Abstract
No-tillage cultivation without molding (NTC) of soybean, which decreases the instability of yield and improves the profitability compared with conventional cultivation (CVC) has spread among large-scale farmers. In Japan, however, due to few experiments on NTC, its advantage is not well recognized. To evaluate successive NTC in the field converted from paddy, we investigated the changes in the growth, yield and quality of soybean (Tamahomare) for 7 years (2003—2009) under NTC and CVC. There was no serious damage by diseases or pests during the period. Total C and available N in soil (0—30 cm) greatly decreased. There was no difference in yield between NTC and CVC, the average yield being 320 g m-2. The change in yield during the successive cultivation tended to be larger in CVC than in NTC. In both NTC and CVC, seed protein content varied with the year, but there was no difference in the protein content between NTC and CVC. A high correlation was observed between Ca content of seed and ex-CaO in 0—30 cm soil (r=0.86**) in both NTC and CVC. Ca content of seed increased during the successive cultivation, and at the fifth harvest was about 2.5 times that in the first year. In addition, the average Ca content of seed was higher in NTC than in CVC, which might be due to the difference in soil management. In NTC, 100-seeds weight, large-seed rate, stem thickness and number of pods per plant were lower, but the number of pods m-2 was higher than in CVC , which might be due to the difference in planting density.
