Sustainable Land Management at Ramu Sugar Plantation: Assessment and Requirements

Ramu Sugar Plantation was established in 1979. This paper presents an overview of changes in soil chemical and physical properties that have resulted from continuous sugarcane cultivation since that time. Between 1979 and 1996, the soil pH decreased from about 6.5 to 5.8 and this acidification was accompanied by a decrease in cation exchange capacity and exchangeable cations. Organic carbon levels declined from about 56 grams per kilogram in 1979 to 32 grams per kilogram in 1996. The inter-row of the sugarcane was compacted and had significantly higher bulk densities and a very slow water intake. Semiquantitative nutrient budgets showed a shortfall in nitrogen, phosphorus and potassium, and levels of these nutrients in the sugarcane leaves significantly decreased between the mid-1980s and 1990s. Yields at the plantation are largely determined by insect pests, diseases and weeds. It is concluded that significant soil changes occurred that may affect the sustainability of sugarcane growing in the long term if such trends continue. THE term ‘sustainable land management’ is difficult to define, but in essence refers to the combination of production and conservation of the natural resources on which the production depends (Young 1997). The soil is the most important component in sustainable land management as indicated by pedologists (Bouma 1994), soil fertility experts (Scholes et al. 1994) and soil biologists (Swift and Sanchez 1984). Assessing sustainable land management is as difficult as defining it. Key problems are choosing the spatial and temporal borders for assessment (Fresco and Kroonenberg 1992) and the indicators for evaluating sustainability in a given locality (Smyth and Dumanski 1995). Long-term data are imperative to evaluate the sustainability of land management practices but they are scarce for tropical regions (Greenland 1994). Most studies dealing with sustainable land management have focused on subsistence agriculture. Relatively little attention has been given to high external input or plantation agriculture, which constitutes a major segment of the national economies in many tropical countries (Hartemink 1998b). An important plantation crop is sugarcane (interspecific hybrids of Saccharum spp.), which is mostly monocropped. Sugarcane production has dramatically increased in the past few decades. In the 1960s, sugar production in the world was about 64 million tonnes, of which half was produced in developing countries (FAO 1996). By the mid-1990s, production had increased to 119 million tonnes. About 76 million tonnes was produced in developing countries, of which 40 million tonnes was produced in Asia and the Pacific. Between the mid-1960s and 1990s, the largest expansion of * International Soil Reference and Information Centre, PO Box 353, 6700 AJ, Wageningen, The Netherlands. Email:[email protected]