The Dynamics Of Soil Nitrogen And Phosphorus Contents In Artificial Grassland Under Goat Manure Application In Three Gorges Reservoir

It was studied the dynamics of nitrogen and phosphorus contents in artificial grassland in Three Gorges Reservoir after applying goat manure to the soils by using Soil—Resin—Core technology under field condition. The objective of the study was to properly estimate the influence of environmental pollution of organic fertilizer, and to provide theory basis for resource management of organic fertilizer, effectively utilizing nitrogen, reducing nitrogen loss and preventing environmental pollution.The field experiment included 9 treatments with 4 replicates; each plot had 3 sampling points. A PVC tube with diameter of 7 cm and 20 cm length was embedded in soil, bottom of which was connected with a PVC tube with bigger diameter that was filled with 1 -2 cm quartz sand. A 20 g bag with DX82 alkali anion exchange resin was placed on quartz sand with two layers of filter paper on the top, and the original soils in fields was then placed PVC tube to collect NO₃-N. And the soils in 20 cm soil depth beside the PVC tube was also sampled to determine the contents of nitrogen and phosphorus in soils.The results showed that: (1) the contents of nitrogen in soils raised with increasing amount of organic fertilizer applied into the artificial grassland. The organic fertilizer itself could induce NO₃-N loss, and the leaching amount of NO3-N raised with increasing amount of organic fertilizer. The changes of NH₄-N and NO₃-N contents in soils were different after goat manure application. Content of NH₄-N descended while the content of NO₃-N was increased. (2) there exist seasonal dynamics of NO₃-N accumulation in soils after goat manure application. NO₃-N accumulated in soils in winter and spring because of lower temperature and slower growing speed of forage. The leaching amount of NO₃-N in soil was also small due to the lower rainfall during this period. In summer, although the forage grew slowly and consumed less nitrogen, the temperature and rainfall were high and the mineralization of organic nitrogen was obvious, the leaching amount of NO₃-N reached a peak. There had no instant increase of leaching amount of NO₃-N after manure application. (3) the contents of available phosphorus and total phosphorus in soil increased with increasing amount of goat manure application. It meant that the soil absorbed phosphorus and accumulated more phosphorus with lower leaching amount from the soil. (4)the contents of nitrogen and phosphorus in the soil were higher in treatment with deep application than those with surface application. Deep manure application could enhance efficiency and reduce losses from soil surface. (5)the grass yield was significantly increased by applying goat manure. When the applying amount reached 45000 kg /m², the grass yield was the highest (40315 kg/hm²) in deep application treatment. When applying amount of manure was bigger than 45000 kg/hm², the grass yield decreased. It meant that too higher amount of manure application that exceeded the amount needed by grass would result in nutrients accumulation in soil, which then limited root growth. In surface manure application, the grass yield increased with increasing amount of manure. The yield applying 75000 kg/hm² manure in surface manure application was significantly lower than that in deep manure application of 45000 kg/hm². (6) the experiments suggested that the recommended amount of goat manure application in artificial grassland was 45000 kg/hm² , the recommended breeding number of goat was 27 per hectare in this kind of grassland.