T. A. Rein

Utilização de calcário em plantio direto e convencional de soja e milho em Latossolo Vermelho

Cerrado soils are acid with toxic levels of aluminum and, in order to overcome these conditions to grow crops, lime is necessary. This experiment evaluated the effects of lime levels and methods of lime application on the grain production of soybean and corn in rotation, under conventional (disk plowing and harrowing) and no-tillage planting systems in a Red Latosol (Oxisol). Cover crops were planted in the dry season; mucuna was cultivated after soybean and millet after corn. One lime treatment was included without cover crop under the conventional system. The occurrence of a dry spell period caused reduction in soybean yield in the first crop, but yield increases were observed due to lime application, under both systems, in the third crop. In the second and fourth crops, corn grain yields increased with lime levels, and were higher in the conventional system in the second crop. In no-tillage system, lime levels without incorporation produced less corn grain yield compared to incorporated lime. The corn response to split lime application was proportional to the incorporated lime levels. The exclusion of cover crops under the conventional system promoted corn grain yield reduction. Surface lime applications affected the soil chemical characteristics mainly at the 0-5 cm depth.

Avaliação do fosfato natural de Gafsa para recuperação de pastagem degradada em latossolo vermelho-escuro

A field experiment was conducted on a Dark-Red Latossol (Haplustox) of the Cerrado of the Federal District, Brazil, to evaluate a coarse-ground Gafsa rock phosphate (CGRP) in the recuperation of a Brachiaria decumbens cv. Basilisk pasture. CGRP was compared with triple superphosphate (TSP) at a P2O5 rate of 100 kg ha-1 both applied by broadcasting. A control treatment without P was included together with two other variables: 1) incorporation of the phosphate with a harrow (with and without) and 2) supplementary fertilization (SF) with Ca, Mg, N, K, S and micronutrients (presence and absence). The response to application of phosphates was only observed with the simultaneous application of SF; incorporation was essential for increasing the efficiency of CGRP; with incorporation, the efficiency of CGRP was equal to that of TSP; without incorporation, TSP was significantly superior to CGRP (p< 0.05).

Manejo de plantas de cobertura na floração e na maturação fisiológica e seu efeito na produtividade do milho

O objetivo deste trabalho foi avaliar o efeito do manejo de plantas de cobertura na floracao e na maturacao fisiologica sobre a produtividade do milho cultivado em sucessao. O experimento, em delineamento de blocos ao acaso com parcelas subdivididas, foi realizado em Latossolo Vermelho, em sistema plantio direto, com nove especies. Foram avaliados: produtividade de materia seca; tempo de ciclagem dos residuos vegetais; teores de N das plantas de cobertura; e produtividade de graos e teores de N nas folhas do milho. As especies Pennisetum glaucum, Mucuna aterrima, Cajanus cajan e Canavalia brasiliensis apresentaram as maiores produtividades de materia seca na floracao. Na maturacao fisiologica, Sorghum bicolor, P. glaucum, C. brasiliensis, Crotalaria juncea e C. cajan apresentaram produtividades mais elevadas de fitomassa. Nao houve efeito da epoca de corte e da interacao planta de cobertura e epoca de corte sobre a produtividade do milho. As maiores produtividades de milho foram obtidos apos cultivo de Urochloa ruziziensis, C. juncea, C. brasiliensis, C. cajan, P. glaucum e Raphanus sativus, e estao relacionadas ao maior acumulo de materia seca e ao menor tempo de ciclagem dos residuos vegetais das plantas de cobertura.

Variability of soil fertility properties in areas planted to sugarcane in the State of Goias, Brazil

Soil sampling should provide an accurate representation of a given area so that recommendations for amendments of soil acidity, fertilization and soil conservation may be drafted to increase yield and improve the use of inputs. The aim of this study was to evaluate the variability of soil fertility properties of Oxisols in areas planted to sugarcane in the State of Goias, Brazil. Two areas of approximately 8,100 m2 each were selected, representing two fields of the Goiasa sugarcane mill in Goiatuba. The sugarcane crop had a row spacing of 1.5 m and subsamples were taken from 49 points in the row and 49 between the row with a Dutch auger at depths of 0.0-0.2 and 0.2-0.4 m, for a total of 196 subsamples for each area. The samples were individually subjected to chemical analyses of soil fertility (pH in CaCl2, potential acidity, organic matter, P, K, Ca and Mg) and particle size analysis. The number of subsamples required to compose a sample within the acceptable ranges of error of 5, 10, 20 and 40 % of each property were computed from the coefficients of variation and the Student t-value for 95 % confidence. The soil properties under analysis exhibited different variabilities: high (P and K), medium (potential acidity, Ca and Mg) and low (pH, organic matter and clay content). Most of the properties analyzed showed an error of less than 20 % for a group of 20 subsamples, except for P and K, which were capable of showing an error greater than 40 % around the mean. The extreme variability in phosphorus, particularly at the depth of 0.2-0.4 m, attributed to banded application of high rates of P fertilizers at planting, places limitations on assessment of its availability due to the high number of subsamples required for a composite sample.

Evaluation of a coarse-ground Gafsa rock phosphate in the recuperation of a degraded pasture on a clayey dark-red latosol

A field experiment was conducted on a Dark-Red Latossol (Haplustox) of the Cerrado of the Federal District, Brazil, to evaluate a coarse-ground Gafsa rock phosphate (CGRP) in the recuperation of a Brachiaria decumbens cv. Basilisk pasture. CGRP was compared with triple superphosphate (TSP) at a P2O5 rate of 100 kg ha-1 both applied by broadcasting. A control treatment without P was included together with two other variables: 1) incorporation of the phosphate with a harrow (with and without) and 2) supplementary fertilization (SF) with Ca, Mg, N, K, S and micronutrients (presence and absence). The response to application of phosphates was only observed with the simultaneous application of SF; incorporation was essential for increasing the efficiency of CGRP; with incorporation, the efficiency of CGRP was equal to that of TSP; without incorporation, TSP was significantly superior to CGRP (p< 0.05).

Evaluation of Gafsa rock phosphate for the improvement of a degraded pasture on a Dark-Red Latosol.

A field experiment was conducted on a Dark-Red Latossol (Haplustox) of the Cerrado of the Federal District, Brazil, to evaluate a coarse-ground Gafsa rock phosphate (CGRP) in the recuperation of a Brachiaria decumbens cv. Basilisk pasture. CGRP was compared with triple superphosphate (TSP) at a P2O5 rate of 100 kg ha-1 both applied by broadcasting. A control treatment without P was included together with two other variables: 1) incorporation of the phosphate with a harrow (with and without) and 2) supplementary fertilization (SF) with Ca, Mg, N, K, S and micronutrients (presence and absence). The response to application of phosphates was only observed with the simultaneous application of SF; incorporation was essential for increasing the efficiency of CGRP; with incorporation, the efficiency of CGRP was equal to that of TSP; without incorporation, TSP was significantly superior to CGRP (p< 0.05).