Effect of spring oilseed rape crop density on plant root biomass and soil enzymes activity

Abstract

A field experiment was carried out at the Experimental Station of the Aleksandras Stulginskis University in 2011 with the objective to establish the influence of spring oilseed rape (Brassica napus L.) crop density (50 100, 100 150, 150 200, 200 250, 250 300, 300 350, 350 400, 400 450 plants m 2) on plant root biomass and soil enzymes urease and saccharase activity. It was found that the highest plant root biomass in the 0 10 and 10 20 cm soil layers was formed at a plant density of 100 150 plants m 2. With rape crop density increasing from 150 to 450 plants m 2, a decreasing trend of plant root biomass in both soil layers was detected. Statistically significant dependencies were determined between the dry biomass of oilseed rape roots in the 0 10 cm soil layer and the content of potassium in the soil (r = 0.76, P < 0.05), and between the dry biomass of rape roots in the 10 20 cm soil layer and soil pH (r = 0.74, P < 0.05). With increasing rape crop density, compared with the thinnest crop, the activity of urease in the soil did not change significantly. At a rape crop density of more than 100 plants m 2 the activity of saccharase significantly increased (by 31 56%) in comparison with saccharase activity in the thinnest crop. The soil urease activity depended on the spring rape crop density (r = 0.81, P < 0.05) and the content of available phosphorus (r = 0.75, P < 0.05). The soil saccharase activity was influenced by the rape crop density (r = 0.79, P < 0.05) and soil pH (r = 0.72, P < 0.05).