Phosphorus Accumulation Distribution And Rhizosphere Characteristics Of Typical Vegetables In Southwest China

That the high phosphorus（P）fertilizer input,the high soil accumulated P,and the potential quality decline are important problems in intensive vegetable production.Solving the excessive input of P fertilizers in intensive vegetable production faces serious challenge.The optimal supply of P fertilizer in the root layer is of great significance for regulating the rhizosphere process,optimizing the accumulation of P in crops,and thereby increases yield and reduces environment risk.In this study,field and pot experiments on purple soil and red soil were conducted to study the effects of soil P supply on the uptake and accumulation of P,root morphology and rhizosphere characteristics of pepper and Chinese cabbage.The main findings are as follows:（1）Under field experiments,soil supply of P fertilizer can significantly increase the output of pepper and cabbage,and with the increase of P supply level,the output showed a certain degree of upward trend.The yield of pepper without P treatment was significantly lower than that of each P treatment.Except for the P amount of 393 kg P/ha,the difference between the P treatments was not significant.The yield of cabbage without P treatment was significantly lower than that of each P treatment,and with the increase of P supply,the yield of cabbage showed a significant increase trend.The total output of pepper and cabbage in purple soil increased first and then stabilized with the increase of P supply.The total output of pepper and cabbage in red soil gradually increased with the increase of P supply.The total output of pepper and cabbage is the highest when the P amount of 393 kg P/ha.（2）Under field experiments,soil supply of P fertilizer can significantly increase the accumulation of P in pepper and cabbage.With the increase of the P supply level,the P concentration of pepper stems and leaves showed a gradual upward trend,the P concentration of fruits did not differ significantly among the treatments,and the P accumulation of stems,leaves and fruits showed a gradual upward trend.With the increase of P supply,the P concentration and P accumulation of cabbage showed a gradual upward trend.The proportion of total P accumulation in stems,leaves and fruits of purple soil pepper showed a downward trend with the increase of P supply,and the proportion of total P accumulation in red soil pepper fruits was not significantly different among treatments.The concentration of Fe in purple soil and red soil pepper showed a downward trend with the increase of P supply.The concentrations of K,Ca,Mg,Mn,Cu,Zn,and B in the fruits of purple soil pepper did not change significantly between treatments.The concentrations of K,Ca,Mg,Mn,Cu,Zn,and B in the fruits of red soil pepper varied with the level of P supply.The increase is showing a decreasing trend.The accumulation of various mineral elements in purple soil and red soil pepper fruits showed a gradual increasing trend with the increase of P supply.With the increase of P supply level,the concentration of B in purple soil and cabbage in red soil first increased and then decreased,the concentration of Fe,Mn,Cu,Zn showed a certain degree of decline,and the concentration of K and Mg showed no obvious change trend,and the accumulation of each mineral element showed a certain degree of increasing trend,and the difference of red soil was significant.（3）Under the field experiments,with the increase of P supply,the root dry weight,root surface area,and root length of pepper showed a gradually increasing tendency,but there was no significant difference for root diameter between the different P treatments.The mycorrhizal colonization of root decreased with increasing P supply,and P supply had no effect on acid phosphatase activity in the rhizosphere soil.The pH value of the rhizosphere soil increased firstly and then decreased.Under the pot experiment,with the increase of P supply,the root dry weight of pepper showed a trend of increasing first and then gradually decreasing due to the inhibition effect of high P.The root mycorrhizal colonization and soil acid phosphatase activity increase firstly and then decrease following P supplies.（4）In the pepper-cabbage rotation system,the critical P requirement of cabbage is higher than that of pepper.The soil available P concentration and soil CaCl₂-P concentration,and the P leaching thresholds of purple soil and red soil are 22.9 mg/kg and 30.1 mg/kg respectively.In summary,soil supplying phosphate fertilizer significantly improves vegetable yields.P fertilizer application had a significant effect on the root morphology and rhizosphere characteristics.The soil P surplus may cause environmental problems such as eutrophication of surface water bodies.Therefore,an appropriate P supply could attain the vegetable yield,P utilization efficiency based on root traits and rhizosphere process in the pepper-Chinese cabbage production.