紫花苜蓿与3种多年生禾草混播草地的土壤养分特征

Nutrient characteristics of soil sowed with different combinations of alfalfa and three perennial grasses

为了探究紫花苜蓿(Medicago sativa)与不同禾草混播草地的土壤养分分布与积累规律,将紫花苜蓿与无芒雀麦(Bromus inermis)、草地早熟禾(Poa pratensis)、苇状羊茅(Festuca arundinacea)均分别按1∶2、1∶1和2∶1比例进行同行混播,研究混播组合和混播比例对0–20 cm和20–40 cm土层土壤养分特征的影响。结果表明,1)较苜蓿单播,紫花苜蓿与3种多年生禾草混播对浅层(0–20 cm)土壤有机质、速效钾、碱解氮、速效磷、全磷的积累有显著的促进作用(P<0.05)。2)3种混播组合中,紫花苜蓿+无芒雀麦改善土壤肥力的效果优于其他两种混播组合。0–40 cm土层紫花苜蓿+无芒雀麦更有利于土壤有机质、氮素、磷素养分的积累,而紫花苜蓿+草地早熟禾混播对于钾素的积累效果更明显。3)混播比例的变化对浅层的速效磷、全磷,深层土壤有机质、碱解氮影响显著(P<0.05),增加苜蓿的比例,土壤养分含量增加。3种混播比例中,0–20 cm土层紫花苜蓿+无芒雀麦配比处理1∶1和20–40 cm土层紫花苜蓿+无芒雀麦配比处理2∶1较其他两个比例混播更有利于速效养分的积累;0–20 cm和20–40 cm土层紫花苜蓿+草地早熟禾配比处理1∶2土壤速效钾、全钾含量最高,2∶1土壤碱解氮、全氮、全磷含量最高,而紫花苜蓿+苇状羊茅配比处理2∶1土壤有机质、全氮、全磷、全钾和速效养分含量均高于其他两个比例混播。4)空间分布上,随着土层加深,除草地早熟禾单播和紫花苜蓿+苇状羊茅配比处理土壤全钾出现深层高于浅层现象外,其余所有混播处理土壤养分含量均为浅层高于深层,呈现养分表聚性现象。

We evaluated the nutrient characteristics of soil sowed with different combinations of alfalfa and three grasses,namely,Bromus inermis,bluegrass,and tall fescues at ratios of 1∶1,1∶2,and 2∶1.The effects of different combinations and ratios on soil nutrients in the 0–20 cm and 20–40 cm soil layers were evaluated.The results revealed the following.1)The combination of alfalfa and three perennial grasses can significantly promote the accumulation of soil organic matter,available potassium,soil hydrolysis nitrogen,soil available phosphorus,and total phosphorus(P<0.05).2)Alfalfa+B.inermis was better than the other two combinations in improving soil fertility.The combination of alfalfa+B.inermis was more conducive to the accumulation of soil organic matter,nitrogen,and phosphorus nutrients in the 0–40 cm soil layer,whereas the effect of alfalfa+bluegrass in improving potassium accumulation was more obvious.3)The ratio of alfalfa and the grasses had a significant effect on available phosphorus,total phosphorus,deep soil organic matter,and hydrolysis nitrogen in the shallow soil layer(P<0.05).The soil nutrient content increased with an increase in alfalfa proportion.Among the three ratios,the 1∶1 ratio of alfalfa+B.inermis in the 0–20 cm soil layer and the 2∶1 ratio of alfalfa+B.inermis in the 20–40 cm soil layer were more conducive to the accumulation of available nutrients.In the 0–20 and 20–40 cm soil layers sowed with alfalfa+bluegrass at a ratio of 1∶2,soil available potassium and total potassium content was the highest,and at the ratio of 2∶1,the content of soil available nitrogen,total nitrogen,and total phosphorus was the highest.The content of organic matter,total nitrogen,total phosphorus,total potassium,and available nutrients in the 0–20 and 20–40 cm layers of soil sowed with alfalfa and reed fescue at 2∶1 ratio was higher than that at the other two ratios.4)In terms of spatial distribution,except for single sowing of bluegrass and combination alfalfa+tall fescue,under all other combinations,the shallow soil nutrient content was higher than that in deep soil,showing a phenomenon of nutrient surface cohesion.