Abstract: The root-growth rhythm of four leguminous forage species in immature loess subsoil was studied by root-tube soil column culture methods.Results indicated that the root growth index of four legume species followed an "S"-shaped growth model(classified as slow-increased period,rapid-increased period and peak period).Root biomass had no sharp decrease with root aging death during a one-year growth period.Vertical distribution of roots had significant difference for all tested legume species.The dry biomass of root showed "T"-shaped distribution model for vertical depth and root biomass followed an index mode of decreasing successive reduction(Y=A·e^-bx).The root and shoot growth model of four leguminous forage species typified the following four categories: synchronous growth type of root and seeding(crown vetch),permanent growth type of seeding strength(sweet clove),persistent growth type of root strength(alfalfa),growth type of weak seed and root(red clover).The root-growth climax of legumes appeared in a subsequent growth period and later than canopy.This study supplied a theoretical basis for developing a sound technical system of high yield and promoting coordinated growth of seedling and root system of leguminous forage in immature loess subsoil.

Key words: Immature loess subsoil, Leguminous forage, Root biomass, Root distribution, Growth model of root and shoot

摘要： 以黄土母质生土为供试土壤,采用根管土柱栽培方法,研究了苜蓿(Medicago sativa L.)、草木樨(Melilotus officinalis Desr.)、小冠花(Coronilla buxifolia Hance.)和红三叶(Trifolium pratense L.)4种豆科牧草根系生长规律的差异。结果表明:4种豆科牧草根系各项指标的增长随生育期变化(时间构型)皆呈"S"型增长模型,可划分为缓增期、速增期和顶峰期,在一个生长季内,根系不存在衰老死亡生物量急剧减少的现象;4种豆科牧草根系垂直分布存在很大差异,根系生物量空间呈"T"型分布,其垂直递减率符合指数递减方程Y=A·e^-bx;4种豆科牧草根冠生长模式分属于4类:根苗增长同步型(小冠花)、苗强持久增长型(草木樨)、根强持久增长型(苜蓿)和苗弱根弱增长型(红三叶草),豆科牧草根系峰值常出现在生育后期晚于冠层。本研究结果对建立黄土母质生土上牧草高产栽培技术体系以及促进根苗系统的协调生长提供了依据。

关键词: 黄土母质生土, 豆科牧草, 根系生物量, 根系分布, 根冠生长模式