Effect of Zn supplementation on Zn concentration of wheat grain and Zn fractions in potentially Zn-deficient soil

To investigate the effect of Zn fertilization on soil Zn fractions and grain Zn concentration in wheat grown on potentially Zn-deficient soil, a field experiment was carried out. The experimental design was split plot consisted of two varieties of wheat (Zhengmai 9023 and Xinong 889) with five Zn levels (0, 7.5, 15, 30 and 45 kg Zn/ha). Results showed that Zn fertilization had no significant effect on wheat yield and grain Zn concentration, and the recovery of Zn fertilizer was only 0.06% to 0.29%. However, the amount of soil DTPA-Zn was increased by 2.3-9.8-folds as Zn supplementation increases during the whole wheat growth stage as compared to the control (Zn0 treatment). Besides, DTPA-Zn was positively correlated with both Loose organic matter bound Zn (LOM-Zn) and Exchange Zn (Ex-Zn), and their partial correlation coefficients were 0.558 and 0.119, respectively. Moreover, these two fractions also showed positive correlation with grain Zn concentration. The amount of LOM-Zn was firstly increased with increasing Zn fertilizer levels then gradually decreased as it get converted to mineral bound Zn (Min-Zn). Zn fertilization in this potentially Zn deficient soil increased the amount of DTPA-Zn in the whole wheat growth stage; however, grain Zn concentration cannot be significantly increased as Zn levels increase, thus suggesting that there are inhibitory factors for Zn absorption and translocation. Furthermore, the amount of soil DTPA-Zn perhaps cannot exactly reflect the capability of soil to supply Zn