Jean Sérgio Rosset

Índice de manejo de carbono e atributos químicos de Latossolo Vermelho sob diferentes sistemas de manejo

The objective of this work was to evaluate changes in the soil chemical attributes, carbon stock and in the C management index of a clayed Oxisol under different management systems. The soil under management systems with different historical usage was evaluated under the following covers: Zea mays, Urochloa decumbens, Panicum maximum cv. Tanzania. A cerrado area was used as check. Four composite samples were collected at 0-5, 5-10 and 10-20 cm soil depths. The phosphorus contents decreased with depth, and the higher values were observed in the area with P. maximum. In the area with Z. mays, higher values for K+, Ca++, Mg++, CEC, and base sum and saturation were observed. The total organic C content (TOC) was higher under cerrado vegetation cover, and smaller under P. maximum at 5-10 cm soil depth. The higher stocks of TOC, and of carbon in particulate fractions (C-POM) and in fractions associate to the soil mineral phase occurred in the area with U. decumbens, which promoted higher values for lability and C management indexes, similar to those for cerrado vegetation. In all coverings, the organic soil matter lability decreased with depth. The C-POM fraction had higher sensibility to variation in management practices, and is related to TOC.

Phosphorus and potassium fertilization in culture of soybean plants in the Oxisol

It is recommended to use phosphorus and potassium fertilization on soybean; however it has been common to verify the absence of effect on crop productivity, especially in no-tillage system. Thus, the study aimed to evaluate the effect of doses of superphosphate and potassium chloride in the leaf tissue nutrient content and yield of soybean growing in Oxisol. The experiment was installed in October 2011 in a randomized block design in split-bands with two factors (4x4), with four replications, totaling 64 plots, being Factor 1 with doses of superphosphate (0, 136, 331 and 700 kg ha-1) at sowing and Factor 2 with doses of potassium chloride (0, 160, 320 and 800 kg ha-1) released with cultivar Vmax RR (SYN 7059RR). In the experiment, the variables evaluated were Ca, Mg, K, P, S, Cu, Zn, Mn and Fe in leaf tissue and grain yield. The fertilization with superphosphate and potassium chloride do not interfere in leaf nutrient content and yield of soybean cultivar Vmax RR (SYN 7059RR) grown on an Oxisol of clayey with levels of P and K classified as high. In these cases, it is advisable to keep only the maintenance fertilization according to the values ​​of P and K exported by grain. Key words: Chemical fertilizer, tillage systems, organic mineral fertilizer, superphosphate, potassium chloride.

Desenvolvimento inicial do milho e atributos químicos do solo em função de diferentes doses de silicato de cálcio

Calcium silicate applied to the soil has an effect on plant nutrition since it is a source of silicon, calcium and magnesium. With the aim to evaluate the effect of doses of calcium silicate on soil chemical properties and on early development of corn, an experiment was conducted in a greenhouse, in pots containing eutroferric Oxisol, testing five rates of calcium silicate (0, 1.2; 2.4; 4.8 and 9.6 t ha -1 ) with four replications in a randomized complete block design. The levels of N, P, K, Ca and Mg in the plant shoot were evaluated, and, at the end of the experiment, shoot dry weight and plant height as well as Ca and Mg, and soil pH were also estimated. Shoot dry matter and plant height were not affected by fertilization with calcium silicate. The application of calcium silicate provided soil amendment, increasing the availability of calcium and magnesium, in addition to increasing the levels of N, K, Ca and Mg in the shoots of corn.