Box 6-2. The importance of crop varietal diversification as a coping strategy to manage risk.
A study of traditional practices of conserving varieties of yam, Dioscorea sp., and of rice, Oryza glaberrima, was carried out in Ghana in 2003-2004 under an IPGRI-GEF-UNEP project on crop landraces in selected sub-Saharan African countries (Gyasi et al., 2004). It identified 50 varieties of yam and 33 varieties of rice that are managed by a wide diversity of locally adapted traditional practices in the study sites located in the semiarid savanna zone in the northern sector. The case study findings underscore the importance of crop varietal diversification as security against unpredictable rainfall, pest attack, fluctuating market and other such variable environmental and socioeconomic conditions, not to mention its importance for modern plant breeding and wider use of farm resources, notably labor and the diversity of on-farm ecological niches. posure of sensitive crop growth stages to seasonal climate variability.
Options for addressing this challenge include improving farmer access to quality seed, adoption of improved crop establishment practices, and the use of healthy seedlings in transplant systems. Seed priming—soaking seeds in water for several hours but short of triggering germination—is an example of a simple but effective technology for improving crop establishment. Priming of some seeds results in more even and fuller stand establishment, accelerates seedling emergence and improves early growth, often leading to earlier flowering and maturity, avoidance of late-season drought and improved yields (Harris et al., 2001; Harris, 2006). Experimental crop transplanting methods in millet-sorghum areas of Africa can also reduce planting risk; e.g., staggered transplanting from seedling nurseries to allow for variable onset of the rainy season (Young and Mot-tram, 2001; Mottram, 2003; CAZS, 2006). This method, though more labor intensive, results in faster crop establishment with fewer gaps, and a harvest 2-3 weeks earlier than conventional seeding methods, leading to higher grain and stover yields.
By reducing crop establishment risk and decreasing the time to maturity, these technologies provide a small measure of flexibility to farmers in high-risk environments. Technologically simple approaches to improve crop establishment and seedling vigor generally have minimal downside risks, immediate and tangible benefits, and can be easily tailored to producer needs; thus they are appropriate options for small-scale rainfed systems. Seed priming, which has been tested in a wide array of dryland cereals and pulses, consistently results in average 30% increases in yield with minimal farmer investment (Harris, 2006). Similar mean yield increases have been observed with seedbed solarization of rice nurseries, though with somewhat greater farmer investment in material and time. While these are simple technologies, they do require some local testing and training to ensure that proper techniques are followed. Millet transplanting systems show good potential, though labor shortages could be an issue in |
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some regions. An analysis of the tradeoff between labor for transplanting versus the labor and extra seed required for multiple resowing of millet fields would help to clarify the issue of labor expenditure.
Soils. Improved adoption of soil conserving practices can also mitigate the damaging effects of climate variability. Methods include the use of cover crops, surface retention of crop residues, conservation tillage, green manures, agro-forestry, and improved fallow (Sanchez, 2000; Benites and Ashburner, 2003; Lal, 2005). Although these are very sound practices for soil protection, achieving broad-scale and long-term adoption of them will be a significant challenge given the current and likely future, disincentives to investment as described in the previous subchapter (Stocking, 2003; Knowler, 2004; Cherr et al., 2006; Patto et al., 2006). The resilience of conservation farming systems in the Central American highlands to recent El Niño drought (Cherrett, 1999), and to the catastrophic soil losses from Hurricane Mitch (Holt-Gimenez, 2001) provide strong evidence of conservation agriculture's potential as an adaptation response to increased rainfall variability and storm intensity with climate change.
Long-term investment in rehabilitating degraded lands is another option for addressing the negative feedback between high rainfall risks and declining soil fertility. Recent evidence of revegetation and agricultural intensification in the Sahel, catalyzed by a crisis of diminished rainfall and declining yields (Herrmann et al., 2005; Reij et al., 2005; Tappan and McGahuey, 2007; USAID, 2006), could inform future AKST efforts at integrating soil and water conservation and land reclamation into adaptation planning. Technologies and practices deployed in these areas to reclaim declining or abandoned land include rock lines, rock "Vs", and manure-amended planting pits. These techniques were used to break soil crusts, enhance water capture and retention, and regenerate N-fixing trees to improve soil fertility. Soil reclamation using these methods encompassed several hundred thousand ha in Burkina Faso and Mali, and well over a million ha in Niger (Reij et al., 2005; Tappan and McGahuey, 2007; USAID, 2006). Important elements gleaned from these studies include:
• Legal code reforms that provided farmer, rather than government, ownership of trees was an essential precondition; the former sometimes taking the lead and the latter following;
• By improving land and claiming ownership, women were one of the main beneficiaries, and improved household food security one of the most tangible outcomes;
• Investment in fertilizer occurred after farmers invested in measures to conserve soil moisture and increase soil organic matter.
AKST could play an important role in documenting the effectiveness of these practices for seasonal climate risk management, e.g., investigating how these soil improvement practices affect soil fertility, soil moisture retention, and crop yields over a range of variable rainfall years, as well as conducting detailed socioeconomic analyses of how the benefits are distributed in local communities. Local control of the resource base is necessary for creating the enabling |