Soil resilience and management of former sugarcane (Saccharum officinarum L.) lands on the Naparima Peneplain, Trinidad and Tobago
Keywords:Naparima Peneplain, soil resilience, land degradation, sugarcane, physical and chemical indices
The lands of the Naparima Peneplain, Trinidad and Tobago, are an invaluable resource with multiple land use characteristics including agricultural diversification. Sections are classified as Class V soils, non-resilient with minimum recovery over the medium term, and as Class IV soils, slightly resilient with improvements in medium term resulting in significant land management and land use changes. These lands were under sugarcane cultivation for centuries, from the colonial era until the closure of the sugar factory in 2003. Since then, as in so many other Caribbean territories, the land has been ear-marked for agricultural diversification and made available to small farmers for the production of commodities for the domestic market. Land use changes in the post-sugarcane era have resulted in approximately 14,000 hectares becoming available for possible agricultural diversification. However, the positive impact on domestic food supply that was anticipated has not materialized.
A land resource study was conducted in 2012–2014 in the La Gloria and Cedar Hill sections of Caroni (1975) Ltd lands on the Naparima Peneplain, to determine the effect of long-term sugarcane (Saccharum officinarum L.) cultivation on land degradation and soil resilience by comparison with data from historical records and to make recommendations on the way forward. Assessment of land use, chemical and physical soil properties, and extent of soil erosion, comprised the study.
The most severe land management factor was identified as chronic and widespread soil erosion, especially in Cedar Hill, with additional problems of subsoil exposure, soil slumping and movement. Soil erosion studies (Universal Soil Loss Equation (USLE)) indicate estimates of 35–74 t/ha affecting 75% of the lands. Historical records on soil physical indices such as bulk density, clay percentage in the profile and available water, revealed that these parameters were stable over the period 1977–2014. However, chemical indices, inclusive of organic carbon, nitrogen and pH, reflect significant decline correlated with reduced soil fertility and land abandonment. While identifying stable soil resilience indices is valuable, the immediate problem is the correction of soil erosion, which results in considerable land abandonment. Therefore, it is recommended that the land be restored to an acceptable level of soil fertility, specifically with respect to its organic matter content, and that infrastructural adjustments be made to stop or greatly minimize soil erosion so that these lands could be used to contribute to national food security as envisaged.