CRITICAL PERIOD OF WEED INTERFERENCE IN FIELD-SEEDED TOMATOES AND ITS RELATION TO WATER STRESS AND SHADING

Abstract

The critical period of weed interference of field-seeded tomatoes (Lycopersicon esculentum L. ''TH 318'') was determined in 1981, 1982 and 1983. The minimum weed-free period varied among years from 7 to 9 wk after sowing, while the maximum weed-infested period varied from 5 to 6 wk after sowing. A minimum of two weed control operations during the critical period was required to prevent yield losses. Reductions in tomato yields were correlated with weed dry weights and could be attributed both to reductions in light levels due to shading and weed competition for water which resulted in stomatal closure.