Cobalt and molybdenum soybean seeds enrichment

Abstract

The application of cobalt (Co) and molybdenum (Mo) directly to soybean seeds is a common practice in Brazil. However, this technique has limitations, causing phytotoxicity, interfering with iron absorption by the roots, reducing the population of the nitrogen-fixing Bradyrhizobium bacteria in seeds and increasing a step in the pre-planting. One way around these limitations would be to use seeds enriched with Co and Mo, via soil and via foliar feeding. However, there is lack of research regarding the increase of Co content in soybean seeds; the enrichment potential of Mo has already been studied. Our intention in this project is to determine the soybean enrichment viability with Co and Mo in order to directly benefit farmers and seed producers. Two tests shall be performed simultaneously, one in field conditions and another under greenhouse conditions. In the greenhouse experiment, plants of two soybean varieties are grown in pots containing a 3 dm³ sample of sandy soil. The following treatments, in g ha-1, will be applied, via soil and via foliar feeding, Co + Mo: 0 + 800, 10 + 800, 20 + 800 and 30 + 800, in the R5.4 development stage, and a control without Co + Mo. The field experiment will be applied to only one of these genotypes and treatments with Co + Mo will be identical to the previous ones, applied only via leaf. The following factors will be evaluated: 1) Co and Mo content in the soil; 2) foliar analysis: Co and Mo contents (and other nutrients) in the leaves; 3) measurement of chlorophyll and flavonoids in the leaves; 4) production of dry matter in roots and shoots; 5) Co and Mo (and other nutrients) levels and accumulation in the roots, shoots and seeds; 6) germination; 7) electrical conductivity test for evaluation of seed vigor and 8) productivity. The results obtained in the greenhouse for each soybean genotype, will be analyzed using a randomized block design, factorial (4x2 + 1), with three replications, totaling 9 treatments for soybean genotype and 54 elements. For the field experiment, the design will be a randomized block design with five treatment and four replications. The effects of Co application on the potential enrichment of seeds in Co and Mo, applied via soil and via foliar feeding, will be evaluated by regression analysis and simple and multiple correlation. (AU)