A model of plant and ear nitrogen for the diagnosis of nitrogen nutrition of malting barley to coordinate the relationship between grain yield and quality

Abstract

Scientific and reasonable application of nitrogen fertiliser is an important agronomic measure to achieve both a high yield and a high quality of malting barley, and determining the appropriate nitrogen concentration is important for optimising the two. To this end, we constructed critical concentration curves for plant and ear nitrogen of malting barley as a tool for diagnosing nitrogen nutrition. Two varieties of barley, Zhepi 33 and Yangnongpi 8, were used as experimental materials, and five nitrogen application levels (ranging from 0 to 300 kg·ha–1) were established in three field experiments. Plant dry matter first increased and then stabilised and the nitrogen concentration increased continuously with an increase in nitrogen application rate. Based on analyses of the relationship between dry matter and nitrogen concentration, dilution models of critical nitrogen concentration in the plant (Np) and ear (Ne) of malting barley were established, and were expressed as power function equations: Np = 3.879PDM–0.444 (R2 = 0.9705) and Ne = 2.198EDM–0.152 (R2 = 0.7968). Next, nitrogen nutrition indexes were constructed to identify nitrogen-limiting and non-limiting treatments. To ensure an optimal grain protein concentration of 10–12%, the Ne index and the Np index were required to be 0.897–1.061 and 0.699–0.992 at the heading stage, respectively. The results provide a theoretical foundation for the diagnosis and regulation of nitrogen nutrition in malting barley and have great significance for the production of high-quality and high-yielding malting barley.