Geographic differentiation of yield-increase efficiency caused by recycled nutrients in agro-ecosystems

The results of field trials at three sites in different parts in China showed that the fluctuation of yield caused by the different climate years was significantly decreased by the application of recycled nutrients. The results also indicated that the yield increase caused by recycled nutrients in agro-ecosystems was significantly affected by the application of chemical fertilizer and the thermal condition of climate. In the case of no chemical fertilizer, the average increase of crop yield caused by recycled nutrients with 80% recycling rate ranged from 262 kg·hm^-2 (average of fourteen years) at Hailun Station (in middle-temperate zone) to 1956 kg·hm^-2 (average of twelve years) at Shenyang station (in middle-temperate zone) and 3063 kg·hm^-2 (average of eleven years) at Taoyuan station (in subtropical zone) respectively. All the results showed that there was a remarkable geographic differentiation of yield-increase efficiency caused by recycled nutrients.