Effects Of Different Amount Of Biochar Based Fertilizer On Soil Properties Of Red Soil Paddy Field Under Nitrogen Reduction Condition

In order to explore the effect of nitrogen reduction and biochar based fertilizer application on soil physical and chemical properties and biological properties of chinese milk vetch.The field experiment in 2018 and the pot experiment in 2019 were conducted on the paddy field red soil,chinese milk vetch returned to the field with22,500 kg/hm²,set different amount of biochar based fertilizer（150,225,300,375,450 kg/hm²）and apply 50%fertilizer,respectively as（MBF₁,MBF₂,MBF₃,MBF₄,MBF₅）.Through the determination of soil physical,chemical and biological indicators,the test results are as follows:1.Effects of different amount of biochar based fertilizer on soil physical propertiesWith the increase of the application amount of biochar based fertilizer,the soil bulk density decreased first and then increased,and the soil porosity and maximum water capacity increased first and then decreased.When the dosage is（MBF₄）375kg/hm²,the best results were achieved with soil bulk density of 1.02 g/cm³,the porosity was 59.55%and the maximum water capacity was 53.29%,all achieving the best results.2.Effects of different amount of biochar based fertilizer on soil chemical propertiesWith the increase of the application amount of biochar based fertilizer,the soil pH,total nitrogen,ammonium nitrogen,nitrate nitrogen and organic matter all increased and then decreased.When the dosage is（MBF₃）300 kg/hm²,the contents of pH,total nitrogen,ammonium nitrogen and nitrate nitrogen reached the peak,at the application rate of（MBF₄）375 kg/hm²,the soil organic matter content reaches the peak.3.Effects of different amount of biochar based fertilizer on soil biological charactersThe number of soil urease,cellulase,sucrase,bacteria,fungi,actinomycetes and the microbial biomass of carbon and nitrogen content increased first and then decreased with the increase of the amount of biochar based fertilizer.When the application amount reaches（MBF₃）300 kg/hm²,the carbon and nitrogen contents of cellulase activity,bacteria,fungi and actinomycetes in soil reached the peak,when the dosage is gradually increased to（MBF₄）375 kg/hm²,the soil urease and sucrase activity reached the peak.