摘要：

合理减氮运筹是解决我国农田氮素损失量大、利用率低等问题的重要途径。为明确减少氮肥投入是否能维持油后密植棉花的产量。以洞庭湖区油后直播棉田为研究对象,比较2 a氮肥减量深施下棉花的产量、主茎叶光合特性、氮肥利用率等差异特征,分析氮肥减量深施的可行性,为油后直播棉田施肥管理措施的制定提供科学依据。于2018-2019年,在湖南省常德市湖南省棉花科学研究所茅湾基地开展了氮肥减量深施试验,设置了5个氮肥施用量处理(0,90,180,270,360 kg/hm²)和2个施肥深度处理(5,15 cm),于棉花主要生长时期取样测定了主茎功能叶净光合速率、可溶性糖及淀粉含量、地上部分植株生物量以及各部分NPK含量,研究氮肥减量深施处理对油后密植棉花的产量、光合特性、地上部分植株生物量、NPK积累与分配规律的影响。结果表明,随施氮量的增加,棉花中后期主茎功能叶净光合速率、可溶性糖和淀粉含量、以及棉株NPK累积量均呈先升后降的变化趋势,均在270 kg/hm²时最高;而氮肥表观利用率、农学利用率、偏生产力与生产效率则相反;另外,相同施氮量条件下,深施15 cm处理的各项指标均高于浅施5 cm处理。合理减少氮肥用量,并配合深施处理利于棉株营养器官和生殖器官生物量积累与平衡,以及氮、磷、钾吸收和分配,以促进产量与品质的提高。基于油后密植模式,推荐棉花以施氮量180~224 kg/hm²,施肥深度15 cm为宜。

关键词: 棉花, 氮肥用量, 施肥深度, 光合特性, 产量, 氮素利用效率

Abstract:

Appropriate reduction of nitrogen fertilization is an important way to deal with serious nitrogen loss and low fertilizer-nitrogen use efficiency in field ecosystem in China.However,it is unclear whether reducing nitrogen fertilizer input can maintain the yield of densely planted cotton after oil.Taking the post oil direct seeding cotton field in Dongting Lake area as the research object,compare the yield,photosynthetic characteristics of main stems and leaves,nitrogen use efficiency and other differential characteristics of cotton under two-year nitrogen fertilizer reduction and deep application,and analyze the feasibility of nitrogen fertilizer reduction and deep application,so as to provide a scientific basis for the formulation of fertilization management measures in direct seeding cotton fields after oiling.From 2018 to 2019,the deep application test of nitrogen fertilizer reduction was carried out in Maowan base of Hunan Institute of Cotton Science,Changde City,Hunan Province.Five nitrogen fertilizer application treatments(0,90,180,270,360 kg/ha)and two deep application treatments(5,15 cm)were set up.Samples were taken during the main growth period of cotton to measure the net photosynthetic rate,soluble sugar and starch content of functional leaves of main stems,the aboveground plant biomass and NPK content of each part.To study the effects of deep application of nitrogen fertilizer reduction on the yield,photosynthetic characteristics,aboveground plant biomass,NPK accumulation and distribution of densely planted cotton after oil.With the increase of N-fertilizer application rate,the Pn,soluble sugar and starch content of functional leaves of cotton main stem and the accumulation of NPK in cotton plant increased first and then decreased in the middle and late stages,all of which were the highest at 270 kg/ha;the apparent utilization rate of nitrogen fertilizer,agronomic utilization rate,partial productivity and production efficiency are opposite;in addition,under the same nitrogen application rate,the indicators of deep 15 cm treatment were higher than that of shallow 5 cm treatment.Reasonably reducing the amount of nitrogen fertilizer combined with deep application treatment is conducive to the accumulation and balance of biomass in vegetative and reproductive organs of cotton plants,as well as the absorption and distribution of nitrogen,phosphorus and potassium,so as to promote the improvement of yield and quality.Based on the dense planting mode after oiling,it is recommended that the amount of nitrogen applied to cotton should be 180-224 kg/ha and the depth of fertilization should be 15 cm.

Key words: Cotton, Nitrogen fertilizer, Fertilization depth, Photosynthetic characteristics, Yield, Nitrogen utilization efficiency