N treatments were split to allow irrigation by furrow (normal method) and a drip system to evaluate the effects of irrigation system on N needs of onion. At the end of the season, a total of 34.6 inches of irrigation water had been applied with the drip system and 79.8 inches with the furrow system. Total marketable fresh onion yields were not significantly increased by N fertilization in 2006. Significantly greater onion yields were obtained with the drip system compared with the furrow irrigation system. Estimated gross economic returns were greater with drip irrigation than with furrow irrigation. This work demonstrates that economic returns can be maintained by using the more efficient drip irrigation system for onion production rather than the less efficient furrow irrigation system. The drip system had significantly more colossal and jumbo size onions and used 57 % less irrigation water than the furrow irrigation system. Nitrogen uptake by onion was greater with the drip irrigation system compared with the furrow irrigation system, resulting in improved N use efficiency.

Technical Abstract: Onion is a high cash value crop with a very shallow root system that requires frequent irrigation and is frequently fertilized with N rates exceeding 200 lb N/a to maximize yield. In 2006, we established six N treatments (0, 40, 80, 120, 160, and 200 lb N/a) in an area cropped to soybean in 2005 to determine N fertilization requirements to optimize onion yields following soybean. The N treatments were split to allow irrigation by furrow (normal method) and a drip system to evaluate the effects of irrigation system on N needs of onion. At the end of the season, a total of 34.6 inches of irrigation water had been applied with the drip system and 79.8 inches with the furrow system. Total marketable fresh onion yields were not significantly increased by N fertilization in 2006. Significantly greater onion yields were obtained with the drip system compared with the furrow irrigation system. Estimated gross economic returns were greater with drip irrigation than with furrow irrigation. This work demonstrates that economic returns can be maintained by using the more efficient drip irrigation system for onion production rather than the less efficient furrow irrigation system. The drip system had significantly more colossal and jumbo size onions and used 57 % less irrigation water than the furrow irrigation system. Nitrogen uptake by onion was greater with the drip irrigation system compared with the furrow irrigation system, resulting in improved N use efficiency.