Page 160 - Ecuador's Banana Sector under Climate Change

ecuador’s banana sector under climate change: an economic and biophysical assessment to promote a sustainable and climate-compatible strategy
The imposition of a fertilizer levy, however, has some negative consequences. The yield and output of bananas would drop, contrary to the goal for “No más hectáreas de banano sino más bananos por hectárea” (Not more hectares of bananas, but more bananas per hectare). While it would be ideal to limit the tax on the excessive use of fertilizer, it is not administratively feasible.60
Another consequence of a fertilizer tax is that there is an extensive traditional agricultural sector in Ecuador, where fertilizer is underused. Higher fertilizer prices would further discourage the adoption and use of fertilizer in the traditional sector. The reduction in household welfare and nutrition could outweigh the benefits of lower GHG emissions by traditional-sector households.
The N2O emissions that are generated within the banana’s life cycle are usually calculated by multiplying the observed nitrogen content of nitrogenous fertilizer, applied by the factor 0.02. This fixed factor was determined by the IPCC (IPCC, 2006) and is applied in IPCC and FAO studies for calculating the agricultural emissions (Table 50) that are based on the agriculture values set by the World Resources Institute (Tables 51 and 9). The fixed factor is applied consistently to arable agricultural activities across the full range of soils and climatic conditions. On a global scale, where a simple standard method is necessary, this fixed factor is considered an appropriate approximation; variations above and below this imputed global mean largely cancel each other when aggregated on a large scale.
The use of this fixed factor in specific applications, however, can be misleading. First, it may over- or under-estimate actual N2O emission levels. Second, it can lead to the assumption that the relationship between applied nitrogen and N2O emissions is fixed and to the erroneous conclusion that the sole means of reducing N2O emissions is through the lesser application of nitrogen. In fact, the relationship between applied nitrogen and N2O emissions is not fixed. A growing body of research has found that agricultural N2O emissions are proportional to the inventory of surplus nitrogen in the soil, rather than to the total amount of nitrogen applied.61 Surplus nitrogen is the stock of nitrogen in the soil in excess of plant nitrogen uptake.62 Thus, closer synchronization of nitrogen applications to plant nitrogen uptake would reduce the surplus of nitrogen in the soil, increase the proportion
of applied nitrogen utilized by plants and reduce the proportion emitted as N2O. Cassman et al. (2002: 139) provides a summary statement:
well as develop information on the best management practices relating to fertilizer use. These efforts would represent a partial, indirect rebate of the fertilizer tax to the banana sector.
60 Ribaudo et al. (2011: 39-43) discusses the problems associated with fertilizer taxation. The study notes that several states in the United States have imposed fertilizer levies, which have not been effective in reducing nitrogen-related emissions.
61 Recent studies include Grassini and Cassman (2012), Venterea et al. (2012), Hoben et al. (2011) and van Groenigen et al. (2010). A seminal contribution is Cassman et al. (2002), which is a useful starting point to this literature, as are Paustian et al. (2004), Mosier et al. (2004) and Grassini and Cassman (2012). For studies focused on bananas and Ecuador, see Corre et al. (2013), Borbor-Cordova et al. (2006) and Veldkamp and Keller (1997).
62 The amount of surplus nitrogen is not easily observed. This justifies the use of the more observable quantity of applied nitrogen as a practical approximation by the IPCC.
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