Soybean Seed Enrichment with Cobalt and Molybdenum as an Alternative to Conventional Seed Treatment.

Biological nitrogen fixation in soybean is enhanced when seed is treated with cobalt (Co) and molybdenum (Mo) prior to planting. In this study, our objective was to verify if Co and Mo application during the reproductive phase of the crop increases seed Co and Mo concentration without adverse effects on seed quality. Two experiments were conducted. First, we investigated foliar and soil Co and Mo application under greenhouse conditions. Next, we validated the results obtained in the first study. The treatments for both experiments consisted of Co doses combined with Mo, and a control without Co and Mo application. The foliar application was more efficient in producing enriched Co and Mo seed; meanwhile, as Co doses increased so did Co and Mo concentrations in the seed. There were no adverse effects on nutrition, development, quality, and yield of parent plants and seed when these micronutrients were applied. The seed showed higher germination, vigor, and uniformity for the development of soybean seedlings. We concluded that the application of 20 g ha-1 Co and 800 g ha-1 Mo via foliar application at the reproductive stage of soybean increased germination rate and achieved the best growth and vigor index of enriched seed.

Improving the quality of organic compost of sewage sludge using grass cultivation followed by composting.

Composting is one of the main processes of stabilization of sewage sludge and its association with cultivation in this residue has a great potential to produce stabilized organic fertilizer and, or substrate for plant development. The aim of this work was to evaluate the physical, chemical, and microbial attributes of sewage sludge (SS) aerated and cultivated with Pennisetum purpureum or Urochloa brizantha and, later, composted. The study was installed in a 2x2+2 factorial scheme, with four replications. The factors consisted of cultivation of P. purpureum or U. brizantha in SS for 90 days, with or without intermittent aeration for 60 days. The control treatments were SS without cultivation, with the presence or absence of aeration. After 90 days of cultivation, the grass was cut, crushed, and incorporated into the SS for composting for 60 days. The composted sewage sludge showed an increase of 26, 24, 17, 123, 19, 32, and 7.7% in the levels of P, Ca, Cu, Fe, Mn, Zn, and Pb; and a reduction of 22, 5.2, 26, 30, 8.8, and 70% in the levels of C, N, K, Mg, Ni, and Na, respectively. The levels of Cu, Ni, Zn, and Pb remained below the maximum limit allowed by environmental resolution. The degradation of SS decreased the particle diameter, increasing the bulk density and total porosity, improving the physical properties of the compost. The SS cultivation and composting, regardless of the grass, led to a reduction in pH, basal and accumulated respiration, nitrification index, and C/N ratio and an increase in the CEC/C ratio, showing adequate maturation of the compost produced. Thus, the SS cultivation and composting with grasses were effective for producing matured and quality organic compost with low risk of environmental contamination.