Characteristics And Mechanisms Of Potassium Transformation In Rhizosphere Soil Of Red Earth With Acidfication After Lime Application

The red soil region of southern China is facing two major problems,including soil acidification and potassium deficiency,which have seriously restricted the improvement of agricultural production potential and sustainable development.This study were base on the typical soil with long-term fertilization experiment in Qiyang,Hunan province?1990?,selected soil with fertilization acidification and lime modified treatment,analyzed the potassium change characteristics of rhizosphere and bulk soil at maize different growth stages.Combined with pot experiment of rhizobox,to explore the change of potassium in rhizosphere and different distances of bulk soil,potassium content and absorption amount of maize and wheat under different fertilization and lime levels.Based on the adsorption and desorption of potassium,discussed the driving mechanism of lime on the availability of potassium,to provides the theoretical basis and support for the lime improvement and potassium cultivation in the red soil.The main results are as follows:?1?In different periods of soil available potassium content showed:seedling>harvest>filling>jointing stage.The available potassium in the rhizosphere of maize were in deficit state,and the most serious deficit were jointing and filling stage.Compared with NP treatment,the available potassium contents of rhizosphere and bulk soil were significantly increased under NPK and NPKS treatments.Compared with treatments without lime,soil available potassium of maize rhizosphere and bulk soil in current season and aftereffect of lime did not change significantly under NP treatment,available and slowly available potassium decreased at first and then increased in total life of maize under NPKCa and NPKSCa treatments.Compared with treatment without lime,the content of available potassium in bulk soil decreased but the content of available potassium relative increased in the rhizosphere after lime applied 4 years later under NPK and NPKS treatments,the surplus and deficit rate of available potassium in rhizosphere of maize increased,eventually,the degree of potassium deficiency slowed down.Under the application of nitrogen,phosphorus and potassium fertilizer,the content of available potassium decreased,and reduced to a certain extent?42.6 mg/kg of maize,wheat,no more than 51.5mg/kg?and tends to be stable with lime increase application.?2?Compared with NP treatment,the adsorption equilibrium constant and the maximum buffer capacity of potassium decreased with lime application under NPK and NPKS treatments,and the maximum adsorption capacity of potassium increased,which promoted the retention of potassium.With the increase of lime dosage,the adsorption equilibrium constant and the maximum buffer capacity of potassium increased,the relative change of maximum buffer capacity was negatively correlated with the relative change of available potassium.Compared with treatment without lime,the soil pH increased by0.5-1.0 after lime,the average of exchangeable aluminum in rhizosphere and bulk soil decreased by 3.9cmol/kg,and the exchangeable calcium and magnesium content increased by an average of 2.8 cmol/kg.There were significant positive correlation between the content of available potassium and the content of slow available potassium,potassium saturation,K⁺/(Ca²⁺+Mg²⁺)and K⁺/Al³⁺.?3?With the increase of lime,the dry matter weight,potassium content,potassium potassium uptake efficiency and biological efficiency of maize and wheat were no significant difference under same partial fertilizer?N,NP or NK?.The dry weight,potassium uptake efficiency,and physiological efficiency of maize and wheat were increase by improving soil pH and reducing exchangeable aluminum under long-term N,P,K fertilizer and appropriate amount of lime?lower 1.41 g/kg?application.At the same time,the potassium of migration from bulk soil to the near rhizosphere was increased,and the amount of potassium uptake were negatively correlated with the distance from the rhizosphere.?4?To sum up,lime promote the crop growth and increase the dry weight,and the potassium absorption efficiency and physiological efficiency by increase the soil pH,potassium saturation,and content of exchangeable calcium and magnesium in the rhizosphere under long-term fertilizer?NPK and NPKS?,than alleviate the deficiency of potassium in rhizosphere.The closer to the root,the greater the effect on the potassium uptake by crops.Under the condition of this experiment,when the soil pH is about 5.0,the effect of potassium fertilization and acidification improve are better with lime apply about1.41 g/kg.In addition,in order to promote the healthy growth of maize and wheat,the right amount of potassium fertilizer should be added when modified acidification with lime.