Rubismar Stolf

Method to estimate soil macroporosity and microporosity based on sand content and bulk density

Macroporosity is often used in the determination of soil compaction. Reduced macroporosity can lead to poor drainage, low root aeration and soil degradation. The aim of this study was to develop and test different models to estimate macro and microporosity efficiently, using multiple regression. Ten soils were selected within a large range of textures: sand (Sa) 0.07-0.84; silt 0.03-0.24; clay 0.13-0.78 kg kg-1 and subjected to three compaction levels (three bulk densities, BD). Two models with similar accuracy were selected, with a mean error of about 0.02 m3 m-3 (2 %). The model y = a + b.BD + c.Sa, named model 2, was selected for its simplicity to estimate Macro (Ma), Micro (Mi) or total porosity (TP): Ma = 0.693 - 0.465 BD + 0.212 Sa; Mi = 0.337 + 0.120 BD - 0.294 Sa; TP = 1.030 - 0.345 BD 0.082 Sa; porosity values were expressed in m3 m-3; BD in kg dm-3; and Sa in kg kg-1. The model was tested with 76 datum set of several other authors. An error of about 0.04 m3 m-3 (4 %) was observed. Simulations of variations in BD as a function of Sa are presented for Ma = 0 and Ma = 0.10 (10 %). The macroporosity equation was remodeled to obtain other compaction indexes: a) to simulate maximum bulk density (MBD) as a function of Sa (Equation 11), in agreement with literature data; b) to simulate relative bulk density (RBD) as a function of BD and Sa (Equation 13); c) another model to simulate RBD as a function of Ma and Sa (Equation 16), confirming the independence of this variable in relation to Sa for a fixed value of macroporosity and, also, proving the hypothesis of Hakansson & Lipiec that RBD = 0.87 corresponds approximately to 10 % macroporosity (Ma = 0.10 m3 m-3).

Incorporação de régua para medida de profundidade no projeto do penetrômetro de impacto Stolf

The Stolf impact penetrometer is a dynamic cone penetrometer to measure soil resistance, in use since its release in 1982. In the original design, a centimeter scale to measure penetration depth was engraved on the proper penetration rod. The idea was to make the equipment easier to understand for farmers and to allow direct readings on the penetration rod while also avoiding additional parts. The purpose of this study was to incorporate a millimeter ruler to enable the operator to read the depth at eye level, to avoid squatting and to increase the reading accuracy. The equipment use and reset procedure of the depth reading (zero) were described and illustrated. The two reading types were compared in terms of sampling time, using a randomized block design. A significant difference (t test, 1 %) was observed, resulting in 21 % less time spent for readings on the ruler. Besides increasing the reading accuracy and reducing the sampling time, the users preferred the new design, which was finally incorporated into the commercial model. A retrospective of the technical development of the penetrometer is presented; this study represents the first modification of the project, which had remained unaltered for 30 years.

Shade Trees Spatial Distribution and Its Effect on Grains and Beverage Quality of Shaded Coffee Trees

Shading coffee trees has gained importance, especially among smallholders, as an option to improve the products’ quality, therefore acquiring place at the specialty coffee market, where consumers are willing to give bonus for quality. This work aims to evaluate the influence of shade trees’ spatial distribution among coffee trees’ agronomic characteristics, yield, and beans and cup quality of shaded coffee trees. The experimental design consisted of completely randomized blocks with six repetitions and four treatments: coffee trees on shade trees planting rows, distant one meter from the trunk; coffee trees on shade trees planting row, distant six meters from the trunk; and coffee plants between the rows of shade trees, parallel to the previous treatments. The parameters analyzed were plant height, canopy diameter, plagiotropic branches’ length, yield, coffee fruits’ phenological stage, ripe cherries’ Brix degree, percentage of black, unripe, and insect damaged beans, bean size, and beverage quality. Shade trees quickened coffee fruits’ phenological stage of coffee trees nearest to them. This point also showed the best beverage quality, except for overripe fruits. The remaining parameters evaluated were not affected by shade trees’ spatial distribution.

Rapid Assessment of Habitat Diversity Along the Araras Stream, Brazil

Agriculture, urbanization, and industrialization are some of the anthropogenic activities that constantly generate negative impacts on natural environments. Part of this degradation directly affects aquatic systems. This study aimed to evaluate the visual characteristics of the Araras Stream, located in the municipality of Araras, São Paulo state, Brazil. Data was collected at six different assessment sites along the river in both rural and urban areas. The evaluation used a Rapid Habitat Diversity Assessment (RHDA) protocol composed of 22 parameters, which define levels of preservation of ecological conditions. According to this protocol, the 32 Km-long study transect along the Araras Stream was rated as impacted (39.6 points). A separate assessment by transects showed that only Transect 1 presented a natural level of preservation (71.8 points). Transects located in the urban area contributed the most to impacts on the aquatic environment. The RHDA protocol proved to be an important tool to evaluate and monitor aquatic environments.