ISHS Acta Horticulturae 724: IX International Symposium on the Processing Tomato
LATE-SEASON DEFICIT IRRIGATION IS A RELIABLE TOOL FOR SOLUBLE SOLIDS IMPROVEMENT IN DRIP-IRRIGATED PROCESSING TOMATO PRODUCTION |
| Authors: | T.K. Hartz, P.R. Johnstone, M. LeStrange |
| Keywords: | Lycopersicon esculentum, irrigation management, evapotranspiration, soluble solids |
| Abstract:
Soluble solids concentration (SSC) is an important quality factor for processing tomatoes (Lycopersicon esculentum Mill.). The use of drip irrigation often results in undesirably low SSC. The effects of late-season deficit irrigation on fruit yield and SSC was investigated in 5 commercial, drip-irrigated field trials in 2004. In each field the grower’s irrigation regime was compared to a treatment receiving 25-50% less water over the final 4-7 weeks before harvest, a period corresponding to fruit ripening. In all fields the growers utilized a deficit irrigation strategy, applying only 32-67% of reference evapotranspiration (ET°) over this period, averaging 53%; the reduced irrigation treatment varied from 20-46% of ET°), averaging 38%. Across fields, the grower irrigation regimes averaged 147 t ha-1 total fruit yield and 5.5 °Brix. The reduced irrigation treatment reduced total fruit yield by only 6 t ha-1, and a corresponding increase in SSC resulted in no net loss of Brix yield (yield x °Brix). Fruit sampling throughout the ripening period confirmed that the SSC of late-maturing fruit was significantly increased by deficit irrigation, but that the SSC of early-maturing fruit was not increased by stress imposed after they had ripened. We conclude that processing tomatoes can tolerate significant late-season moisture stress without loss of Brix yield, and that late-season deficit irrigation provides a flexible tool for fruit SSC management. SSC monitoring of ripening (pink stage) fruit can help determine the severity of late-season deficit irrigation required to achieve desirable fruit SSC. | |
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