Chapter three - Agricultural Practices in Oil Palm Plantations and Their Impact on Hydrological Changes, Nutrient Fluxes and Water Quality in Indonesia: A Review
Introduction
Oil palm (Elaeis guineensis) is one of the most rapidly expanding crops in the tropics. Since the early 1980s, the global land area under oil palm production has more than tripled, reaching almost 15 million ha in 2009 and accounting for almost 10% of the world's permanent crop land (FAOSTATS, 2011, Sheil et al., 2009) Most of this increase has taken place in Southeast Asia. Together, Malaysia and Indonesia account for almost 85% of the 46.5 million tons of crude oil palm produced in the world, Indonesia being the top producer since 2007 (Oil World, 2011, USDA (United States Department of Agriculture), 2007). The area covered by smallholder plantations in Indonesia increased nearly 1000-fold between 1979 and 2008, reaching almost 3 million ha, representing 39% of Indonesian oil palm plantations currently, the remaining 4.5 million ha being large private (52%) and government-owned (8%) plantations (IMA, 2010).
Although oil palm cultivation is a strong driver of economic development in Indonesia, providing jobs and incomes to millions of people (USDA, 2007), it is strongly denigrated for its environmental impacts. Many media and NGOs accuse oil palm plantation development in Southeast Asia of triggering deforestation, loss of biodiversity, peatland degradation, and high greenhouse gas (GHG) emissions (Greenpeace, 2011; WWF, 2011). In the scientific community, there is controversy about the positive and negative aspects of the expanding oil palm cultivation and potential environmental risks, which has been discussed at length in the scientific literature (Basiron, 2007, Lamade and Bouillet, 2005, Nantha and Tisdell, 2009, Sheil et al., 2009). The development of oil palm plantations, which frequently cover tens of square kilometers in Southeast Asia, involves land clearing, road and drainage network construction, and sometimes earthworks such as terracing on undulating areas. The use of agrochemicals, such as fertilizers and pesticides, might represent a potential risk for the sustainability of aquatic ecosystem and hydrological functions when agricultural practices are not optimized. In particular, oil palm growers usually apply large amounts of commercial fertilizer and thus are among the largest consumers of mineral fertilizers in Southeast Asia (Härdter and Fairhurst, 2003). However, hydrological processes within oil palm plantations are still not fully understood, and few studies have examined the impacts of agricultural practices on terrestrial hydrological functions and water quality in nearby aquatic ecosystems (Ah Tung et al., 2009), although aspects that impact on water quality are by far the largest component of an environmental risk register accounting for nearly 50% of all entries in oil palm plantations (Lord and Clay, 2006).
This review aims to document the current state-of-knowledge of agricultural practices in oil palm plantations that potentially impact hydrological functions and water quality in surface waters, with a focus on nutrient loading of surface waterways, and to highlight research gaps in the understanding of these processes. This work focuses on the situation in Indonesia, with examples from other oil palm producing countries in the humid tropics as appropriate. First, the expansion of oil palm cultivation in Indonesia, relevant environmental issues, and polemics will be presented. Next, typical agricultural practices in industrial and smallholder oil palm plantations will be discussed, focusing on nutrient, soil, and water management. Finally, the last section gives the state-of-the-art knowledge of hydrological changes and associated nutrient fluxes from oil palm plantations compared to tropical rainforests, which were the dominant natural ecosystem prior to oil palm plantation establishment. Relevant processes in the hydrological cycle and their magnitude and relevance in oil palm plantations will be explained in this section, but we do not provide an in-depth discussion of hydrological processes in rainforests, as a number of reviews were already published on this topic (Bruijnzeel, 1991, Bruijnzeel, 2004, Elsenbeer, 2001).
Section snippets
Palm oil utilization
Palm oil is derived from the plant's fruit, which produces two types of oils: crude palm oil (CPO), which comes from the mesocarp of the fruit, and palm kernel oil, which comes from the seed in the fruit. Most CPO is used for food products, while most palm kernel oil is used in nonedible products such as detergents, cosmetics, plastics, as well as a broad range of other industrial and agricultural chemicals (Wahid et al., 2005). The oil palm is the most productive oil crop in terms of oil yield
Climate and soil conditions
The African oil palm (Elaeis guineensis, family Arecaceae) is a tropical forest palm native to West and Central African forests. Oil palm needs humid equatorial conditions (1780–2280 mm annual rainfall and a temperature range of 24–30 °C) to thrive, and so conditions in Southeast Asia are ideal (Corley and Tinker, 2003). Palm productivity benefits from direct sunshine: the lower incidence of cloud cover over much of Southeast Asia is thought to be one reason why oil palm yields are higher there
Hydrological Processes and Associated Nutrient Transfers in Oil Palm Plantations
Replacing a natural forest with an oil palm plantation is expected to drastically change the existing characteristics of the area and to modify the hydrological cycle, shown in Fig. 4 (Henson, 1999). The activities related to the oil palm plantation establishment and exploitation (e.g., complete clearing of forested areas, construction of roads and drainage networks, fertilizer and agrochemical use, wastewaters release from mill and worker residences) are expected to cause problems related to
Conclusion
Since the 1960s, research effort focused on plot-scale trials in Southeast Asia to provide agronomic recommendations for plantation managers that would increase productivity and economic returns for the palm oil industry. Growing awareness of environmental impacts from the rapidly expanding oil palm sector, driven by media and socioenvironmental NGOs, led to the creation of RSPO to promote a sustainable palm oil production. This organization encourages planters to assess the environmental
Acknowledgments
This study was partly funded by the International Cooperation Centre in Agronomic Research for Development (CIRAD) and the Natural Sciences and Engineering Research Council of Canada (NSERC).
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