Effects Of PGRs On Physiological Characteristics,Production Performance And Cultivated Soil Of Continuous Cropping Alfalfae

In order to study the alleviating and the regulating effect of plant growth regulator on alfalfa continuous cropping obstacle,alfalfa variety Longmu 801（Medicago sativa L.Longmu No.801）was used as the tested material.At the branching stage,three kinds of PGRs(Uniconazole,S₃₃₀₇,Brassinolide,BR and Anti-hydrolyze Stablilized Ionic Titanium,ASIT)were foliar sprayed the non-continuous and continuous pot cropping alfalfa,then the morphology,biomass and physiological indexes were determined at squaring stage,aiming to select the appropriate concentrations for the three different PGRs.The non-continuous and continuous field cropping alfalfa were sprayed on the leaves in the same methods,the indexes of morphology,biomass accumulation,physiological characteristics,soil nutrients and soil microbial numbers were determined at squaring stage.The experimental results were as follows:1.Different S₃₃₀₇ concentrations（0mg·L-1（CK）,5 mg·L-1,10 mg·L-1,20 mg·L-1,40 mg L-1W/V）had different effects on the plant growth and the physiological indicators of non-continuous and continuous pot cropping alfalfa.At the concentration of 20 mg·L-1,the plants height were decreased,the root length,internode numbers,biomass,POD activity,SOD activity,proline content,soluble sugar content and chlorophyll content were increased,the MDA content was decreased.All the indexes were significantly better than CK treatment（P<0.05）.Therefore,the optimal concentration of S₃₃₀₇ was 20 mg·L-1.The non-continuous and continuous field cropping alfalfa were foliar sprayed with 20mg·L-1S₃₃₀₇,then the index of plants height were decreased,the root length,the fresh and dry weight of above ground and underground of continuous cropping alfalfa were increased,and the physiological indexes were improved.The contents of available phosphorus,available potassium and organic matter in 0-20 cm of continuous cropping soil were significantly higher than those of CK（P<0.05）,the content of available potassium in 20-40 cm of continuous cropping soil was significantly higher than that of CK（P<0.05）.There were no significant changes in p H value and soil microorganisms numbers（P>0.05）.2.Non-continuous and continuous pot cropping alfalfa were foliar sprayed with different BR concentrations（0 ‰（CK）,0.25 ‰,0.50 ‰,0.67 ‰ and 1 ‰ V/V）.When the BR concentration was 0.50 ‰,the plant height,root length,fresh and dry weight were increased;the POD activity,SOD activity,soluble sugar,proline and chlorophyll content of roots and leaves were significantly increased（P<0.05）,the MDA content was reduced.Therefore,the optimal concentration of BR was 0.50 ‰.Foliar sprayed with 0.50 ‰ BR on non-continuous and continuous field cropping alfalfa could promote the plant and root growth,could significantly promote the above ground fresh and dry weight of continuous cropping alfalfa（P<0.05）,but it had no significant effect on physiological indexes compared with CK（P>0.05）.The contents of available potassium and organic matter in 0-20 cm of continuous cropping soil were significantly higher than those of CK（P<0.05）,the content of available potassium in 20-40 cm of continuous cropping soil was significantly higher than that of CK（P<0.05）.There were no significant changes in p H value and soil microorganisms numbers（P>0.05）.3.Non-continuous and continuous pot cropping alfalfa were foliar sprayed with different ASIT concentrations（0（CK）,1400,1200,1000,800（diluted solution）V/V）.When the ASIT concentration was 1200,the plant height,root length,branches numbers,fresh and dry weight were significantly increased（P<0.05）;The antioxidant enzymes POD,SOD activity,soluble sugar,proline and chlorophyll content were increased,the MDA content was reduced.Therefore,the optimal concentration of ASIT was 1200 times.Foliar sprayed with 1200 times solution of ASIT on non-continuous and continuous field cropping alfalfa could promote plant height and root length,could significantly increase the above ground fresh and dry matter of continuous cropping alfalfa（P<0.05）,but it had no significant effect on underground dry weight（P>0.05）;other physiological indexes were significantly better than those of CK（P<0.05）except POD activity and SOD activity of continuous cropping alfalfa leaves.The contents of available potassium and organic matter in0-20 cm of continuous cropping soil were significantly higher than those of CK（P<0.05）,the available potassium in 20-40 cm of continuous cropping soil was significantly higher than that of CK（P<0.05）,but the p H was not changed;the number of bacterias in non-continuous cropping soil were significantly increased（P<0.05）,but there were no significantly changed in actinomycetes and fungi numbers（P>0.05）.In summary,the application of PGRs has positive regulatory effects in the continuous cropping alfalfa.The alfalfa grows well to resist continuous cropping stress.The appropriateconcentration of PGRs can achieve the desired regulatory effects.