Phosphorus Fractions In Animal Manure And Soil Phosphorus Management In China

With expand scale of animal production and increase of intensive, a shift in the animal diet and the extensive application of feed additives, the concentration and fractions of phosphorus (P) in animal manure have changed significantly, in comparison with the1990s in China. However, until now there have been short of systemic research on animal manure P, and little is known about the difference of manure P fractions in animal manures produced in intensive feeding system. Based on the integrated comparison of measuring methods, sequential manure P fractionation, a simplified two-step procedure and31P-NMR (nuclear magnetic resonance spectroscopy) were used in this thesis to quantify the concentration of P fractions in animal manures, identify the difference of manure P components excreted at different animal growth stages and assess the influence of feed on manure P fractions. Besides, after the application of P fertilizers, a series of physical and chemical processes will occur in soil, which will impact significantly the availability of P fertilizers to crops. These processes are influenced by soil types, soil pH, animal manure application and natural environment climate, etc. Meanwhile, both of the data collected from the long-term experiments and the data of soil analysis by the room culture method were used to analyze the soil P fertility, the rate of soil fertilizing and the environmental thresholds. Different soil P management zones and soil P status in the corresponding zones in China were identified with the general soil characteristics and the data collected from "3414" experiments. Finally, on the basis of the above findings, the construction and perfection of the model for soil P management in China was finished in this thesis. Scenario Analysis was used to predict the P fertilizers demands, soil P status and the potential environmental risk in P management zones with different management strategies in2030in China. The main results were concluded as follows:1) P concentration of animal feed was one of the main factors that affected the level of P content in animal manure. There was a significantly positive relation between P concentrations in animal feed and animal manure. Therefore, optimize the animal feed formula was considered as one of the strategies of animal manure management.2) More than70%of total P in animal manure was soluble forms. The average of total P concentration in intensive-feed swine, poultry and cattle manures and scatter-feed cattle manure were14.9g P kg-1,13.4g P kg-1,5.8g P kg-1and4.1g P kg-1, respectively. It was demonstrated that the variance range of P concentration in animal manures was wide. About73%,74%and79%of total P in intensive-feed swine, poultry and cattle manures were available to crops, respectively, comparing with78%of total P in scattered-feed cattle manure.3) The results of manure P fractionation by two different methods, which were excreted by the animals at the specific growth stage, demonstrated that: total P concentration in pregnant swine,130-day poultry and cattle manures were31.9g P kg-1,13.5g P kg-1and7.1g P kg-1, respectively. About48%of swine manure P,87%of poultry manure P and69%of cattle manure P were soluble forms, which was extracted by H2O and NaHCO3. The P forms in animal mauure mainly included orthophosphate, pyrophosphate, orthophosphate monoesters and orthophosphate diesters. Among them, the proportion of orthophosphate was highest. According to the proportion and activity of P fractions in animal manure, the order of the potential environmental risk caused by the application of equal amounts of manure from high to low was:swine manure> poultry manure> cattle manure.4) The change-points between Total-P and Olsen-P in three different types of soil were:Total-P0.44g P kg-1and Olsen-P21.4mg P kg-1for neutral soil in Haerbin, Total-P1.32g P kg"1and Olsen-P71.8mg P kg"1for calcareous soil in Yangling, and Total-P0.51g P kg-1and Olsen-P4.6mg P kg-1for acid soil in Qiyang, respectively. The change-points between Olsen-P and CaCl2-P in three different types of soil were:Olsen-P51.6mg P kg-1and CaCl2-P0.61mg P kg-1for neutral soil in Haerbin, Olsen-P39.9mg P kg-1and CaCl2-P0.87mg P kg-1for calcareous soil in Yangling, and Olsen-P90.2mg P kg-1and CaO2-P0.39mg P kg-1for acid soil in Qiyang, respectively. There was a significant linear relationship between Olsen-P and PSR in all of three types of soil. The order of the increase of PSR caused by each unit increase of soil Olsen-P from high to low was:Haerbin> Qiyang> Yangling. The change-points between PSR and CaCl2-P in three different types of soil were:PSR0.081and CaCl2-P1.43mg P kg-1for neutral soil in Haerbin, PSR0.026mg P kg-1and CaCl2-P0.85mg P kg-1for calcareous soil in Yangling, and PSR0.12mg P kg-1and CaCl2-P1.86mg P kg"1for acid soil in Qiyang, respectively. There was a significant linear relationship between soil P budget and Olsen-P in all of three types of soil. There was a positive interaction between animal manure P and mineral P fertilizer. The ratio of increase in soil Olsen-P between chemical P fertilizers plus manure together and chemical P fertilizer input alone was1.04,1.88and1.31in neutral, calcareous and acid soils, respectively.5) Based on soil pH and the regional climate variations, five soil P management zones were distinguished in China, namely Northeast, North, Northwest, Yangtze Plain and South China. There were big variations of soil P status and potential environmental risk in different P management zones. In China, the available P content in14.9%of arable land in Northeast,46.8%in North,67.5%in Yangtze Plain,69.3%in Northwest and91.5%in South was lower than the optimal value, while the P content in6.8%of arable land in Northeast,5.1%in North,0.3%in Yangtze Plain,7.2%in Northwest and2.1%in South was higher than the environmental thresholds. According to the results of scenario analysis, we will face the severe resource-environmental pressure because of the present unsustainable soil P management in2030, including the shortage of phosphate reserves, losses of animal manure P and environmental pollution. More scientific and reasonable fertilization techniques and the change of governments’ policies are needed to relieve the pressure in the future in China.