Study On Nutrient Balance And Zoning Control Of Farmland In Yangtze River Economic Belt

The Yangtze River economic belt is the basin economic zone with the longest development history,the best development foundation and the largest economic scale,and it is also an important agricultural production base in China.To support the implementation of the green sustainable development strategy in Yangtze River economic belt,this study took the analysis of nutrient balance in farmland as the starting point,to understand the relationship between agricultural production and ecological environment and provided decision support for the optimal allocation of nutrient resources.With nutrient balance model of farmland based on statistical data and literature,the paper analyzed the spatiotemporal variation characteristics of nutrient surplus and deficit,evaluated the nitrogen use efficiency and nutrient management in Yangtze River economic belt from 2000 to 2016.The main results were as follows:(1)The nutrient input and output of fannland were on the rise,and the high intensity areas of nutrient input and output were concentrated in the middle and lower reaches.In terms of changes,the intensity of nutrient input and output decreased in Shanghai,the input intensity decreased in Jiangsu and the output intensity decreased in Zhejiang,the intensity of nutrient input and output in the other provinces increased,but except for the nitrogen input decreased in Zhejiang.From the changes of nutrient input and output composition,chemical fertilizer was the first input item,followed by organic fertilizer,and the crop harvest was the main input item.(2)The nitrogen surplus of farmland decreased,high surplus area disappeared,low surplus area increased,and high surplus area was distributed in Zhejiang,Hubei,Guizhou,Yunnan and Chongqing;the nitrogen loss of farmland increased,low loss areas disappeared,high loss areas increased,and high loss areas were Shanghai,Jiangsu,Hubei and Hunan.The phosphorus surplus of farmland increased,low surplus areas increased,high surplus areas appeared,and high surplus areas was Hubei;the phosphorus loss of farmland increased,high loss areas increased and mainly concentrated in the middle and lower reaches.The potassium deficiency of farmland showed a trend of improvement,high deficiency in Shanghai and Jiangsu;the change in potassium loss of farmland was not obvious and remained basically stable.(3)The nitrogen surplus of farmland was higher in upstream areas,which had great potential for soil pollution;the nitrogen loss was higher in the middle and lower reaches,which had great potential for air and water pollution;Zhejiang and Hubei should consider the two risks of nitrogen.The risk of phosphorus surplus of farmland pollution was small,but the risk of phosphorus loss pollution was higher,which mainly concentrated in the middle and lower reaches,Hubei needed to take the two risks of phosphorus.Potassium was deficient and had little loss,which had no pollution risk basically,but potassium deficiency could be a limiting factor for sustainable agricultural production,Jiangsu and Shanghai needed to pay attention to the risk of deficiency.(4)The nitrogen use efficiency of farmland increased,phosphorus and potassium use efficiency decreased slightly.Compared provinces based on nutrient utilization,the key remediation objects included nitrogen in Zhejiang,Hubei,Chongqing,Guizhou and Yunnan,phosphorus in Anhui,Hubei,Chongqing,Sichuan and Yunnan;Phosphorus in Zhejiang and Guizhou were the prevention and control areas,which needed to strengthen detection and prevention.Potassium output were greater than potassium input in all provinces,which were the key supplementary objects of potassium fertilizer.(5)Coupled partition results of nutrient management showed:Nitrogen output and surplus improved significantly with the output increased and surplus decreased;Phosphate output and surplus increased;Potassium deficiency declined and the output rose except Shanghai and Zhejiang.Compared provinces based on nutrient output and surplus,phosphorus in Anhui,Jiangxi and Hubei were the high-output and high-surplus problem areas;Nitrogen in Zhejiang,Chongqing,Guizhou and Yunnan,phosphorus in Chongqing,Sichuan and Yunnan were the low-output and high-surplus problem areas,which were the key remediation objects.Nitrogen in Sichuan and phosphorus in Zhejiang and Guizhou were double-low problem areas.Potassium was deficient,Shanghai and Jiangsu were the high-output and high-deficiency problem areas,the upstream four provinces and Zhejiang were the low-output and low-deficiency problem areas.