Sustainable Land Management for Mitigating Climate Change

E. Biochar

74. Biochar refers to charcoal produced from biomass. Appropriately used, biochar can be applied as soil amendment for improving soil physical and biological properties (Sombroek et al., 2003; Rumpel et al., 2005; Lehman and Joseph, 2009). With high application rates, it can also lead to SCS especially in situations where biochar may be available. Biochar can by produced from surplus biomass such as those from sawmill, dairy farms, food processing units, rice husking mill, timber yard, etc. Biochar may also be produced as a co-product of a biofuel production system. The rate of application of biochar on cropland soils can be as high as 50-150 t/ha (Lehmann et al., 2006). However, the availability of biochar at such a high rate has logistic challenges. Apart from benefits of SCS and mitigating CC (Morris, 2006; Fowles, 2007), biochar can also improve soil fertility and increase agronomic production (Whitford, 2008). In Laos, Asai et al. (2009) reported that application of biochar improved saturated hydraulic conductivity of topsoil. It also increased grain yields at sites with low P availability and improved the response to N and NP chemical fertilizer treatments. In Colombia’s Orientale Savanna Oxisol, Major et al. (2006) reported that biochar application of 8 to 20 t/ha did not have a significant effect on maize yield during the first year, but increased it by 15% and 23%, respectively during the second and third year. In a pot culture experiment conducted on a hard-setting Alfisol in NSW Australia, Chan et al. (2007) reported significant changes in soil quality, SOC concentration, tensile strength at biochar application rates of >50 t/ha. Steiner (2007) also reported the beneficial effects of biochar application on soil fertility. But biochar may not be suitable in every situation. Apart from the logistics with regards to the biomass feedstock for producing biochar, application of fire-derived charcoal may also enhance loss of forest humus (Wardle et al., 2008). Therefore, identification of specific niches for biochar application is crucial to harvesting its benefits.

F. Water Management

75. Rainfall deficit and variability are serious constraints to increasing productivity of rainfed agriculture in places like the Sahel (Ayoub, 1999), and elsewhere. Droughts also aggravate the problem of soil degradation and erosion, vegetation damage, slough and lake deterioration and wildlife loss (Maybank et al., 1995). Production uncertainty associated with rainfall variability remains a fundamental constraint in SSA, a constraint which will be exacerbated with the projected CC (Cooper et al., 2008). During the 21^st century, climate change and the growing imbalance among fresh water supply, consumption and population may alter the water cycle dramatically (Jackson et al., 2001). Thus, addressing drought stress and uncertainties in rainfall amount and seasonal distribution is an essential first step in adapting to current and future CC in many affected developing countries (Esikuri, 2005). About 18% of the world’s irrigated cropland area generates 40% of agricultural produce. While irrigation is extensively used in Asia (China, India, Pakistan), it is scarcely used in other areas especially SSA. Currently, only 5% of agricultural land in SSA is irrigated, compared with more that 60% in parts of Asia. It is estimated that crop yields can be increased by a factor of 2 to 4 in many parts of SSA through better water management (NRC, 2009). Rockström et al. (2006, 2007) have emphasized the importance of water harvesting technologies, and increasing water retention with tied-ridges, rock bunds and other simple structures, which conserve, harvest and recycle water. In addition, there are several sustainable irrigation management technologies (Lorenzini and Brebbia, 2006) such as condensation irrigation and sub-surface irrigation by condensation of humid air (Lindblom and Nordell, 2006) which can save water and decrease risks of salinization (Figure 9). Thomas (2008) described several opportunities of water management for reducing the vulnerability of dryland farmers in Central and West Asia and North Africa to CC. Important among these opportunities are supplemental irrigation along with water harvesting and recycling using modern irrigation techniques (e.g., drip sub-irrigation), growing salt-tolerant plant species (see following section), and converting to conservation agriculture. Drip irrigation is a demonstrated water-saving technology, and has the potential to improve crop production in SSA (Karlberg and de Vries, 2004). Maintaining and enhancing productivity of irrigated land through improvements in water use efficiency is essential to increasing NPP (Hargreaves, 2003), improving ecosystem services, and adapting to CC.

76. Adoption of various SLM options in soils of managed ecosystems has a high technical potential for SCS (Table 14). Rates of SCS in croplands vary widely depending on SLM option, soil type, and climate (Table 14). In most cases, the rates of SCS in intensively managed cropland soils (NT farming, rotations, manuring, etc.) range from 300 to 600 kg/ha/yr. The rates of C sequestration in the biomass (above and below ground) are extremely high in forest ecosystems, and can be as high as 3000 kg/ha/yr in well-managed forest plantations, and especially when degraded soils are converted to perennial land uses.

Table 14. Experimentally measured rate of soil carbon sequestration with adoption of various sustainable land management options (Lal, 2008).
SLM Option	Region	Rate (kg C/ha/yr)
I. Cropland soils
(i) Conservation tillage	North America	200-1200
	South America	300-600
	Australia	100-1000
(ii) Rotations	North America	200-300
(iii) Nutrient management	North America	300-500
	South Asia	500-1000
	Tropics	100-200
(iv) Intensive farming	North America	500-1000
	Europe	500-1000
II. Grazing land soils
(i) Rangeland management	North America	20-500
(ii) Pasture management	North America	500-1000
III. Forest land soils
(i) Stand management	Europe	400-500
	North America	600-800
(ii) Afforestation	Europe	500-3000
	Sub-Saharan Africa	100-3000
(iii) Agroforestry	Central America	500-800
IV. Minesoil Reclamation
(i) Afforestation	North America	300-3000
	Pacific	1500-2500