氮肥用量对披碱草属牧草种子产量和氮肥利用效率的影响

Effects of nitrogen application rate on seed yield and nitrogen use efficiency of Elymus

氮素是禾本科植物生长和发育所必需的大量元素之一,但过量施用氮肥不仅造成环境污染,而且增加生产成本、降低收益。基于青藏高原地区披碱草属牧草种子需求量大、产量较低的现状,本研究以同德短芒披碱草、青牧1号老芒麦2个披碱草属牧草品种为试验材料,设置0、45、90、135、180和225 kg N·hm^(-2)等6个氮肥施用水平,研究分析了施氮量对披碱草属牧草种子生产和氮肥利用效率的影响,以期为披碱草属牧草种子生产提供理论依据。结果表明,施氮可促进披碱草属牧草生长,能够显著提高其株高、分蘖数等牧草营养生产性状,同时可提高种子产量及单位面积生殖枝数、每穗小穗数、每穗种子数和种子千粒重等产量组分;且随着施氮量的增加,各生长性能指标呈现先增加后降低或趋于稳定的变化趋势。随着施氮量的增加,除青牧1号老芒麦氮肥利用效率先增加后降低外,2个品种氮肥农学利用率和偏生产力逐渐降低。本研究中,同德短芒披碱草和青牧1号老芒麦的种子产量分别为712~1661 kg·hm^(-2)和701~1626 kg·hm^(-2)。从节约成本角度考虑,在川西北高寒地区开展披碱草属牧草种子生产适宜施氮量为135~180 kg·hm^(-2)。相关分析和通径分析的结果表明,种子产量组分中,单位面积生殖枝数和每穗种子数对种子产量的直接贡献较大。

Nitrogen is one of the crucial macroelements contributing to the growth and development of gramineous(poaceous)plants.However,excessive nitrogen application will result in environmental pollution,increased production costs and a decrease in profitability.Based on the strong demand and the low seed yield of Elymus in the Qinghai-Tibet Plateau area,this study investigated the seed yields of two Elymus species under six nitrogen fertilizer application rates.The cultivars investigated were Elymus breviaristatus cv.Tongde and Elymus sibiricus cv.Qingmu No.1.The six nitrogen application treatments in this study were 0,45,90,135,180 and 225 kg N·ha^(-1).The effects of nitrogen application on seed production and nitrogen use efficiency of Elymus were analyzed to provide reference data for seed production in Elymus.It was found that nitrogen application promoted the growth of both tested Elymus varieties.Forage vegetative growth was enhanced,including plant height,tillers per unit area,the seed yield and yield components such as fertile tillers per unit area,spikelets per ear,seeds per ear and 1000-seed weight.With increase in nitrogen application rate,the various yield indexes initially increased and then plateaued or decreased.As successive nitrogen increments were added,the agronomic use efficiency of E.sibiricus cv.Qingmu No.1 initially increased and then decreased,while the agronomic use efficiency and differential N response of both cultivars gradually decreased.In this study,E.breviaristatus cv.Tongde and E.sibiricus cv.Qingmu No.1 had seed yields of 712-1661 kg·ha^(-1)and 701-1626 kg·ha^(-1),respectively.In order to manage and reduce N fertilizer inputs,the recommended N fertilizer application rate was 135-180 kg·ha^(-1).Correlation analysis and pathway analysis showed that fertile tillers per unit area and seeds per ear contributed more to the increase of seed yield among seed yield components.