Luís César Cassol

Evolução de atributos físicos de solo em sistema de integração lavoura-pecuária

The objective of this work was to assess the effect of sward height and successive grazing cycles over soil physical attributes in an integrated crop-livestock system. The experiment was established in 2001, in the Planalto Medio region, RS, Brazil, in a Rhodic Hapludox (Oxisol), with annual ryegrass (Lolium multiflorum) intercropped with black oat (Avena strigosa), under continuous grazing, during the winter, and single cropped soybean (Glycine max) during the summer. The treatments consisted of different grazing intensities, determined by sward height (10, 20, 30, and 40 cm), and a no-grazing area was used as a control. Soil bulk density and soil porosity were evaluated at the end of the grazing and soybean cycles, as well as soil resistance to mechanic penetration and aggregate stability in the seventh year of the experiment. No significant differences were found on soil bulk density and soil porosity after seven years under crop-livestock integration. Soil resistance to penetration is higher on the superficial layer after the grazing cycle. Soil aggregation increases in grazing areas, regardless of grazing intensities.

Atributos químicos do solo em função da aplicação superficial de calcário em sistema de integração lavoura-pecuária submetido a pressões de pastejo em plantio direto

A utilizacao de extensas areas usadas unicamente com culturas para cobertura do solo no inverno para pastejo de animais para producao de carne ou leite pode se tornar uma fonte alternativa de renda aos produtores de graos no verao, no sul do Brasil. A presenca de bovinos em areas utilizadas apenas com lavouras em plantio direto pode, no entanto, promover alteracoes em atributos do solo, cuja magnitude depende do manejo adotado. Este trabalho teve por objetivo avaliar o efeito de diferentes pressoes de pastejo sobre a correcao da acidez do solo a partir da aplicacao superficial de calcario em um Latossolo Vermelho sob plantio direto. Os tratamentos consistiram do manejo do pasto em diferentes alturas (10, 20, 30 e 40 cm), alem de areas sem pastejo, aplicadas durante o inverno. Em dezembro de 2001, foi feita uma amostragem de solo para avaliacao de atributos quimicos do solo apos o primeiro ciclo de pastejo, nas camadas de 0-25, 2,5-5, 5-7,5, 7,5-10, 10-12,5, 12,5-15, 15-17,5, 17,5-20 e 20-25 cm. Na sequencia, foram aplicados 4,5 t ha-1 (PRNT 62 %) de calcario em superficie, em toda a area, sendo cultivada soja em sucessao ao pastejo. Amostragens de solo seguiram-se ao final do primeiro, segundo, terceiro, quarto e quinto ciclos de soja, correspondendo aos 6, 12, 24, 36 e 48 meses apos a aplicacao de calcario. Foram avaliados: o pH-H2O; o indice SMP; os teores de Ca, Mg, K e Al trocaveis e de carbono orgânico total (COT). A aplicacao superficial de calcario foi eficiente na correcao da acidez, de forma variavel em profundidade, com o atributo quimico avaliado e com o tempo, atingindo ate 25 cm de profundidade. A presenca de bovinos em pastejo na area incrementou o efeito em profundidade da calagem superficial. As diferentes adicoes de residuo ao solo nao afetaram os teores de COT do solo.

Efeitos de diferentes intensidades de pastejo em pastagem nativa melhorada sobre o desempenho animal

A grazing trial was carried out to evaluate the effect of two forage masses on the animal yield from natural pasture over-sown with exotic legumes species (white clover - Trifolium repens, red clover - Trifolium pratense and birdsfoottrifoil - Lotus corniculatus). The grazing method consisted of a variable continuous stocking rate over the period from July 2003 to April 2004. The experimental treatments were two forage masses: low forage mass (LFM) (1,021 kg of DM/ha) and high forage mass (HFM) (1,751 kg of DM/ha). Pasture and animal evaluations were accomplished nearly at 30 days intervals. Heavy treatment ´ experimental period interaction was observed for the stocking rate that showed an average of 690 and 437 kg of DM/ha to LFM and HFM respectively. Forage mass affected the animal average daily gain estimates of 480 and 262 g/animal/day for HFM and LFM, respectively, but had no effect on animal body weight yield per unit of land area estimates of 231 and 207 kg/ha for the LFM and HFM, respectively. These results point out that the improved natural pasture management must be accomplished under herbage mass valus near to 1,700 DM/ha, because it maintain good weight gain rate.

