Effect Of Exogenous Substances And Zn Fertilizer Application On Zn Available Fractions,transformation,and Winter Wheat Grain Concentration In Calcareous Soil

Zinc is an essential micronutrient for human and plants.Millions of hectares of agricultural land are affected by Zn deficiency and it has been estimated that about one-third of the world's population to be at risk of Zn deficient.In China,wheat as the staple food of the northern people is mainly distributed in the calcareous soil area in the north where The content of soil available Zn is mostly at the potential deficiency level(DTPA-Zn content 0.5to 1.0 mg kg^-1).The application of zinc fertilizer before wheat sowing is an effective agronomic measure to solve the problem of zinc deficiency in soil.However,most of zinc will be fixed due to poor chemical properties of calcareous soil such as high pH and low organic matter content,resulting in the reduction of the Zn availability in the soil solution and Zn for plant root uptake and accumulation,Ultimately results the lower content of Zn in the edible part of the crop that can be absorbed by people.In this study,indoor analysis and field location experiments were conducted.Using a field test for soil samples in one block.For the first time,a method combining chemical fraction of soil Zn with DTPA extraction was proposed.The quantitative relationship between soil DTPA-Zn and various chemical fractions of soil Zn was attempted to evaluate the effect of application of straw with zinc in calcareous soil to available zinc fractions plant roots.Zinc and different exogenous substances were used to determine the content of DTPA-Zn and zinc in the soil in different growth period of the wheat.The conversion rate?CR?,transfer factor?MF?and distribution index?DI?of exogenous zinc were calculated by measurement indicators.The objective is to reveal the effects of exogenous substances on soil Zn availability,morphological transformation and grain zn concentration of winter wheat.By comparing with the effect of EDTA-Zn chelated fertilizer,agronomic measures suitable for the application of zinc fertilizer in combination with the exogenous substances on calcareous soil were screened.The obtained result were as follows:?1?Calculating the contribution of zinc to DTPA-Zn in soil of combination of straw and zinc fertilizer with the indoor analysis and the improvement of soil Zn sequential extraction procedure.The results showed that the calculation method of soil zinc contribution to soil DTPA-Zn was not feasible.Single application of straw?S?only increased the content of DTPA-Zn by 73.9%.The application of zinc fertilizer with straw?Zn+S?and zinc fertilizer alone?Zn?were not only greatly increased the DTPA-Zn content in soil by 8.3⁹.4 times,but also increased the 1.9².4 times of soil weak bingding organic of zinc?Wbo-Zn?.The addition of straw had no significant effect on the adsorption and desorption characteristics of zinc in soil.?2?Exploring the effect of exogenous substances?organic manure,straw and fulvic acid?with zinc fertilizer on the content of available Zn fractions,transformation and the concentration of zinc in winter wheat with the method of field location experiment.The results showed that the content of dissolved organic matter in calcareous soil increased with the application of exogenous substances and zinc fertilizer and had a significant positive correlation with soil DTPA-Zn and Wbo-Zn;the content of DTPA-Zn in soil increased by2⁷ times.The ratio of zinc fertilizer to DTPA-Zn also increased under the effect of exogenous substances which reduced the fixation of the soil to zinc;the application of exogenous substances and zinc fertilizer greatly increased the Wbo-Zn in the soil and the effect of EDTA-Zn was 1¹.5 times of the other treatments.It is known that the content of the available component of soil zinc increased under the use of combining exogenous substances with the significant increase of soil zinc transfer factor?M_F?value.The application of exogenous zinc fertilizer reduced the distribution index of zinc?D_I?to a certain degree,which directly proved that the application of exogenous substances and zinc fertilizer could promote the transformation of the available fractions and relative available state of and the unavailable zinc in the soil.All in all,in the calcareous soil with potential zinc deficiency,application of zinc fertilizer and exogenous material increased the content of available zinc components in the soil and promoted the conversion of the unavailable soil zinc component to the effective state and significantly increased the grain zinc content in winter wheat.the best treatment of application of organic and zinc fertilizer could improve the grain zinc concentration To 32.8mg kg^-1,while there was no significant difference with EDTA-Zn treatment.Above all,on the potential zinc deficient calcareous soil in the north of China,the application of exogenous substances with zinc fertilizer can improve the availability of zinc content in soil and the zinc concentration in wheat grains to a certain extent.The application of chelate zinc fertilizer EDTA-Zn had the same effect on the content of grain zinc with the application of exogenous substances with zinc fertilizer.Therefore,the application of the relatively cheap exogenous substances with the zinc fertilizer is more in line with the production practice.