The increase in conservation tillage offers possibles benefits of decreasing soil compaction risk by wheeling. The objective this work was to evaluate the effect of the minimum tillage and direct drilling system after four and eight yars of continuous no-tillaging, on the soybean yield in function of the soil density and organic matter content. This trial was carried out on Oxisol, at Parana, subtropical region from Brazil. The relationship between yield of soybean and tillage system was analyzed as function of the soil density and organic carbon using linear regression model. No-tillage system four years (NT4) and minimum cultivation system in eight years of no tillage (MT8) showed greater decrease in soil density on the surface layer as a function of time, respectively, 0.22g cm-3 (1.318-1.098) and 0.24 g cm-3 (1.248-1.010). Adjust of response curves of soybean yield as function of soil density and organic matter describes strong positive contribution of organic carbon in soybean productivite on the NT4 system and describes no interference of soil density on this system. In both systems (NT8 and MT8), the soybean yield decreases with increasing soil density. Soil sub-surface management after continuous periods of no-tillage should be investigated.

A garantia de sementes com elevado vigor e boa qualidade é fundamental para o sucesso de qualquer cultura. Sementes com baixo vigor podem apresentar dificuldades na germinação e emergência em campo, sob condições não favoráveis, como a falta de umidade ou baixas temperaturas. Portanto, os produtores, na tentativa de reduzir custos de produção, têm separado grãos da safra produzida para serem utilizados como sementes e isso tem sido cada vez mais frequente. Assim, este trabalho teve como objetivo avaliar o potencial fisiológico de sementes de soja Roundup Ready com sementes convencionais, e comparar sementes "salvas", produzidas por um produtor com sementes comerciais. As sementes foram caracterizadas em laboratório (pureza, massa de mil sementes e teor de água), submetidas a testes de vigor (envelhecimento acelerado, teste de frio e condutividade elétrica), teste de germinação, emergência em areia, índice de velocidade de emergência, crescimento de plântulas, comprimento de raízes e parte aérea das plântulas e matéria fresca e seca. Foi possível identificar maior pureza nas sementes comerciais do que nas sementes "salvas". Os lotes das cultivares convencionais apresentaram potencial fisiológico superior às cultivares de soja Roundup Ready, porém, entre as sementes "salvas" e comerciais não houve diferença quanto ao vigor.Palavras-chave: germinação, pureza, sistema de produção, teste de vigor. A B S T R A C TThe guarantee of seeds with high vigor and good quality is the most important characteristic for the success in soybean cropping. Seeds with low vigor may show some difficulty on germination and field emergence, mainly under adverse conditions, such as moisture deficiency or low temperatures. Thus, this study aimed at evaluating the physiological potential of Roundup Ready (RR) and conventional soybean seeds, 'saved' by a farmer as well as commercial seeds. Nevertheless, some farmers, in an attempt to reduce production costs, have already separated cropped grains produced to be used as seeds and it has been increasingly common. So, this trial aimed at evaluating the physiological potential of Roundup Ready soybean seeds with conventional seeds, and compare the 'saved' seeds, produced by a farmer with commercial seeds. The seeds were characterized in the laboratory (purity, mass of thousand seeds and moisture content). Vigor (accelerated aging, cold test and electrical conductivity test), germination test, emergence on sand, emergence speed index, seedling growth, roots and shoots length of seedlings as well as fresh and dry matter were determined. It was possible to identify that the commercial seeds showed higher purity when compared to the saved ones. Plots of conventional cultivars showed higher physiological potential, and there was no difference concerning the vigor between the 'saved' seeds and commercial ones.

No abstract

No abstract