Effects Of Zinc Application Methods On Its Transformation In Calcareous Soil And Absorption In Wheat

In China, wheat is mainly grown on calcareous soils with a level of potentially deficient DTPA-Zn(ranged from 0.5 to 1 mg·kg-1) in North area, the wheat grain Zn concentration in this region is relatively low(about 30 mg·kg-1), which is not enough to meet the zinc nutrition needs for the local population. soil application of Zn is a convenient measure to improve the wheat grain Zn concentration, however, the special physical and chemical properties of local soil lead to the non-significant effect in improving the wheat grain Zn content when inorganic zinc fertilized to soil, Previous studies showed that, zinc fertilized to soil will exist as varieties of chemical forms, and the chemical forms is closely related to the bioavailability of Zn. So, if we can change the Zn application methods to change the Zn fractions in soil, and then change the bioavailability of Zn? Therefore, three field experiments(two sourses of Zn with different soil application methods, soil application of Zn SO4 and priming with Zn SO4, combined Zn SO4 with straw and K) on potentially Zn-deficient soil were conducted to study effects of zinc application methods on its transformation in soil and absorption in wheat, in order to provide scientific basis for improving Zn fertilizer utilization rate on the potentially Zn deficient calcareous soil. Main results were as follows:(1) To research the effect of Zn carriers and Zn fertilization methods on its fertilizer efficiency and Zn fractions in soil. A field experiment was carried out over two consecutive cropping seasons, with no Zn application as control, using two Zn sources(Zn EDTA and Zn SO4) and under two application methods(broadcast and band), to compare the difference of soil zinc fractions and zinc availability under two consecutive wheat cropping seasons with different sources and application methods of Zn. The results showed that, compared to broadcast application, band application significantly increased the contents of soil DTPA-Zn,exchangeable Zn(Ex-Zn), weakly bond to organic matter Zn(Wbo-Zn) in the first season,then these fractions reduced to the similar level with broadcast application in the subsequent season; compared to 4 kg·ha-1 EDTA-Zn application, 20 kg·ha-1 Zn SO4 application had a better effect of increasing the contents of soil DTPA-Zn, Wbo-Zn, carbonate bound Zn(CarbZn) in two cropping seasons, then the effect reduced in the subsequent season, however,EDTA-Zn application could maintain higher contents of Ex-Zn in the first season, and most of the Ex-Zn was fixed in the subsequent season.(2) A field experiment was conducted to research the effect of two Zn application methods(soil application of Zn and seed priming with Zn) on wheat yield, Zn accumulation and Zn use efficiency. The results showed that, There was no significant effect on wheat yield and Zn accumulation of two Zn application methods, both of the two methods showed a little improvement of grain Zn content and a low Zn use efficiency; In wheat cropping season, it presents a fluctuating changes of plant Zn content, the roots absorbed Zn from soil and stored in the plant before filling stage, then absorbed a small amount of Zn at filling stage, a large portion of Zn accumulated by grain was transported by the crown organs through phloem.(3) To research the effect of combined Zn with straw and K on Zn fractions and Zn accumulation on the potentially Zn deficient calcareous soil. The results showed that, there is no significant effect on Zn fractions and accumulation combined Zn with K and Zn with straw on the potentially Zn deficient calcareous soil, the treatment of Zn with straw can nosignificant increase Wbo-Zn and Sbo-Zn content in the late stage. Therefore, tillage measure combined Zn with straw on the potentially Zn deficient calcareous soil can be a choice to solve soil and plant Zn deficiency.In conclusion, on the potentially Zn deficient calcareous soil in the north of China, band application of a lower level of Zn EDTA can effectively increase the contents of soil DTPA-Zn in the first cropping season, however, the efficiency is low in the subsequent cropping season;seed priming with Zn can decrease fixation of zinc fertilizer, and increase the Zn content in plant at the early growth stage of wheat, but the effect of increase grain Zn content is not significant; soil application of Zn combined with K and straw have no negative effect on the absorption of Zn for wheat, Wheat straw returning to the field can increase the Wbo-Zn content.