The Effect Of Earthworms On Carbon And Nitrogen Decomposition During Composting Of Maize Straw

The yield of straw in China is increasing,but most of the straw is discarded,which cannot form good economic benefits.In order to solve the pollutional problem of agricultural waste and make carbon and nitrogen metabolism beneficial to agriculture.The paper combines the vermicomposting to study the carbon and nitrogen metabolish and analyzes the effect of earthworms on carbon and nitrogen degradation.In this study,natural air-dried corn straw and rotten cow dung were used as substrates,four different experimental groups were mixed according to different proportions,and four different quantities of earthworms were inoculated with each proportionate substrate.,and the total weight of the substrate was 1 Kg.The experiment lasted 56 d.The sampling interval was 7 d,physicochemical properties and enzyme activities related to carbon and nitrogen metabolism in the samples were determined.Some greenhouse gases related to carbon and nitrogen metabolism during the stacking process were analyzed.Mathematical models of changes of organic carbon and total nitrogen were established.The main results were as follows:?1?The pH values of the all four groups A?B?C and D decreased firstly,then increased and later decreased,then rose to the stabilized state finally,the pH values of group D4 decreased to 7.43 on 56 d.The electrical conductivity of the four groups increased,especially in the experimental group inoculated with earthworms.The changes of organic carbon and total nitrogen in the experimental group inoculated with earthworms were more obvious than groups uninoculated earthworm.At the end of 56 d stacking,the carbon-nitrogen ratio of the B4?C3?C4?D3 and D4 groups fell below 20.The degradation rates of cellulose?hemicellulose and lignin in groups A?B?C and D showed an increasing trend,and the degradation rates in groups inoculated with earthworms were higher than groups uninoculated with earthworms.Ammonium nitrogen and nitrate nitrogen are two different substances in the process of nitrogen metabolism.In the early stage of composting,ammonium nitrogen had a slightly upward trend,and in the middle and late stages,ammonium nitrogen declined rapidly,while nitrate nitrogen had been in a increasing trend.In the late stage of composting,both kinds of nitrogen were in a stable state,there were greater changes in ammonium nitrogen and nitrate nitrogen in the group inoculated with earthworms.?2?The key enzymes in carbon metabolism are?-glucosidase and xylanase.?-glucosidase showed the change trend of rising and then stable,while xylanase showed a trend of first rising,then declining and stabilizing finally.The enzyme activities of inoculated earthworm groups were higher.Nitrate reductase is a key enzyme in nitrogen metabolism.The activity of nitrate reductase in the groups inoculated with earthworms was higher than the groups uninoculated with earthworms.Earthworms can affect the activity of nitrate reductase.?3?Methane and carbon dioxide were the greenhouse gases produced by carbon metabolism in the composting process.The methane emission of the groups inoculated with earthworms decreased significantly,and earthworms affected methane emissions.Earthworms had no significant effect on carbon dioxide emissions.Nitrous oxide is a greenhouse gas produced in the process of nitrogen metabolism,and the groups inoculated with earthworms had a less gases emissions.?4?Through the experimental results of high-throughput sequencing,it could be seen that the most abundant abundance of bacterial communities was the C3 group of 21 d,the highest bacterial richness was the C3 group of 21 d;the most abundant diversity of fungal communities was the C1 group of 21 d,the highest fungal richness was the C1 group of 21d.The Planomicrobium and the Devosia were dominant flora in the bacteria,and the Aspergillus and Penicillium were dominant flora in the Fungi.Earthworms could affect the relative abundance of different population communities.?5?The functional relationships of organic carbon change K₁ with time change?X?and the number of earthworm change?Y?were established.Functional relationships of total nitrogen change K₂ with time change?X?and the number of earthworm change?Y?.The relationships between the change of carbon-nitrogen ratio K₃ and the change of time?X?and the change of the number of earthworm?Y?were established.