陇东黄土高原混播草地牧草叶片N、P、K重吸收及生态化学计量特征

Leaf N, P and K resorption and stoichiometry of forages in the legume-grass mixture in the loess plateau of east Gansu

以紫花苜蓿和无芒雀麦为主建立单、混播栽培草地,研究叶片N、P、K重吸收及生态化学计量特征,揭示陇东黄土高原雨养农区栽培草地N、P、K养分限制及循环利用策略,为栽培草地的合理建植、施肥管理提供理论指导.结果表明:不同牧草配比草地中紫花苜蓿和无芒雀麦叶片养分重吸收效率均为N>P>K.无芒雀麦N、P、K重吸收效率显著高于紫花苜蓿.单、混播下紫花苜蓿养分重吸收效率差异不显著,混播下无芒雀麦养分重吸收效率低于单播.不同牧草配比草地中,紫花苜蓿趋于w(N)∶w(P)>16∶1,无芒雀麦w(N)∶w(P)<14∶1,表明紫花苜蓿与无芒雀麦的生长分别受P、N限制,二者生长均不受K限制.因此,混播草地牧草叶片养分重吸收受混播种类搭配和比例的影响,其中P重吸收效率和混播比例关系最为密切.

A mixture involving alfalfa(Medicago sativa) and smooth bromegrass(Bromus inermis) was established in the loess plateau of east Gansu to study leaf N, P and K resorption and stoichiometry, and to reveal the nutrient limitations and recycling strategy of N, P and K in the cultivated grasslands in this area, thus providing theoretical instructions for cultivated grassland establishment and fertilization management. Leaf nutrient resorption efficiency of alfalfa and smooth brome grass under different combinations and sowing ratios showed the same pattern as N resorption efficiency > P resorption efficiency > K resorption efficiency. Leaf N, P and K resorption efficiencies of smooth brome grass were significantly higher than those of alfalfa. There was no significant difference in leaf nutrient resorption efficiency of alfalfa between mixture and monoculture, but for smooth brome grass, it was higher under monoculture.Leaf w(N)∶w(P) of alfalfa tended to be >16∶1 and that of smooth brome grass <14∶1, which implied that the growth of alfalfa was primarily limited by soil P and that of smooth brome grass by soil N. Conclusively, leaf resorption efficiency in these mixtures significantly varied with species combination and sowing ratio. There was a significantly close relationship between P resorption efficiency and sowing ratio.