Paulo Roberto da Rocha Junior

Soil surface roughness under tillage practices and its consequences for water and sediment losses

The present study aims to determine the effects of soil management practices on soil surface roughness and the consequences of these phenomena on water and sediment losses. Laboratory experiment was conducted on a Chernozems clayey soil subjected to a sequence of two 30 min simulated rainfall of 50.8 mm h-1 and 114.3 mm h-1 and four soil management practices: contour tillage (CT), downhill tillage (DT), no-tillage simulated (NTs) and bare soil (BS). Soil surface roughness was evaluated using a laser distance meter. Results showed that the soil tillage in downhill or contour increased soil roughness by 2.90 and 2.76, respectively, reducing the water losses under low rain intensity by 12.8% and 6.4%. Soil surface roughness quickly changed after the onset of rain, and higher values of changes in soil roughness were observed for contour (22.73%) and downhill tillage (21.05%) managements. Soil coverage factor and the direction of tillage were the most important characteristics in contrast with soil surface roughness to reduce the sediment losses. No-tillage simulated (0.59 tha-1) and contour tillage (1.30 t ha-1) were the soil management practices with lower sediment losses compared to other managements studied. The principal theoretical implication of this study is that land use planning with agriculture, livestock must be designed to prevent the soil from being exposed, or if exposed, tillage in contour should be adopted. The input of litter on soil surface had an important role in reducing the sediment and water losses.

Soil, water, and nutrient losses from management alternatives for degraded pasture in Brazilian Atlantic Rainforest biome

The objective of this study was to evaluate sediment, water and nutrient losses from different pasture managements in the Atlantic Rainforest biome. A field study was carried out in Alegre Espiríto Santo, Brazil, on a Xanthic Ferralsol cultivated with braquiaria (Brachiaria brizantha). The six pasture managements studied were: control (CON), chisel (CHI), fertilizer (FER), burned (BUR), plowing and harrowing (PH), and integrated crop-livestock (iCL). Runoff and sediment samples were collected and analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and organic carbon contents. Soil physical attributes and above and below biomass were also evaluated. The results indicated that higher water loss was observed for iCL (129.90mm) and CON (123.25mm) managements, and the sediment losses were higher for CON (10.24tha-1) and BUR (5.20tha-1) managements when compared to the other managements. Majority of the nutrients losses occurred in dissolved fraction (99% of Ca, 99% of Mg, 96% of K, and 65% of P), whereas a significant fraction of organic carbon (80%) loss occurred in a particulate form. Except for P, other nutrients (Ca, Mg and K) and organic carbon losses were higher in coarse sediment compared to fine sediment. The greater losses of sediment, organic carbon, and nutrients were observed for CON followed by BUR management (p<0.05). Our findings indicated that the traditional pasture management adopted in the Atlantic Rainforest needs to be rethought and burned management should be avoided. Based on the water, soil, and nutrient losses from various practices, to reduce pasture degradation, farmers should adopt edaphic practices by applying lime and fertilize to improve pasture growth and soil cover, and reducing soil erosion in the hilly Brazilian Atlantic Rainforest biome.

SOIL COVER AND CHEMICAL AND PHYSICAL ATTRIBUTES IN OXISOL IN THE ATLANTIC FOREST BIOME

The objective of this study was to evaluate the chemical and physical attributes of different soil cover in a Oxisol with a strong wavy relief in the Atlantic Forest Biome, in which were selected three watersheds, employed with grazing (watershed P), forest (watershed M) and coffee (watershed C). Deformed and not deformed samples were collected in three depths for physical and chemical characterization. The chemical characteristics of soil in different watershed studies presented low levels of fertility. It was observed an elevation of pH in the soil and contents of Ca2+ and Mg2+ in the watersheds P and C in relation to the watershed M. Due to deforestation and the establishment of agriculture and livestock, there was a decrease in the contents of soil organic matter in the watershed P and C, not altering the physical characteristics of the soil in the watershed P. The implementation of coffee plantation is causing a reduction in the soil quality of watershed C in comparison to the watershed P and M, therefore indicating a need to adequate soil management in this area.

Soil carbon stock in silvopastoral system, pasture and sugarcaneculture

espanolLa conversion de sistemas naturales en tierras agricolas es uno de los principales factores responsables por la reduccion de la reserva de C en el suelo y el aumento de la liberacion de C-CO2-1, 3494 Mg ha-1 y 1964 Mg ha-1 para las areas con cana de azucar, sistema silvopastoril y pastizal, respectivamente. El manejo de lafertilizacion y de la cosecha de cana de azucar en la region de Gobernador Valadares es eficiente en el incremento de las reservas de C en el suelo, siendo incluso superior que las reservas encontradas en el fragmento florestal, y el area silvopastoril presenta mayor potencial para el almacenamiento de C en los estratos superficiales (0-10 cm y 10-20 cm) comparado con las areas de pastoreo continuo. EnglishThe conversion of natural system in tillage agriculture areas is largely responsible for the reduction of Organic Carbon stock (OC-stock) in the soil and increases C-CO2 atmospheric release in tropical countries. The objective of this study was to evaluate the impacts of different situations of soil uses (silvopastoral, pasture and sugarcane) in OC-stocks of Utilsols in the regions of Vale do Rio Doce in the state of Minas Gerais. It was determined contents of total soil organic carbon (SOC) and soil bulk density (Bd) in different situations studied. The use of anthropic soil is promoting the increase of the soil Bd due to the deployment of cultures being preformed mechanically, therefore the systems provided higher content of SOC and consequently increased the OC-stock. The highest content of SOC was found in the area with sugarcane. The studied situations provided increase in the OC-stock in depth 0-10 cm, of 5,397 Mg ha-1, 3,494 Mg ha-1 and 1,964 Mg ha-1 for sugarcane, silvopastoral system and pasture. The management of fertilization and harvesting of sugarcane in the region of the city Governador Valadares is efficient in increasing the OC-stock, including being greater than the secondaryforest, and the silvopastoral site shows a greater potential in carbon stocking in the surface layers (0-10 cm and 10-20 cm) compared to continuous grazing areas.

Cutting frequency effect on barium phytoextraction by macrophytes in flooded environment: A field trial

In anoxic environmental conditions and with a drastic reduction of the redox potential, the barium sulphate used in petroleum drilling fluids becomes a hazard to the ecosystem. A field study was conducted in Brazil in an area with a history of accidental Barium (Ba) contamination to evaluate the role of frequent plant cutting on phytoremediation. The plant species Typha domingensis and Eleocharis acutangula, cultivated in a combined plantation, were subjected to four different cut frequencies: every 90 days (four cuts), 120 days (three cuts), 180 days (two cuts), or 360 days (one cut). The total amount of Ba extracted from the soil by the plants was evaluated for each treatment and at different soil depths Overall, total Ba in the soil decreased the most dramatically for cut frequencies of 120 (37.83%) and 180 (47.73%) days at 0-0.2 m below the surface, and with cut frequencies of 120 (51.98%) and 360 (31.79%) at 0.2-0.4 m depth. Further, total Ba in the plant biomass was greatest in the 120 and 360-days frequency groups. Thus, cuts at intervals of 120 days or more are associated with high levels of Ba in the plant tissue and a decrease of soil Ba.