摘要
采用分室装置 ,利用不同孔径的膜研究大豆连作条件下 ,化感物质、土壤有害生物和大豆胞囊线虫等因素不断累加对植株生长、生物固氮作用和矿质养分吸收和分配的影响。结果表明 ,随着各因素不断累加 ,植株的地上部、根系和根瘤干重逐渐降低 ;除 Ca元素外 ,植株组织的 P、K等矿质元素单位含量下降 ,吸收总量下降 ,地上部分配的养分比例下降。在化感物质和土壤有害生物因素的基础上接种线虫 ,对生物固氮和矿质养分的吸收和分配影响明显。
Growth of citrus,apple and other fruit trees in replant woodlands may be significantly reduced due to a replant problem and now it has occurred in intensive cropping systems as well.Soybean is a main crop in the north-east part of China.When soybean is cropped continuously in the same field for years,the yield would be reduced by 10%~30% or more.The phenomenon is called soybean continuous cropping problem(SCCP).For easy management,farmers would rather plant soybean year after year than rotate with maize,or other crops.The area with continuous cropping problem is about 700 000 hm+2 only in the east part of the north-east China.Much work on the problem has been done in China since 1980s.However,the main reason why continuous cropping system causes growth problem remains unclear.Nematode,deleterious organism and allelopathic substances are now three factors under consideration,but which factor is the most important?An experiment was designed to answer the question.The experiment was conducted in a greenhouse,in the campus of China Agricultural University,Beijing,China.A specific growth device was designed for the experiment.The device had two compartments,an outer and an inner cylinder in which soybean was planted.The outer cylinder was a Wargernel pot,and the inner one was a PVC tube(90mm×300mm)sealed completely at the bottom with a plastic sheet.Two windows(85mm×190mm)were made in opposite positions in the inner cylinder.These windows were covered either by plastic sheet(0μm),nylon net(30μm),or mixed cellulose ester membrane(Millipore <0.22μm),which limited plant root growth in the inner compartment.There were 2 kg sterilized sandy soil placed in inner compartment,and 6.75kg black soil filled in outer compartment.Water was added to the water inlet of the Wargernel pot in three treatments in order to carry some substances in soil of outer compartment into inner one and its effect on the plant growth was examined.Water was applied directly to the top of the inner pots in the control.Two soils were used in the experiment.The first soil,a Haphic Pheanozems(black soil)based on FAO-UNESCO classification,in which plant growth was seriously inhibitied,was collected from a field where soybean had been cropped continuously for wo years in Dancheng,Shuangcheng County,Heilongjiang Province,China.The second soil,a sandy soil,was sampled from Daxing County,Beijing.The sandy soil was autoclaved at 121℃ for 2h and then enough micronutrients and macronutrients were supplied to the sandy soil.Four treatments were prepared as follwows:for the membrane treatment,the windows were covered by a mixed cellulose ester membrane(0.22μm),which only allowed first soil solutions to pass through but not the soil bacteria or fungi in the first soil:for the nylon treatment,the windows of inner cylinder were covered by nylon net(30μm),which permitted soil microbes to cross beside the soil solutions; for the third treatment,based on the nylon treatment,the suspension of SCN eggs was inoculated into inner compartment; in control,the windows were covered by plastic sheet(0μm)in order to separate completely the inner compartment from the outer one.Each treatment was replicated for 7 times. In the experiment,four soybean seeds(Hefeng 25,a susceptible cultivar to SCN race 3)were sowed per pot,inoculated with Bradyrhizobiom japoncium 911 at the level 2×108 cell pot+{-1}(provided by Department of Microbiology,China Agricultural University)and SCN at the level 2×105 egg pot+{-1}.Six weeks after sowing,soybean seedlings were harvested.Total root length,nodule number,cyst number,and the dry weight of roots,shoots and nodules were noted.P,K,Ca,Mg,Fe,Cu,Zn,and B contents in roots,shoots and nodules were also measured with ICP (PE OPTIMA 3300).Several ceresin slides of nodule tissue for light microscopic observation were made.All data were analyzed with SAS(SAS,1988).Means were compared using LSD at P≤0.05 probability level. The results showed that the dry weight of soybean root and shoot and the number of nodules were significantly depressed in the treat.
出处
《生态学报》
CAS
CSCD
北大核心
2003年第1期22-29,共8页
Acta Ecologica Sinica
基金
国家重点基础规划研究资助项目 ( G1 9990 1 1 70 9)
国家自然基金资助项目 ( 39870 4 88)~~
关键词
连作障碍因素
大豆
养分吸收
固氮作用
影响
胞囊线虫
化感作用
soybean continuous cropping problem
allelopathy
soybean cyst nematode (Heterodea glycines)
soybean(Glycine max L.)
