| The mode of legume-cereal intercropping is one of the most common combination.Preceding researches had paid more attention to the efficient use of resources such as light,heat and water,and the changes of root which included the absorption and conversion of nitrogen,phosphorus and potassium.At present,the research emphases of intercropping is transferring to the rhizospheric biological characteristics.Because intercropping has very important significance on solving the use of limited land resources,food shortage caused by overgrowth of relative population and pollution of ecological environment.The researches of rhizosphere micro-ecology had been the focal point by scientists,increasingly.This study through the design of three separate treatments:no barrier(NB.There was interaction in roots of maize and soybean.),mesh barrier(MB.There was no direct interaction in roots of maize and soybean,but the rhizosphere moisture and nutrients could pass each other.),polythene film barrier(PB.Roots without interaction.)and Monoculture researched the interspecific interaction characteristics of soybean/maize rhizosphere micro-ecology.The objective of this study was measuring the growth of maize and soybean in the process of photosynthesis,SPAD value and determination of the production,and the physiological and biochemical of rhizosphere and soil enzyme activity,and the rhizosphere soil microbial diversity through the techniques of BIOLOG and T-RFLP.The main results were as follows:experiment mainly obtained the following results:1.Under the optimized ratio of maize/soybean intercropping crop plant line to line(2:3)determined in pre-experiments,land equivalent ratios,LER were 1.39,1.13 and 0.98 under the three rhizosphere blocked treatments,i.e.,no barrier,NB,mesh barrier,MB and polythene film barrier,PB between the two crop plant rhizspheres in the intercropping system.This finding suggested that Interspecific root interaction has obvious effect on intercropping system productivity.Further analysis showed that compared with Monoculture,net photosynthetic rate of soybean and maize in NB significantly increased by 20.49%and 22.72%,respectively.Relative chlorophyll contents obviously increased by 9.65%and 10.36%.The yields of soybean and maize had enhanced by 39.15%and 61.02%,respectively.Thus inferred that there was interspecific facilitation on intercropped maize and soybean.2.In the treatment of NB,available nitrogen(N)of soybean and maize obviously improved by 6.22%and 5.10%over Monoculture,and available phosphorus(P)significantly enhanced by 96.18%in the maize.Acid phosphatase,relating with P deficiency,increased significantly.And soil acid phosphatase activity in the rhizosphere of soybean and maize obviously increased by 18.25%and 21.00%,respectively.In conclusion,the roots interacting of two crops had improved the nutrient conditions of rhizosphere and soil enzyme activities;mainly led to optimizing the soil fertility conditions.3.The diversity and activity of soybean and maize rhizosphere microbial improved obviously in NB and MB treatments.Meanwhile,the results of rhizosphere microorganism by BIOLOG showed that,utilization rate of related substrates in the plate changed by rhizosphere microorganism in different treatments.Comparing with Monoculture,utilization of amine substance by soybean and maize rhizosphere microorganism in NB significantly increased by 169.65%and 10.18%.All of these results showed that the interactions between roots of the two crops system which included that secretion from roots of communication promoted the intercropping soybean and maize rhizosphere microorganism diversity and activity.4.Through the analysis on the results of T-RFs fragments:comparing to PB,Proteobacteria of soybean and maize rhizosphere microorganism in NB had reduced obviously by 31.40%and 27.78%,and the proportion of gram positive bacteria of Firmicutes significantly increased by 106.95%and 51.95%,and Actinobacteria,obviously enhanced by 17.46%and 71.34%.So the interactions of the intercropping had inhibiting effects on Proteobacteria,but promoted gram positive bacteria of Firmicutes and Actinobacteria,which affected the structure and composition of rhizosphere microflora.Overall,intercropping cultivation of soybean and maize had effects of promoting each other.The mechanism would be due to full contact on underground part of two crops and the exchanges of root secretion,which improved the nutrients,physical and chemical property of rhizosphere soil and the structure and composition of rhizosphere microorganism. |
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