Visual Evaluation of Soil Structure in Brachiaria Decumbens Cv. Basilisk Swards.

Grassland ecosystems sustainability depends on the evaluation and monitoring of soil properties in order to avoid soil degradation. A visual evaluation of soil structure (VESS) method based on field assessment can provide a reliable, quick, simple and easily understood test to enable researchers, farmers and consultants to score soil quality (Sq). This way, present works aimed to evaluate the soil structure applying VESS method in an area with Brachiaria decumbens cv. Basilisk swards under different levels of soil base saturation (V%) and grazing intensities. Experiment was carried out at Faculdade de Zootecnia e Engenharia de Alimentos (FZEA/USP), Pirassununga, SP, Brazil, in a dystrophic Red Latosol (Oxisol). Pasture was seeded in November 2012 in 18 plots (80 m²), and it was maintained under free growth until October 2014, then rotational stocking was employed based on the criterion of 95% of light interception. Treatments comprised of combinations between three levels of soil base saturation (V% 35, 50 and 65) and two grazing intensities (40% and 60% of pre-grazing height) and were distributed in a randomized complete block design in a 3x2 factorial arrangement. The Sq score ranges from 1 (good) to 5 (poor soil structure), and were evaluated every 2 cm from 0 to 20 cm depth in triplicate. Measurements were made at the end of the growth period, in May 2016. VESS varied according and interaction between soil base saturation and grazing intensity (P < 0.0001). For all combinations, VESS Sq score were lesser than 2, indicating good structural quality of the soil and no changes needed in current management. However, more intensity of grazing with lower V% promoted higher value of VESS, indicating a possible injury in soil structure. On the other hand, a higher V% helps to keep Sq score close to 1, regardless grazing intensity.