Comparison of sub-irrigation and overhead irrigation of tomato and lettuceseedlings

Overhead irrigation is a common irrigation practice in nurseries, yet it ca n be wasteful of water and nutrients. We compared the water use, fertilizer use and growth of 'Top Gun' lettuce (Lactuca sativa L.) and 'Grosse Lisse' tomato (Lycopersicon esculentum Mill.) seedlings in sub and overhead irrig ation systems. Five rates of controlled release fertilizer were used - 0.62 5, 1.25, 2.5, 5 and 10 kg m(-3). Sub-irrigation used 86% less water than ov erhead irrigation. Irrigation type had a significant effect on some growth measurements by final harvest, 43 d after sowing. The sub-irrigated lettuce seedlings were significantly taller. The overhead irrigated lettuce seedli ngs had a higher dry weight and more leaves. The sub-irrigated tomato seedl ings were taller, had longer leaves, a larger leaf area and more leaves. In creasing levels of controlled release fertilizer produced quadratic type re sponses over time for shoot dry weight, with 10 kg m(-3) producing tomato a nd lettuce transplants with a higher biomass in a shorter time than lower l evels of fertilizer.