Silicon Rates for Marandu Palisadegrass Under Conditions of Aluminum Toxicity.

Silicon (Si), although not an essential element of plants, can have beneficial effects in relation to the stress reduction caused by aluminum (Al). The aim of this work was to study rates of Si (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 Marandu palisadegrass (Brachiaria brizantha cv. Marandu) 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 number of leaves, tillers and the height of plants on the day of the cuts were quantified. Silicon rates did not influence (p>0.05) the number of leaves, tillers and plant height for the three harvests. The mean number of leaves per pot for the first, second and third harvests were 92, 108 and 146, respectively. For the number of tillers per pot, the averages were 30, 53 and 67, respectively for the first, second and third harvests. The mean plant height was 68.82, 50.69 and 56.43 cm, respectively for the first, second and third harvests. The application of Si rates in the presence of Al toxicity did not increase the studied variables.