| The development of protected horticulture in China is very rapid,and the cultivation area increases year by year,forming different types of facilities,production models and technical systems with different regional characteristics,but the production of protected vegetables is mostly continuous cropping,the continuous cropping obstacle of vegetables in some old production areas is becoming more and more serious,which restricts the sustainable development of protected vegetable.Vermicompost has a good effect on improving soil environment,promoting vegetable growth,increasing yield and quality,and biochar has a porous structure on the surface.The effects of earthworms in situ replacing continuous cropping soil and biochar on soil remediation and plant growth under continuous cropping barrier were studied in this paper.The experiment was carried out on the soil of tomato variety "Fandeli"for 4 years:Factor 1 was root zone soil substitution,including:①non-replacement of continuous cropping soil as control soil;②in-situ replacement of continuous cropping soil by earthworms.Factor 2 was biochar,which included:①no biochar was applied;②biochar was applied at a rate of 1.5 t/hm2 in the top layer of soil;③biochar was applied at a rate of 3 t/hm2 in the top layer of soil;④biochar was fully mixed with 0～15 cm of soil and applied at a rate of 1.5t/hm2;⑤the biological carbon and 0～15cm soil layer were well mixed,the application rate was 3 t/hm2.10 processes.The results showed that:(1)Effects of earthworm-biochar in situ bioregulation on soil properties under continuous cropping in greenhouseIn-situ substitution of earthworms for continuous cropping soil significantly decreased soil pH and increased soil EC value of 0～15cm soil layer,the contents of total N,total P,total K,available N,available P,available K and organic matter in continuous cropping tomato soil were significantly increased by 722.86%,133.33%,54.25%,301.67%,1516.42%,400.79%,24.75 times,the application of biochar significantly increased the contents of total phosphorus(28.57%-45.23%),total potassium(10.73%-39.97%),available phosphorus(26.74%-316.5%)and available potassium(10.68%-128.25%)in continuous cropping tomato soil.In situ substitution of earthworms for continuous cropping soil significantly increased urease activity by 620.40%,invertase activity by 962.14%and Catalase activity by 431.03%in 0～15cm soil layers,the activity of sucrase was increased by 241.68%-365.97%and the activity of Catalase was increased by 203.45%.The earthworm-biochar synergy could promote the accumulation of medium elements and micronutrient s and Ca in 0～15cm soil layer,and significantly increase the content of micronutrient Fe and Cr.In-situ treatment with earthworms instead of continuous cropping soil can increase the diversity of soil bacterial community,and the application of biochar can decrease the diversity of soil bacterial community,in-situ application of biochar by earthworms instead of continuous cropping soil had the most obvious effect on the bacterial and fungal communities in continuous cropping soil.(2)Effects of earthworm-biochar in situ bioregulation on growth,quality and yield of tomato under continuous cropping in greenhouseThe relative growth rate of plant height was increased by 6.53%with earthworm in situ replacing continuous cropping soil,and 17.14%-18.78%with biochar,however,the relative growth rate of plant height and stem diameter decreased significantly by 6.12%and 37.23%when the earthworm was applied in situ instead of continuous cropping soil.The total root length,root surface area and root volume of tomato plants treated with earthworm in situ instead of continuous cropping soil decreased significantly by 44.53%,56.86%and 64.58%.The application of biochar was beneficial to the growth of the underground part of the continuous cropping tomato plant,but the growth of the aboveground part was slow,and the dry mass accumulation of the aboveground part and underground part of the tomato plant.The N,P and K contents of the plants were decreased by applying biochar on the surface of continuous cropping soil,but the nutrient contents of the plants were increased by adding 1.5 t/hm2 biochar,and the absorption of N,p and K by the plants was enhanced by using earthworm in situ instead of continuous cropping soil The application of biochar could’ promote the absorption and accumulation of medium elements s and MG in the aboveground and underground parts of the plant,and the in situ substitution of earthworms for continuous cropping soil could increase the content of S in the aboveground part of the plant by 76.73%,the contents of Ca and Mg were increased by 48.11%and 79.06%respectively.For micronutrient Al and Cu,biochar was more effective than surface biochar in increasing their accumulation in plants,and the content of Mn and CR in plants was significantly reduced by 22.58%and 5.88%respectively by in situ substitution of earthworm for continuous cropping soil.The content of vitamin C and soluble sugar in tomato fruit increased by 227.01%,133.76%,and the content of organic acid and nitrate decreased by 66.51%and 70.97%,respectively,the quality of tomato fruit is the best.The yield of tomato grown by earthworm in situ instead of continuous cropping soil was significantly increased by 160.52%,and the yield of tomato grown by earthworm in situ instead of continuous cropping soil mixed with 1.5 t/hm2 biochar was the highest,reaching 9377.62 kg/667m2,which was 248.37%higher than that of continuous cropping soil.(3)Through the principal component analysis of soil physical and chemical characteristics,nutrient content and tomato growth index,quality and yield index,the comprehensive score ranks,it was concluded that the treatment of earthworm in situ instead of applying 3 t/hm2 biochar under continuous cropping soil was the optimal treatment for comprehensive evaluation in this study,which provided a theoretical basis for adjusting continuous cropping obstacles of tomato in greenhouse. |
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