Interaction Ghyphosate and ZINC On Soybean Plants Cultivated In Tropical SOIL.

Soybean is a main grain crop for Brazil, and zinc (Zn) plays an important role in improving its yield in Brazilian Oxisols, which represent 50% of the actual cropland. The use of Glyphosate-Resistant Soybean (RR) has increased together with nutritional deficiency of Zn. This is because the Glyphosate inhibits the biosynthesis of aromatic amino acids, such as tryptophan precursor of indole acetic acid (IAA) which needs Zn for its synthesis. Limited information is available regarding the influence of Zn and Ghyphosate application on soybean yield and its nutritional status in tropical conditions. The objective of this study was to determine the effects of the interaction Glyphosate and Zn in soybean plants. The experiment was conducted in a greenhouse using pots of 3.0 kg of capacity. The soil used was a Xanthic Ferralsol (Red Yellow Latosol) with 1.4 mg kg^-1 of Zn available (DTPA-TEA) and 620 g kg^-1 of clay. The experimental design consisted in a randomized complete block with four replicates. The treatments consisted of 0, 5, 10, 20 and 40 mg kg^-1 of Zn (source ZnSO₄x7H₂O), and two soybean parental cultivars non-transgenic and transgenic [BRS 133 and BRS 245-RR (with and without Glyphosate – Roundup Ready^® application)]. Glyphosate was sprayed at a rate of 540 g a.e.ha^-1 to 50% of the plants (BRS 245-RR) with Zn rates at stages V₃ and V₆. The Ghyphosate application significantly influenced the soybean yield and Zn concentration. The increase in grain yield and Zn concentration in the leaves were 27.1% and 4.1%, respectively at BRS 245-RR without Glyphosate compared to the treatment with herbicide application. Zn rates significantly increased grain yield. Based on regression analysis, the maximum grain yield was achieved at 12.3 mg kg^-1 of Zn (BRS 133, yield = 36.4 g pot^-1), 37.1 mg kg^-1 of Zn (BRS 245-RR without Glyphosate application, 29.7 g pot^-1), and 20.3 mg kg^-1 of Zn (BRS 245-RR with Ghyphosate application, 26.8 g pot^-1).