Effects Of Earthworms From South China On The Fertility Characteristics In Lateritic Red Soil And Growth On Laboratory Conditions

In recent years,the problem of soil degradation is becoming more and more serious.How to repair and improve the degraded soil at a low cost and effectively is one of the important research directions in current academic circles.As ecosystem engineer,earthworm plays a positive role in soil impact and improvement.To explore how to affect soil and the growth and reproduction characteristics of native species of earthworms is the premise of constructing earthworm-biological system to repair degraded soil.The changes of biomass and quantity of Pontoscolex corethrurus and Amynthas robustus in red soil mixed with different organic materials（cattle manure and mushroom compost）during 0-90 days were studied under laboratory conditions.And discussed the effects of two kinds of earthworms on the physicochemical properties,enzyme activities and microbiological characteristics of red soil.In this study,the effect of earthworms on soil physicochemical properties and microbiological characteristics of mixed organic materials was closely related to the species of organic materials and the difference between earthworms.The results are shown as follows:（1）In the culture period,under the conditions of 5%cattle manure+95%soil and 5%mushroom compost+95%soil,the biomass of two kinds of earthworms were all higher than 0%+100%soil treatment.The addition of organic materials helped earthworms to grow better.The Pontoscolex corethrurus grew best in the soil with 5%cattle manure,while the Amynthas robustus grew best in the soil with 5%mushroom compost.In the condition of 5%cattle manure+95%soil,the number of the Pontoscolex corethrurus increased in 30 days.But Amynthas robustus no sign of reproduction was found.（2）The effects of earthworms on the physicochemical properties of red soil were closely related to the addition of organic materials,the species of organic materials and the difference between earthworms.After 90 days of culture,earthworm activity increased soil p H in soils without organic materials.The contents of soil organic carbon,total nitrogen and total phosphorus were positively correlated.The Pontoscolex corethrurus increased the contents of 1.28 g·kg^-1,0.16 g·kg^-1and 0.03 g·kg^-1,and the Amynthas robustus reduced contents of organic carbon and total nitrogen 2.06 g·kg^-1and 0.17 g·kg^-1,respectively,in the soil without adding organic materials.The activities of earthworms in the soil with cattle manure reduced the contents of all three,but increased the content of all three in soil with mushroom compost.In the soil without organic materials,adding cattle manure and mushroom compost,the soluble organic carbon content of the Pontoscolex corethrurus decreased by 84.85%,72.04%and 85.71%,respectively,while that of the Amynthas robustus decreased by 87.88%,87.10%and 93.23%,respectively.In the soil without organic materials,the Pontoscolex corethrurus increased the content of soil alkalytic nitrogen and available phosphorus by 39.29%and 66.63%,respectively.（3）The effects of earthworms on the microbiological characteristics of red soil were closely related to the addition of organic materials,the species of organic materials and the difference between earthworms.（a）In the soil without organic materials,compared with the control group,the soil microbial biomass carbon of the Pontoscolex corethrurus and the Amynthas robustus increased by 117.2%and 120.7%respectively,the basal respiration and metabolic entropy of soil were decreased by 19.6%,50.3%,62.6%and 78%,and Microbial entropy increased by 109.8%and 135.2%.Compared with the control group,the catalase activity of the two species was decreased by 39.1%and 21.7%,respectively.The activities of soil urease and acid phosphatase were increased by Pontoscolex corethrurus,but decreased by Amynthas robustus.（b）In the soil with cattle manure,compared with the control group,the soil microbial biomass carbon and nitrogen in the treatment of add the Pontoscolex corethrurus and the Amynthas robustus were significantly reduced by 51.7%,85.7%,63.4%and 88.3%,soil basic respiration and microbial entropy decreased by 71.3%,74.3%,47.4%and 83.7%,respectively.Compared with the control group,the treatment with earthworm reduced the catalase significantly.The invertase in the treatment of the Amynthas robustus were increased by 160.9%.The activity of urease was decreased by earthworm inoculation,and was decreased 66.1%by the Pontoscolex corethrurus.（c）In the treatment of soil with mushroom compost,compared with the control,the soil microbial biomass carbon of the Pontoscolex corethrurus and the Amynthas robustus were reduced by36.0%and 92.5%respectively.Soil basic respiration and microbial entropy decreased by76.5%,77.6%,48.3%and 93.1%.Compared with the control group,the catalase levels of the two species were reduced by 30.6%and 33.9%.Both invertase and urease were increased,the soil invertase was increased by 70.3%in the treatment with Pontoscolex corethrurus and the urease was increased by 153.2%in the treatment of the Amynthas robustus.Therefore,earthworms can significantly affect the chemical and biological characteristics of red soil mixed with organic materials,and the growth and reproduction conditions are different under different substrates.The activities of earthworms in red soil with high organic carbon content can accelerate the decomposition and release of organic carbon.Activities in red soils with low organic carbon content contribute to the storage of soil organic carbon.Earthworm activity can be used as an effective biological resource in soil remediation because it can improve soil physical and chemical properties and soil microbiology.However,the effects of earthworms on soil physical and chemical properties are closely related to the ecological types of earthworms and local soil characteristics.Therefore,it is necessary to according to different soil characteristics screen earthworm species and add suitable organics.