Effects of application of nitrogen fertilizer and of organic matter on soybean growing in dry fields which were converted from paddy fields were examined.
　1) When organic matter was not applied, the yield-increasing effect of basal or top dressing of nitrogen could hardly be expected. However, when wheat straw or compost was successively applied, the yield-increasing effect of nitrogen applied by basal or top dressing was markedly increased. Particularly, top dressing of 5-10 kg of nitrogen at the flowering stage caused a high rate of yield increase. It seemed to get the yield increase by about 10%.
　2) High positive correlation was observed between grain yields and the total top weight or the total amount of nitrogen absorbed by plants.
　3) Application of nitrogen fertilizer and of organic matter influenced root nodule formation. Application of top dressing of 10 kg nitrogen apparently inhibited the root nodule formation , and 5 t/10 a of compost also inhibited root nodule formation .
　4) Weak negative correlation was observed between the root nodule formation (expressed in weight of nodules) and grain yields. Although the positive application of nitrogen and organic matter tends to inhibit root nodule formation, it was pointed out that the positive applicable of nitrogen and organic matter could be a powerful measure to attain high yields of soybean grains.
　5) Since soil moisture at the flowering stage and pod-setting stage greatly influences grain yields, it was pointed out that the furrow irrigation was useful in preventing the yield decrease when soil moisture was very deficient.