Urease is an enzyme that hydrolysis urea in carbon dioxide and ammonia. Urease distribution and influencing factors are highly relevant for the use of urea in agriculture. In this context, the purpose of this study was to verify the adequate time of soil sampling to measure urease activity, after N application to common bean as related to different soil tillage systems and cover plant species. The experiment was conducted on a dystrophic Dark Red Latosol where common bean cultivar Valente was planted on June 2005 in succession of four cover plants: mombassa grass (Panicum maximum cv. Mombassa), corn/brachiaria association (Brachiaria brizantha cv. Marandu), grain sorghum (Sorghum bicolor (L.) Moench), and stylosanthes (Stylosanthes guianensis cv. Mineirão). Two soil tillage methods were studied, direct sowing and conventional tillage. The experiment was arranged in a random block design in split-split-plots. Soil samples were collected 3, 6, 8, 10, and 12 days after urea application as topdressing. The highest activity of urease in soil occurred when common bean was grown after Panicum maximum, regardless of the tillage system and time of evaluation. Due to the degree of soil mobilization urease activity was lowest under no-tillage, irrespective of the cover crops and time of evaluation. Urease activity peaked between the seventh and eighth day after application, regardless of cover crops and soil tillage system under irrigated common bean.
biochemical properties; ureolitic profile; direct sowing system; conventional sowing system; soil plant cover
