Atributos físicos e químicos e desenvolvimento de soja transgênica sob sistemas de semeadura direta

Abstract

As soil alterations, that result from applied management, can influence negatively soybean crop development, it was done a work in Rhodic Hapludox (Oxisol), clay texture, with the aim of evaluating chemical and physical attributes in three direct sowing system, with different history of using on the development of transgenic soybean. The experiment was carried out at field conditions, in a rural property located in Ponta Pod, MS. Chemical and Physical attributes were determined in depths of 0-5; 5-10; 10-15; 15-20; 20-25 and 25-30 cm. Determined physical attributes were: soil densities, total porosity, clay disperse in water and flocculation degree, larger and smaller than two mm of diameter of aggregates, dried phase and penetration resistance. Evaluated chemical attributes were: pH in H2O, contents of exchangeable potassium, aluminum, calcium and magnesium, sum of bases, CTC, V% and total carbon determination. Soybean crop and yield, plant height, stand and length of roots were evaluated. It was also determined mulching and superficial biomass. Treatments consisted in direct sowing SDI (continuous crop), SD2 (nine years with pasture and 27 years with crop) and SD3 (19 years with pasture and 17 years with crop). For every system there was compaction, which reached 3.7 MPa, the highest in 15-20 layer in SDI, with water content in 24 kg kg-1 and 4.9 MPa when water content reduced to 21 kg kg-1. Even in those compaction values there was not damage on crop yield. Soybean yield correlated positively with studied chemical attributes, except to exchangeable acidity.