Effects Of Different Potassium Levels On Availability Of Calcium And Magnesium In The Soil And Effection

Calcium(Ca)and magnesium(Mg)are essential nutrients for plants.In recent years,calcium and magnesium nutrition disorder of vegetables frequently occurs in calcareous soil in northern China.It is aims to explore the relationship between excessive application of potassium(K)fertilizer to the availability of Ca and Mg.Two season(spring and autumn)field experiment and one season pot(spring)experiment were conducted by control(K2O 0kg/hm2)and four different K levels(375、750、1125、1500kg/hm2)in tomatoes.Ralative parameters which content and transformation of K and Ca and Mg in soil and physiological characteristics and growth and absorption were measures after application different K fertilizer.The main results are as follows:1)The amount of 0 to 20cm and 20 to 40cm quick-acting K,water-soluble K and exchangeable K in soil increased significantly by increasing the amount of K;soil water-soluble Ca content continues to increase gradually and then decreased;when putting the amount of(K2)at a 750 kg/hm2,the amount of soil water-soluble Mg occupies the most proposition,which content and Ca have the same characteristics as those of Ca and Mg;soil exchanged amount of Ca decreased significantly;soil exchange amount of Mg increased and then decreased;when the amount of K1 is 375 kg/hm2,soil exchange Mg amount is the highest,and the pH and EC also up with the increase of K.2)The amount of chlorophyll a and b increased,when K amount was 375 to 750 kg/hm2;and the amount of chlorophyll a and b was not significantly different,when the amount of K was 750 to 1500 kg/hm2;the photosynthesis parameters of tomato leaves(net photosynthesis rate,pore conductivity,intercellular CO2 concentration,steaming rate)showed a trend of first increase and then decrease,and the amount of K applied reached the maximum of 4 photosynthesis parameters at 750 kg/hm2;the parameter outcomes decrease in varying degrees,when the amount of K is 1125kg/hm2 to 1500kg/hm2;and the high K(750 to 1500kg/hm2)makes the tomato leaves propylene formaldehyde(MDA)increased,however,the superoxide dismutase(SOD)and peroxide enzyme(POD)of tomato leave decreased with the increasing of K application;and K amount reached at 1125 kg/hm2,the number of diseased roots of tomato plants increased and the total yield decreased.3)The concentration of K and Mg in the roots,stems and leaves of tomato increased obviously,When the K application increased,but when the K concentration was too high(1125kg/hm2),the Mg concentration of tomato roots and stems had a downward trend;the concentration of Ca and Mg of fruits decreased significantly with the increase of K application rate.with the increase of amount of the K absorption of tomato roots increased first and then decreased;when the K application was 750 kg/hm2(K2),the K absorption amount of tomato roots was the largest,and then gradually decreased,while significant changes in Ca and Mg absorption have;The absorption of K and Mg in the stems gradually increased,and there was no significant change in the absorption of Ca;the absorption of K and Mg in the leaves gradually increased,and the absorption of Ca gradually decreased;the absorption of K and Ca in the fruit and the Ca absorption of the fruit gradually decreased,the Mg absorption did not change significantly,when the fertilizer rate was 375kg/hm2;for the whole tomato plant,the K and Mg absorption gradually increased,When the K application increased,and the Ca absorption gradually decreased,and the K application was the largest(1500 kg/hm2),the Ca absorption is significantly reduced.In view of this,K application can increase the amount of available K,water-soluble K,and exchangeable K in the soil to varying degrees.When the K application rate is 750 kg/hm2,K and Ca,K and Mg in the soil are coordinated with each other,which is conducive to tomato growth and increase tomato yield;when the K concentration is higher than 750 kg/hm2,soil K,Ca,and Mg will antagonize each other,affecting the absorption of K,Ca,and Mg by tomato vegetative organs,and also affect K,Ca,and Mg and the transfer of Mg to the fruit.