Differences in grain zinc concentration and its relationship to NPK uptake and utilization for high-yielding wheat cultivars in dryland

Objectives The purpose of this study was to clarify the relationship between grain zinc concentration and nutrient N, P, K uptake and utilization, providing scientific information for new variety breeding and nutrient management.

Methods A split field experiment was conducted in the dryland area of the Loess Plateau from 2013 to 2016. The main factor was no fertilization control and fertilization of N 150 kg/hm² (urea, N 46%) and P₂O₅100 kg/hm² (calcium superphosphate, P₂O₅ 16%), and the sub-factor was the 123 wheat cultivars, which were collected from the main wheat production areas in China. After harvest, 30 plants were chosen from the middle two rows of each cultivar, rooted out, and cut at the base joint of shoot and root. The roots were discarded, and the shoots were divided into stems, leaves, husks (including cobs) and grains, dried naturally and weighed. The contents of N, P, K and Zn in the samples were analyzed, and the uptake and reallocation of the nutrients were calculated.

Results Significant differences existed in grain Zn concentration among high-yielding wheat cultivars under fertilization treatment, grain Zn concentrations of high-Zn cultivars were 54% higher than those of low-Zn cultivars. Grain N and P concentrations of high-Zn cultivars were respectively 9% and 7% higher than those of low-Zn cultivars, no significant difference was observed for grain K concentration. Fertilization increased grain N concentrations, decreased grain P and K concentrations for two group cultivars. N and P uptake were higher in high-Zn cultivars, while K uptake was not significantly different from low-Zn cultivars. The increase of NPK uptake by fertilization in high-Zn cultivars was significantly more than that of low-Zn cultivars. No significant difference was found in N and P harvest indices between the two groups, while the K harvest indices of high-Zn cultivars were significantly lower than those of low-Zn cultivars. The decrease of NPK harvest indices of high-Zn cultivars by fertilization was similar to low-Zn cultivars.

Conclusions Under sufficient nutrient supply in dryland, high-yielding and high-Zn cultivars had significantly higher grain N and P concentration, more NP uptake and lower K harvest index than low-Zn cultivars, but no significant difference in grain K concentrations between two groups of cultivars. This result indicates that breeding new high-yielding cultivars can increase grain Zn and protein content as well as P concentration of dryland wheat. Considering high P concentrations may decrease grain Zn bioavailability, fertilization practice should rationally control P use while increasing N supply to increase grain N, Zn concentrations and Zn bioavailability.