The Spatial And Temporal Change Of Nitrogen And Phosphorus Produced By Livestock And Poultry & Their Effects On Agricultural Non-point Pollution In China

Investigations revealed that the nitrogen (N) and phosphorus (P) discharges from animal production to the water system are the leading source of the eutrophication of water bodies all over the world. The N and P eutrophication of the Chinese major lakes and water systems has been getting worse and worse in recent years. To understand the tendency of N and P eutrophication in major Chinese water systems, we investigated the spatial and temporal changes of N and P produced by livestock and poultry as well as their effects on agricultural non-point pollution in China.The industry of livestock and poultry production in China has been growing very fast since 1980s. The amount of animals on hand weighed by pig unit increases 300 million every 10 years and the average per person consumption of meat, egg and milk has been doubled every 10 years since 1970s. However, the average per person amount of meat, egg and milk consumption in China is still much lower than that of the world. The industry of livestock and poultry production will keep growing in the next 10 years due to the huge requirement on the market.Consequently, the total amount of N and P from animal excretion increased greatly in the past years. In 2002, for example, the amount of N and P from animal excretion reached 16.8 million tons and 9.48 million tons respectively, which equals to 66% and 89% of N and P fertilizer application in the same year. With the development of highly-concentrated livestock and poultry production in China, the N-load from animal production to agricultural land increased rapidly in some rural areas. In more than 1/10 of the rural areas, the N-load from animal production to agricultural land has reached 150 kgN-hm"2; whereas in the 1980s, there were only 1.4% of the areas with N-load over 50 kgN·hm^-2.We have performed on-the-spot investigation in the main watersheds which covers 22 counties including 254 townships. The investigation results revealed that in some highly developed areas with big population but less agricultural land and some certain townships with very high concentration of animal breeding farmers, both N and P loads from animal husbandry to agricultural land have reached very high levels. For instance, in Taihu Lake watersheds, the average N load from animal husbandry to agricultural land was 80 kg N per hectare agricultural land area in early 1980s; there were about 17% of the townships whose N load was above 150 kg N per hectare agricultural land area; there were only 4% of the townships whose N load reached 250 kg N per hectare agricultural land area. However, the current average N load from animal husbandry to agricultural land has reached 226 kg N per hectare agricultural land area and there are 22% of the townships whose N load has reached 250 kg N per hectare agricultural land area. Similar case was observed for the P load from animal husbandry to agricultural land. The average P load was 52 kg P₂O₅per hectare agricultural land area in early 1980s, the current number is 163 kg P₂O₅ per hectare agricultural land area. Similarly, in the Dianchi Lake watershed, the average N load is 275 kg N per hectare agricultural land area and the there are 41% of the townships whose N load is above 250 in this area. The average P load in the Dianchi Lake watershed is 169 kg P₂O₅ per hectare agricultural land area. Investigation of over 100 townships in the Northern agricultural area with very high concentration of animai breeding farmers revealed that in...