Effects of basic application of chlorocholine chloride combined with nitrogen fertilizer on nitrogen use of summer maize in North China Plain.

To clarify the effects of combined applications of chlorocholine chloride (CCC) and nitrogen fertilizer (CN) on nitrogen metabolism and nitrogen use efficiency of summer maize, we conducted a field experiment in Xinxiang experimental station of Chinese Academy of Agricultural Sciences in 2018 and 2019, with four nitrogen application rates (0, 62.5, 125 and 187.5 kg·hm ^-2 ), and two maize varieties of Jingnongke 728 (JNK728) and Zhongdan 909 (ZD909). The results showed that across the two years CN-CCC increased maize yield by 7.7% and 5.0% under the nitrogen application rates of 62.5 kg·hm ^-2 and 125 kg·hm ^-2 , respectively. CN-CCC increased the contents of nitrate reductase, glutamine synthetase, glutamate synthetase and soluble protein, and finally promoted nitrogen metabolism. Under the low and middle nitrogen application conditions (62.5 kg·hm ^-2 and 125 kg·hm ^-2 ), plant nitrogen content of JNK728 and ZD909 increased by 17.6% and 30.3%, grain nitrogen content increased by 10.3% and 17.4%, nitrogen partial productivity, agronomic efficiency of applied nitrogen, recovery efficiency of applied nitrogen, nitrogen use efficiency increased by 10.0%, 15.7%, 23.3%, 24.8% and 5.7%, 15.0%, 49.9%, 71.7%, respectively. In conclusion, appropriate basic application of CN-CCC could enhance nitrogen metabolism, increase nitrogen use efficiency and grain yield of summer maize. Our results showed that CCC combined basic nitrogen application of 125 kg·hm ^-2 had the best effect.