Paul, Sankar Ch.Kumar, Ajeet2017-02-252017-02-252016-07http://krishikosh.egranth.ac.in/handle/1/5810002552Nutrient recycling is now being considered as part of the concept of integrated nutrient management. The fertilizer potential of vermicompost is often attributed to its different concentrations and amounts of nutrients, especially nitrogen. Therefore, a dissertation work was taken at Department of Soil Science and Agricultural Chemistry, Bihar Agricultural University, Sabour to study the Effect of vermicompost application on nitrogen dynamics in soil. So, pot experiment has been taken under two different sets: (a) N transformation under the effect of root rhizosphere and (b) through laboratory incubation study. Treatments were T1 = control, T2 = chemical fertilizer (N:P:K :: 80:40:40), T3 = 2250 mg vermicompost kg-1 soil, T4 = 4500 mg vermicompost kg-1 soil, T5 = 9000 mg vermicompost kg-1 soil, T6 = 18000 mg vermicompost kg-1 soil. Results showed that vermicompost of water hyacinth and coconut leaf showed almost similar pH and EC values. CEC value for both vermicompost were 74.20 and 72.60 cmol(+)kg-1. Organic carbon content in water hyacinth vermicompost was 23.1% and in coconut leaf vermicompost 22.5%. Water holding capacity was much higher. Available form of N, P, K, S, Zn, Cu, Mn and Fe found very less content with respect to total content except K and Na content in both types of vermicompost. Available part was more pronounced in water hyacinth vermicompost. Microbial population accounted higher in water hyacinth vermicompost than coconut leaf vermicompost. Water hyacinth vermicompost also contains higher values of dehydrogenase activity, microbial biomass carbon content and urease enzyme activity. Results represented that water hyacinth vermicompost is better in quality than coconut vermicompost with respect to microbial properties. Under greenhouse study with cauliflower at different levels of vermicompost resulted maximum release of available N at 10th day in T6 which was 49.38% over control followed by T5, T4, T2, T3 and T1. But changes of its content in soil through incubation study over the period showed maximum release at different dates under different treatments. Available nitrogen content increased slowly and reached to peak at 40th day and 50th day that may be due to addition of organic substrate through vermicompost which leads to the maximum activity of microbes. Ammonium N content changes in soil is quite similar to the available nitrogen in greenhouse study. But in incubation study changes is differ. Nitrate nitrogen content changes quite dissimilar to the ammonium content. Nitrate content increased slowly and reached to maximum at 40th day after addition of vermicompost in both experiment. N content in cauliflower whole plant significantly and positively correlated (r = 0.88**) to soil available nitrogen content. Average content of soil available nitrogen was significantly and positively correlated to N content in curd (r = 0.94**) and plant dry matter weight (r = 0.98**).From this study, it may be inferred that vermicomposts produced from different biomass substrate are different in quality with respect to nutrient contents and microbial properties. Ten days prior application of vermicompost can provide maximum support of nitrogen to the plant which can maximize nitrogen use efficiency for crop production.ennullThesis