| Wheat is as a staple food for the north residents especially the rural areas of the population in China. Daily calories and minerals uptake is mainly derived from wheat. However, wheat was mainly grown in calcareous soil in which the amount of DTPA-Zn was among 0.5-1.0 mg·kg-1. Low available Zn in soil attributed to the low grain Zn concentration. Some anti-nutrients also existed in wheat grain, especially phytic acid which is the mainly storage form of P in grain. High phytic acid content could significantly reduced Zn bioavailability and then the absorption of Zn in human body was relatively reduced. Therefore, improving grain Zn concentration and bioavailability in calcareous soil has become equally important.There are litter researches about Zn fertilization on wheat grain Zn concentration and bioavailability in China. It is generally accepted that there is a significantly interaction between Zn and P. P had a significantly negative effect on Zn absorption. A question should be raised that how to improve grain Zn concentration and reduce phytic acid on the condition that P fertilization was also at a high level in wheat field. In order to study the interaction between P and Zn and effect of Zn fertilization on grain Zn concentration and bioavailability in calcareous soil, a hydroponic and a field experiment was carried out. These researches included effect of P combined with Zn fertilization on grain Zn concentration and other micronutrients and effect of P combined with Zn supplied to soil and foliar spray of Zn in different wheat growth stages on grain Zn concentration and bioavailability. The main results from our studies were as follows:1. A nutrient solution experiment was conducted to investigate the interaction of Zn and P nutrition of wheat plants at the seedling stage in chelater-buffered solution. Zn rates were supplied at three levels of 0, 3 and 30μmol·L-1, P was also designed in three rates, namely, 0, 0.6, 3.0 mmol·L-1. The results showed that the growth of the wheat seedlings were decreased under the deficient or excessive supply of P and Zn, the effect of deficient P supply was more remarkable than that of the excessive P supply, and the effect of excessive Zn supply was stronger than that of the deficient Zn supply; the effects of deficient P supply and excessive Zn supply were mainly reflected in the tillers and the biomass of shoot. The obvious content of the roots were decreased, but the translocation rate of Zn was increased when P was supplied. A large mount of P were accumulated in the leaves of the wheat under the condition of Zn deficiency, and the translocation rate of P was decreased by the supply of Zn.2. In addition, in wheat seedling plant, there was obvious antagonism between Zn and Cu at wheat seedling stage, but the translocations from root to shoot of Zn and Cu were increased under the supply of Zn, while that of Mn was decreased; A large mount of Zn was transported to the shoot under excess Zn supply, and the total translocation of (Fe+Cu+Mn) was decreased drastically at the same time. The uptake of Fe was inhibited by the P supply, but the translocation ratio of Zn, Cu and Mn increased under the P supply; the effect of Zn itself was more remarkable than P on the uptake between Zn and Fe, Cu, Mn, the uptake of Zn was increased obviously under the Zn supply. To the shoot of wheat seedling, the uptake of Zn was easier than Fe under P supply, but the uptake of Fe overmatched that of Zn without P supply; For Zn and Cu, the uptake of Zn excelled that of Cu with no P supply, but the uptake of Cu outbalanced Zn after P supply, the same as the uptake between Zn and Mn.3. To investigate the effects of supplying Zn and P on the harvest wheat plant, an experiment in chelater-buffered solution was conducted, P rates were supplied at three levels of 0.1, 0.6, 3.0 and 6.0 mmol·L-1, Zn was designed in two rates of 0 and 3.0 mmol·L-1. The results indicated that when supplying with Zn, the Zn concentration and content of wheat grain were 2.74 and 3.64 times to those of no Zn supplying, respectively, the concentration of phytic acid and the molar ratio of phytic acid to Zn of wheat grain was decreased by 9.64% and 68.19% under Zn supply compare to no Zn supplying, respectively; In addition, the dry weight of wheat grain was increased under Zn supplying, so did the concentration of P, and the translocation of P and Zn to wheat grain were also increased by Zn supplying; There was obvious P-Zn antagonism in roots of wheat; The uptake of Zn to wheat was depressed when excess P supplying, and the translocation of Zn to wheat grain was inhibited too; moreover, the translocation of P decreased with the elevation of P supply.4. A field experiment with zinc and phosphorus fertilization using split-split design was conducted. The main factor was wheat genotype, namely Zhengmai9023, Xiza1, Xiaoyan22 and