| Guanzhong Plain is an important wheat producing area in northwest China.The soil in this region is mostly calcareous soil,which is at the potential Zn deficiency level.The DTPAZn content is hard to meet the requirement of wheat Zn enrichment and improve the human Zn nutrition in this soil.Application of Zn fertilizer,espically soil Zn fertilization with its relatively convenient advantage is considered to be a potential measure to improve the wheat grain Zn nurtritional quality.Previous studies indicated that soil Zn fertilization can significantly increase the soil DTPA-Zn concentration,but the poor chemical and physical propeties would decrease the effect of addition of the inorganic Zn fertilizer on the wheat grain Zn concentration.In this study,in order to provide some scientific basis for reasonable applicationof Zn fertilizer,we first studied the effects of exogenous substances on soil Zn diffusion by improving soil restrictive factors with using lab and field experiments.Then,we investigated the effects of different Zn fertilizers and application method on the soil DTPA-Zn and grain Zn biofortification in the second growth season.The main results obtained were as follows:(1)The incubation experiment using the half-cell device was carried out to assess the effect of exogenous substances and Zn fertilizer on Zn diffusion in calcareous soil.Results showed that application of exogenous substances with Zn could increase the soil DTPA-Zn diffusion rate,and with the increasing of time and distances,the DTPA-Zn diffusion rate showed a significant decrease.On the average,the positive effect of application of sulfur and organic fertilizer on DTPA-Zn diffusion rate was better than application of FA.During the incubation,application sulfur and organic fertilizer could increase soil DTPA-Zn content,then application of FA.Comprehensive consideration,application of sulfur and organic fertilizer with Zn fertilizer could affect the soil Zn diffusion rate,and it can provide the possibility of effective uptake Zn by wheat.(2)Soils with the addition of Zn combinating with exogenous substances were incubated in the field in situ to investigate the response of the availability and fractions of Zn fertilizer to exogenous substances in calcareous soil.The results showed that the application of exogenous substances with Zn fertilizer could increase the DTPA-Zn concentration in the calcareous soil,and the positive effect of application organic fertilizer on DTPA-Zn content was was better than application of sulfur or FA.For the soil Zn fractions,the treatments of applying organic manure and FA had a significant improvement on soil Wbo-Zn fraction.With the increasing of incubation time,the concentration of Car-Zn,MnO-Zn and Sbo-Zn increased significantly.However,application of exogenous substances with Zn fertilizer could alleviate the conversion process of Zn fertilizer turned into ineffective transformation.Application of exogenous substances,easpically application of organic manure with Zn fertilizer could increase the conversion of soil DTPA-Zn.(3)A two-year field experiment with the split plot design was conducted using ZnSO4 and Zn-EDTA as Zn sources to investigate the effect of different Zn sources and application method on soil DTPA-Zn and wheat grain Zn biotification.The results showed that in the second growth season,soil Zn-EDTA(4 kg Zn/ha)and ZnSO4(20 kg Zn/ha)could maintain a high DTPA-Zn concentration(1.44~2.22 mg/kg),but have no effect on wheat grain Zn concentration.Different with Zn-EDTA,soil combined with foliar ZnSO4 had a significant increasing in wheat grain Zn concentration.In sum,soil Zn fertilizer combining with organic manure or sulfer could increase soil DTPA-Zn diffusion rate and alleviate the process of aging of Zn fertilizer.For different Zn sources,although it could lead to a high level of soil DTPA-Zn and Zn fractions with higher mobility(Ex-Zn,Wbo-Zn),application of Zn-EDTA and ZnSO4 has little effect on grain Zn concentration in the next cropping year. |
