Effect Of Consecutive Application Of Biochar On Phosphate Morphology And Effectiveness Of Brown Soil

Poor availability of phosphorus in soil and low utilization rate of phosphorus fertilizer are the main limiting factors for agricultural development.As a new type of soi l modifier,biochar has unique physical and chemical properties that affect the morphology and availability of phosphorus.This study through the analysis of continuous application of different dosage of biochar on brown soil physical and chemical properties,phosphorus holding ability,different forms p content and maize growth,explore the biochar on brown soil fertility,phosphorus adsorption capacity,corn and various forms of phosphorus fertilizer effect of contribution to the brown soil phosphorus removal efficiency,in order to clear biochar in brown soil phosphorus removal efficiency,provide theoretical basis for its reasonable agricultural.This experimental research object for five consecutive years increasing biochar brown soil continuous cropping of corn,a total of five processing:this test set 7 fertilizer treatments,including CK?no fertilizer control?,NK?potassium?,NPK?NPK?,C1NK?1.5 t/hm²biochar N+K?,C1NPK?1.5 t/hm² biochar+NPK?,C2NPK?3 t/hm² biochar+NPK?,C3NPK?6 t/hm² biochar+NPK?.The effects of different amount of biochar combined with chemical fertilizer on phosphorus morphology,phosphorus adsorption capacity and phosphorus utilization rate of brown soil were studied.The results showed that the application of biochar for five consecutive years significantly reduced the bulk density,porosity,field water capacity,organic matter,total phosphorus,Olsen-P content,bulk density and acidification of brown soil.The application of biochar significantly reduced the Qm value of the maximum adsorption capacity of brown soil,and the maximum adsorption capacity of C1NPK,C2NPK and C3NPK increased by 37.09,65.04and 115.97 mg/kg respectively compared with that of NPK treatment.The adsorption constant k value and the PSI value of phosphorus holding index were significantly lower than those of NPK treatment.Phosphorus saturation was significantly higher than NPK treatment.The contents of total phosphorus,available phosphorus and the activation coefficient of phosphorus in brown soil were significantly increased by applying biochar for 5 consecutive years.The contents of Ca₂-P,Ca₈-P,Al-P,Fe-P,LOP,MLOP and MROP in brown soil were significantly increased.Among the phosphorus components,MLOP and o-p respectively accounted for the largest proportion of organic phosphorus and inorganic phosphorus in brown soil,64.32%and 28.43%,respectively.The proportion of Ca₂-P and Ca₈-P in inorganic phosphorus was increased by biochar.The maximum correlation coefficient between Al-p and Olsen-P content is 0.945,and the direct path coefficient of LOP,Al-p and MROP on available P is larger,which is 0.318,0.285 and-0.261 respectively.The decision-making coefficients of available P of Al-p and HROP are respectively 0.295 and-0.130,which are the main decision-making factors and limiting factors of available P of brown soil.The application of biochar significantly increased the stem diameter,chlorophyll content,plant height and phosphorus uptake of maize in brown soil.There was no significant effect on maize yield,utilization rate of phosphate fertilizer,partial productivity of phosphate fertilizer and agronomic efficiency of phosphate fertilizer.However,the true utilization rate of phosphate fertilizer was significantly improved by 3.08%,11.08%and 14.51%in C1NPK,C2NPK and C3NPK,respectively.?3?The TC and TN content,reserve and C/N ratio of 0?20 cm soil were higher than those of 20?40 cm soil layer.The TC,TN content and C/N ratio decreased with aggregate size decreasing,while TC and TN reserve showed the opposite trend.Adding straw or lime increased the content of TC and TN in the bulk soil and>1,1?0.25 mm size aggregates in two soil layers.In the 0?20 cm soil layer,the TC content of MRCa treatment increased 20%,40%and 55%relative to the MR,MCa and M treatments,respectively.The TC content and reserve of>1 and 1?0.25 mm size aggregates were all the highest in the MRCa treatment.TC and TN content mainly distributed at the size of<0.25 mm,and MRCa treatment was significantly higher than other treatments in the contribution rate of TC and TN content at>1 mm size aggregate to the bulk soil;while the MR treatment was significantly higher than that of other treatments in the 1?0.25 mm size aggregate.The conclusions are as follows:?1?Continuous application of biochar can reduce the bulk density of brown soil,improve the water holding capacity of brown soil,slow down soil acidification,promote the accumulation of organic matter,total nitrogen and total phosphorus,and enhance the activity of acid phosphatase.?2?Continuous application of biochar can limit the adsorption of phosphorus in brown soil,promote the release of phosphorus in brown soil,and improve the effectiveness of phosp horus in brown soil.?3?Tthe application of biochar can promote the accumulation and activity of phosphorus in brown soil,and the application of biochar can increase the contents of ca2-p,ca8-p,al-p,LOP and MLOP in brown soil,and reduce the contents of MROP.Under the condition of carbon application,LOP and al-p directly affect the availability of phosphorus in brown soil,and are active components of phosphorus in brown soil.Al-P and HROP are the main decision factors and limiting factors of available P in brown soil.?4?Continuous application of biochar can promote the growth of brown soil maize,improve the ability of phosphorus absorption and phosphorus utilization of maize,but has little effect on its yield.