Effects of different nitrification inhibitor DCD addition ratios in nitrogen fertilizer on cotton growth and yield

Objectives The growth and fiber quality of cotton are sensitive to nitrogen nutrition. We studied the effects of adding different ratios of nitrification inhibitor dicyandiamide (DCD) in conventional nitrogen fertilizers on the growth, yield and quality of cotton, to provide an alternative way of nitrogen management in cotton production.

Methods Field experiments were carried out in 2017 and 2018 in Hebei Province, with cotton cultivar Nongda 601 as the material. At the base of applying N 240 kg/hm², DCD was added into urea in ratios of 0 (CK), 1.5% (C1.5) and 3% (C3), and applied with urea. The plant growth, leaf area and assimilate substance contents, the yield of cotton bolls formed in different periods and the quality indices of cotton fiber were investigated.

Results Compared with CK, the addition of DCD 1.5% treatment significantly improved the plant height of cotton in the early flowering stage, full boll stage and boll opening stage, increased the stem diameter of cotton in budding stage, full boll stage and boll opening stage, and enhanced the leaf area index of cotton in budding and full boll stage, which were conducive to the formation of favorable morphological characteristics of cotton plants. Compared with CK, C1.5 treatment significantly increased the chlorophyll content of cotton leaves at budding stage, the soluble sugar contents at budding, early flowering and full-bloom stages, and the soluble protein contents at budding stage and early flowering stage. The dry matter accumulation of functional leaves in main stems in the early flowering and full-bloom stages were increased significantly by treatment C1.5. However, comparing with CK, treatment C3 had neither the mentioned promotion effects in cotton growth and assimilate substance contents in functional leaves, nor in the dry matter accumulation as well. The C1.5 treatment significantly increased cotton yields by 812 kg/hm² and 324 kg/hm² in two years, respectively, without decreased any fiber quality index.

Conclusions The two years experimental results showed that without increasing nitrogen rate, adding 1.5% DCD could optimize the nitrogen supply of cotton, thus benefit the formation of satisfactory morphology of plants, increase the contents of assimilate substances in leaves, and increase the cotton yields without decrease the fiber quality. Adding 3.0% of DCD in nitrogen fertilizer has no promoting effects. So adding 1.5% of DCD in nitrogen fertilizer is recommended as an alternative nitrogen management in practical cotton production.