Root Discrimination in a Soybean/Ruzigrass Cropping System.

The growth of ruzigrass (Brachiaria ruziziensis) as a cover crop during the spring can influence the summer crop root system development in no-till system. The objective of this research was to quantify soybeans root system using the stable isotope concentration of the ¹³C, in conventinal till and no-till systems with ruzigrass as cover crop. The experiment was carried out during the growing season 2011/2012 at São Paulo State University, Brazil. The experiment consisted in three cropping systems: soybeans under conventional till, soybeans under no-till after ruzigrass and fallow after ruzigrass. The root systems were sampled at 0-10 and 10-20 cm depth using a  soil probe at 30, 60, 90 and 120 days after the soybeans sowing (DASS). Throughout the root density values (root dry mass per sampled soil volume) and ¹³C/¹²C ratio of each cropping system, discrimination of soybean root stock from ruzigrass root stock in the no-till system was possible. And it also allowed the comparison of soybeans root development in convential till and no-till system. The highest root system density was observed at 90 DASS in all three treatments. The use of ruzigrass as a cover crop had negative effect  in soybeans root stock at 10-20 cm at 60 DASS.