A acidez pode alterar a disponibilidade dos nutrientes no solo. Objetivou-se com o presente trabalho avaliar o efeito da aplicação de calcário líquido e calcário convencional na correção da acidez de um Latossolo Vermelho-Amarelo distrófico do Cerrado. O delineamento experimental utilizado foi inteiramente casualizado, com três repetições. As doses de calcário líquido aplicadas foram equivalentes a 5; 10; 15 e 20 L ha-1 e as doses de calcário convencional utilizadas foram equivalentes a 1,0; 1,5; 2,0 e 2,5 t ha-1. Após a aplicação dos corretivos de acidez, o solo foi acondicionado em recipientes com capacidade para 0,4 dm 3 com umidade próxima a capacidade de campo. Aos 70 dias após a aplicação dos corretivos foram mensurados o pH do solo, teores de potássio (K +), cálcio (Ca 2+), magnésio (Mg 2+), alumínio trocável (Al 3+), acidez potencial (H+Al) e calcularam-se a capacidade de troca de cátions (CTC), saturação de bases (V%) e saturação de alumínio (m%). O calcário líquido não corrigiu a acidez do solo e não elevou a saturação por bases, apenas elevou os teores de Ca no solo. A aplicação de doses de calcário convencional proporcionou correção da acidez do solo e elevação da saturação de bases. Palavras-chave: calagem, pH do solo, química do solo, fertilidade do solo.

Soils of the tropics are prone to a decrease in quality after conversion from native forest (FO) to a conventional tillage system (CT). However, the adoption of no-tillage (NT) and complex crop rotations may improve soil structural quality. Thus, the aim of this study was to evaluate the physical properties of an Oxisol under FO, CT, and three summer crop sequences in NT: continuous corn (NTcc), continuous soybean (NTcs), and a soybean/corn rotation (NTscr). Both NT and CT decreased soil organic carbon (SOC) content, SOC stock, water stable aggregates (WSA), geometric mean diameter (GMD), soil total porosity (TP), macroporosity (MA), and the least limiting water range (LLWR). However they increased soil bulk density (BD) and tensile strength (TS) of the aggregates when compared to soil under FO. Soil under NT had higher WSA, GMD, BD, TS and microporosty, but lower TP and MA than soil under CT. Soil under FO did not attain critical values for the LLWR, but the lower limit of the LLWR in soils under CT and NT was resistance to penetration (RP) for all values of BD, while the upper limit of field capacity was air-filled porosity for BD values greater than 1.46 (CT), 1.40 (NTscr), 1.42 (NTcc), and 1.41 (NTcs) kg dm-3. Soil under NTcc and NTcs decreased RP even with the increase in BD because of the formation of biopores. Furthermore, higher critical BD was verified under NTcc (1.62 kg dm-3) and NTcs (1.57 kg dm-3) compared to NTscr and CT (1.53 kg dm-3).

A adubação nitrogenada na cultura da soja, associada a inoculação com a bactéria Bradyrhizobium japonicum é uma prática comum na agricultura, no entanto, muito contestada. Objetivou-se neste estudo avaliar a resposta da soja à aplicação foliar de N em diferentes estádios fenológicos e à aplicação de inoculante com Bradyrhizobium japonicum. O experimento foi realizado em casa de vegetação da Universidade do Estado de Mato Grosso, Alta Floresta-MT. Foi utilizado o delineamento experimental inteiramente casualizado em arranjo fatorial 4x2, sendo quatro épocas de aplicação de nitrogênio (R1 - Início de floração, R3 - Final da floração, R5.1 - Grãos perceptíveis ao tato e R5.3 - Maioria das vagens entre 25-50% de granação) e presença ou ausência de Bradyrhizobium japonicum, com quatro repetições. Conclui-se que a aplicação de nitrogênio foliar na cultura da soja no estágio R1 proporcionou aumento no acúmulo de nitrogênio na parte aérea, no número de vagens e de grãos por planta. A presença do inoculante proporcionou maior número de vagens quando aplicou se N nas épocas R1 e R3, já para a matéria seca de parte aérea, o melhor resultado foi obtido, quando o N foi aplicado em R 5.3, na ausência do inoculante.Palavras-chave: adubação nitrogenada, fixação biológica, inoculante. LEAF APPLICATION OF NITROGEN IN DIFFERENT PHENOLOGICAL STAGES IN SOYBEAN AND INOCULATION WITH Bradyrhizobium japonicum ABSTRACT:Nitrogen fertilization in soybean crop, associated with inoculation with a bacterium Bradyrhizobium japonicum is a common practice in agriculture, however, much contested. The objective of this study was to evaluate the response of soybeans to foliar application of N in different stages of phenology and the application of inoculant with the diazotrophic bacterium Bradyrhizobium japonicum. The experiment was carried out in a greenhouse at the State University of Mato Grosso, Alta Floresta-MT. The completely randomized experimental design was used in a 4x2 factorial arrangement, with 4 nitrogen application times (R1 - Beginning of flowering, R3 - Final flowering, R5.1 - Grains perceptible to touch and R5.3 - Most pods between 25 -50% granulation) and presence or absence of Bradyrhizobium japonicum, with 4 replicates. It was concluded that the application of leaf nitrogen in the non-stage soybean crop provided an increase in the accumulation of nitrogen in the aerial part, there is no number of pods and grains per plant. The presence of the inoculant provided a larger number of pods when applicable. N in the periods R1 and R3, and for the aerial part dry matter, the best result obtained when it was obtained in R 5.3, in the absence of the inoculant.Keywords: nitrogen fertilization, biological fixation, inoculant.

