THE FATE OF NITROGEN FROM N-15-LABELED STRAW AND GREEN MANURE IN SOIL-CROP-DOMESTIC-ANIMAL SYSTEMS

In this study, N-15-labeled rice straw and green manure were used to feed goats and pigs separately, and the feces and urine from the animals were applied to rice plants as base fertilizer. It was shown that a total of 33.4-33.7% of the nitrogen in the feed straw was recovered by the goats' body and rice grain, which was significantly higher than the N recovery (9.914. 5%) by rice grain when rice straw was returned directly to the field as a base fertilizer. The total N recovery from green manure as feed by the pigs' body and grain totalled 30.2-30.8%, which was significantly higher than that of grain (22.7-26.7%) recovered from green manure when it was directly applied to the soil. It was concluded that rice straw and green manure are used most economically by feeding goats and pigs and returning the feces and urine to the field.