MOISTURE STRESS TO MAXIMIZE PROCESSING TOMATO YIELD AND FRUIT QUALITY

Properly controlled moisture stress through irrigation management during fruit development and ripening of processing tomatoes results in maximum yield of raw products and paste. In 1991, a detailed field study was conducted in the San Joaquin Valley, the major processing tomato production area of California, USA, to assess the effects of moisture stress. Main plot treatments were irrigations at 20, 40, and 60% depletion in the top four feet of soil. In the sub-plots, irrigation water was cut off 20, 40, and 60 days before harvest. Sub, sub-plots used two popular California cultivars: Brigade, predominantly used for whole canned tomatoes, but also used for paste; and, Peto 111B, used for paste.

Low stress resulted in maximum yield of raw product, Mg/ha and best viscosity, but resulted in low soluble solids. High stress resulted in the lowest yields, highest soluble solids, and poorest viscosity. Intermediate stress resulted in some yield loss, but, substantially improved soluble solids with good viscosity.

Using potential evapotranspiration (ETo) and estimates of actual crop ET to properly control water management instead of scheduling irrigation on a calendar basis has allowed California tomato processors and growers to maintain high yields. Controlled moisture stress through irrigation management has also improved fruit quality and increased paste yield per ton of raw product.