| China possesses the largest area of vegetable cultivation in the world.However,the problems of continuous cropping and pests become the important factors of restricting sustainable production because of highly intensive cultivation.The determinations indicate that the disinfection of the continuous cropping soil and the addition of beneficial microorganisms can effectively control soil pests and overcome the continuous cropping obstacles,but the non-target microorganisms in the soil are influenced.The study aims to reconstruct the continuous soil by means of Bacillus subtilis and Bacillus subtilis combined with 1,3-D soil disinfection and build a more excellent micro-ecological environment,which can overcome continuous cropping obstacles and promote the formation of a continuous self-repair ecological system.Effects of Bacillus subtilis and Bacillus subtilis combined with1,3-D soil disinfection on the root-knot nematode and the growth of tomato were evaluated by field test.Meanwhile,Effects of Bacillus subtilis and Bacillus subtilis combined with 1,3-D soil disinfection on the number of cultured microbes and the activity of soil enzyme were studied by traditional methods.Effects of Bacillus subtilis and Bacillus subtilis combined with1,3-D soil disinfection on the abundance of bacteria and ammoxidation microbial communities were investigated by qPCR.The work above could support its pesticide registration in China as a substitute for methyl bromide.Moreover,it can provide scientific basis for its safe and rational application in the facilities vegetables.In addition,it could provide a theoretical basis for overcoming the soil continuous cropping obstacles and safeguarding sustainable production of facilities vegetables.The main findings are as follows:(1)The results show that 1,3-D has an obvious effect on root-knot nematodes,but the effect of Bacillus subtilis on root-knot nematode is not obvious.The addition of Bacillus subtilis to the soil treated with 1,3-D fumigation has a certain role in promoting the growth of tomato plants,and the height and yield of the plants are increased apparently.The large and medium fruit of the samples treated by Bacillus subtilis combined with 1,3-D fumigation are 12.75 and61.27 t/ha,and the samples show the highest yield-increasing efficiency(33.55%).(2)The addition of Bacillus subtilis to the soil treated with 1,3-D fumigation significantly accelerates the recovery of urease and protease activity,and it show a certain activation effect on promoting soil enzyme activity.It is found that the treatment not only increases the number of culturable bacteria,but also is beneficial to the colonization of Bacillus subtilis(2.86×10~5CFU/g at 16 WAT).(3)The results of qPCR show that the number of total bacteria and the abundance of AOB and AOA genes in tomato continuous cropping soils are 0.85×10~9~1.61×10~9,1.78×10~6~5.01×10~6 and 0.88×10~7~2.83×10~7 copies/g soil.It can be found that AOA is greater than AOB by an order of magnitude.The addition of Bacillus subtilis to the soil treated with 1,3-D fumigation significantly increases the gene abundance of total bacteria and AOB,but has little effect on AOA gene abundance.(4)The correlation analysis shows that there is a significantly positive correlation between nitrate nitrogen and AOB at pH=6.85~7.15,while nitrate and ammonium nitrogen were negatively correlated with AOA,which indicates that the increase of nitrogen fertilizer input in agricultural land reduces the abundance of AOA-amoA gene,but improves the abundance of AOB-amoA gene.There is a significant correlation between pH and the abundance of ammonia microbial gene,soil urease activity,the number of culturable bacteria and the content of nitrate.In general,pH is the key factor for soil microbial gene abundance,soil nutrient composition and soil enzyme activity. |
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