关键词: 杨树, 杨树, 黑斑病菌, 超微结构变化

Abstract:

Livestock feces have become a huge threat to China's water quality. Based on four conditions, the difficulty to reduce the feces emission by livestock, the limit effect on N/P removal of the current manure treatment technologies, the high cost to transport the feces, and the limit N/P capacity of the land, the total quantity control of regional livestock rising was proposed theoretically. Then, the permitted amounts of livestock in China and the provinces were calculated according to the arable land, and compared with the actual amounts. It was shown that, in 2007, based on N (P), the permitted amount of livestock in China was 2.50 (6.44) billion standard pigs which was used by 64.39% (100.20%) and there were 5 (17) provinces where the actual amounts were over the permitted amounts. It was concluded that it was urgent to control the amount of rising livestock in some provinces and special areas.