控释尿素和普通尿素配比对不同氮效率玉米叶片衰老特性和土壤酶活性的影响

控释尿素和普通尿素配比施用可以同步玉米氮素需求，延缓后期衰老，增加产量。本试验以黄淮海区域两种氮效率玉米作为对象，研究控释尿素和普通尿素不同配比对其叶片衰老特性、土壤酶活性和土壤无机氮的影响。试验选取黄淮海主栽玉米品种豫禾988（氮低效）和郑单958（氮高效）作为试验材料，设置6个施氮处理（CK、N180U、N180C1、N180C2、N180C、N300U），其中CK为不施氮处理，180、300代表施氮水平分别为180 kg/hm²和300 kg/hm²，U代表全尿素处理（基肥：追肥=2：3），C1、C2分别代表控释氮：尿素氮为1：2和2：1（基肥一次施用），C代表全控释尿素处理（基肥一次施用）。2018-2019年结果表明：与CK相比，豫禾988在N180C1和郑单958在N180C2处理下，能够在玉米生育后期显著提高穗位叶超氧化物歧化酶（SOD）和过氧化物酶（POD）活性，降低膜脂过氧化物（MDA）含量，同时也增加了土壤无机氮含量、脲酶和蔗糖酶活性。综上所述，针对不同氮效率玉米品种，通过控释尿素和尿素合理配施，利用速效氮和控释氮的释放来延缓玉米功能叶片衰老，延长功能期，提高生育后期土壤无机氮含量和酶活性，共同促进玉米生长，增加玉米产量，其中豫禾988和郑单958分别在N180C1和N180C2处理下效果最佳。

Effects of combination of controlled release urea and normal urea on the leaf senescence and soil enzyme activity of different maize cultivars

Mixture of controlled release urea and urea one-application can synchronize the need of nitrogen requirement, postpone leaf senescence and increase yield for summer maize, coupling with labor saving, which will be the most effective way of nitrogen application in the future. In our experiment, two maize cultivars of different nitrogen efficiency were selected to study the effects of different ratios of controlled-release urea and urea on leaf senescence characteristics, soil inorganic nitrogen content, enzyme activity and yield of different maize varieties. Using cultivars YH988 and ZD958, which were mainly planted cultivars in Huang Huaihai Plain as test materials, 6 treatments (CK, N180U, N180C1, N180C2, N180C, and N300U) were set up, of which CK was no nitrogen treatment, 180 and 300 represented nitrogen application levels of 180 kg/hm² and 300 kg/hm², respectively. U stands for total urea treatment (basal nitrogen and top dressing was 2:3), C1 and C2 stand for the controlled release urea:ordinary urea being 1:2 and 2:1 (basal nitrogen one-application), and C stands for full controlled release urea treatment (basal nitrogen one-application). The results during 2018 and 2019 showed that one-off application of the blend of controlled release urea (CRU) and urea (U) before sowing at 180 kg N hm^-2 was able to satisfy the N demand of a summer maize system with varieties YH988 and ZD958 in Huang Huaihai Plain. One-off application a mixture of CRU and urea with 1:2 and 2:1 of cultivars YH988 and ZD958 at 180 kg N hm^-2 achieved the highest yield, which indicated N180C1 and N180C2, respectively. During the maize growth period, comparing with CK treatment, the superoxide dismutase (SOD) and peroxidase (POD) activities of ear leaves increased significantly and the membrane lipid peroxides (MDA) content of ear leaves reduced significantly in treatment N180C1 and N180C2 for cultivars YH988 and ZD958, respectively, while also increasing soil inorganic nitrogen content, urease and sucrose enzyme activity in the post-silking stage for summer maize. In summary, for the two maize cultivars with different nitrogen efficiencies, optimizing the mixture of controlled-release urea and urea can delay the senescence of functional leaves of maize through the complementary effects of the release of urea in the early stage and the release of CRU in the later stage, prolong the functional period, and increase the soil inorganic nitrogen content and enzyme activity in the later growth period. The treatments N180C1 and N180C2 are most suitable for YH988 and ZD958, respectively.