Nitrogen and Phosphorus Flow in Agro-livestock System and Strategies of Optimization in Hebei Province
|School||Agricultural University of Hebei|
|Keywords||Intensive production Farming system N P Nutrient management|
Nitrogen and phosphorus is both the necessary nutrient elements for plants andanimals and the factors of environment pollution, its utilization and destination inago-livestock production system related to plant and animal production performance andenvironmental effect. With the development of intensive production of ago-livestocksystem,the unreasonable utilization of nitrogen and phosphorus has been becoming moreand more serious, thus to optimize the nitrogen and phosphorus management came to themost important task with the regular pattern of nitrogen and phosphorus flow explicated.However, the research is barely for the combination and its close degree betweenagro-livestock system. Therefore, the paper analyzed the nitrogen and phosphorus nutrientelements flow in ago-livestock system and its environmental effects, aims to expliciting thecurrent intensity degree of agriculture development in ago-livestock system in hebeiprovince and explore the optimize management approaches,in order to provide the basisfor the healthy development of the farming system in hebei province in the future.Themain reasons are as follows:（1）Since1980,the nitrogen and phosphorus inputs in farmland system of Hebeiprovince increased heavily, the change can be divided into2stages, the input quantityincreased rapidly from1980to1996, respectively increased from8.27×10~5t and1.1×105t to2.5×10~6t and4.4×10~5t, increased by2and3.2times; and then the growth tendedto stable, Compared the amounts in2010with that in1996increased by2.6%and26.9%respectively. The fertilizer has been the main input of N and P, nitrogen ratioremained at about70%, phosphate fertilizer is increased from56.9%in1980to75.4%in2010. Nitrogen and phosphorus harvest of crops showed an increasing tend, but far lessthan the growth in the quantity of nitrogen and phosphorus input. This leads to the surplusof nitrogen and phosphorus in farmland increased, respectively from7.1×10~5t and3.2×104t in1980, increased to1.8×10~6t and2.8×10~5t in2010; increased by1.5times and7.5times. There is a big difference between input and output of nitrogen and phosphorus in2010in farmland, which is the highest in Shijiazhuang.（2）Since1980, nitrogen and phosphorus inputs also increased substantially inlivestock system of Hebei province, it also can be divided into2stages, which from1980 to2005is the fast growth stage, nitrogen and phosphorus input from19802.3×10~5t and4.5×10~4t respectively increased to1.3×10~6t and3.0×10~5t in2005, increased by4.7times and5.7times; and then hit a plateau. The production of Hebei Province native feed isdifficult to meet the requirements in livestock production, the proportion of the total inputof nitrogen and phosphorus were reduced from49.5%and21.3%in1980to6.4%and14.1%in2010. At the same time, livestock system nitrogen and phosphorus resource ofmanure is also increased a lot, from2.2×10~5t and3.4×10~4t in1980to1.1×10~6t and2.3×10~5t,increased by4times and5.6times respectively. There were huge differences both innitrogen and Phosphorus Input and output and exogenous demand for feed in livestocksystem of different areas in2010, of which the unit area manure amount of nitrogen andphosphorus produced in livestock system in Handan is the highest.（3）Compared the2010with1980, the exogenous input amount of nitrogen andphosphorus (fertilizer and exogenous feed) in ago-livestock system were increased by3.3and5.1times in Hebei Province; animal and plant production nitrogen and phosphorus forlocal consumption of were increased by49.1%and34.5%; the number of export productsnitrogen and phosphorus were increased by6%and2.6%; the number of nitrogen andphosphorus discharged to the environment were increased by3.9times and18.1times.From1980to2010, the nitrogen emission into water increased from20.3%to48.9%oftotal amount; at the same time, environmental emissions of nitrogen contribution rate inlivestock system is on the rise, the atmospheric nitrogen emissions contribution rateincreased from20.2%to23.6%, water contribution rate increased from25.8%to71.6%;although the quantity of water phosphorus emissions increased by15.1times, thephosphorus contribution rate also increased from80%to87.6%. From1980to2010, thedegree of dependence on exogenous nitrogen and phosphorus feed is increasing, from60.5%and45%in1980to93.6%and82%in2010; over the same period, livestock systemin the waste recycling rate continued to decline,decreased from95.0%to37.0%. There is aserious gap between Hebei Province agro-livestock production system in nitrogen andphosphorus’s utilization and circulation.(4) Based on the analysis of nitrogen and phosphorus nutrient flow conditions indifferent areas and different ancient of ago-Livestock system, the results came to aconclusion that nitrogen and phosphorus flow has the character of high flow amount,more output requirement, low use efficiency, poor recycle situation, high dischargeamount. The scenario analysis showed that the optimization of nitrogen and phosphorusmanagement in agro-livestock system is beneficial to increase manure nutrient cycleefficiency and improve the efficiency of nitrogen and phosphorus nutrients,at the sametime,it can also reduce fertilizer amounts, exogenous feed demand,reduce air emissionsand water discharge.Therefore, there is huge potential in hebei province,we should take improving the efficiency of nitrogen and phosphorus nutrient utilization and circulation asthe core, with the technical of adjustment of plant and animal products productiontarget,manure nutrient management and recycling, etc. However we should ensureagriculture and livestock products demand, reduce environmental emissions, nitrogen andphosphorus to achieve agriculture sustainable development and this will finally lead to thedecreasing in environmental pollution and the improvement in the utilization efficiency ofnitrogen and phosphorus nutrient resources.