Abstract:A field experiment was carried out to study the effects of different mixed ratios of controlled-release urea (CRU) and conventional urea (CU) on soil nitrogen content, its uptake and utilization of maize (Zea mays L.) and grain yield. All treatments were applied with the same rate of nitrogen. The results showed that nitrogen fertilization significantly increased soil available nitrogen and total nitrogen contents in tillage layers of 0-20 cm and 20-40 cm. When using conventional urea, single basal application increased soil nitrogen content in the early growth stage, while twice application could improve the nitrogen content in the late growth stage. Compared with the conventional urea application, the single basal application of urea with a certain proportion of controlled-release urea significantly improved soil nitrogen content in tillage layer in each growth period. The suitable proportion of controlled-release urea mixed with conventional urea increased the nitrogen accumulation in maize in the middle and later stages to some extent, improved the apparent utilization rate of nitrogen fertilizer, the efficiency of nitrogen fertilizer, fertilizer contribution and the key enzymes activities of nitrogen metabolism in function leaves. At the same nitrogen application rate, the effect of the single basal application of the mixed fertilizers was even better than the twice applications of conventional urea. With the increasing proportions of controlled-release urea, the maize yield first increased and then decreased, and the yield under the treatment of 75% controlled-release urea+25% conventional urea was the highest, which was 12.09% (2014) and 21.58% (2015) higher than single basal application of conventional urea fertilizer, 8.27% (2014) and 14.19% (2015) higher than the twice fertilizations, respectively. Therefore, the conventional urea mixed with 75% controlled-release urea could not only harmonize the soil nitrogen supply throughout the maize growing period, but also reduce the times of fertilization, and consequently cut the labor input.