Temporal And Spatial Variation Of Phosphorus Balance And Solutions To Improve Phosphorus Use Efficiency In Chinese Arable Land

Research on the temporal and spatial variation of phosphorus?P?balance and solutions to improve P use efficiency can provide a theoretical basis for major decisions in China such as the rational fertilization,the reduction of chemical fertilizer application and the control of non-point source pollution.However,current studies have mainly focused on individual regions or years,information on temporal and spatial changes of soil P under different scales in Chinese arable land is limited.Therefore,it is necessary to conduct the research on the temporal and spatial changes of soil P.Total of 59,956 soil samples were analyzed for the temporal and spatial changes of soil available P in China,and a modified OECD model was used to analyze the temporal and spatial changes of soil P balance and P environmental risks in Chinese arable land.The results are as follows.1.Temporal and spatial changes in soil available P.Soil available P content showed an increasing trend from 1990 to 2012.On average,the soil analysis showed that soil available P increased from 17.1 mg L^-1 in the 1990s to 33.3 mg L^-11 in the2000s and it was cash crops that were primarily responsible for this increment.For relative yield,there were great differences within same regions from the 1990s to the 2000s.The relative yield for grain crops in the NE,NC,MLYR,SE and SW increased by 2.6%,8.0%,7.2%,4.1%and 4.3%,but decreased by 3.5%in the NW from the 1990s to the 2000s.The relative yield for cash crops decreased by 3.4%,2.3%,1.0%and 3.3%for the NE,NW,SE and SW regions,but increased by 18.3%and 3.7%for the NC and MLYR regions,respectively.2.Temporal and spatial changes in soil P input,output and balance.At the national scale,the unit area of P input increased from 51.5 kg P₂O₅ ha^-1 in 1980 to 181.1 kg P₂O₅ ha^-1 in 2012 and fertilizer-P was the most important P source.In regard to P output,the unit area of P output increased from 40.9 kg P₂O₅ ha^-1 in 1980 to 84.6 kg P₂O₅ ha^-1 in 2012,in which crop removal accounted for about 95%of total output.Average soil P balance increased from 10.6 kg P₂O₅ ha^-1 in1980 to 96.4 kg P₂O₅ ha^-1 in 2012.The average P use efficiency decreased from 76%in 1980 to 43%in2003,and then a slight increase to 47%in 2012.At the regional scale,the total P input,output and balance increased from 1980 to 2012.From 1980 to 2012,the order of unit area P input,output and balance increased rate in different regions can be expressed as:NC>SE>MLYR>SW>NW>NE,NC>MLYR>SW>NW>NE>SE,and SE>NC>MLYR>SW>NW>NE,respectively.The P use efficiency in six regions decreased from 1980 to 2012 and the order of decreased rate of P use efficiency was:NC>MLYR>SE>SW>NW>NE.At the provincial scale,both the total and unit area P input,output and balance in each province increased from 1980 to 2012.The analysis of soil P balance between 1980 and 2012 indicated that the soil P surplus was higher in provinces predominant in arable farming than in provinces predominant in animal husbandry and grazing,even when returned manure-P and straw-P were considered.At the county level,the comparison between 2001-2003 and2008-2010 showed that the proportions of counties in northeast China with very low,low,low-moderate and high-moderate P input and output decreased,respectively,but the proportions of the counties with high and very high P input and output increased,respectively;unit area P balance showed an increasing trend.In addition,for P use efficiency,the order was as followed:Heilongjiang>Jilin>Liaoning.3.Efficient use of P in arable land.The accumulation of soil P between 1980 and 2012 averaged 1926 kg P₂O₅ ha^-1 across the whole China.The long-term accumulated soil P could theoretically meet crop P demands for approximately 4.8–12.0 years,depending on its bioavailability.Increasing the return rate of organic materials can greatly reduce the demand for chemical P fertilizer.The Nutrient Expert systems,a scientific fertilizer recommendation method,can meet the demand of China's current agricultural production.Rational arable land P management can reduce the rate of P application,improve P use efficiency.In summary,facing the temporal and spatial variation of soil P and P balance,it is urgent to conduct site-specific P nutrient management.