Long-term Effects Of Biochar On The Productivity And Phosphorus Regulation In Calcareous Soil

Biochar amendment in agricultural soils plays an important role in soil carbon sequestration,soil fertility improvement and crop yield increasing in agricultural production.However,it’s a gap of biochar application on soil phosphorus regulation.This study was based on 2 long-term field experiment,we aimed to investigate the effects of biochar application on the productivity and the regulation on soil phosphorus availability in calcareous soils of fluvo-aquic soil and cinnamon soil,respectively.In 2013 and 2014,the biochar was applied at 20 t·ha-1 in fluvo-aquic soil and cinnamon soil.The main results are as follows:1.The long-term effect of biochr amendment on the productivity of calcareous soil.This study based on the long-term field experiment in fluvo-aquicl soil.And a pot experiment was carried out using the soils with and without biochar application.The leaf biomass and root biomass of Pakchoi were significantly increased by 75.7%and 59.7%with wheat straw biochar and maize straw biochar treatment,compared to CK.The content of nitrogen,phosphorus and potassium in leaves were increased by 15.0%,4.4%and 5.2%,and the content of nitrogen,phosphorus and potassium in root were increased 38.6%,18.6%and 91.5%,respectively.The activities of nitrogen cycling enzymes of glutamine synthase increased by 15.98%,nitrate reductase increased by 10.26%,respectively,compared to CK.The application of biochar can effectively enhance crop productivity and promote the accumulation of nutrients in crop.2.Long-term effects of biochar on the fertility of calcareous soil.Compared with the control,biochar application significantly increased the organic carbon and available nutrient contents in the two calcareous soils.In the fluvo-aquic soil,the organic carbon content with wheat straw biochar and maize straw biochar treatment significantly increased by 16.19%and 16.33%,the availability nitrogen content increased by 33.47%and 23.88%,the available potassium content increased by 107.96%and 102.12%,and the available phosphorus content increased by 49.09%and 13.15%,respectively.In cinnamon soil,the organic carbon content under wheat straw biochar treatment was significantly increased by 38.62%,compared with the control,and the contents of availability nitrogen,available potassium and available phosphorus were increased by 52.25%,67.48%and 15.32%,respectively,compared with CK.Biochar treatment significantly increased the activities of extracellular enzymes such as xylosidase,βfibrinose hydrolase,leucine aminopeptidase,which were related to the cycling of soil nitrogen and carbon,and biochar treatment significantly increased the normalized enzyme activity.Therefore,the application of biochar persistently regulate the fertility of calcareous soil,enhance the enzyme activities related to C,N and P cycles,and promote the nutrient turnover of calcareous soil.3.Long-term effect of biochar on phosphorus availability in calcareous soil.Based on the morphological classification of soil inorganic phosphorus and liquid phase 31PNMR technique,the content of orthophosphate and polyphosphate increased by 14.28%and 21.38%,20.80%and 40.63%,respectively,after the application of wheat and maize straw biochar in aquic soil.The contents of inorganic phosphorus in different forms were also significantly increased,especially the most active Ca2-P,which was increased by 25.09%and 7.05%with wheat and maize straw biochar treatments,respectively.In cinnamon soil,Ca2-P significantly increased by 55.04%,and Ca8-P significantly increased by 96.54%,and alkaline phosphatase activity increased by 23.87%.Therefore,the application of biochar can promote the activation of stable phosphorus in calcareous soil and pertently increase the availability of soil phosphorus.4.The effect of biochar amendment on the adsorption and release characteristics of phosphorus in calcareous soil.Compared with the control,the maximum phosphorus adsorption capacity of wheat straw biochar treatment was significantly increased by 17.99%in fluvo-aquic soil and 5.62%in cinnamon soil.The adsorption capacity of different biochar to phosphorus was wheat straw biochar>maize straw biochar.Langmuir equation could well fit the isothermal adsorption curves of soil phosphorus under different treatments.And the phosphorus adsorption kinetics of soil under different treatments could described by pseudo-second-order kinetic equation.The application of biochar significantly increased the content of available Ca,Mg and Fe in calcareous soil,which further increased the adsorption capacity of soil phosphorus.In calcareous soil,biochar application persistently increased crop biomass and nutrient content,increase soil fertility,enhance the stable phosphorus activation,improve the phosphorus availability.This study provided a theoretical and practical practice on the efficient and rational agricultural production,and the reasonable application of biocahr in agricultural production.