Cambios en la estructura de un campo natural del litoral bajo dos métodos y dos intensidades de pastoreo

The present work was carried out at the Mario A. Cassinoni Experimental Station of the Faculty of Agronomy - University of the Republic, located on National Route No. 3 Gral. José Gervasio Artigas, Kilometer 363, in the department of Paysandú, Uruguay. The study was developed in on paddock 13 (La -32.387511°S y Lo -58.033235°O), covering an area of 37,8 hectares of reestablished natural grassland, where an experiment with factorial treatment structure (2x2) is set up to evaluate two grazing methods (Continuous and Rotational) and two forage allowance levels (High and Low, with combinations being 12% in spring-summer and 8% in autumn-winter, and 8% in spring-summer and 4% in autumn-winter, respectively). The animals used are Holando steers in the rearing phase. The forage allowance levels (FAL) are adjusted monthly according to forage availability (kg DM/ha) and the expected growth rate, regulating animal loads based on monthly weighing data. The evaluation period extended from July 24 to October 30, 2023, encompassing the winter-spring. The objective of the study was to characterize the structural heterogeneity and botanical composition of the natural grassland subjected to two different levels of forage supply and two different grazing managements, associated to the different types of soil presented in the pasture (Lowland, Mid-slope and Lithosol), according to cartography and visual field estimation. The variables determined were forage height (cm), forage mass present (kg DM/ha) and botanical composition. For the analysis of the results, the statistical software InfoStat was used, applying multivariate and univariate inferential statistical techniques (ANOVA). Subsequently performing mean comparison tests using Tukey’s test with significance level of 10%. The results showed that the pasture structure (height) was conditioned by the grazing method, more than the forage allowance level; with greater heights in the Rotational method. The botanical composition was primarily defined by the studied zone, with independent responses according to the grazing method and forage allowance level; observing contrasting sets in vegetative and productive types, according to these latter two factors.