Fixação biológica de nitrogênio por plantas de trevo (Trifolium spp) em sistema de integração lavoura-pecuária no Sul do Brasil

The objective of this research was to study the effect of including grazed clover plants, in crop-pasture systems, on the amount of N fixed, maize productivity and yield components, and soil nitrate concentration. It was used a split-plot arrangement in a complete randomized block design, with three replications per treatment. The main plots were formed by two types of residues of winter pastures (oat and clover) and the split-plots were formed by different doses of broadcasted N in the urea form (0, 60, 120, and 240 kg/ha N). The effect of the previous residue was observed during all periods of the corn crop (2004/2005). All plots that contained clover residue presented greater N-nitrate concentration in the soil layer of 0-5 cm compared to those plots cultivated previously with oats. These results showed that the white clover residues after grazing would provide practically all nitrogen demand by the maize crop. It was not observed nitrate leaching caused by legume residues until the depth of 20 cm. In the second experimental year, the clover residue contributed, at the very least, with 90 kg/ha of N, resultant from the N biological fixation, to the corn crop. However, maize plants cultivated on oat residual mulch showed maximum grain yield under 180 kg/ha of N-fertilizer.

Produtividade e composição estrutural de aveia e azevém submetidos a épocas de corte e adubação nitrogenada

Dairy farming represents an important activity to small farmers, in south-west of Parana State, Brazil. The objective of this study was to evaluate the effect of the harvest period of oat and rye grass pastures, with and without nitrogen fertilization, on dry matter and pasture quality in order to determine the best time to start grazing. The experiment was carried out in Pato Branco, PR, in a randomized block design in split plot arrangement, with four repetitions. The main plot consisted of nitrogen fertilization levels (0 and 100 kg ha-1 of N), in the form of urea. The sub plots consisted of three cutting times of oat and rye grass pasture (30, 45 and 60 days after plants cropping up). The nitrogen applied provided dry mass accumulation of 1133 kg DM ha-1 45 days after emergence, close to the amount considered adequate to start grazing. The first cutting, at this time, in association with the use of nitrogen also influenced the pasture regrowth capacity, which was indicated by the dry mass accumulation of 2398 kg of DM ha-1 obtained 30 days after this cutting. Nitrogen fertilization increased the number of oat leaves , which contributed to the high level of crude protein content (27%), showing the high quality of the material.

Grazing intensities and poultry litter fertilization levels on corn and black oat yield

The objective of this work was to assess the effect of poultry litter fertilization levels on corn and black oat yield using different grazing intensities, poultry litter levels (mixture of manure and bedding material) and a chemical fertilization level. The experimental design was a randomized complete block in a split‑plot arrangement with four replicates. Black oat + ryegrass grazing intensities, characterized by different pasture sward management, with animal entrance at 25, 30 and 35‑cm heights and exit at 5.0, 10 and 15‑cm heights, were established at the main plots. After the grazing period, corn was grown at the subplots with four levels of poultry litter (0, 4,953, 9,907 and 14,860 kg ha‑1), aiming to supply 0, 100, 200 and 300 kg ha‑1 of nitrogen, and a treatment with chemical fertilizer, according to soil analysis. Grazing intensities had no effect on corn yield. Corn yield was 7,493, 8,458, 9,188, 10,247 and 11,028 kg ha‑1, respectively, for the treatments without and with 4,953, 9,907 and 14,860 kg ha‑1 of poultry litter, and the treatment with chemical fertilization. Poultry litter levels have a residual effect on the production of black oat grown in succession to corn.

Application limestone forms and doses for Alfalfa in no-tillage system

Alfalfa (Medicago sativa L.) requires good soil fertility. Brazil is characterized by acidic soils which reduce the potential of the crop. Generally, liming is incorporated into the soil, but in tillage systems it is inadvisable. This study aimed to evaluate the effects of the lime application method and dose on pH, Al+3, V % and Ca+Mg in the soil and on dry matter yield of alfalfa cultivated under a consolidated no-tillage system. The experiment was conducted at the Experimental Station of Parana Agronomic Institute, located in Pato Branco city, in Parana state. The plots consisted of the types of lime application (plowing+harrowing, subsoil and surface), the sub-plots was the lime dose (0, 2, 4, 6 and 8 Mg ha-1) and the sub-sub-plots were the sampled soil depth (0-5; 5-10; 10-20 and 20-30 cm). The results show the application of lime, even superficially, caused increases in pH, concentration of Ca and Mg and base saturation of the soil, while also reducing the concentration of Al, especially in the surface layers of the soil. The practice of plowing and harrowing or of subsoiling, with the aim of lime incorporation in a consolidated no-tillage system is unnecessary. If it is required, the application of lime to the soil should be done superficially for alfalfa cultivated in this system.