-The objective of this work was to evaluate total soil carbon and nitrogen, as well as their contents in particulate and mineral-associated C fractions; to determine C stock and sequestration rates in the soil; and to verify the effect of C and N contents on soil aggregation, using different crop rotations and crop sequences under no-tillage. The study was carried out for nine years in a clayey Oxisol. The treatments consisted of different cropping systems formed by the combination of three summer crops (cropped until March) -corn (Zea mays) monocropping, soybean (Glycine max) monocropping, and soybean/corn rotation -and seven second crops (crop successions). Soil samples were taken at the 0.00-0.10-m layer for physical fractionation of C and N, and to determine soil aggregation by the wet method. Soybean monocropping increased C and N in particulate C fraction, while the crop systems with corn monocropping x pigeon pea (Cajanus cajan), corn monocropping x sun hemp (Crotalaria juncea), and soybean monocropping x corn as a crop succession increased total C in the soil. Greater rates of soil C sequestration were observed with soybean/corn rotation and with soybean monocropping, as well as with sun hemp as a second crop. The increase in total N increases soil C stock. Soil aggregation was most affected at particulate C fraction. Increases in soil N promote C addition to particulate fraction and enhance soil aggregation.

SUMMARYThe no-till system with complex cropping sequences may improve the structural quality and carbon (C) sequestration in soils of the tropics. Thus, the objective of this study was to evaluate the effects of cropping sequences after eight years under the no-till system on the physical properties and C sequestration in an Oxisol in the municipality of Jaboticabal, Sao Paulo, Brazil. A randomized split-block design with three replications was used. The treatments were combinations of three summer cropping sequences -corn/corn (Zea mays L.) (CC), soybean/soybean (Glycine max L. Merryll) (SS), and soybean-corn (SC); and seven winter crops -corn, sunflower (Helianthus annuus L.), oilseed radish (Raphanus sativus L.), pearl millet (Pennisetum americanum (L.) Leeke), pigeon pea (Cajanus cajan (L.) Millsp), grain sorghum (Sorghum bicolor (L.) Moench), and sunn hemp (Crotalaria juncea L.). Soil samples were taken at the 0-10 cm depth after eight years of experimentation. Soil under SC and CC had higher mean weight diameter (3.63 and 3.55 mm, respectively) and geometric mean diameter (3.55 and 2.92 mm) of the aggregates compared to soil under SS (3.18 and 2.46 mm). The CC resulted in the highest soil organic C content (17.07 g kg -1 ), soil C stock (15.70 Mg ha -1 ), and rate of C sequestration (0.70 Mg ha -1 yr -1 ) among the summer crops. Among the winter crops, soil under pigeon pea had the highest total porosity (0.50 m 3 m -3 ), and that under sunn hemp had the highest water stable aggregates (93.74 %). In addition, sunn hemp did not differ from grain sorghum and contained the highest soil organic C content (16.82 g kg -1 ) and also had the highest rate of C sequestration (0.67 Mg ha -1 yr -1 ). The soil resistance to penetration was the lower limit of the least limiting water range, while the upper limit was air-filled porosity for soil bulk densities higher than 1.39 kg dm -3 for all cropping sequences. Within the SC sequence, soil under corn and pigeon pea increased least limiting water range by formation of biopores because soil resistance to penetration decreased with the increase in soil bulk density.Index terms: Cerrado, crop rotation, winter crops, soil aggregates, least limiting water range, bulk density.(