The influence of biological preparations and humus content on soil biological activity

Abstract

In 2014 and 2015 experimental years, in the soil with a regular humus layer there were established strong correlations between the number of earthworms and oilseed rape root length (in 2014 – r = 0.94, P<0.05; in 2015 – r=0.85, P<0.05), between the number of earthworms and root area (in 2014 – r=0.86, P<0.05; in 2015 – r=0.85, P<0.05). In 2014–2016, strong and very strong correlations were established between the number and mass of earthworms (in 2014– r=0.94, P<0.01; in 2015 – r=0.91, P<0.05, in 2016 – r=0.89, P<0.05). In the soil with a thickened humus layer, there were established strong and very strong correlations between saccharase activity and organic carbon content in the soil (in 2015 –r=0.97, P<0.01; in 2016 – r=0.87, P<0.05). Soil biological activity has been shown to be closely related to agricultural activities, various soil factors and climate. Scientists and farmers are looking for the methods to sustain and increase soil fertility for high and good quality agricultural production. The application of sustainable technologies and bio-preparations in agriculture could increase biological activity of the soil, which has been proved to be powerful indicator of soil quality. Field experiments were carried out in 2014–2016 at the Experimental Station of Aleksandras Stulginskis University (54°53' N, 23°50' E), Kaunas District, Lithuania. The aim of the research was to estimate the effects of bio-preparations and humus content on the soil biological activity using non-chemical weed control methods (thermal, mechanical and self-regulation) in organic spring rapeseed crop (Brassica napus L. spp. oleifera annua Metzg.) cultivated in soil with regular and thickened humus layers. Experiments showed, that the activity of soil enzymes urease and saccharase, number and mass of earthworms, CO2 emission from the soil depended on the meteorological conditions. In the soil of both humus layer types, the highest average number and mass of earthworms and the strongest activity of saccharase and urease were identified in the plots of self-regulation, compared with thermal and mechanical weed control. Positive effect of the bio-preparations on the abundance of earthworms and the activity of soil enzymes was established in the droughty year of 2015. The application of mechanical and thermal weed control methods without bio-preparations decreased CO2 emission from the soil, while their combination with bio-preparations increased it.