Forage production and diversification for climate-smart tropical and temperate silvopastures
Climate change creates much uncertainty for the future of animal agriculture, particularly due to an increase in summer droughts that result in the loss of range productivity. Silvopasture, the intentional integration of livestock, trees, and pasture on the same unit of land, is a promising option to diversify forage resources, compensate for losses caused by droughts during the summer forage gap, and in some cases, even increase agricultural production while maximizing conservation benefits. We examined three distinct silvopastures, two in the country of Panama and one in the state of Missouri, to better understand how the integration of woody perennial trees and shrubs affects forage productivity, availability, and nutritional value, particularly during the driest months. In Panama, we studied both recently established and mature silvopastures with the objective of assessing soil physical and chemical properties, plant water availability, and pasture dry matter production in different successional stages. In the mature silvopasture, we found that annual grass accumulation was greatest in open pastures, but was highest in silvopastures with moderately-spaced trees (~500 trees ha-1) early in the dry season. In the recently established silvopasture, the simultaneous growth of grasses, trees, and fertilizer shrubs resulted in significant increases in soil fertility and marginally significant increases in grass production in plots that included the shrub Leucaena leucocephala. Further, cumulative forage production in plots with shrubs provided on average 9.66% more forage than plots without shrubs during the dry season. In Missouri, we assessed the feasibility of integrating the potential alternative forage shrub red mulberry (Morus rubra L.) into the understory of an existing silvopasture and found that seedling survival, growth, leaf productivity, and nutritive value could be optimized at an overstory planting density of ~123 trees ha-1. High leaf mineral content and low fiber fractions during the late summer forage slump suggest that this species could serve as an effective supplemental forage to livestock in multi-strata silvopastures during drought conditions. Results of all three studies confirm that silvopasture has both competitive and facilitative influences on forage production, and that facilitative factors may be more prevalent during extreme drought.
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