Effects Of Planting Patterns On Soil Aggregate Carbon,Nitrogen And Phosphorus Pools In Northwest Hebei

The Bashang area in northwestern Hebei has experienced the development process of high value-added agriculture such as animal husbandry-agriculture and animal husbandry interlaced extensive planting-facility agriculture.Due to different soil utilization intensity and inputs,soil nutrient inventory and supply capacity have changed.The dry sieving method was used to classify the soil aggregates under seven planting patterns in Bashang,Northwest Hebei,and analyze their carbon,nitrogen and phosphorus form content,carbon,nitrogen and phosphorus pool management index and dissolved organic matter composition changes,and comprehensively explore the soils of different planting patterns.The nutrient supply and holding capacity of the aggregates,and explore the planting mode to enhance the water retention and fertility of the soil aggregates in this area.The results are showed in the below:（1）The soil in Bashang area of northwest Hebei is dominated by1.00～2.00 mm aggregates,followed by 0.25～0.50 mm aggregates,and the distribution of<0.25 mm aggregates is the least.The MWD and GMD of the aggregates in the greenhouse vegetable field were the highest,followed by the open field vegetable field,and the lower MWD and GMD of the potato field.The application of organic fertilizer is beneficial to enhance the stability and corrosion resistance of the aggregates,and reduce soil erosion;the application of inorganic fertilizers reduces the stability of the soil aggregates and causes soil erosion.（2）The SOC content of each particle size aggregate is between15.29～18.38g·kg^-1and the ASOC content is between 9.33～11.18 g·kg^-1,mainly distributed in<0.25 mm aggregates;H-LOM content is between1.80～2.09 g·kg^-1,it is mainly distributed in aggregate>5.00 mm.The CPMI of each particle size aggregate is between 65.51～88.93,which first rises and then decreases with the increase of particle size.The CPMI of H-LOM is between 53.56～90.87,which first decreases and then rises with the increase of particle size.Vegetable field with organic fertilizer increased the carbon supply capacity of>5.00 mm aggregate,potato field with inorganic fertilizer increased the carbon supply capability of<0.25mm aggregates,and extensively managed oats field increased the carbon supply capacity of 0.50～1.00 mm aggregate.（3）The content of soil TN is between 793.06～1158.80 mg·kg^-1,mainly distributed in 0.25～0.50 mm aggregates;NH₄⁺-N content is between 7.63～79.88 mg·kg^-1,mainly distributed in 1.00～2.00 mm aggregates;NO₃^--N content is between 26.93～62.42 mg·kg^-1,mainly distributed in 2.00～5.00 mm aggregates.The NPMI of NH₄⁺-N is between3.31～319.09,and the NPMI of NO₃^--N is between 22.15～181.45,and both increase first and then decrease as the particle size increases.Vegetable field with organic-inorganic fertilizers increase the supply capacity of soil 2.00～5.00 mm aggregates of NH₄⁺-N,and inorganic fertilizers increase the supply capacity of 1.00～2.00 mm aggregates of NH₄⁺-N and>5.00 mm aggregates of NO₃^--N.the extensively managed oats field improves the supply capacity of 1.00～2.00 mm aggregate NH₄⁺-N and<0.25 mm aggregate NO₃^--N.（4）The content of soil TP is between 211.72～441.94 mg·kg^-1and is mainly distributed in aggregates<0.25 mm;the content of WSTP is between 267.68～421.83 mg·kg^-1and is mainly distributed in aggregates of0.50～1.00 mm.The PPMI of soil aggregates was between 79.25～152.94,and it first decreased and then increased with the increase of particle size.Fertilization significantly improves the phosphorus supply capacity of<0.25mm aggregate,and extensive management improves the phosphorus supply capacity of>5.00 mm aggregate.（5）Soil DOM in Bashang area of Northwest Hebei is mainly composed of humic acid-like components,followed by fulvic acid-like components.Greenhouse vegetable field with organic fertilizers promote the distribution of humic acids to 1.00～5.00 mm aggregates and the distribution of soluble microbial components in each particle size,increase the biological source of DOM,and the extensively managed oat field promotes the aggregation of tryptophan.The increase of acid components increases the terrestrial source of DOM,and the application of inorganic fertilizers promotes the distribution of fulvic acid-like components to large,medium and small aggregates and increases the biological source of DOM.The Bashang area of Northwest Hebei should develop a protective planting model based on increased application of organic fertilizers,implement conversion of farmland to grassland to increase grassland area,increase the number and stability of large aggregates,improve soil water and fertilizer retention capacity,and prevent soil erosion and soil erosion.