Abstract:

【Objective】 The objective of the study is to investigate the effects of application rates of normal urea (NU) and controlled release urea (CU) on ear leaf senescence, yield and economic benefit of summer maize under different water conditions. 【Method】 Five nitrogen rates and two irrigation levels were designed to investigate the effects of water-nitrogen coupling on photosynthetic rate, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA) content and soluble protein content in maize ear leaves after anthesis, and their relationship with grain yield and economic benefit. 【Result】 At the same irrigation level, net photosynthetic rate of maize applied with controlled CU was lower (P < 0.05) than that applied with NU at anthesis, but the situation was just contrary after anthesis. At the same nitrogen level, compared with the NU, CU can significantly increase water content, activities of SOD, POD and CAT, and the content of soluble protein in ear leaves, but reduce MDA content. So, the grain yield and economic benefit of maize applied with CU was higher than that applied with NU, and irrigation is beneficial to improve the superiority of CU. But because of the higher cost of CU, when higher CU were used with irrigation, the economic benefit was lower than NU. 【Conclusion】 Compared with the NU, the positive coupling effect of CU might be caused by the higher SOD, POD and CAT activities and soluble protein content, and the lower MDA content after anthesis, which could delay the senescence and increase the net photosynthetic rate of ear leaf, and as a result, increase the grain yield of maize. With the increase of CU production, its cost will be decreased and its use prospect will be wider in crop production.

Key words: irrigation, urea types, maize, senescence, yield, economic benefit