Search

The root exudates produced by sorghum contain a biologically active constituent known as sorgoleone. The behavior of sorgoleone in a Red-Yellow Latosol was studied. The sorption model of sorgoleone in soil was better adjusted to the Freundlich equation, through the coefficients Kf (capacity of sorption) and 1/n (linearity of the isotherm). The persistence of sorgoleone in soil and its possible degradation were also evaluated by monitoring their residues in the soil along the time. Recovery rate of sorgoleone from the soil reached 93% after 24h. It was verified that sorgoleone is strongly sorbed in the soil and its half-life is 10 days, under the experimental conditions. The presence of sorgoleone or its metabolites was not detected in the soil after 60 days.

Rice and bean plants were grown in nutrient solution in the presence of three levels of N, P and K. The method of the bioevaluation of the nutricional status, in which excised roots are allowed to take up tagged elements, in this case 15N and 32P, was compared with foliar analysis. Two main conclusions were drawn: 1) the bioevaluation proved to be an useful and rapid procedure for the diagnosis of the nutricional status of both species, since there was a significant negative correlation between absorption of N and P and dry matter yield; 2) the uptake of the tagged ions with either element by the roots of plants grown under deficient levels of N and P in the nutrient solution was inversely proportional to the leaf concentration of both nutrients.