沼液不同氮素水平对狼尾草产量、质量、氮素利用率和土壤剖面硝态氮分布的影响

Yield, Quality and N Utilization Efficiency of Pennisetum and Nitrate-N Distribution in Soil Profile as Influenced by Different N Levels of Biogas Slurry

采用田间试验,研究了不同氮素水平的沼液（设N0～N6共7个氮素水平,即每次浇灌折纯氮0、5、10、20、40、80、160kg·hm^-2,每45d刈割周期浇灌3次）对＂闽牧6号＂狼尾草产量、质量、氮素利用效率和土壤剖面全氮及硝态氮含量的影响。结果表明,＂闽牧6号＂狼尾草3个刈割期和全年干草产量均随着沼液氮素浓度的增加而增加,其中N6处理全年干草总产量达27.51 t·hm^-2,显著高于N0～N5处理（P〈0.05）。植株硝酸盐含量、全氮含量和牧草粗蛋白产量也随着沼液氮素水平的提高呈上升的趋势,牧草刈割期的硝酸盐含量为355.1～572.5 mg·kg^-1,均低于牧草畜牧利用的有毒限量指标0.25%,牧草粗蛋白产量最高达2459 kg·hm^-2（N6处理）。对全年牧草生产的氮素利用率、氮素生理利用率、粗蛋白生产效率、氮素农学生产效率、氮素偏生产力等5个氮素利用效率指标分析可知,随着沼液中氮素水平的提高,氮素利用效率逐渐降低。牧草地全氮含量和硝态氮含量随着沼液氮素水平的增加而增加,不同土层间（0～60cm）随着土层深度的增加而降低。土壤硝态氮含量的增加,表明高氮量的沼液可能增加土壤硝态氮淋失的风险。

A field trial was conducted to study the effects of different N levels of biogas slurry on yield, quality, and N utilization efficiency of P.americanum×P.purpureum CV. Minmu 6, and the distributions of total-N and nitrate-N in soil profile. Biogas slurry was applied at 0, 5,10, 20, 40, 80 kg N·hm^-2and 160 kg N·hm^-2of nitrogen equivalent for three times during each cutting period（45 days）. Pennisetum hay yields increased with increasing N levels. The annual hay yield was the highest in the treatment with 160 kg N·hm^-2 or 27.51 t·hm^-2biogas slurry, significantly higher than that in the other treatments（P〈0.05）. Plant nitrate contents, total N contents and forage protein yields also increased with increasing amount of nitrogen applied. The concentrations of plant nitrate were 355.1～572.5 mg·kg^-1during three forage harvesting, lower than the toxic nitrate limit of 0.25%. The maximum crude protein yield was 2459 kg·hm^-2at the highest biogas slurry rate. Nitrogen utilization efficiency decreased with increased rates of biogas slurry nitrogen. Soil total-N and nitrate-N increased as biogas slurry nitrogen rates increased, but decreased with soil depth in 0 cm to 60 cm soil profile. Elevated nitrate-N in soil implies that applying biogas slurry of high nitrogen content may increase the risk of nitrate leaching.