ABSTRACT Machinery traffic intensification has been recurrent in intensive agriculture in annual crops, which may lead to structural soil degradation and, consequently, a reduction of its productive capacity. Therefore, this study aimed to assess the influence of tractor traffic intensification on soil physical attributes and soybean yield components. The study was performed in an Oxisol under no-tillage for 10 years, using a randomized block design with five tractor traffic intensities (0, 2, 4, 6, 8, and 12 passes) and five replications. Density, porosity, macroporosity, microporosity, and penetration resistance were assessed in the soil and stem diameter, number of pods per plant, number of grains per pod, grain weight per plant, thousand-grain weight, and grain yield were assessed in the soybean crop. Tractor traffic intensification changed soil physical attributes, which were not limiting factors to soybean yield under the no-tillage system, providing higher stem diameter, number of pods per plant, grain weight per plant, and grain yield after 12 passes.

ABSTRACT Soil resistance to penetration is an indicator of easy measurement which can be used to make scarification / subsoiling recommendations in areas that work with localized management. The objective of this study was to evaluate the spatial variability of soil resistance to penetration (RP) in the area of direct sowing system, and to carry out the recommendation of scarification / subsoiling in a localized way through precision agriculture. The research was conducted in commercial area, in a field of 49.12 ha. The RP collection was with an electronic penetrometer in a sample mesh of 47 points distributed regularly in the area, with georeferenced points. The data were analyzed every 0.10 m being collected up to 0.40 m depth, in addition to obtaining the mean and maximum RP values in the profile (0 – 0.40 m), and the depth value of the maximum RP in the profile. Soil samples were collected randomly in the area to characterize the water content at the time of RP collection. Data were analyzed using descriptive statistics and geostatistics. The resistance to penetration (RP) presents moderate to strong spatial dependence in the evaluated layers. The RP is in most of the area below the critical limits which demonstrates that there is no need to perform a scarification / subsoiling in the total area, only in a localized way.

ABSTRACT With the short period of the sowing process, we observed an increase in the seeder speed set in several soil management systems that may result in decreased soybean yield and problems with penetration resistance. We aimed to assess the penetration resistance (PR) and agronomic characteristics of soybean on soil tillage and sowing speed. The randomized block design in split plot with four replications was used. The treatments consisted of six management systems, applied to the plots: no tillage (NT), no tillage and chiseling (NTc), no tillage and cross chiseling (NTcc), conventional tillage (CT), reduced tillage (RT) and conservation tillage (CsT) and four speeds, (4.6; 5.5; 7,3 and 7.8 km h-1) applied in the subplot at the time of soybean seeding. We observed in the deep layers 0.0 – 0.10; 0.10 – 0.20 and 0.20 – 0.30 m significant effect of tillage systems on the PR of the soil. The NT system showed the highest value of PR compared to other management systems studied. In the NT should be used sowing speeds above 5.5 km h-1 to decrease the compression. Low speeds favor higher yield by improving pods per plant. Speeds in the working range (5-7 km h-1) promote higher productivity by improving the number of pods per plant, and provide better stand.

RESUMO O conhecimento da sorção de água pelos produtos agrícolas é extremamente importante para a tomada de decisões durante os procedimentos pós-colheita; visando aperfeiçoar este conhecimento as propriedades termodinâmicas relativas à sorção de água fornecem dados úteis. Propriedades termodinâmicas de grãos de mamona relacionadas à sorção, foram determinadas. A técnica de gravimetria estática em diferentes temperaturas (25, 35, 45 e 55 ± 1 °C) foi usada e soluções salinas saturadas na faixa de 37-87% ± 2% foram utilizadas para criar o requerido ambiente controlado de umidade relativa. Entalpia diferencial, entropia diferencial e energia livre de Gibbs foram calculadas e decresceram com o aumento dos valores de teor de água de equilíbrio.

ABSTRACT Knowledge on the water sorption within agricultural products is extremely important for decision making during post-harvest procedures. In order to improve this knowledge, thermodynamic properties regarding water sorption provide useful data. Thermodynamic properties of castor beans, related to sorption, were determined. Static gravimetric technique under different conditions of temperature (25, 35, 45 and 55 ± 1 °C) was used. Saturated salt solutions in the range of 37-87% ± 2% were utilized to create the required controlled humidity environment. After the sorption procedure, differential enthalpy, differential entropy and Gibbs free energy of this process were calculated and decreased with increased values of equilibrium moisture content.