Abstract
Nitrogen emission from Nagoya University Farm, where both livestock farming and crop cultivation are carried out and animal feces are recycled through composting, was estimated and scenarios for the reduction of N emission were evaluated. Higher than 80% of nitrogen in feeds and fertilizers were emitted through composting and fertilization. After long-term application of compost, most nitrogen applied as compost became apparently emitted in the same cropping season. In the soil receiving only chemical fertilizers (CF soil), the soil nitrogen concentration decreased, indicating the needs of compost. About 40% of fertilizer nitrogen were absorbed into crops in CF soil, and mulch improved it by several percentages. The absorption rates were lower in the soils receiving compost. Nitrogen loss by denitrification was not observed in CF soil, while about 10% or higher in the soils receiving compost. Nitrate leaching was the major pathway of emission. Higher nitrate concentration in leachate from the soils receiving compost was observed. Reduction of fertilizer nitrogen was effective to reduce emission by 24%. A scenario allowing the highest nitrogen flux by the less nitrogen loss during composting with rice straw and the lowest nitrogen inflow into the Farm achieved to reduce the estimated emission by 40%.
