Conserving Soil Quality On Farms In Hawaii - Research Paper Example

?Conserving Soil Quality on Farms in Hawai'i Soil quality and the conservation of soil quality is an often overlooked part of environmental and economical maintenance. Without quality soil available for the use of plant and microbial life, neither crop production for human consumption nor an area's natural ecosystem can be supported. Soil quality conservation is a major concern because it directly and significantly affects the world's food supply. As soil quality declines, the food quality and food security from that soil also declines. However, crop yield declines at rate exponential to the rate of decline in the soil quality, meaning that soil quality conservation must begin before the soil is clearly suffering. By the time measurable damage to the soil quality has occurred, crop yield may already be irrecoverably failing (Stocking, 2003). This relationship can even hold true in areas that with volcanically-enriched soil such as the tropical islands of the state of Hawai'i. To understand soil conservation for farming in Hawai'i, the first step is to understand the background of soil quality conservation, with a focus on the issues specific to the tropical islands. Only then can workable solutions be found and analyzed for suitability to the specific situation found on the Hawai'ian islands. A clear definition of soil quality is necessary for a conservation project to be undertaken. Unless soil quality is clearly and definitively described, it is impossible for researchers to design tests and measurements to study the current state of the soil quality. However, soil quality has proven a very difficult concept to define, especially as soil quality has so many different parameters in many different spheres of scientific study. Defining soil quality as a term is not the same as defining other widespread environmental terminology such as air quality or water quality. This is due to the fact that air quality or water quality are not based on the usage of the material or its relationship relative to a “natural” state, but merely on the lack of specific pollutants or on the levels of such pollutants (Sojka & Upchurch, 1999). Since pure soil cannot exist by definition, and clean soil varies dependent on location, pollutants within soil can be limited only to specific non-natural products, such as industrial wastes or household chemicals (Cowan & Talaro, 2006). Soil quality, on the other hand, is determined by the soil's ability to support certain usage and by healthy levels of bacterial, animal, and plant life (Sojka & Upchurch,1999). Measuring soil quality in tropical regions, on the other hand, is simplified because of the reduction in the number of related variables. Many attributes of topsoil quality in tropical regions of the world, including Hawai'i, are quantitative and measurable. Assuming those conditions to be true, soil quality can then be measured using a fertility capability soil classification system (Sanchez, Palm, and Buol, 2003). Other single-attribute measurements of soil quality are such concerns as soil compactability or erodibility based on location or use, but the fertility classification most affects the ability of the soil to support intensive crop farming, which is the concern of this review (Parr et al., 1992). The fertility capability classification systems are not without their faults, but they provides a starting point for measuring the success of a given conservation program by providing a quantitative standard. A measurement that makes use of this system would be comparable to future measurements under the same system, allowing a researcher to compare numerically the success of the method under study (Sanchez, Palm, & Buol, 2003). Soil systems in tropical regions tend to be extremely dynamic, changing rapidly over short periods of time. Within these systems, soil quality may vary widely from location to location even between patches of soil in the same forest (Parr et al., 1992; Stocking, 2003). In such a dynamic system, nutrients rarely have time to accumulate in the tropical topsoil. Instead, these nutrients are metabolized almost as soon as they are released by other life (Cowan & Talaro, 2006). For example, carbon in Hawai'ian topsoil may undergo a complete cycling in less than thirty years (Townsend, Vitousek, & Trumbore, 1995). This rapid cycling is related to the reduction of variables in studying tropical soil quality, because it leaves the soil itself without many factors to be measured with regard to nutrient availability and potential soil fertility. The carbon and nitrogen in a tropical ecosystem are primarily caught up in the living biomass of the ecosystem, not passive within the soil (Parr et al., 1992). Hawai'i soil quality has been steadily declining, as evidenced by a reduction in nitrogen in the soil. The soil with the highest fertility, and the highest nitrogen gas production from the soil, is the oldest, over twenty thousand years of decomposition buildup. As this quality soil is exhausted, it is not given time to regain enough nitrogen to meet demand. The recent soil, less than three hundred years old, is measured with significantly lower nitrogen levels and therefore will sustain much less crop production before it is completely exhausted of nutrients (Crews et al., 1995). Study of soil quality conservation is especially important in Hawai'i because of its unique combination of highly variant temperature, due primarily to large changes in altitude on single islands and between various islands, and variations in land use (Townsend, Vitousek, & Trumbore, 1995). Additionally, the presence of prevailing ocean winds means that the windward side of any island will have markedly different soil characteristics from the protected side of the same island, as they could be considered to have different climates. Additionally, Hawai'i contains examples of ten of the twelve soil orders, making it an extremely unique and valuable resource (Deenik and McClellan, 2007). Much of the Hawai'ian islands' forests have been left in a natural state due to their tourist attraction, but many areas have also been intensively farmed for a single crop, usually sugarcane, or converted into residential usage (State of Hawaii Land Use Commission, n.d.). Nutrient turnover time in the topsoil doubles with changes as small as ten degrees Celsius, which indicates a need for quality conservation efforts to take altitude and temperature in consideration when measuring the effect of the program (Townsend, Vitousek, & Trumbore, 1995). Soil conservation solutions depend primarily on the farmers in a targeted area actually implementing them. Neither smallholders nor commercial farms will implement soil quality initiatives that have a negative