DECREASE OF NITROGEN FERTILIZER APPLICATION IN TOMATO PRODUCTION IN NO-TILLED FIELD WITH HAIRY VETCH MULCH

Growth and yield of tomatoes were estimated when they were planted in a no-tilled field with hairy vetch (Vicia villosa) mulch (NT+HV) with 80, 160 and 240 kg/ha of nitrogen fertilizer, and compared with tomatoes grown in a tilled field with black polyethylene film mulch (Till+BP). Seed of hairy vetch (50kg/ha) was sown in the Field Center of Niigata University on October 21, 1999, and hairy vetch (3,200kg/ha in dry weight) was mowed on May 17, 2000, to make residue mulch. Twenty percent of nitrogen was applied by fast-effect fertilizer and the rest (80%) by slow-effect fertilizer. Tomato cv. Momotaro was planted in NT+HV and Till+BP on May 19, 2000, and grown until early in September. The nitrate concentration in the petiole of the leaves near 2-3cm fruit in diameter decreased from 50 or 60 days after planting in the Till+BP. However, it maintained more than 1,500 ppm until 70-80 days after planting in NT+HV. The growth index of tomatoes grown in NT+HV with 80 kg/ha of nitrogen became higher after 50 days compared with Till+BP. The tomato yield in NT+HV was lower than that of Till+BP in the first and second fruit cluster in 80 kg/ha of nitrogen, but was higher from third to 7th cluster. No definite effect of nitrogen fertilizer in the yield was recognized among 80, 160 and 240kg in NT+HV. In 80 kg/ha of nitrogen fertilizer application, the total marketable yield of NT+HV was higher than that of Till+BP. There was no difference in total yield between NT+HV and Till+BP in 160 and 240 kg/ha. In no-tilled field with hairy vetch mulch, even if nitrogen fertilizer is decrease to the 80 kg/ha, recommended level for ‘N reduced tomato production’, the marketable yield will be the same level obtained in conventional production with 160 and 240 kg/ha of nitrogen.