不同释放期控释肥和水氮用量对冬小麦产量的综合影响

为揭示不同释放期控释肥及其水肥用量对冬小麦产量的影响，优化冬小麦水氮管理措施，采用裂区设计进行田间试验，以灌水量为主处理，施氮量和控释肥类型分别为副处理和次副处理，其中，灌水量设30、60和90 mm；施氮量设0、75、150和225 kg/hm2的施肥梯度；控释肥类型包括释放期分别为60、120 d的聚氨酯包膜尿素（PCU60，PCU120），以普通尿素作为对照（U）。结果表明：灌水量、施氮量、控释肥类型单一因素均对冬小麦有效穗数、千粒质量、干物质质量、籽粒产量有显著影响。各因素两两之间的交互作用对籽粒产量有显著影响。相较于U处理，增加灌水使PCU60产量平均提高308 kg/hm2，PCU120产量平均下降270 kg/hm2；增施氮肥刚好相反，使PCU60产量平均下降289 kg/hm2，PCU120产量平均提高118 kg/hm2。根据所构建3种肥料的水氮生产函数可知，在U处理取得最高理论产量6 823 kg/hm2时的水氮用量下，2种释放期的控释肥PCU120和PCU60可分别获得14.31%和12.08%的增产效果。利用水氮生产函数和频率分析法得到不同控释肥类型获得较高产量的水氮用量区间，以PCU120产量最高、所需灌水量最低，分别为7 744～7 826 kg/hm2、47.72～52.28 mm；PCU60所需施氮量最低，为145.42～187.91 kg/hm2。综合考虑增产节肥节水效果，推荐PCU120为冬小麦季适宜的控释肥类型，其适宜水氮用量区间分别为47.72～52.28 mm、159.23～199.47 kg/hm2。

Comprehensive effects of irrigation water and nitrogen levels for controlled release fertilizer with different release periods on winter wheat yield

The application of traditional urea usually causes low efficiency of nutrient utilization, and environmental pollution, due to the excessive use of fertilizers, and mismatching between the nutrient release stage of fertilizers and the growth stage of crops. The controlled-release fertilizer, serving as a promising new fertilizer, can be used to improve nutrient use efficiency and crop yields via adjusting the stage of nutrient release. The objective of this study was therefore to explore the effects of controlled-release fertilizers in different release periods, and the nitrogen levels in irrigation water on winter wheat yield. A field experiment was conducted in the Modern Agriculture Demonstration Park, Wugong Town, Xianyang City, Shaanxi Province, China. The optimum combinations of water and fertilizer inputs were determined for both single-objective and multi-objective optimizations through the frequency and multiple regression analysis method. The main, sub, and sub-sub plots were designed in the field experiments. In the main zone plots, three irrigation levels were set as W1 (30 mm), W2 (60 mm), and W3 (90 mm). The sub plots comprised of four nitrogen fertilization levels, including N0 (0 kg/hm2), N1 (75 kg/hm2), N2 (150 kg/hm2), and N3 (225 kg/hm2). The sub-sub plots included three different nitrogen fertilizer types, namely PCU60 (a controlled-release fertilizer with a release periods of 60 days), PCU120 (a controlled-release fertilizer with a release periods of 120 days), and U (traditional urea). A controlled release fertilizer was applied at one time during planting, where the application mode of traditional nitrogen fertilizer (basic application: topdressing during winter irrigation: top dressing at jointing stage = 6:2:2, U) as a control. The effect of water and nitrogen dosage on winter wheat yield was clarified under the condition of controlled-release fertilizer, thereby to propose the optimal range of water and fertilizer dosage in various fertilizers. The results showed that the amount of irrigation water, nitrogen application rates, and different types of controlled-release fertilizer had significant effects on the spike number, grain number per spike, 1000-kernal mass, amount of dry matte, and grain yield of winter wheat. The interaction between two factors also had a significant impact on the grain yield. In the same irrigation levels, the winter wheat yield increased first, and then decreased with increasing nitrogen fertilizer application levels, where the maximum was obtained when the application rate of nitrogen fertilizer was 150 kg/hm2. In the same nitrogen fertilizer levels, the winter wheat yield increased first, and then decreased with increasing the irrigation levels, where the maximum was achieved, when the irrigation level was 60 mm. The interaction effect between the type of controlled release fertilizer and the amount of irrigation/nitrogen application showed that: compared with the U treatment, with the increase of irrigation levels, the average yield of PCU60 increased by 308 kg/hm2, and PCU120 decreased by 270 kg/hm2; on the contrary, with the increase of nitrogen application rates, the average yield of PCU60 decreased by 289 kg/hm2, and PCU120 increased by 118 kg/hm2. According to the water and nitrogen production functions of three fertilizers, the yield-increasing effects of two controlled-release fertilizers were 14.31% (PCU120) and 12.08% (PCU60), respectively, under the water and nitrogen application when the U achieved the highest theoretical yield of 6823 kg/hm2. In a frequency analysis, the most appropriate ranges of water and nitrogen for different fertilizer types were: 67.20-70.22 mm and 145.42-187.91 kg/hm2 under the PCU60 fertilizer treatment; 47.72-52.28 mm and 159.23-199.47 kg/hm2 under the PCU120 fertilizer treatment; 77.51-79.99 mm and 167.55-207.45 kg/hm2 under the U treatment. The yield-increasing ranges were 7 647-7 719 kg/hm2 (PCU60), 7 744-7 906 kg/hm2 (PCU120), and 6 733-6 823 kg/hm2 (U) under the most appropriate ranges of water and nitrogen application for different fertilizer types, respectively. Therefore, it can be recommended that an optimal irrigation level (47.72-52.28 mm) and fertilizer application (PCU120, 159.23-199.47 kg/hm2) ranges can be considered as the best water and fertilizer management strategy for maximizing water-fertilizer productivity of winter wheat.