Effects Of Chicken Manure And Chemical Fertilizer Application On Soil Fertility And Transfer Of Soil N And P In Rice-wheat Rotation Systems

Poultry production in China is becoming increasingly concentrated, both at the farm and regional level. Currently, a growing problem associates with intensive poultry production is the utilization of the large amounts of poultry manure produced. Nitrogen and phosphorus loss in runoff from poultry manure has been identified as important contributor to non-point pollution. Proper management practices of poultry manure are crucial to the development of agricultural sustainability. But in areas of intensive poultry production, large amounts of poultry manure are often applied to local farm land. To assess the agronomic and environmental impacts caused by chicken manure application, we investigated and quantified the variations of soil fertility properties and water quality after long-time application of chicken manure and chemical fertilizer in Hai'an county, Jiangsu Province.The results indicated as follows:1. Compared to chemical feterliazer application, chicken manure increased the content of soil total nitrogen, available nitrogen, total phosphorus, available phosphorus, soil pH, and the capacity of soil water retention, while decreased soil bulk density, in long-term field experiment.2. The level of soil P increased significantly after long-term poultry manure application and the content of available-P in plow layer varied from 75.5 mg/kg to 100mg/kg, increasing the risk of P losses from field to waterbody inhence stimulating eutrophication.3. Incubation experiment showed that poultry manure addition enhanced the capacity of soil water retention, reduced soil bulk density, increased soil electrical conductivity and soil pH, and promote soil biological activiyies (soil respiration rate and soil microbial biomass).4. In the chemical fertilizer treatment in rice season, in fluvo-aquic soil in Dagong Town, NO₃-N concentrtion in leachate is in the order of 30cm>60cm>90cm. The risk of NO₃-N leaching downwards increased rappidly with fertilizer application rates. The average concentration of NO3-N in entire rice season in the treatment of 315kg N ha^-1 was as high as 2.34 mg·L^-1. In the poultry manure treatment, there was positive correlation between NO₃-N concentration in surface water and the manure application rates and NO₃-N concentration in leachate in soil profile showed the same trends to chemical fertilizer treatment. The average concentration of NO3-N in leachate at maximum manure application was 0.531 mg·L^-1, and it correlated positively with manure application rates (r=0.977, p<0.05). In fluvo-aquic soil in Haibei Town receiving chemical fertelizer or poultry manure, NO₃-N concentration had similar distribution pattern in soil profile to the fluvo-aquic soil in Dagong Town.5. In wheat season, NO3-N was the dominant form of dissolvable nitrogen in lechate both in Dagong and in Haibei soils, while NH₄⁺-N was very low (neglectable). In soil profile, NO₃-N concentration in leachate was in the order of 30cm>60cm>90cm at any rate of manure application, and the peak concentration was 14.71 mg·L^-1 (30cm). Besides, it was found that the high risk period of NO3-N leaching losses was within one month after manure application.6.In Dagong soil profile, the concentration of total dissolved phosphorus (TDP) in leachate was in the order of 60cm>30cm>90cm and TDP concentration in the leachate at 90cm positively correlated with manure application rates (r=0.937, P<0.05). In all manure treatments, leachate TDP concentration of all samples in rice season was more than 0.02 mg·L^-1, and some was as high as to 0.7 mg·L^-1. In Haibei soil, however, TDP concentration in the leachate was much lower in comparison with Dagong soil, which is attributed to relative high content of clay, strong fixation and weak transfer of phosphorus for Haibei soil.