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 f eed goats and pigs separately, and the feces and urine from the animal s 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 t he N recovery (9.914. 5%) by rice grain when rice straw was returned d irectly to the field as a base fertilizer. The total N recovery from g reen manure as feed by the pigs' body and grain totalled 30.2-30.8%, w hich was significantly higher than that of grain (22.7-26.7%) recovere d from green manure when it was directly applied to the soil. It was c oncluded that rice straw and green manure are used most economically b y feeding goats and pigs and returning the feces and urine to the fiel d.