油菜专用控释尿素用量对冬油菜产量和氮素吸收的影响

【目的】明确不同冬油菜种植区域油菜专用控释尿素用量对冬油菜产量和氮素吸收的影响,验证油菜专用控释尿素一次性施用的可行性和适宜用量,为指导冬油菜轻简化生产提供依据。【方法】于2015—2016年分别开展油菜专用控释尿素静水释放试验和田间埋袋养分释放以及控释尿素用量施用效果田间试验。油菜专用控释尿素用量试验布置于冬油菜3个主产地区——湖南衡阳、江西九江和湖北武穴。试验共设5个氮肥用量梯度,分别为0、60、120、180和240 kg N·hm~(-2),探究油菜专用控释尿素对不同区域冬油菜产量和氮素吸收的影响。【结果】田间埋袋试验结果表明,油菜专用控释尿素的缓释期在150 d左右,累积释放量为83.4%,与冬油菜氮素需求吻合。施用油菜专用控释尿素可以调控收获密度,增加冬油菜的单株角果数和每角粒数。与不施氮处理相比,单株角果数、每角粒数分别增加15.0—81.5角/株和0.2—2.4粒/角,收获密度随氮肥用量增加或降低协调群体与个体。3个产地的籽粒产量均在施氮量达到180 kg N·hm~(-2)时最高,分别较不施氮增产1 118、1 088和2 049 kg·hm~(-2)。用线性加平台模型拟合的最佳控释尿素用量,湖南衡阳、江西九江和湖北武穴分别为174、180和192 kg N·hm~(-2)。油菜专用控释尿素施用显著增加地上部生物量、氮素含量和氮素积累量。在成熟期时,随氮肥用量增加,茎秆中的氮素分配比例逐渐增加,籽粒中氮素积累分配比例减小,而角壳的氮素分配比例保持在10%左右。不同时期氮肥利用率存在差异,苗期最小,花期最大,成熟期居中,分别为19.20%—23.45%、50.69%—56.89%和39.39%—46.71%。苗期和花期的氮肥利用率随着施氮量的增加,出现先增加后降低的趋势,在控释尿素用量为180 kg N·hm~(-2)时达到最大;成熟期的氮肥利用率随着施氮量的增加呈降低趋势。【结论】油菜专用控释尿素一次性施用可以增加油菜各生育时期的氮素吸收、促进油菜生长发育,提高收获密度、单株角果数和每角粒数,增加油菜产量。不同冬油菜主产区所需专用控释尿素推荐用量差异不大,平均为180 kg N·hm~(-2)。

Effects of Different Special Controlled Release Urea Dosages on Yield and Nitrogen Uptake of Oilseed Rape

【Objective】This study investigated the effects of different dosage of special controlled release urea (CRU) on the yield and nitrogen (N) uptake of winter oilseed rape in different areas. Our aim was to evaluate the suitable rate of the special CRU for oilseed rape and provide the basis for guiding light simplification of oilseed rape production.【Method】Field experiments were conducted in Hengyang (Hunan Province), Jiujiang (Jiangxi Province), and Wuxue (Hubei Province) during the period of 2015-2016, investigating nutrient release and fertilization effects of the special CRU. Each site included 5 nitrogen application rates being 0, 60, 120, 180 and 240 kg N·hm^-2, respectively.【Result】Field bagging experiment showed that the release time of special CRU was about 150 days, with the accumulative release amount of 83.4%, which coincided with the N demand of oilseed rape. The application of special CRU could control the harvest density of winter rapeseed, increasing the number of pods per plant and seed number per pod. Compared with no N treatment, the number of pods per plant and seed number per pod increased 15.0-81.5 pods per plant and 0.2-2.4 seeds per pod, respectively. Harvest density changed the coordination group and individual with N fertilizer variation. Oilseed rape production performed the highest grain yield when applying 180 kg N·hm^-2 among the sites, which increased by 1 118 and 1 088 and 2 049 kg·hm^-2, Compared with the without N treatment, respectively. By fitted with linear and platform model, optimal special CRU dosages were 174, 180 and 192 kg N·hm^-2 in Hengyang, Jiujiang and Wuxue, respectively. The biomass, N concentration and N accumulation of aboveground biomass were significantly increased with the application of the special CRU. With the increase of N application rate, the proportion of N in the stem was raised gradually, and the proportion and distribution of N in the seed decreased, while the ratio of N distribution in the shell kept about 10%. The nitrogen use efficiency (NUE) was different in different periods. The NUE was 50.69%-56.89% at flowering period, 39.39%-46.71% at harvested period, and only 9.20%-23.45% at seedling stage, respectively. At seedling and flowering stages, the NUE showed increase first and then decrease with N application rate increase, reaching the maximum when the amount of the special CRU dosage was 180 kg N·hm^-2. However, at harvest stage, the NUE reduced with the increase amount of nitrogen application. 【Conclusion】The special CRU for winter oilseed rape could improve N uptake and promote the growth and development of rape in each growth period, especially in regulating the harvesting density, increasing the pod number per plant and seed number per pod, and eventually enhancing the rapeseed yield. The recommended amount of special CRU was 180 kg N·hm^-2 among the sites.