Spatiotemporal characteristics of nitrogen and phosphorus input,surplus,and emission during crop production in the Baiyangdian basin
To clarify the application,surplus,and loss characteristics of nitrogen and phosphorus in crop production of the Baiyangdian basin,and identify the influencing factors.The ultimate goal is to provide a reference basis for effective nutrient management and nitrogen and phosphorus pollution control in crop production of the basin.This study quantifies the relative contribution of nitrogen and phosphorus emissions of different crops during crop production in the Baiyangdian basin.It also analyzes the characteristics of spatial and temporal changes in nitrogen and phosphorus emissions from the perspective of nitrogen and phosphorus application,surplus,and loss.The research spans from 2015 to 2020 and encompasses 36 counties and districts within the basin.The results showed the following.The nitrogen and phosphorus application intensity in Baiyangdian basin decreased by 30.2%and 31.4%,respectively,from 2015 to 2020,showing spatial distribution characteristics of low in the upper reaches and high in the middle and lower reaches.The contribution of nitrogen and phosphorus applications in corn was 31.0%-41.8%and 32.6%-48.0%,respectively.The nitrogen and phosphorus application intensities were the highest in fruit trees,reaching 247.0-299.6 kg·hm-2 and 145.6-199.4 kg·hm-2,respectively.The nitrogen and phosphorus surplus intensity in the Baiyangdian basin decreased by 37.0%and 33.1%,respectively,from the beginning of the study period to the end of the study period,showing spatial distribution characteristics of low in the upper reaches and high in the middle and lower reaches.The nitrogen surplus of each crop in the basin changed from vegetable>corn>wheat>fruit trees to corn>wheat>vegetable>fruit trees,and the phosphorus surplus was always corn>wheat>vegetable>fruit trees.The nitrogen and phosphorus surplus intensity of fruit trees was the highest,reaching 395.8-480.1 kg·hm-2 and 148.4-202.3 kg·hm-2,respectively.The intensity of nitrogen and phosphorus loss in the Baiyangdian basin decreased by 28.4%and 33.3%,respectively,from 2015 to 2020,with the same spatial distribution characteristics as nitrogen and phosphorus application and surplus.Corn contributed the most to the loss of nitrogen and phosphorus,reaching 33.3%-43.3%and 31.8%-47.1%,respectively.Nitrogen loss intensity in vegetables was the highest(4.46-5.60 kg·hm-2).The phosphorus loss intensity of fruit trees was the highest(0.52-0.72 kg·hm-2).The intensity of nitrogen and phosphorus surplus and loss depends greatly on the intensity of fertilization.To reduce nutrient loss,targeted management should be implemented for crops and regions with high nitrogen and phosphorus application intensity.
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