Response of Onion to Drip Irrigation

The effect on onion yield of different water applications applied with drip irrigation was investigated for onions. In 2002, both surface and subsurface drip irrigation were used with water applications ranging from 60 to 120% of the potential ET for both fresh-market and processing onions. The 2005 and 2006 experiments used surface drip irrigation on fresh-market onions with water applications ranging from 80 to 160% of the potential ET. Root and soil water distributions around drip lines were also determined. Results showed that onion yield increased with increasing applied water indicating that water applications based on the potential ET were insufficient for maximum yield. Most of the roots occurred in the top 200 mm of the soil profile. However, the 160% treatment resulted in considerable wetting below the zone of high root density, indicating considerable deep percolation and lower irrigation efficiency compared to the smaller water applications.