Wheat grain zinc concentration as affected by soil nitrogen and phosphorus availability and root mycorrhizal colonization

Official URL: https://dx.doi.org/10.1016/j.eja.2022.126469

Nitrogen (N) fertilization increases zinc (Zn) acquisition in cereal crops. However, little is known about the effects of N fertilization on grain Zn concentration in relation to availability of soil N and phosphorous (P) and root mycorrhizal colonization. The present study used a 12-year location-fixed field experiment with winter wheat grown at five N fertilization rates (0, 80, 160, 240 and 320 kg N ha−1). The objective was to assess effects of phytoavailability of soil N and P and root mycorrhizal colonization on wheat Zn nutrition during three-year field measurements. Zinc concentration in wheat grains was increased with N fertilization in a linear-plateau fashion, and it reached the plateau of 30.3 ± 0.4 mg kg−1 when soil mineral N (nitrate-N) levels were 8.5 ± 1.0 mg kg−1 and above at maturity. Similarly, total shoot Zn uptake and Zn remobilization from vegetative tissues to grains were also increased significantly and then attained a plateau as the N rates increased. The enhancements in grain Zn concentration by N fertilization mainly occurred in the crease tissue, embryo and aleurone fractions of the grain. Long-term N fertilization was also associated with increases in root mycorrhizal colonization up to 8.8 ± 2.9 mg kg−1 soil available mineral N at maturity. Shoot Zn uptake at maturity increased quadratically with the increase in shoot N uptake and root mycorrhizal colonization rate, whereas there was an inverse relationship between shoot Zn uptake and soil P availability. The results suggest that grain Zn concentration of wheat plants grown under long-term N fertilization was closely related to the soil mineral N status and showed clear increases with decreased soil available P concentration and improved root mycorrhizal colonization rates.