紫色土区3种草本植物根系特征及改土培肥效应

摘要

In order to explore the effects of herb roots on soil physical properties and soil nutrients,alfalfa (Medicago sativa ),Bermuda grass (Cynodon dactylon )and vetiver grass (Vetiveria zizanioides ),planted for three years,were used for these experiments.Taking bare plots as a contrast,soil and root samples from 0-10 cm,10-20 cm and 20-30 cm soil layers were collected.Then the WinRHIZO (Pro.2004c)root analy-sis system was used to measure root parameters and conventional methods were used to measure soil physical and chemical properties.In all three soil layers,vetiver grass root parameters were excellent,especially root length density and root surface area density,for these two traits the maxima averaged 13.46 cm/cm3 and 5.75 cm2/cm3 ,respectively.Overall,root weight density (RWD)of alfalfa was the greatest,with a minimum aver-age of 18.10 mg/cm3 .None of the three herbs had any significant effects on soil physical properties 3 years af-ter planting,but data for the herb plots showed that the proportion of sand particles had decreased and the pro-portion of finer particles (silt and clay)had increased,compared to bare CK plots.Most herbs had significant effects on soil organic matter and available potassium in most soil layers,with content of organic matter in-creasing and content of available potassium decreasing.However,the herbs had almost no effect on soil total nitrogen,alkali-hydrolyzable nitrogen,total phosphorous,available phosphorous and total potassium.The to-tal potassium contents of all herb plots (3.93-4.83 g/kg)were higher than the bare plots,but the available potassium levels of all herb plots were low,especially in alfalfa.The maximum deficient number was 20.24 mg/kg.All soil nutrients had significant correlations (P <0.05)with all or some of the root parameters,and the maximum correlation coefficient was 0.833,for the relationship between organic matter and RWD.%为探讨紫色土区草本植物根系的改土培肥效应，选取已种植3年（2011－2013年）的水土保持常用草类紫花苜蓿、狗牙根和香根草为目标物种，分0～10 cm，10～20 cm，20～30 cm 土层采集根系和土壤样品，WinRHIZO （Pro．2004c）根系分析系统测定根系指标，常规方法测定土壤理化性质。结果表明：所有土层，香根草的各项根系指标均较优，尤其是根长密度和根表面积密度（最大均值分别为13．46 cm／cm3和5．75 cm2／cm3），紫花苜蓿则总体上的根重密度最好（最小均值为18．10 mg／cm3）；定植3年，这3种草本植物并未对试验区紫色土的机械组成产生显著影响，但在数值上草本区有粗颗粒减少、细颗粒增多的趋势；多数草本植物对多个土层的土壤有机质和速效钾产生显著影响（有机质增加，速效钾亏损），而对土壤全氮、碱解氮、总磷、有效磷和全钾的影响却很微弱；所有草本区的全钾含量较高3．93～4．83 g／kg，却在几乎所有土层出现速效钾的亏损，尤其是紫花苜蓿区最大亏损量达20．24 mg／kg；相关分析中，所有土壤养分与全部或部分根系指标呈现显著或极显著相关（最大相关系数为0．833）。