Resumo

LOK MEJIAS, Sandra; CRESPO, G  e  TORRES, Verena. Influence of forage legumes on the soil-grass system. Cuban J. Agric. Sci. [online]. 2017, vol.51, n.2, pp. 261-270. ISSN 2079-3480.

The research was conducted during 15 years at the Instituto de Ciencia Animal, located in Mayabeque, Cuba, to evaluate the ecological and productive impact of legumes in the soil-grass system of tropical livestock areas. Two grasslands were studied: 1) Silvopastoral with Leucaena leucocephala / Megathyrsus maximus and 2) Herbaceous legume mixture in association with grasses. By means of principal components analysis, the indicators with higher contribution to the variability of each grassland were selected to evaluate their performance every five years. Those with a preponderance value higher than ± 0.78 and explained at least 65 % of the accumulated variance were chosen. In the vegetation, up to 50 indicators were studied and 7 to 9 were selected, in which the plant coverage, the density of the grass and the presence of natural grasses coincided. From the 76 soil indicators, between 6 and 9 were selected, in which the distribution of aggregates in dry and humid conditions, structural stability, Value n and underground phytomass were highlighted. Also, the soil quality index and the organic carbon stored in the soil (CSS) were evaluated. The silvopastoral grassland during the first 12 years of continuous explotation had plant coverage higher than 95 %, 6 and 9 plants m² of Guinea grass, 4 and 6 t DM ha^-1 and a gradual improvement of soil fertility, with a predominance of aggregates in humid conditions between 1 and 5 mm, with values between 25 and 58%. From the 14 explotation years, there was no difference in the performance of the indicators, which showed their stability and the balance in the soil-grass system. In the mixture of legumes with grasses from the 12 years of exploitation decreased glycine but recovered the total legumes percentage, which were characterized to have higher predominance in the dry season. Both grasslands had good soil quality, increased the organic carbon stored in the soil (CSS) and maintained productive and ecological stability. Confidence tables for indicators are showed which can be used as reliable and sensitive tools to detect changes in grasslands and can be used in research, teaching and production.

Palavras-chave : grass- legumes associations; soil; livestock; sustainabi-lity.

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