60. The choice of seedbed preparation, of methods and timing of tillage operations, is important to adaptation to and mitigation of CC. Crop residues constitute more that 50% of the world’s agricultural biomass (Smil, 1999), and are important to recycling of C and nutrients. Effectiveness of NT farming on improving soil quality depends on retention of crop residue mulch. It is widely documented that conversion of conventional tillage (CT) to NT farming, with use of crop residue mulch and cover crops in the rotation cycle along with INM, conserve soil and water and improve soil quality. In southwestern Nigeria, Lal (1976) documented a higher SOC pool in NT compared with the CT system of seedbed preparation. In Zimbabwe, Gwenzi et al. (2009) reported that the SOC pool in 0-60 cm depth after 5 years were 27.8-30.9 t C/ha in CT, 32.8-39.9 t C/ha in minimum tillage (MT) and 32.9-41.6 t C/ha in NT system. The rate of SOC sequestration was 0.55-0.77 t C/ha in MT and 0.70-0.78 t C/ha in the NT system. In Sudano-Sahelian West Africa, Bationo and Buerkert (2001) concluded that SOC improvement is critical to sustainable management of soils. Conversion of PT to NT in the Cerrado region of Brazil has increased SOC pool at the rate of 0.3 to 1.5 t C/yr (see Table 10). In the Cerrados of Brazil, Metay et al. (2007a, b) reported that taking into account all three gases (CO2, CH4, and N2O) on CO2-C equivalent basis, ecosystem C sequestration is more in NT system by 350 kg C/ha/yr in the top 0-10 cm layer. Also in Brazil, Sa et al. (2001) concluded that conversion to NT system with crop residue mulch for a long time attains SOC pool equivalent to or more than natural fallowing. In addition to SOC sequestration, NT farming is also an effective technique for erosion control (Kent, 2002; Lal, 1976). Despite some soils and climatic limitations to adoption of NT farming (Lal, 1976), there is wide spread recognition of the NT concept and practice both for SCS and CC adaptation and mitigation (Xiao-Bin et al., 2006).
61. Research on NT farming in relation to soil, water conservation, and soil quality restoration started in early 1960s in North America, and early 1970s in the tropics. Despite repeated documentation of its usefulness in conserving soil and water, enhancing soil quality, sequestering C and mitigating CC, the acceptance of this technology is rather low. Global adoption of NT farming is estimated at ~90 Mha or about 6% of the cropland area of the world. It is primarily practiced for large-scale cultivation of row crops (maize, soybeans, wheat) in USA, Brazil, Argentina, Canada, Australia, Paraguay etc. It has not been adopted by the resource-poor farmers and small-size landholders of SSA and SA. Yet, it is in SSA and SA that NT and other SLM technologies are needed the most. Among several reasons identified for the lack of adoption of such SLM technologies include poor infrastructure, low institutional support, land tenure and ownership issues, and non-availability of inputs. Lack of adoption of NT and other SLM practices could also be due to lack of stakeholder sensitization to land management issues and NT opportunities so as to create the requisite awareness and willingness to change pre-existing practices (Pieri et al. , 2002). Some of the inputs required for adoption of SLM technologies are either not available, are prohibitively expensive that resource-poor farmers cannot afford, or farmers are not sure of their effectiveness because of the uncertainties due to climate, soil degradation, and market fluctuations. Yet, NT has important benefits for CC adaptation and mitigation in these areas.
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