Luciano Colpo Gatiboni

ALTERAÇÕES DE ATRIBUTOS DO SOLO PELA CALAGEM SUPERFICIAL E INCORPORADA A PARTIR DE PASTAGEM NATURAL

Superficial liming is an alternative way to correct soil acidity in no till system. The objective of this study was to evaluate the effects of superficial and incorporated liming on native pasture. The experiment was carried out at the experimental field of the Soil Science Department, at the Universidade Federal de Santa Maria (Brazil), on a Plinthaquult medium texture and with high potential acidity under native pasture. Lime rates of 0.0, 2.0, 8.5 and 17.0 Mg ha-1 were used. On half of the plots lime was mixed with the topsoil by disk plow and left on the surface on the other half of the plot. The experimental design was arranged in completely randomized blocks with four replications. After 6, 18, 36, and 48 months, soil was sampled at four depths, 0.0-2.5, 2.5-5.0, 5.0-10.0 and 10.0-15.0 cm and the attributes related to soil acidity evaluated. The surface applied lime was effective in neutralizing soil acidity, at a depth proportional to the rate and time. With 2.0 + 2.0 t ha-1, aluminum saturation reached near zero (0.0-2.5 cm layer) at 36 months; with 8.5 t ha-1, it reached near zero (2.5-5.0 cm) at 36 months; with 17.0 t ha-1 it reached near zero (5.0-10.0 cm) at 48 months.

Dessorção de fósforo avaliada por extrações sucessivas em amostras de solo provenientes dos sistemas plantio direto e convencional

The phosphorus is retained in the soil solid phase with several degrees of energy, which depends on the characteristics and amount of the soil colloids. The no tillage system (NT) may promote phosphorus accumulation in different forms from those observed in the conventional tillage (CT) and thus, may modify the dessorption capacity of the soil. The objective of this work was to estimate the phosphorus dessorption capacity of different soils submitted to NT and CT. Samples from three soils with variable clay contents (Rhodic Hapludox - 680g kg-1 clay, Rhodic Hapludox - 530g kg-1 clay and Rhodic Paleudult - 220g kg-1 clay) cultivated under NT and CT were submitted to successive extractions with anion exchange resin (AER) and adjusted first order kinetics equations to estimate the maximum phosphorus dessorption of the soil. The dessorption by the first extraction and maximum dessorption were higher in the superficial layer of the soil under NT, comparatively to CT. Only one extraction with AER represented, on average, 38, 46 and 49% of the maximum dessorption on soils with high, medium and low clay content, respectively, while that estimated by Mehlich 1 extractor represented, for the same soils, 32, 46 and 89% of the maximum dessorption.

Estimativa da acidez potencial em solos e sua implicação no cálculo da necessidade de calcário

Lime requirement diagnostic by base saturation (H + Al) estimation methods are critical in CEC calculation since they are bound to a potential soil acidity of pH 7.0. This study was carried out in order to evaluate a relation between the H + Al obtained by direct soil incubation with calcium carbonate and the estimation by the extractors acetate salt and SMP index. Twelve south Brazilian soils, incubated with increasing calcium carbonate rates to establish the real soil acidity at a pH of 7, were compared with acidity potential values obtained by different direct and indirect evaluation methods. Significant correlation was observed between the real and the extractant-estimated H + Al, but the angular coefficients in all situation were higher than one. To improve the H + Al estimation by the SMP index, the use of the real incubation data is necessary. The equation which best describes the relationship between H + Al and the SMP index is log (H + Al) = 3.020-0.371 SMP.

Influência da adubação fosfatada e da introdução de espécies forrageiras de inverno na oferta de forragem de pastagem natural

The beef cattle production in Rio Grande do Sul, Brazil, is based on natural pasture grazing, which are of low productivity and seasonal growth. The present work was done to test the effects of Italian ryegrass and arrowleaf clover introduction in natural pasture under different phosphorus fertilizer, soluble and natural, associated or not to the lime, on forage improvement from natural pasture. The study was conducted at Universidade Federal de Santa Maria on a Paleudalf. The treatments were: foscal (simple superphosphate + lime); triple superphosphate + lime; triple superphosphate; rock phosphate of Gafsa; without phosphorus fertilizer and without lime, and natural pasture. Except for the last treatment, the others received potassium and nitrogen fertilizers and introduction of Lolium multiflorum and Trifolium vesiculosum. The autors used 3.2 Mg ha of lime (elevation of the pH-H 2 O to 5.5), 180 kg ha-1 of P 2 O 5 , 130 kg ha-1 of K 2 O and 70 kg ha-1 of N. The productivity of dry matter was evaluated for the following periods: winter, spring, spring-summer and summer-autumn. The phosphorus fertilization increased the productivity of dry matter of the pasture and the soluble phosphates provided greater productions than the rock phosphate. The lime did not increase productivity of Lolium multiflorum and natural pasture, but Trifolium vesiculosum responded to this input.

