Effects Of Long-term Fertilization On Potassium Availability And Crop Yield In Black Soil

This experiment studied the availability,evolution characteristics and crop yield changes of potassium in black soil under long-term different fertilization measures.This is of great significance for regulating rational fertilization,soil fertility effect and sustainable agricultural development in black soil areas.In this experiment,a 43-year(from 1979)long-term fertility localization experiment of black soil was used,including CK,NP,K,NPK,M,NPM,KM and NPKM.The evolution of potassium,the distribution of aggregates,the content of different forms of potassium and the characteristics of crop yield in black soil with long-term fertilization were analyzed.The main findings are as follows:(1)Long-term fertilization treatment,except K and KM treatments,the available potassium in other treatments is lower than the initial soil potassium content and decreases year by year.However,NPKM treatment can slow down the decreasing trend of available potassium content,which is 0.99 mg·kg^-1·a^-1.The total potassium contents of black soil in each fertilization treatment decreased year by year.Among all fertilization treatments,NPK treatment can alleviate the decreasing trend of total potassium in black soil to the greatest extent,which is 0.05 g·kg^-1·a^-1.(2)In the analysis of the proportion of soil aggregates in black soil after long-term fertilization,M treatment can significantly increase the proportion of soil macro-aggregates and reduce the proportion of<0.25mm aggregates.Compared with CK,the composition of soil macro-aggregates in K,NPK and KM treatments had no significant change(P>0.05).The contents of potassium in different fractions of soil were mainly higher in K and KM treatments,followed by M and NPKM,and the lowest in NP treatments.M and NPKM can provide high content of exchangeable potassium,non-exchangeable potassium and total potassium.(3)Under long-term fertilization,the yield of wheat and maize is significantly affected by fertilizer application.In the treatment of applying nitrogen and phosphorus fertilizers,the yield has an increasing trend.Among them,NPKM and NPK are 39.17kg·hm^-2·a^-1,34.71 kg·hm^-2·a^-1,156.23 kg·hm^-2·a^-1 and 140.18 kg·hm^-2·a^-1 respectively.The average yield of soybean was not significantly different among treatments(P>0.05).The yield increasing trend of NPK and M treatments is 40.43 kg·hm^-2·a^-1and 38.70kg·hm^-2·a^-1respectively.Except CK treatment,K had the worst effect on the yield change of the three crops.(4)Considering the long-term fertilization of black soil potassium and crop yield,balanced fertilization(NPK and NPKM treatments)can maintain the balance of potassium content in the soil while maintaining the soil structure,and promote the high and stable yield of crops.