Harvesting more grain zinc of wheat for human health.

Increasing grain zinc (Zn) concentration of cereals for minimizing Zn malnutrition in two billion people represents an important global humanitarian challenge. Grain Zn in field-grown wheat at the global scale ranges from 20.4 to 30.5 mg kg-1, showing a solid gap to the biofortification target for human health (40 mg kg-1). Through a group of field experiments, we found that the low grain Zn was not closely linked to historical replacements of varieties during the Green Revolution, but greatly aggravated by phosphorus (P) overuse or insufficient nitrogen (N) application. We also conducted a total of 320-pair plots field experiments and found an average increase of 10.5 mg kg-1 by foliar Zn application. We conclude that an integrated strategy, including not only Zn-responsive genotypes, but of a similar importance, Zn application and field N and P management, are required to harvest more grain Zn and meanwhile ensure better yield in wheat-dominant areas.

[Effects of nitrogen fertilization on population dynamics and yield of high-yielding wheat and on alteration of soil nitrogen].

Taking wheat varieties Yumai 49-198 (multi-spike phenotype) and Lankao Aizao 8 (large-spike phenotype) as test materials, field experiments were conducted at Wenxian and Lankao sites of Henan Province to study the effects of nitrogen fertilization on their population dynamics and yield and on the alteration of soil nitrogen. Five nitrogen application rates, i. e., 0, 90, 180, 270, and 360 N kg x hm(-2) were installed. The population amount of the two test varieties were all increased after emergence, reached the highest at jointing stage, and decreased afterwards. As for Yumai 49-198, its population amount had no significant differences at wintering and turning-green stages among the five nitrogen application rates and two experimental sites, but differed significantly after jointing stage with the nitrogen application rates. For Lankao Aizao 8, its population amount had no significant differences among the nitrogen application rates during whole growth period. The grain yield of the two varieties increased with the increase of nitrogen fertilization rate, but excessive nitrogen fertilization decreased the grain yield. Yumai 49-198 had the highest yield at 270 N kg x hm(-2), being 9523 and 9867 kg x hm(-2) at Wenxian and Lanako sites, respectively, while Lankao Aizao 8 had the highest yield at 180 N kg x hm(-2), being 9258 and 9832 kg x hm(-2) at Wenxian and Lanako sites, respectively. With the increase of nitrogen fertilization rate, soil nitrate N concentration and apparent nitrogen loss increased. At Wenxian and Lankao sites, the apparent soil nitrogen loss for Yumai 49-198 was 32.56% - 51.84% and - 16.7% - 42.6% of fertilized nitrogen, and that for Lankao Aizao 8 was 18.58% - 52.94% and - 11.5% - 45.8% of fertilized nitrogen, respectively. Considering the yield and environmental effect comprehensively, the nitrate N concentration in 0-90 cm soil layer in our case should not be exceeded 120 - 140 kg x hm(-2), and the maximal nitrogen application rate should not be exceeded 180 kg x hm(-2).