Mechanism Of Alkaline Slow Release Fertilizer(ALF) To Remediate Soil Acidification And Cd,Pb Pollution And Effect Of The ALF On Crop Growth

In order to solve problem of soil acidification and Cd and Pb pollution caused by large and long-term irrational application of chemical fertilizer,the current research recommended firstly a creative,being alkaline slow release compound fertilizer?ALF?and its application method developed by the authors'research center.The ALF could be recorgnized as founctional fertilizer because it would neutralize the acid and supply NPK and the other necessary nutrients to crop at the same time.Instead of conventional chemical fertilizer by the ALF could ultimately solve soil acidification and control soil heavy metal pollution.In order to promote and application of the alkaline fertilizer in agricultural,the mechanism and influences of the ALF on decline of soil acid or on soil pH value,soil extractable acid,Cd and Pb availability or activity and their accumulation in plants were studied through laboratory incubations,banana?Musa paradisiaca?and leek?Allium porrum L.leek?pot and field experiments.The main results were as followings.1.Compared with the conventional fertilizer treatment,the soil pH values of ALF treatment increased 0.1⁰.7,1.4².2,0.0¹.9 units in laboratory incubation,pot experiment and field experiment,respectively.Moreover,the soil pH value increased with the amount of alkaline fertilizer applied.Compared with ALF blended with urea treatments,the pH value of soil increased 0.2⁰.3 unit by single application of ALF.2.In comparison with the conventional fertilizer,the amount of total extractableacid,soil exchangeable H⁺and Al³⁺in ALF treatment decreased by 18.3%⁵5.3%,35.1%⁹2.5%and 19.2%⁶7.0%under the laboratory incubation,repectively.The soil extractable acid decreased with increasing amount of ALF application could significantly reduce soil exchangeable acid under both pot and field experiments and especially in pot ones.The amount of total extractable acid,exchangeable H⁺and exchangeable Al³⁺in ALF treatment were 21.5%,16.5%and 27.4%of the conventional fertilizer treatment in pot experiment,respectively,and which were 45.0%,53.2%and 41.6%of the conventional fertilizer treatment,correspondingly in field experiments.The effect of ALF single application on reducing soil extractable acid was better than that of combined with urea treatments,the amount of total extractable acid decreased by 33.9%⁴1.6%while exchangeable H⁺decreased by 28.4%²1.8%and exchangeable Al³⁺decreased by 38.9%⁴6.7%.3.ALF could significantly inhibit the activity of available Cd and Pb in soil under the laboratory incubation.The amounts of available Cd and Pb in soil were decreased by12.8%³1.8%and 2.6%⁶.2%,respectively.Meanwhile,the inactivity effect of ALF on available Cd and Pb in soil was increased with the increasing of ALF application amount.During the growth period of leek,ALF could not only significantly reduce the amount of available Cd in soil,but also reduce the accumulation of Cd in leek.Compared with the conventional fertilizer,the soil available Cd content was reduced by 17.9%²7.4%,and the Cd accumulation in the shoot,root part and whole leek were reduced by 86.4%⁹5.1%,82.3%⁹6.8%and 86.2%⁹5.1%,respectively.Although the amount of Cd accumulation increased with the increasing of soil Cd pollution,but the application of ALF could reduce the accumulation of Cd in leek significiantly.4.The application of ALF could change the fraction distribution coefficient of soil Cd and Pb.Compared with conventional fertilizer,ALF could significantly reduce the proportion of weak acid extracted Cd and Pb,which decreased by 5.8%⁹.1%and0.7%¹.6%,but increased residual Cd and Pb by 9.0%²0.3%and 3.6%⁵.7%.Compared with low amount of ALF,fraction distribution coefficient of weak acid extracted Cd and Pb by high amount of ALF were reduced by 2.9%⁹.1%and 1.8%⁹.5%,while the residual Cd and Pb were increased by 11.3%¹2.6%and 5.8%¹5.2%.5.The fraction distribution coefficient of Pb and Cd by weak acid extraced was negatively correlated with soil pH value,and which was positively responded with the amount of soil extractable acid and exchangeable Al³⁺.ALF could achieve the purpose of inactivating the bioavailability of Cd and Pb by increasing soil pH and reducing soil potential acid to change soil Cd and Pb fraction distribution coefficient.There was a significant negative correlation between soil pH and available Cd content,Cd accumulation of leek.The higher of the soil pH value,the lower of the soil Cd activity and the less accumulation of Cd in leek.ALF could obviously inhibit the transfer of Cd from the root part of leek to its shoot,and reduce the accumulation of Cd in the leek,which finally reduced the leek toxicity of Cd pollution.6.Compared with the conventional fertilizer,the ALF could promote banana and leek growth and increase the yield and the individual banana yield increased by 8.8 kg,while the leek dry weight and wet weight were improved by 57.0%and 70.2%,respectively.Fruit stalk dry weight of banana treated with the ALF treatment was increased by 24.9%.The fruit hand weight was increased by 21.7%⁷3.9%,single fruit weight was increased by42.5%.Compared with the single application of alkaline fertilizer,the application of ALF blended with urea was not beneficial to enhance the banana fruit and fruit stalk dry weight.The growth period was reduced by the application of ALF which was 1.5 month earlier than that conventional fertilizer.Meanwhile,the content of reducing Vc,the ratio of sugar to acid and the edible rate of fruit increased by 15.9%,34.6%and 6.8%,respectively.However,the quality of banana fruit decreased with the increase of urea application rate.7.The ALF could replace the conventional fertilizer to meet the nitrogen consumption and utilization by banana leaves,stems and roots during the growth period,and provided enough nitrogen fertilizer for banana growth.Compared with the conventional fertilizer,ALF could significantly increase the accumulation of nitrogen in banana leaves,and promote the transfer of nitrogen to leaves and hands.The nitrogen distribution rate of leaves and hands in ALF treatment were increased by 5.6%and 15.3%to conventional fertilizer treatment,respectively.The application of ALF lonely could significantly increase the accumulation of nitrogen in banana leaves and promote the transfer of nitrogen to leaves and hands,which improving the distribution of nitrogen in leaves and hands.Compared with the conventional fertilizer treatment,the nitrogen use efficiency of banana increased 33.7%by using ALF.The application of alkaline fertilizer lonely did not induce the loss of nitrogen,while the alkaline fertilizer blended with urea could increase the loss of nitrogen,and with the increasing urea amount,the nitrogen loss increased.