Superphosphate and Rock Phosphates as Phosphorus Sources for Grass‐Clover Pasture on a Limed Acid Soil in Southern Brazil

The native pastures of Rio Grande do Sul, Southern Brazil, have low productivity because of summer and spring species growing seasons on low fertility soils. The objective of this research was to evaluate sources of phosphorus (P) and lime rates surface applied on natural pasture for exotic cold season forages species introduction. The results showed that the rock phosphates Gafsa and Arad were efficient sources of P in moderate to high soil acidity. The soil acidity attenuation by liming increased the forage production and the efficiency of the soluble superphosphate, but reduced the performance of rock phosphates. The surface liming was effective in neutralizing exchangeable aluminum only in the topsoil layers.

Quantificação do fósforo disponível por extrações sucessivas com diferentes extratores em Latossolo Vermelho distroférrico

A determinacao do fosforo potencialmente disponivel por meio dos extratores quimicos e dificultada em solos de carga variavel, uma vez que existem diversos graus de energia de ligacao com os coloides. O objetivo do presente trabalho foi avaliar o numero minimo de extracoes sucessivas necessarias para estimar o fosforo potencialmente disponivel, com os metodos de Mehlich-1 e Mehlich-3 e resina de troca anionica (RTA). Foram realizadas treze extracoes sucessivas com os tres metodos em amostras de um Latossolo Vermelho distroferrico tipico sob sistema plantio direto com doses crescentes de fosforo. Os resultados mostraram que uma unica extracao com Mehlich-1, Mehlich-3 ou RTA extrai apenas 29, 35 e 37 % do fosforo potencialmente disponivel, respectivamente. Para obter o fator quantidade, foram necessarias sete extracoes sucessivas com a RTA e quatro com os metodos Mehlich-1 e 3. O metodo da RTA foi mais eficiente no diagnostico dos teores de fosforo nos tratamentos com baixa disponibilidade, enquanto os metodos Mehlich-1 e 3 foram mais eficazes naqueles com alta disponibilidade de fosforo.

Composição florística de pastagem natural afetada por fontes de fósforo, calagem e introdução de espécies forrageiras de estação fria

Natural pastures of Rio Grande do Sul State, South of Brazil, have low forage productivity in the autumn-winter. An alternative to improve systems based on these pastures is introduction of winter forage species, fertilization and liming of soil. The present work had the objective of evaluating the effect of phosphorus sources, lime and introduction of winter forage species in the pasture botanical composition dynamics. The treatments used were: T1 - simple superphosphate + lime + winter forage species introduction; T2 - triple superphosphate + lime + winter forage species introduction; T3 - triple superphosphate + winter forage species introduction; T4 - Gafsa rock phosphate + winter forage species introduction; T5 - winter forage species introduction without phosphorus and lime; T6 - reference only with natural pasture. To evaluate the botanical composition dynamics, periodic botanical evaluations were done during twenty two months, using BOTANAL method. The results showed that treatments did not modify the botanical composition of natural pasture during the evaluation period.

Alterações nos atributos químicos de solo arenoso pela calagem superficial no sistema plantio direto consolidado

Surface liming of soil under no-tillage forms a concentration gradient of lime or its reaction products in the soil profile. The objective of this study was to evaluate the

Effect of phosphorus fertilizer application and introduction of winter forage species on forage availability in natural pastures.

The beef cattle production in Rio Grande do Sul, Brazil, is based on natural pasture grazing, which are of low productivity and seasonal growth. The present work was done to test the effects of Italian ryegrass and arrowleaf clover introduction in natural pasture under different phosphorus fertilizer, soluble and natural, associated or not to the lime, on forage improvement from natural pasture. The study was conducted at Universidade Federal de Santa Maria on a Paleudalf. The treatments were: foscal (simple superphosphate + lime); triple superphosphate + lime; triple superphosphate; rock phosphate of Gafsa; without phosphorus fertilizer and without lime, and natural pasture. Except for the last treatment, the others received potassium and nitrogen fertilizers and introduction of Lolium multiflorum and Trifolium vesiculosum. The autors used 3.2 Mg ha of lime (elevation of the pH-H 2 O to 5.5), 180 kg ha-1 of P 2 O 5 , 130 kg ha-1 of K 2 O and 70 kg ha-1 of N. The productivity of dry matter was evaluated for the following periods: winter, spring, spring-summer and summer-autumn. The phosphorus fertilization increased the productivity of dry matter of the pasture and the soluble phosphates provided greater productions than the rock phosphate. The lime did not increase productivity of Lolium multiflorum and natural pasture, but Trifolium vesiculosum responded to this input.