[Temporal-spatial variations of root and soil nutrient under continuous intercropping of alfalfa and oat].

We investigated root and soil nutrient characteristics in the monoculture and continuous alfalfa/oat intercropping in the high-yield years by using soil filling and frame planting method in the field, and analyzed the relationship between root systems and soil nutrients. The results showed that intercropping reduced root weight and total root length proportion of oat in the 0-10 cm soil layer compared with the monoculture. However, intercropping significantly increased root weight and root surface area of oat in the 20-30 cm soil layer, root length and root density of alfalfa in the 10-20 cm soil layer, and the contents of available phosphorus and organic matter of the alfalfa/oat intercropping system in the 0-40 cm soil layer. As the planting years increased, total root length, root weight, root surface area, and proportion of root weight and root length of alfalfa in the 0-20 cm soil layer gradually increased in the intercropping system, and the root weight, total root length, root surface area, and root average diameter of oat increased, especially the root weight and root surface area of oat in the 20-30 cm soil layer. Moreover, the content of available nutrients in all soil layers decreased subsequently. In the alfalfa/oat intercropping system, continuous intercropping could significantly increase total root length of alfalfa in the 10-20 cm soil layer, improve root weight and root surface area of oat in the 20-40 cm soil layer (especially in the 20-30 cm soil layer). With the increases of planting years, intercropping intensified the absorption and competition of available nutrients by the roots of alfalfa and oat in the 0-40 cm soil layer, thereby reduced the accumulation of available nutrients in the soil.本试验采用田间框栽土培法,以紫花苜蓿单作和燕麦单作为参照,对紫花苜蓿和燕麦连续间作下不同时空根系特征、土壤养分特性以及高产年份中根系变化与土壤养分内在联系进行分析。结果表明: 与单作相比,间作降低了燕麦0～10 cm土层内的根重和总根长占比,显著提高了燕麦在20～30 cm土层内的根重和根表面积,显著增加了紫花苜蓿在10～20 cm土层内的根长和根长密度,并大幅度提高了间作系统中0～40 cm土层内的有效磷和有机质含量。随着种植年限的增长,间作下紫花苜蓿总根长、根重、根表面积及其在0～20 cm土层内的根重和根长占比均逐渐增加,燕麦根重、总根长、根表面积和根平均直径明显提高,尤其是20～30 cm土层内燕麦的根重和根表面积,而各土层速效养分含量降低。因此,在紫花苜蓿与燕麦间作体系内,连续间作可促进紫花苜蓿10～20 cm土层内总根长显著增加,有效改善燕麦20～40 cm土层(尤其20～30 cm土层)内根重和根表面积;且随着种植年份的增长,间作使紫花苜蓿与燕麦根系对0～40 cm土层内速效养分的吸收和竞争加剧,从而降低了速效养分在土壤中的累积。.