Study On Determination Methods For Available Nitrogen And Potassium In Soil Testing And Fertilizer Recommendation

Methods of available nutrient testing are the most basic and important question in soil testing and fertilizer recommendation.The purpose of soil testing is to design a suitable application of nitrogen,phousphorus and potassium fertilizer for high-yield,high quality and efficiency of fertilizer application rate.In conventional measurement of soil nutrient,nitrogen and potassium is measured using chemical reagents in the extraction.The method and indicator are not the same in differentarea.The correlation between measurement of which method and crop is better need further inspectand verify.In this paper,using biological detection method to study the determinayion methods of soilavailable nitrogen and potassium,it means that use field trials to carry out correlation research.It takes the crop reaction as standard reflect the crop as a benchmark.Strike a different method fordetermining the value and crop yield,relative yield,increase rate,and uptake of the correlationcoefficient,compared:with the reference standard for conducting relevant studies.Fitting then combined to evaluate the extentThe object of this study is main agricultural soils in Sichuan Basin.The purpose of this research isto find the interrelation among measurement of different methods between the reactions of crop by field trials.So as to enhancing and improving the reflect extent on soil nutrient availability,selectedsuitable methods for the regional soil available nitrogen and potassium testing,offer scientific basisfor available nitrogen and potassium test in soil testing and fertilizer recommendation.The mainresults are as follows:Avarage content of available nitrogen in 33 paddy soils were respectively alkaline hydrolysisnitrogen 103.7mg/kg,40℃mineralization nitrogen 42.7mg/kg,35℃mineralization nitrogen 39.6 mg/kg and ammonium nitrogen 27.6 mg/kg.The correlation coefficient between alkaline hydrolysisnitrogen and 40℃and 35℃nitrogen mineralization were 0.894** and 0.863**, there was significantcorrelation between ammonium 40℃nitrogen mineralization only,r=0.519*.The avarage value of soil available nitrogen in 26 upland soils were respectively alkalinehydrolysis nitrogen 81.4mg/kg,ammonium 23.9mg/kg and nitrate 12.2 mg/kg.The correlationcoefficients between base nitrogen and ammonium,nitrate were 0.759** and 0.450*; the relation ofammonium and nitrate was not significant(r=0.381).Nitrate is not only greater variability,but alsotoo small in value.Ammonium content has increased in the plow pan soil,compared with thefanning layer,in modest decline.The correlation analysis between rice and wheat yield,relative yield,increace rate,nitrogen uptakeby rice and wheat,total nitrogen uptake and soil available nitrogen by different methods in plow pansoils showed that:add to the initial nitrogen,the correlation coefficients between 35℃mineralizationnitrogen and rice yield are 0.601*,0.701**and 0.842**,the correlation coefficients between 35℃mineralization nitrogen and total nitrogen uptake are 0.577*and 0.547*.Although the alkalinehydrolysis nitrogen had not significant correlation with wheat yield,relative yield,increase rate,nitrogen uptake by rice and wheat and total nitrogen uptake,it was better than the other soil nitrogen.Therefore,35℃mineralization nitrogen added to initial nitrogen and alkaline hydrolysis nitrogen aresuitable methods for paddy soil and upland soil to determine soil available nitrogen in soil testing andfertilizer recommendation in the area of this study.Results of continuous incubation at 35℃indicated that when raises to 1 week the accumulationmineralization nitrogen adds to initial nitrogen had significant correlation with rice yield and totalnitrogen uptake,the correlation coefficients are 0.601*,0.701**,0.842**,0.577*,0.547*,they weredrops with the incubation time extension.Avarage value of available potassium determinated by different methods in 33 paddy soils werefollow:nonexchangeable potassium 427.8 mg/kg,NH₄OAc-K 77.0mg/kg,ASI-K 52.0 mg/kg andM3-K 88.0 mg/kg.The correlation coefficients between nonexchangeable potassium and NH₄OAc-K and M3-K were 0.477** and 0.398*,and the correlation coefficient betweennonexchangeable potassium and ASI-K was not significant (r=0.049).The conelation coefficientsbetween NH₄OAc-K and ASI-K,M3-K were 0.451**and 0.674**; but the correlation coefficientbetween ASI-K and M3-K was 0.883**.4 extraction methods besides ASI-K and nonexchangeable potassium had significant (M3-K and nonexchangeable potassium)or great significant interactiveeffects.Relation of M3-K and ASI-K was the closest among 4 methods.Mean determination value of available potassium by different methods in 26 upland soils were asfollow,nonexchangeable potassium 377.0 mg/kg,M3-K 56.2 mg/kg,NH₄OAc-K 49.6 mg/kg andASI-K 22.0 mg/kg.Correlation coefficients between nonexchangeable potassium and NH₄OAc-K,ASI-K,M3-K were 0.737**,0.568** and 0.902**; NH₄OAc-K and ASI-K,M3-K were 0.764** and0.859**; ASI-K and M3-K r=0.721**.The determination value by different methods had a great significant interactive effects.The relevance of nonexchangeable potassium and M3-K is best.The correlation analysis of rice and wheat yield,relative yield,increase rate,the rice and wheat potassium uptake,total potassium uptake and soil available potassium value by different methods in plow pan soils showed that correlation coefficients between NH₄OAc-K and rice yield withoutpotassium,the yield with fertilizer were 0.549*and 0.655*; the correlation coefficient between ASI-K,M3-K and total potassium uptake by rice without fertilizer were 0.686 **and 0.534*;theother correlation coefficients were not significant The contents of soil potassium extracted bydifferent methods in upland soil had a inverse correlations with yield,relative yield and potassiumuptake,and the degree of correlations were not significant and could not play the role to forecast thepotassium supplying power of soil completely.