Changes in the Chemical Properties of Soil Cultivated with Brachiaria ruziziensis Regarding Nitrogen Fertilization

The present study aimed to determine the effects of nitrogen fertilization on the chemical properties of Oxissol (Red Latosol), in an area cultivated with Brachiaria ruziziensis cv. Common where crop succession system was used (“safrinha” corn (second growing season) planted in succession to soybean) in no-tillage system, regarding the combinations of nitrogen doses. The experimental treatments consisted of two doses of nitrogen applied in the planting of Brachiaria ruziziensis and four doses of nitrogen applied after the first grass cut. The treatments were arranged in 2x4 factorial design, as follows: 0.0; 0.15; 0.30; 0.45; 15.0; 15.15; 15.30 and 15.45 mg dm-3. The experimental design used was completely randomized blocks with four repetitions The soil chemical properties assessed were: pH; cation exchange capacity; base saturation; potential acidity; soil contents of organic matter, phosphorus, sulfate, potassium, calcium, magnesium, boron, copper, iron, manganese and zinc. F test was used in the comparisons between nitrogen means during planting, and regression analyzes were used for the nitrogen treatments after the first grass cut. The nitrogen fertilization does not interfere in the values of pH, organic matter, phosphorus, boron, iron, manganese and zinc of the soil cultivated with Brachiaria ruziziensis. It is necessary to monitor the contents of K, Ca, Mg and B in the soil when nitrogen is applied to Brachiaria ruziziensis. The minimum sulfate content in soil cultivated with Brachiaria ruziziensis is 4.94 mg dm-3 for the dose of 36.3 mg dm-3 of nitrogen. The non-application of nitrogen at planting associated to the application of 28.5 mg dm-3 of nitrogen after the first grass cut results in higher copper content in soil (4.14 mg dm-3). The application of 15 mg dm-3 of nitrogen at planting associated to the increase in nitrogen doses after the first grass cut led to increase in copper content.