Visual assessment of pasture degradation: validation by ground cover and seasonal variation1 1 Parte da Dissertação de Mestrado do primeiro autor, apresentada ao Programa de Pós-Graduação em Produção Vegetal da Universidade Federal do Espírito Santo, Centro de Ciências Agrárias e Engenharias, Campus Alegre, ES

Avaliação visual da degradação em pastagens: validação pela cobertura do solo e variação sazonal

Edevaldo de Castro Monteiro Diego Lang Burak Alexson de Mello Cunha Renato Ribeiro Passos Eduardo de Sá Mendonça About the authors

ABSTRACT

Visual assessments of pasture degradation levels are widespread because they are rapid, practical and inexpensive. However, they can be subjective, making it difficult to distinguish between degradation levels to establish management practices. This fact, in association with the lack of standardization of the number of levels and the assessment periods, suggests a need for further studies. The objective of this study was to evaluate the relation between the degradation levels of visually evaluated pastures and the soil cover measured in fields in summer and winter. Percentages of Brachiaria grass, bare soil, spontaneous vegetation (broad and narrow leaf) and mulch were evaluated in 35 areas with different levels of visual degradation. Canonical discriminant analysis showed that a reduction in the visually assessed degradation level correlates better with the field-measured soil cover in summer. Visual distinctions between the degradation levels were difficult by the visual ambiguity between spontaneous vegetation and pasture in both assessment periods and the visual ambiguity between bare soil and mulch in winter. Visual assessments of pasture degradation should be standardized in the summer period and simplified to two degradation levels, making them more accurate and better related to the vegetation cover measured directly on the field.

Key words:
Brachiaria spp; Soil cover; Multivariate analysis; Quality assessment

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