Onion yield and quality affected by soil water potential as irrigation threshold

Onion (Allium cepa L.,'Great Scott') was grown on silt loam soils and submi tted to four irrigation thresholds (-25, -50, -75, and -100 kPa) in 1992 an d six irrigation thresholds (-12.5, -25, -37.5, -50, -75, and -100 kPa) in 1993 and 1994. Irrigation thresholds (soil water potential measured at 0.2- m depth) were used as criteria to initiate furrow irrigations. Onions were evaluated for yield and grade after 70 days of storage. In 1992 and 1994, t otal yield, marketable yield, and profit increased with increasing irrigati on threshold. In 1993, total yield increased with increasing irrigation thr eshold, but marketable yield and profit were maximized by a calculated thre shold of -27 kPa due to a substantial increase of decomposition during stor age with increasing threshold.