Efetuou-se revisão de literatura sobre diversos aspectos ligados à produção e consumo da soja. Abordou-se a importância nutricional da soja, comparando-a com outros alimentos de forma a evidenciar suas vantagens e desvantagens. São mostradas as funções das isoflavonas na fisiologia da planta, como o efeito protetor contra insetos e estimulante da fixação biológica de nitrogênio. São reportados os efeitos da soja no organismo humano, evidenciando seu potencial na redução dos riscos de diversas doenças crônicas e degenerativas e caracterizando-a como alimento funcional. Abordouse também o cultivo da soja em sistema orgânico de modo a situar a inserção da soja nesse contexto. As informações coletadas evidenciaram que o consumo humano da soja e de produtos orgânicos, entre os quais a soja, deve manter crescimento devido maior conhecimento de seus benefícios à saúde. PALAVRAS-CHAVE: Glycine max (L.) Merrill; ISOFLAVONAS; PRODUÇÃO ORGÂNICA; ALIMENTOS FUNCIONAIS.

Weed control has always been an important issue in agriculture. With the advent of no-till systems, soil erosion was reduced but herbicide use was increased. Organic no-till systems try to adjust reduced erosion to the no use of herbicides. Nevertheless, this adjustment is limited by the cost of mechanical weed control. This cost may be reduced by improved cultural weed control with cover crops mulches. In this paper we report a study on the application of compost manure on an oats winter cover crop, preceding soybean, instead of on the soybean summer crop. Treatments comprised a control without compost manure, and compost manure doses of 4 and 8 Mg ha-1 applied either on oats in winter or soybean in summer, organized in a randomized block design, with five replications. In summer, plots were split into weed-controlled or not controlled subplots. The timing of application and the manure doses did not affect the oats biomass or the soybean performance. However, in summer, without water stress, the application of manure at 8 Mg ha-1 directly on soybean has reduced weed biomass in this crop.

The common bean (Phaseolus vulgaris L.) is an important species for human nutrition in Brazil and its cultivation has been hampered in recent years by the interference of sourgrass [Digitaria insularis (L.) Mez ex Ekman] populations. However, just a few studies evaluated sourgrass interaction with common beans. Therefore, we aimed to evaluate the influence of sourgrass density on common bean agronomic characteristics. Seven sourgrass densities, equivalent to populations from 0 to 12 plants m-², were established in a common bean crop field with a randomized block design and four replicates. The increase in sourgrass density boosted weed dry matter and the common bean plant’s height and leaf area index. Contrarily, the same increase in weed density reduced the crop chlorophyll content, stem diameter, shoot, root and total dry mass, and grain yield. The variables’ behavior testifies to the high sensitivity of the common bean to sourgrass interference reported by farmers. Variables such as common bean chlorophyll, stem diameter, and the shoot and root dry mass presented a strong negative correlation to the reduction in crop grain yield. The decrease in yield reached 69% with 12 sourgrass plants m-2 when compared to control. The density of 3.7 weed plants m-2 reduced the maximum common bean grain yield by half. Such significant results suggest the need for developing efficient sourgrass management methods and strategies to avoid common bean yield loss.

In soybean production in Brazil, the ends often justify the means. The high marketing prices of grains have motivated producers to adopt new techniques for cultivation of the legume in an empirical way or without adequate scientific support. Thus, we hypothesized that soybean cross-sowing in equal populations or twice (as used in conventional sowing in parallel rows) may increase soybean yield and decrease weed infestation in crops. In this study, we aimed to evaluate the spatial arrangements of plants associated with the presence or absence of chemical treatment for weed control in the soybean crop. A randomized block design was used with five treatments (four replicates per treatment): 1) uncrossed with the recommended plant population; 2) crossed with the recommended plant population; 3) crossed with double the plant population; 4) crossed with the same plant population and without herbicide; and 5) crossed with double the plant population and without herbicide. Soybeans cross-sowed with the recommended plant population had the same growth as uncrossed soybeans in terms of height and dry matter of shoot and roots, but had a higher leaf area index. Moreover, root nodulation increased in number with soybeans cross-sowed with the recommended plant population and in mass for soybeans cross-sowed with double the plant population, without differences in indirect measures of chlorophyll. Thus, our findings suggested that crosssowing with the recommended plant population or double the recommended plant population did not aid in weed control and did not increase the yield of soybean grains. Highlighted Conclusion Soybean cross-sowing with the recommended or double the recommended plant population does not aid in weed control or increase soybean grain yields.