Fertilization of Tanzania Guineagrass with Silicon Rates.

The toxicity of aluminum (Al) in plants is a problem for agriculture in acid soils. In the literature it is reported that the addition of silicon (Si) minimizes the toxicity of Al. The aim of this study was to study Si rates (0, 25, 50, 75 and 100 mg dm^-3 - sodium silicate) under Al toxicity conditions (22.3 mmol_c dm^-3) in the soil for Tanzanian guineagrass (Panicum maximum cv. Tanzania) in three harvests (10/24/2016, 11/19/2016 and 12/15/2016), in Dourados, MS, Brazil (22^o 12' S, 54^o 49' W and 430 m). The experiment was carried out under greenhouse conditions and the pots contained 4.5 dm³ of soil. Silicon rates were applied at a single time 15 days before seedling transplanting, so that it could react with the soil and neutralize Al. It was applied 300 mg dm^-3 of nitrogen (ammonium sulphate), 150 mg dm^-3 of potassium (potassium chloride) and 200 mg dm^-3 of phosphorus (single superphosphate). The experimental design was a randomized complete block with four replications. The dry matter yield (DMY) was quantified for the three harvests and the concentration of Al was determined in the diagnostic leaves and in the roots. Silicon rates did not influence (p>0.05) DMY and Al concentration in diagnostic leaves and roots. The average of DMY was 17.94, 20.14 and 26.95 g per pot, respectively for the first, second and third harvests. Aluminum concentrations in the diagnostic leaves were 90, 100 and 90 mg kg DM, respectively for the first, second and third harvests, and the mean concentration of Al in the roots was 3030 mg kg DM, being higher in the roots when compared in the diagnostic leaves. Silicon rates in the presence of Al toxicity did not increase the DMY and did not reduce the concentration of Al in the diagnostic leaves and roots.