膜下滴灌棉田土壤氮素变化特征及合理施氮量

通过2a田间滴灌试验,在6个不同施氮梯度水平下,研究施氮量与土壤无机氮储量、氮素盈余率的关系。结果表明,随着施肥量增加,土壤剖面60~100cm NO_3~--N质量分数显著增加,峰值达5.70mg/kg;土壤剖面0~100cm土层无机氮总储量在年际间呈累积增加趋势,并与施氮量的相关性随施肥期进程而增强。氮素养分平衡值与施氮量均呈指数函数变化规律,相关性强,显著高于其他氮素指标;氮素盈余率和施氮量的关系可以通过线性函数模型来拟合。选择优化施氮量,有利于降低棉田土壤无机氮的残留量,从而降低硝态氮向90cm以下土壤淋洗的风险。以棉花产量为指标,通过施氮量与氮素养分平衡值的关系得到的氮肥投入量为357.61~375.54kg/hm~2。综合考虑棉花高产和环境安全,南疆巴州棉区的合理施氮量为285.30~375.54kg/hm~2。

Variation Characteristics of Soil Nitrogen and Proper Nitrogen Rate in Cotton Field under Mulch-drip Irrigation

The field drip irrigation experiment designed 6 different nitrogen application levels was conducted in 2013-2014 to explore the relationship between nitrogen fertilizer and storage and surplus rate of soil nitrogen.With the increase of fertilization,the mass fraction of nitrate nitrogen (NO^-₃-N) in the soil profile ranged from 60 to 100 cm, and the peak value reached 5.70 mg/kg;the total soil inorganic nitrogen in the soil profiles from 0 to 100 cm increased with the accumulation of the range of the soil inorganic nitrogen, While, with the fertilization process, there was a correlation between the amount of fertilizer and the total soil inorganic nitrogen.N nutrient balance value and N application showed a variation of the exponential function, which were significantly higher than other nitrogen indicators; a strong correlation can be fitted for the relationship between the rate of surplus nitrogen and nitrogen fertilization.A linear platform was fitted for the relationship between nitrogen surplus rate and nitrogen fertilization rate.Optimized N fertilization helped reduce residue of cotton soil inorganic nitrogen and reducing the risk of nitrate leaching to below 90 cm soil.From the effect of N fertilization on cotton yield was simulated by nitrogen applied and nitrogen nutrient, the input rate of N fertilizer should be controlled at 357.61-375.54 kg/hm.Considering high cotton yield and environmental security, the input N fertilizer should be controlled at 285.30-375.54 kg/hm in Bazhou contton-planting area of southern Xinjiang.