Zhongyu6. The sub-factor was P fertilizer, P rates were supplied at three levels of 0, 50, 100, 150 and 200 kg P2O5·ha-1, sub-sub-factor was zinc fertilizer, Zn was designed in two rates of 0 and 7.0 kg Zn·ha-1. The results indicated that in potentially zinc deficiency soil, there was no obvious influence of zinc fertilization on the yield of wheat, but phosphorus fertilization performed well. The effects of zinc fertilization on different wheat genotypes were various. The synergism between phosphorus and zinc happened at the rate of 0150 kg·ha-1(P2O5), but there was an antagonism between phosphorus and zinc when the phosphorus fertilization reached more than 200 kg·ha-1(P2O5). The effect of phosphorus was stronger than that of zinc in the interaction of them. The phytic acid concentration and the phytic acid to zinc molar ratio increased remarkably with phosphorus fertilization. There was no evident effect of zinc fertilization on the concentration of wheat grain, but zinc supply decreased the phytic acid to zinc molar ratio on the condition of phosphorus fertilization.5. In order to investigate the effect of foliar application of zinc on zinc nutritional quality of wheat grain on potentially zinc-deficient calcareous soil. Field experiments using split-split design of foliar application of zinc were carried out in 2007-2008 and 2008-2009 cropping seasons. The main factor was zinc spraying stage, namely, jointing stage, flowering stage, early grain filling stage and late grain filling stage. The sub-factor was nitrogen fertilization, N rates were supplied at three levels of 0, 120 and 240 kg N·ha-1. Sub-sub-factor was zinc rate; two Zn rates of spaying with Zn and without Zn (distilled water). The results showed that the Zn concentrations of wheat grain of the first and the second cropping season were increased by 51.65% and 73.53% after foliar application of zinc, respectively; the concentrations of phytic acid were decreased by 11.06% and 16.84%, respectively; and the molar ratios of phytic acid : zinc were decreased by 11.06% and 16.84%, respectively. The zinc concentrations of two cropping seasons after foliar application of zinc were in the order of early-filling stage > late-filling stage > flowing stage > jointing stage; The zinc concentrations and their increasing rates of wheat grain of two cropping seasons were both highest when foliar application of zinc at earlier filling stage among the four different growth stages, the zinc concentrations of wheat grain of the first and the second cropping season were 59.71 and 54.63 mg·kg-1, respectively, and the increasing rates were 67.35% and 107.48%, respectively; so did the decreasing rates of the molar ratios of phytic acid: zinc; and they decreased by 47.24% and 59.12%, respectively. The increasing rates of zinc concentrations of wheat grain of two cropping seasons were more significant with no nitrogen fertilization than that with nitrogen fertilization. The concentration of P of wheat grain was decreased by zinc foliar application, but the effect of zinc spraying on the concentration of P was much smaller than that of the concentration of zinc. Nitrogen was the main factor to the concentration of protein of wheat grain, and the protein concentration increasing visible along with the increasing nitrogen fertilization.6. In the field experiment of zinc spraying, during the first and second year, Fe concentrations were increased by 12.4% and 12.9% on average, but foliar Zn application at seed filling stage decreased the Cu concentration wheat grain, and there was no significant effect of Zn spraying on the grain Mn concentration, the total content of(Zn+Fe+Mn+Cu)of wheat grain were increased by 17.8% and 19.9%, the phytic concentration decreased by 11.06% and 16.92%, respectively; so the availability of micronutrients were improved. N fertilization decreased grain Mn concentration, but increased the total content of (Zn+Fe+Mn+Cu), and it decreased the phytic acid concentration of wheat grain.To sum up, some conclusions can be made as follows: (1) the antagonism of Zn and P exists mainly in the roots, and it also will happen in other organs of wheat; This antagonism not only occurs when the levels of P and Zn are abnormal but also occurs even when P and Zn is well-balanced. (2) On potentially zinc deficient soil, zinc fertilization has no remarkable effect on the zinc nutritional quality of wheat grain; foliar zinc application is the better choice. (3 The optimum time of zinc spraying is the early-filling stage, the zinc concentration of wheat grain can be increased obviously by zinc spraying at this growth stage, and the phytic acid concentration also can be decreased by doing so. The zinc nutritional quality can be improved remarkably when foliar zinc application is conducted at early grain filling stage.
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