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Title: Nitrogen Effects on Onion Yield Under Drip and Furrow Irrigation

Author
item Halvorson, Ardell
item Reule, Curtis
item BARTOLO, MICHAEL - CSU-AVRC, ROCKY FORD, CO
item BERRADA, ABDEL - CSU-AVRC, ROCKY FORD, CO

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2008
Publication Date: 7/1/2008
Citation: Halvorson, A.D., Reule, C.A., Bartolo, M., Berrada, A. 2008. Nitrogen Effects on Onion Yield Under Drip and Furrow Irrigation. Agronomy Journal 100:1062-1069.

Interpretive Summary: Onion is a high cash value crop with a very shallow root system that is frequently irrigated and fertilized with high N rates to maximize yield. Converting from furrow-irrigated to drip-irrigated onion production may reduce N fertilizer needs, water inputs, and NO3-N leaching potential. Onion growth and N uptake, fresh onion yield, and residual soil NO3-N were measured under drip and furrow irrigation with N fertilizer rates from 0 to 224 kg N ha-1. In 2005, 72% less water was applied with the drip system compared with furrow system, and 57% less in 2006. Onion yields were significantly greater with the drip system. Total marketable fresh onion yield increased with increasing N rate in both systems. The drip system had more colossal and jumbo sized onions and less medium sized onions than the furrow system. Biomass production and N uptake accelerated in mid-June each year with a total N uptake (tops + bulbs) of 121 kg N ha-1. Irrigation water use efficiency (IWUE) and N use efficiency (NUE) were higher with the drip system than with the furrow system. Residual soil NO3-N levels were greater in the drip-irrigated treatments after onion harvest in 2005 than in the furrow-irrigated treatments. Adjusted gross economic returns (less cost of N, water and drip system) were greater with drip irrigation than with furrow irrigation. This study demonstrates that fresh onion yields, potential economic returns, IWUE, and NUE can be improved in Colorado by using drip irrigation for onion production rather than furrow irrigation which has a greater gross water requirement and NO3-N leaching potential.

Technical Abstract: Onion (Allium cepa L.) is a high cash value crop with a very shallow root system that is frequently irrigated and fertilized with high N rates to maximize yield. Converting from furrow-irrigated to drip-irrigated onion production may reduce N fertilizer needs, water inputs, and NO3-N leaching potential. Onion growth and N uptake, fresh yield, and residual soil NO3-N were determined under drip and furrow irrigation on a clay loam soil with N fertilizer rates from 0 to 224 kg N ha-1. Onions were sampled bi-weekly from 25 May to 30 August in 2005 and 2006 from each treatment. In 2005, 72% less water was applied with the drip system compared with furrow system, and 57% less in 2006. Onion yields were significantly greater with the drip system. Total marketable fresh onion yield increased with increasing N rate in both systems. The drip system had more colossal and jumbo sized onions and less medium sized onions than the furrow system. Biomass production and N uptake accelerated in mid-June each year with an average total N uptake (tops + bulbs) of 121 kg N ha-1. Irrigation water use efficiency (IWUE) and N use efficiency (NUE) were higher with the drip system than with the furrow system. Residual soil NO3-N levels were greater in the drip-irrigated treatments after onion harvest in 2005 than in the furrow-irrigated treatments, but soil NO3-N levels were similar after harvest in 2006. Adjusted gross economic returns (less cost of N, water and drip system) were greater with drip irrigation than with furrow irrigation. This study demonstrates that fresh onion yields, potential economic returns, IWUE, and NUE can be improved in Colorado by using drip irrigation for onion production rather than furrow irrigation which has a greater gross water requirement and NO3-N leaching potential.