financial impact on their production. Therefore, any proposed solution must be cost-effective and, if possible, even profitable. The solutions must also be easy to implement and require low amounts of effort to maintain (Lutz, Pagiola, & Reiche, 1994). Though these costs cannot ever be completely eliminated, all possible effort must be undertaken to reduce the initial impact of required manpower to implement such necessary changes. Additionally, solutions requiring land loan, such as risers or terraces, must attempt to minimize the land needed for the changes to be effective (Sheng, 1989). While such limitations may seem to reduce the effectiveness of a soil quality conservation program, no conservation program can be effective at all if the farmers it is intended to help refuse to implement it due to cost concerns or lack of the required manpower. Making use of the input of the local farmers is another method that will improve the implementation of a conservation program, since their beliefs about science will affect their openness to certain ideas about farming and conservation (Lutz, Pagiola, & Reiche, 1994). One major impact on soil quality for cultivated crops is the presence of crop residue (Kumar and Goh, 1999). Crop residue is vital in providing nutrients for future crop production, especially in returning useful levels of nitrogen to the soil. Decomposition of plant matter in the soil is what provides the habitat for the microbes that recycle nutrients and allow continued plant growth in a particular patch of soil (Cowan & Talaro, 2006). Determination and implementation of a superior crop residue management system would be highly beneficial to the future conservation of soil quality on intensive production farms in Hawai'i (Kumar & Goh, 1999). Additionally, use of efficient crop residue management techniques can help reduce the speed of global warming by trapping the carbon produced by the plant life as passive soil organic carbon. Reducing the human addition to the carbon impact on global warming will have long-term effect on food security and crop yield for generations to come (Lai, 1997). An additional method for reducing loss of soil quality on farms is the usage of conservation tillage. Conservation tillage systems may be extremely complex and varied, or they may be as simple as stopping tillage on certain areas for periods of time. The use of these types of tillage systems allows the soil to recover its nutrient load before it is used again for crop production, and are also designed to reduce erosion and manage crop residue. Since loss of topsoil due to erosion is another issue that reduces soil quality, conservation tillage has a multi-faceted effect on the ability of the soil to support farming (Magdoff & Weil, 2004). Removal of just seven centimeters of topsoil in research done in Hawai'i significantly reduced nitrogenase activity, indicating that the largest percentage of nitrogen-fixing bacteria live in that upper portion of the soil. Erosion of this layer would then have a major impact not only on the current fertility of that soil but also on the soil's future ability to restore nutrient balance and maintain future crop production levels (Young, 1989). Areas of soil that have previously been used for farming in Hawai'i are sometimes used as space to replicate tropical tree stands and help reforest the islands. However, there is still a concern that planting trees on the possibly compromised soil would have a negative effect on the surrounding ecosystem. Zou found that the presence of abnormally high levels of earthworms under the leaf litter in these farms helped control the effect of the trees on the tropical soil, since nitrogen content in the leaf litter had a positive correlation with the density of earthworms in the leaves but a negative correlation with nitrogen ratio (1993). Perhaps the addition of these earthworm species into intensively farmed areas could help restore the nitrogen balance of the soil and maintain crop yield without further detracting from the soil. Other uses of trees to help restore soil quality involve using artificial tree farms to reduce soil erosion (Young, 1989). As discussed above, reducing topsoil erosion helps to reduce the loss of overall soil quality, since most of the nutrients in the soil are found in the topsoil layer. This may also help meet the other desired characteristic of a a conservation program: profitability. Depending on the species of tree being forested, sustainable logging could be used to harvest wood from the forest, simultaneously protecting the soil and the economy of the local areas. None of the solutions listed here will unilaterally solve the problem of soil quality conservation on farms in Hawai'i. The problems of wind erosion, human impact both today and historically, and fundamentals difficulties in soil studies are currently insurmountable. But with further research and analysis, perhaps in the future a researcher will find the perfect fix. Today's solutions of communication with and understanding of local farmers, reduction of erosion through the usage conservation tillage, and the use of replicated eucalyptus tree forests will, however, go a long way toward achieving this goal. References Cowan, M. K., and Talaro, K.P.. "Soil Microbiology: The Composition of the Lithosphere." Microbiology: A Systems Approach. New York: McGraw-Hill, 2006. 779-81. Crews, T. E., Kitayama, K., Fownes J.H., Riley R.H., and Herbert, D.A.. "Changes in Soil Phosphorus Fractions and Ecosystem Dynamics across a Long Chronosequence in Hawaii." Ecology 76.5 July (1995): 1407-24. Deenik, J. and McClellan, A.T. College of Tropical Agriculture and Human Resources. 2007. Soils of Hawai‘i. Retrieved 4 Mar. 2011 from http://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-20.pdf Kumar, K, and Goh K.M. "Crop Residues and Management Practices: Effects on Soil Quality, Soil Nitrogen Dynamics, Crop Yield, and Nitrogen Recovery." 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Sojka, R E., and Upchurch. D.R. "Reservations Regarding the Soil Quality Concept." Soil Science Society of America Journal 63.5 Sept. (1999): 1039-54. State of Hawai'i Land Use Commission, n.d. http://luc.state.hi.us/ Stocking, M A. "Tropical Soils and Food Security: The Next 50 Years." Science 302.564921 Nov. (2003): 1356-59. Townsend, Alan R., Vitousek, P.M., and Trumbore. S.E. "Soil Organic Matter Dynamics Along Gradients in Temperature and Land Use on the Island of Hawaii." Ecology 76.3 Apr. (1995): 721-33. Young, A. Agroforestry for Soil Conservation. Wallingford: CAB International, 1989. Science and Practice of Agroforestry. Zou, X. "Species effects on earthworm density in tropical tree plantations in Hawaii." Biology and Fertility of Soils 15.11 Jan. (1993): 35-38. Read More