Abstract
The aim of this study was to verify the applicability of the critical nitrogen concentration dilution curve (Nc) of wheat grown under different irrigation conditions in the field, and discuss the feasibility of using the N nutrition index (NNI) to optimize N fertilizer application. The high-yield, medium-protein wheat varieties Zhoumai 27 and Zhoumai 22 were used in field experiments in two different locations (Zhengzhou and Shangshui) in Huang-Huai, China. Plants were grown under rainfed and irrigation conditions, with five N application rates. Nc models of the leaves, stems, and whole plant were constructed, followed by establishment of an NNI model and accumulative N deficit model (Nand). As previous research reported, our results also showed that the critical N concentration and biomass formed a power function relationship (N = aDW−b). When the biomass was the same, the critical N concentration was higher under irrigation than rainfed treatment. Meanwhile, the fitting accuracy (R2) of the Nc model was also higher under irrigation than rainfed treatment in both sites, and was higher in the stems and whole plant. The NNI calculated using the Nc model increased with increasing N application, reflecting N deficiency. Moreover, there was a significant negative linear correlation between NNI and Nand, and both indices could be uniformly modeled between locations and water treatments. The accuracy of the Nand model was highest in the whole plant, followed by the leaves and stems. The models constructed in this paper provide a theoretical basis for accurate management of N fertilizer application in wheat production.
Highlights
Henan Province is the main wheat producing area in China, representing 22.1% of the entire production area and producing 25% of the national wheat output
The results showed that these three factors and most of the interaction effects were significant in terms of tissue dry matter, highlighting the importance of the environmental conditions
The biomass of the wheat leaves tended to increase decrease with growth, and the maximum value appeared at 170−180 days after planting
Summary
Henan Province is the main wheat producing area in China, representing 22.1% of the entire production area and producing 25% of the national wheat output. N is the most demanding element of wheat growth, and wheat is sensitive to N levels in soils. Insufficient N fertilizer limits crop growth, while excessive application leads to a low N utilization rate, thereby wasting resources and increasing environmental pollution. Traditional methods of N nutrition diagnosis include analyses of growth, leaf color, and overall symptoms and so on. These diagnostic tools tend to rely on experience and subjective judgment, and, the likelihood of error is relatively large, greatly restricting their accuracy and application. Accurate diagnosis of the Nstatus at various stages of growth is vital for the optimal management of N fertilizer application in crop fields
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