Evaluating the Effects of Water-Nitrogen Interactions on Carbon and Nitrogen Accumulation As Well As Related Metabolic Enzymes Activity in Autumn Maize

Water deficiency and nitrogen shortage are key factors limiting agricultural development. Therefore, it is particularly important to clarify the appropriate irrigation system and nitrogen application method. The aim of this study was to assess the effect of water-nitrogen interactions on carbon and nitrogen accumulation and related metabolic enzyme activities in autumn maize. The experiment was arranged in a split-plot design comprising two factors. The main factor was rainfed (natural rainfall dependent) and supplemental irrigation, and the sub-plot factor was five levels of nitrogen application (0, 150, 200, 250, and 300 kg ha(-1)), with three replications. Phosphoenolpyruvate carboxylase (PEPC), sucrose phosphate synthase (SPS), nitrate reductase (NR), glutamine synthetase (GS), and glutamate dehydrogenase (GDH) were determined by enzyme-linked immunosorbent assay; plant carbon and nitrogen accumulation were determined by the potassium dichromate method and nitrogen determination by flow analyzer, respectively. Supplemental irrigation and nitrogen addition significantly affected the carbon and nitrogen accumulation in maize plants. The carbon and nitrogen contents of stems, leaves, bracts, and grain under N300 treatment were significantly higher than those under N0 treatment. The carbon and nitrogen content of each organ was increased with the increase in nitrogen application. Moreover, PEPC, SPS, NR, GS, and GDH enzyme activities were also increased by 20.03%, 22.01%, 37.94%, 35.82%, and 21.52%, respectively in the supplemental irrigation treatment as compared to the rainfed treatment. Besides this, carbon and nitrogen metabolic enzyme activities of the highest dosage (300 kg ha(-1)) were significantly higher than other nitrogen fertilizer treatments. Apart from this, both autumn season experiments showed that water-nitrogen combination increased the plant carbon and nitrogen accumulation as well as their metabolic enzyme activities. These finding may provide scientific basis for agronomic management measures for autumn maize in Guangxi and other areas with similar ecological conditions. Water and nitrogen treatments significantly affected the carbon and nitrogen accumulation of autumn maize plants, and the most optimal plant carbon and nitrogen accumulation and related metabolic enzyme activities were obtained with supplemental irrigation and nitrogen application of 250 kg ha(-1).