Yield variation of winter wheat and its relation to yield components, NPK uptake and utilization in drylands of the Loess Plateau

ObjectivesIn the Loess Plateau, Northwest China, low-fertility fields are widely distributed. Winter wheat yields are varied among farmers and field plots. Exploring the key factors affecting the yields is extremely important for increasing the yields and management level of winter wheat.

MethodsSamples of soils at 0–100 cm depth and winter wheat plants were collected in 282 farmers’ fields in Shanxi and Shaanxi Provinces, Northwest China. The winter wheat yields were divided into high, middle and low groups, the yield variations were correlated with yield components, NPK uptake and utilization.

ResultsThe mean grain yield of winter wheat in surveyed farmers’ lands was 3815 kg/hm², the average yields of the middle and low groups were respectively 32% and 57% lower than that of the high-yield group. The grain N content of the high-yielding group was 7% lower than that of the low-yielding group, the P and K contents of winter wheat grain and the N, P and K contents of stems and leaves showed no significant variance among the yield groups. Compared with the high-yielding group, the biomass in the middle and low yielding groups were 27% and 50% lower, the harvest indices of dry matter were 5% and 13% lower, the spike numbers were 15% and 31% lower, the kernel numbers were 19% and 41% lower, the aboveground N uptake were 28% and 51% lower, the P uptake were 32% and 55% lower, and the K uptake were 28% and 50% lower. The N harvest index in the low-yielding group was respectively 5% and 4%, the P harvest index 4% and 3%, and the K harvest index 13% and 8% lower than those in the high- and middle-yielding groups. The N requirements of the high-yielding group were respectively 5% and 12% lower than those of the middle and low yield groups, but no significant difference was observed for the P requirement among the groups, no significant difference between high and middle yield groups for K requirement was found, although they were respectively 5% and 15% lower than the low-yielding. The average of N physiological efficiency of the high-yielding group was 4% and 11% higher than those of the middle and low yield groups. For P physiological efficiency, there was no significant difference among yield levels. In addition, the average K physiological efficiency of the high and middle yield groups also showed no significant difference, but they were respectively 16% and 10% higher than that of the low-yielding group.

ConclusionsWinter wheat yields are varied significantly in farmers’ lands in the Loess Plateau. The main reason is from the differences in crop dry matter accumulation, yield formation, and N, P and K uptake and distribution caused primarily by the variable N nutrition status. To reduce the farmers’ wheat yield difference in this area, the key measures should be adopted to regulate the crop N nutrition and optimize the fertilizer input based on the crop nutrient requirements, meanwhile improve crop cultivation, promote dry matter accumulation in wheat plant, increase the ear number and grain number, and then achieve its yield increase in a large scale.