The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

No abstract

RESUMOGonçalves 7712, CEP 91540-000 Porto Alegre (RS).

ResumoO experimento foi conduzido em ambiente protegido (estufa), na Faculdade de Engenharia, UNESP de Ilha Solteira, com o objetivo de avaliar fontes (calcário e escória silicatada) e doses (0,0 -0,5 -1,0 -1,5 -2,0 vezes a dose recomendada) de corretivos na composição bromatológica, perfilhamento e produção de matéria seca do capim-mombaça (Panicum maximum Jacq.). O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições. Avaliou-se o número de perfilhos, a produção de matéria seca e os teores de proteína bruta (PB), fibra em detergente neutro (FDN) e fibra em detergente ácido (FDA). Os corretivos influenciaram o perfilhamento em quase todas as contagens. O calcário proporcionou maior produção de matéria seca nas doses de 1,5 e 2,0 vezes a dose recomendada. A composição bromatológica da forragem não foi influenciada pelos corretivos e doses utilizadas. Palavras-chave: Calcário, escória silicatada, Panicum maximum Jacq. AbstractThe experiment was carried in protected (greenhouse) atmosphere, in University of Engineering, UNESP of Ilha Solteira-SP, with the objective of evaluating sources (limestone and calcium silicate slag) and doses (0,0 -0,5 -1,0 -1,5 -2,0 times the recommended dose) of corrective in the bromatologic composition, tillering and production of dry matter of the grass mombaça (Panicum maximum Jacq.). The lineation was completely randomized design, with four repetitions. It was evaluated the tiller number, the production of dry matter, the gross protein, neutral detergent fiber (NDF) and acid detergent fiber (ADF). The corrective influenced the tillering in almost all of the countings. The limestone provided larger production of dry matter in the doses of 1,5 and 2,0 times the recommended dose. The bromatologic composition of the forage was not influenced by the corrective and doses.

Chemical attributes, production and quality of signal grass in soils amended with limestone and calcium silicate slagPastures are the basis of cattle production systems, evidencing their importance and the need for other management practices that result in higher efficiency of these systems. This study aimed to evaluate the soil chemical properties (pH, Ca, Mg and H+Al), the potential production and the chemical composition of signal grass (Brachiaria decumbens Stapf) in soil amended with different limestone doses and calcium silicate slag. The experiment was carried out in a greenhouse, in the period 2006/2007, at the Universidade Estadual Paulista, Ilha Solteira-SP. Five doses of limestone and calcium silicate slag were tested, 0.0; 0.5; 1.0; 1.5; 2.0 times the recommended dose. A complete randomized design was used with four repetitions. Soil chemical composition was evaluated after incubation with the amendment, tillering, dry matter, protein, NDF (neutral detergent fiber) and ADF (acid detergent fiber). Both amendments provided to the soil positive effect in relation to the pH and content of calcium and magnesium. The variables dry matter and ADF were not significantly influenced by the types and doses of the amendments.