Nutrient Management Research Database

Onion (Allium cepa) production in California’s San Joaquin Valley (SJV) typically involves intensive tillage and sprinklers for crop establishment followed by drip irrigation (DR). Studies were conducted at Five Points, California, in 2011 and 2013 to compare minimum tillage (MT) practices under overhead irrigation (OH) and DR relative to crop growth, yield, and costs. The experimental design was a randomized complete block with four replications of each irrigation treatment. Crop growth in both systems was similar; however, there was a year X irrigation system interaction for crop yields. In 2011, yields were not affected by irrigation, but in 2013, irrigation type affected yield with the OH system having 15.4 t/ha higher production than the DR system (78.6 t/ha vs. 63.4 t/ha). Onion size was not affected by irrigation system. Cost estimates indicated that onion production could be $564 per hectare lower with the OH system compared with the DR system, if yields were maintained. Because of cost savings from OH, in both years the OH system was more profitable than DR. The study showed that onions could be successfully grown with MT using the OH system in the SJV and similar amounts of water.

• In the San Joaquin valley, onions pose a challenge to grow while sustaining economic viability. Particularly, onions' low profit margins result from costly seeds and pest management along with the complexities of managing drip irrigation systems.
• The practice of "controlled traffic," where a permanent separation is established between areas of cropping and farm machinery traffic lanes, can decrease bulk density, reduce compaction, increase water holding capacity, and improve water use efficiency.
• This study compared crop growth, yield, onion size, and overall costs of minimum tillage operations utilizing either a surface  drip system or a precision overhead irrigation system rarely used in California.

• In year 1 of the study, no differences in yields were observed.
• However, in year 2 of the study, the overhead irrigation system resuled in yields that were higher by 7 tons/ac.
• In the first year, overhead irrigation resulted in an net reutrn increase of $72/ac. While in the second year net returns were $860/ac higher for the overhead system.
• Issues with drip tape movement and lack of even water distribution limited the effectiveness of the drip system.
• This study shows that implementing overhead systems in onions can be economically viable.