Foliar Micronutrient Levels in Cotton in Function of Underdoses and Application Epochs of Glyphosate.

The herbaceous cotton (Gossypium hirsutum L. var. Latifolium Hutch.) is among the major crops farm in Brazil by volume and value of production, being cultivated in more than 15 states. It is an agricultural activity recognized socioeconomic importance both for the occupation of hand labor, directly and indirectly in the countryside in the urban area, as in the production of manufactured responsible for generating income for the country (CORDÃO SOBRINHO et al. 2003). Is globally more than 40% of the garb of humanity. In Brazil, about 60% of textile inputs are from the cotton fiber and the United States this percentage rises to 65%.

Thus the present study aimed to evaluate the behavior of cotton with the use of glyphosate in underdosing associated with different application times. The experiment was conducted in Selvíria - MS in Experimental Farm, UNESP, Ilha Solteira, being installed in the experimental design in randomized blocks (GOMES, 2000), with 20 treatments and three replications, totaling 60 plots to test the factorial 4x5. The treatments consisted of four sub-doses of glyphosate, being: 0.0 (control); 52.0; 104.0; and 130.0 g ha-1 and five moments of application: 30, 40, 50, 60, 70 days after emergence for each dose.

Foliar micronutrient content in accordance with the rates and timing of application of glyphosate by collecting 20 leaves per experimental plot (the 5th leaf blade on the main stem), eighty days after emergence was evaluated according to the recommendations of Silva (1999), in order to verify the effect of the treatments studied in the concentration of nutrients.

Statistical analysis of data related to foliar micronutrient shows that there was no significant effect of application timing or even doses of glyphosate for Cu, Fe and Zn elements. Likewise, there was no significant interaction found between doses and times for all nutrients.

There was significant for foliar B as a function of doses of glyphosate effect. A linear reduction of foliar B. Therefore, as you increase the dose of glyphosate occurred.

Also significant for foliar Mn depending on the time of application of glyphosate effect was observed. Thus there was a curve in the concentrations of Mn in the leaf while the 50 and 60 days after emergence larger foliar nutrient levels were observed.