Effects Of Rotation On Microbial Community Structure,Enzyme Activities And Nutrients In Soil Of Continuous Cropping Tomato

The continuous cropping of tomato is a common phenomenon,it has become the main reason to limit the high yield and quality and sustainable production of tomato.The cause of continuous cropping obstacle is complex,soil micro-ecological imbalance and self poisoning are the main reasons.At present,the main countermeasure is to change root exudates and regulate soil microbial environment through by different cropping patterns to alleviate continuous cropping obstacles.A large number of studies had showed that rotation can improve the micro-ecological environment of the soil,increase the number of bacteria,reduce the number of fungi,and alleviate the continuous cropping barrier in some extent.In this experiment,two crops of peanut and yellow okra were rotated in continuous cropping tomato soil for five years in Long-ji,an old town in Cheng-mai County,the suburbs of Hainan,the southernmost tip of China.This field experiment were treated with tomato continuous cropping(TTC),tomato and peanut rotation(TPR),tomato and yellow okra rotation(TOR)and Un treatment(UT).Soil bacterial and fungal community structure and abundance and functional were analysis,and the number of micro-organism and nutrient content and enzyme activity in the soil were measured to test the effect of rotated different crops on preventing of the continuous cropping obstacle of tomato,to provide reference for establish a reasonable rotation pattern.The main results are as follows:1.As to enzyme activities,rotation significantly increased the activity of catalase,urease,sucrase and phosphatase.The activity of catalase,sucrase,acid phosphatase and urease in TPR soil increased by 8%,27.99%,15.42%and 35.87%compare to TTC soil respectively;and the activity of the above four enzymes in TOR soil increased by 13.68%,18.36%,14.40%and 50.41%,compare to TTC soil respectively.2.At the same time,rotation also significantly increased the ability of soil to absorb alkaline hydrolysis nitrogen and organic matter contents,increased the contents of soil available P and available K.The alkali hydrolysable nitrogen,available phosphorus,available potassium and organic matter in TPR soil increased by 10.42%,51.41%,76.04%and 22.8%respectively compared with TTC soil,and increased by 19.38%,32.99%,141.33%and 16.3%respectively compared with TTC soil in TOR.3.The first 10 of the abundances Bacteria phylum are related to the carbon metabolism,cycle(Proteobacteria,Actinobacteria,Chloroflexi,Acidobacteria,Firmicutes),these phylum have different abundance in different soil treatments,which indicates that rotation can alter the composition and abundance of soil bacteria and thereby affect the physiological activities of carbon cycle.4.Rotation has a significantly effect on bacterial community structure,and the abundance of dominant populations in continuous cropping,rotation and un treatment soil has changed.Chloroflexi has the largest proportion in the soil of TTC,but Acidobacteria and Gemmatimonadetes occupy the largest proportion and the largest number in TPR and TOR soil,which indicates that the soil environment has changed under rotation.Among the bacterial genera with significant differences in the first 20 of the abundances,TTC contains higher abundance of the Defluviicoccus genus,which associated with glycogen synthesis.Roseiflexus genus shared in UT and TOR soil and TPR unique Bryobacter genus are related to carbon metabolism,TPR unique Nitrospira related to nitrogen cycle,indicating that rotation regulate the circulation of carbon and nitrogen by changing the composition and abundance of related bacterial genus,thereby affecting the growth of tomato.5.Rotation also changes the population structure of fungi in the soil.Among the first 20 fungi genera with significant differences,the abundance of some harmful fungi in continuous cropping soils is high,such as Penicillium and Aspergillus.Penicillium is a unique fungus in TTC,and the number of Aspergillus is the most in TTC soil,while the least in TPR、TOR soil.There are also a number of beneficial bacteria in experiment soils,such as Zopfiella and Sporobolomyces,which are resistant to crop resistance,and Humicola,which is related to cellulose decomposition,can produce a variety of resistant compounds,and Acremonium,Cladorrhinum,Chaetomium,which can inhibit the growth of pathogens.The abundance of these fungi in rotation is higher than that in continuous cropping soil.6.It show that the rotating of peanuts and okra are significantly increased the number of bacteria and actinomycetes,total soil micro-biomass and ratio of bacteria to fungus;however,the number of fungus are decreased.The number of bacteria in TPR and TOR can be increased by 44.47%and 85.46%more than that in TTC,and the number of cultured fungi is 17.66%and 42%less than that in TTC.It was indicated that rotation can effectively improved the micro-ecological environment of the soil by increasing the numbers of bacteria and reducing the numbers of fungi.The composition and abundance of soil bacteria and fungi had changed significantly under rotation.Rotation can enhance the resistance of the crop to the pathogen,improve the activity of the enzyme,enhance the utilization of soil nutrient that promote the growth of the crop by increasing the abundance of the beneficial bacteria and fungi;and reducing the abundance of the harmful bacteria and fungi.