Wilk Sampaio de Almeida

Erodibilidade, fatores cobertura e manejo e práticas conservacionistas em argissolo vermelho-amarelo, sob condições de chuva natural

The soil loss prediction models have become important tools for conservation planning, being fundamental the local estimation of the parameters that influence the erosion processes. The objective of this work was to determine the soil erodibility (K factor), soil cover and management factor (C factor) and conservation practice factor (P factor) of the Universal Soil Erosion Equation (USLE), in an Ultisol. Soil losses (SL) were measured in Wischmeier standard-plots from 2006 to 2011, with the respective erosivity index (EI30). Soil erodibility was calculated by the ratio of SL and the annual (Ka) and total period EI30 (Kt), considering the angular coefficient generated from the linear regression analysis between those parameters (Kci, for each rainy period, and Kct, for the studied period). The factors C and P were estimated for three years of maize in contour cultivation (MCL) and down in the slope (MDS). The Kt and Kct values were 0.0090 and 0.0106 Mg ha h ha-1 MJ-1 mm-1, respectively. The average calculated values for factors C and P are 0.0070 Mg ha Mg-1 ha-1 and 0.45, respectively, indicating a soil loss reduction of 55 % in MCL, compared to MDS. The values of the factors K, C and P obtained can be used as first approximation to soil and water conservation management projects in the region.

Evapotranspiration and crop coefficient for potato in organic farming.

The aim of this study was to quantify the water consumption and the crop coefficients (Kc) for the potato (Solanum tuberosum L.), in Seropedica, Rio de Janeiro (RJ), Brazil, under organic management, and to simulate the crop evapotranspiration (ETc) using the Kc obtained in the field and the ones recommended by the Food and Agriculture Organization (FAO). The water consumption was obtained through soil water balance, using TDR probes installed at 0.15m and 0.30m deep. At the different stages of development, the Kc was determined by the ratio of ETc and reference evapotranspiration, obtained by Penman-Monteith FAO 56. The crop coefficients obtained were 0.35, 0.45, 1.29 and 0.63. The accumulated ETc obtained in the field was 109.6 mm, while the ETc accumulated from FAOs Kc were 142.2 and 138mm, respectively, considering the classical values and the values adjusted to the local climatic conditions. The simulation of water consumption based on meteorological data of historical series from 1961 to 2007 provided higher value of ETc when compared with the one obtained in the field. From the meteorological data of historical series, it was observed that the use of Kc recommended by FAO may overestimate the amount of irrigation water by 9%, over the same growing season.