Study On Correlation Of Measured Values Of Soil Available Trace Elements And Plant Uptake

The trace elements of Zn, Cu, Fe, and Mn are necessarynutrients for plants. They play a number of functions and havestronger specificity, and are mainly the activators of the lifeactivities as well as the composition of enzyme and coenzyme in theplantkindom. The shortage of these elements will result into adecrease in crop yield and quality, and become the limiting factorsfor plant growth.The trace elements utilized by plant mainly come from the soils.Therefore, timely and reasonable fertilization based on soil nutrientstatus is particularly important. Moreover, the exactly testing forsoil available nutrient is a base for the reasonable fertilization. InChina, the conventional methods has been used for traditionaltesting for available Zn, Cu, Fe, and Mn in soils. For example, thedetermination of trace elements in the acid soil was extracted by0.1mol·L-1HCl solution, and the DTPA extracts reagent were used tousually extract the neutral and the calcareous soils. Because theDTPA extracting soil is a non-equilibrium system, the soil sample fineness, weight, soil liquid ratio, vibration intensity, vibration time,leaching temperature, and extracting reagent pH value should bestandardized. On the other hand, as much time is spent on thisextracting, and so extracting efficient is relatively lower for a largeamount of samples. Therefore, the analysis results are difficult tobe used for timely guiding the production practice of agriculture.Chinese scientists have introduced some foreign systematicresearch methods for soil nutrient status such as ASI method andMehlich3method (M3method), etc. and joint-extracts were used forrelative studies.In this study, ASI and M3methods were used to extract fourmain farmland soils in northern area of China including thecinnamon soil, moisture soil, brown soil and black soil for thedtermination of available Zn, Cu, Fe, and Mn, and performedcorrelation and difference analysis with measured values of theconventional methods, and the extracting characteristics of ASImethod and M3method was also assessed by combining with r fivestep sequential extraction from Tessier method. Meanwhile, a potexperiment was carried out to measure the relevance between theavailable Zn, Cu, Fe extracted by ASI method, and is expected toexplore the application possibility of ASI method in the four majorarable soils in northern China. The major conclusions are stated asfollows:(1) The determination of soil available Zn, Cu, Fe, Mn by boththe ASI and M3methods are significantly correlated with DTPAmethod for in the major agricultural soils in northern China(p＜0.01),and ASI and M3methods can replace the DTPA method for application in soil testing and fertilizer recommendation. Thedetermination efficiency of soil available nutrient by the ASI and M3methods are significantly higher than that by DTPA method, and thatthe conclusions from the three methods are inconsistent.(2) Analysis on the extracting characteristic from ASI method,M3method, DTPA method and the Tessier method suggested thatavailable Zn extracted are mainly composed of exchangeable andcarbonate bound fractions with a little of iron manganese-bound,organic matter-bound and residuals. Available Cu extracted mainlyincludes exchangeable and organic matter bound fractions with apart of carbonate-bound, iron manganese bound, and residuals.Data showed that compared with DTPA method, ASI method and M3method could extract more available Zn, Cu fractions of ironmanganese-bound as well as the residual states, although theamounts of organic matter-bound forms extracted are lower. Theeffective states extracted by ASI method, M3method and DTPAmethod represents metal ion activity in soil solution and totalcapacity of these ions desorbed from the soil solid phase. Therefore,it is necessary that extracting characteristics from three methodsduring formula soil testing and fertilization should be consideredaccordingly to establish critical index of abundance and deficiencyof trace elements.(3) Both the determination values of available Zn, Cu, Fe, Mn byASI and wheat biomass are not reached significant correlation (n=40P>0.05), and determination value ofCu, Fe by the ASI and uptakeof Cu, Fe by wheat are not reached significant correlation (n=40P>0.05), while determination values of available Zn, Mn by the ASI and uptake of Zn, Mn by plant, are significantly correlated (n=40, P<0.05). We conclude that supplementation of the trace elementcould be2.5times of critical value by ASI method for the soil. Theuptake of Zn by wheat is reasonable and effective, but uptake of Cu,Fe and Mn is unreasonable and invalid, suggesting that theestablishment of ASI method for soil nutrient index remains to bestudied for providing more scientific and reasonable reference forreasonable fertilization in the northern farmland area of ourcountry.