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AGRONOMIC ADAPTATIONS TO CLIMATE EXTREMES (AF23) P. O. Aina1 and J. O. Adejuwon2 1Department of Soil Science; 2Department of Geography; Obafemi Awolowo University, Ile-Ife. Nigeria REGIONAL WORKSHOP ON ASSESSMENTS OF IMPACTS AND ADAPTATIONS TO CLIMATE CHANGE (AIACC) DAKAR, SENEGAL. MAR 24-27, 2004
Presentation Focus • INTRODUCTION • STUDY METHODOLOGY & OBJECTIVES • ECOLOGICAL ENVIRONMENT • AGRICULTURAL SYSTEMS • AGRONOMIC ADAPTATION STRATEGIES • CONCLUSIONS • LESSONS LEARNED, RESEARCH NEEDS & PROPOSED APPROACH FOR FUTURE WORK • NIGERIA CASE STUDY
INTRODUCTION • Climate change inevitable • Increasing trend of climate extreme events • Agriculture is vulnerable • crop yield reductions; global food security • Autonomous adaptation • Planned adaptive strategies needed • Study: assessment of agronomic adaptation strategies in long-term yield response exps in Nigeria
NIGERIA …. • Lat 4o and 14o N, Long 2o 45’ & 14o 30’E. • landmass of 924,000 km2 & 110m people. • diverse people, ecological regions, soils and agricultural systems • varied crop responses to climate impact and adaptation strategies
Ecological Environment Humid zone • annual rainfall >1500mm; growing season - 270 days. • biophysical constraints - low soil fertility, water erosion low resilience to cultivation, poor drainage Sub-humid zone • annual rainfall: 600-1500mm; growing period - 150-269 days. • constraints - vulnerable soils, erosion, water stress, poor rainfall distribution and poor soil water retention capacity Semi-Arid zone • annual rainfall 400-600mm & growing season - 75-149 days • constraints: wind erosion, low permeability, salinity, heat and water stress. Arid zone • annual rainfall 100-400mm <75 days growing period. • constraints: same for Semi-arid region
Agricultural Systems and Agricultural Potential • shifting cultivation & rotational bush or grass fallowing • wide range of crop husbandry methods • < 0.5% of the land under irrigation • Small-holder, subsistence & rain fed • low and unsustainable crop yields - low input technology biophysical constraints to crop production
Agronomic Adaptation Strategies • crop diversification • changes in planting date and timing of field operations • changes in crop growing conditions and crop choices • soil fertility management and erosion control • tillage technology • water management
Crop Diversificationmixed cropping or intercropping systemsInsurance against total crop failure -- range of maturities and climatic tolerances due to diversity in genetic structure & compositions Table 1: Effect of intercropping on crop yields, kg ha-1 (Aina, 1989)
Changes in Planting Date • adjusting to earlier (?) planting dates • sensitive growth stages, extend the growing season • increases crop yields by between 20% and 40% - Udom and Adebitan (1998), Fakorede (1985), Fakorede and Opeke (1985), Lal (1973) and Aina (1988) (?) depends on the predictability of the precipitation pattern.
Soil Fertility Management and Erosion Control • Fertility -- adequate crop nutrition will enhance resilience of agriculture to climate hazards • Inorganic fertilizer application, manure amendment, rotational cropping, adequate soil organic matter, increase soil fertility, crop yields (by 50% -120%) • erosion leads to rapid soil degradation, physical loss of plants & soil productivity. Control Practices: • Optimum plant population, residue mulching, Agroforestry, changing land topography (land contouring, terracing and construction of diversions and reservoirs and water storage)
Table 2. Effect of fertilizer application on maize yields (kg ha-1) in long-term experiments at locations in Nigeria (Aina, 1989)
. Table 3: Soil loss and runoff from plots and watersheds under different management systems (Aina, et al 1991)
. Table 4. Crop yields soil and water conservation effects of tied-ridges in the Semi-Arid region
Appropriate Tillage Technology • adjustments in tillage for optimizing soil temperature, moisture regimes and crop plant establishment • Conservation tillage - minimum, reduced tillage and no-tillage technologies in combination with crop residue mulch, Fallow and tillage practices such as the planting of hedges
Table 5: Effect of tillage on crop yield in the semi-arid region
TABLE 6: Effect of Cover (Stylosanthes) Crop on crop yield TABLE 7. Effect of cover-cropping on maize yields
Improved Water Management • less than 0.5% of the land in Nigeria • Practices to reduce water stress -- irrigation, reduced runoff and improved water intake into soil • extreme rainfall events -- drought/runoff, flooding • positive yield response (3-fold yield increase) to irrigation even in humid area rainfall variability
Table 8. Effect of supplementary irrigation on yields of cowpea and maize (Fapohunda et al, 1984).
Table 9:Changes (%) in crop yields in long-term experiments with and without agronomic adaptation in different ecological regions in Nigeria
. Climate-induced & bio-physical constraintsto crop production & adaptation measures Inadequate or excessive moisture • irrigation/drainage, mulching, short-cycle, drought resistant varieties High Temperature • mulching, irrigation Soil • tillage, fertilizer application, manure, liming, Erosion control Crop • high yielding, drought & disease resistant varieties, hybrid seeds and pest control
Constraints to achieving full measure of potential adaptation • Low economic status to adopt tech innovations • traditions dictate local practices • poor knowledge of appropriate alternative adaptation options • poor predictability of future climate variability and extreme events -- high level of uncertainties
Conclusions • crop yield response to agronomic adaptation significant • wide gaps betn exp’l and farmers’ low yields • (little change (success) to existing agric systems) • resources for substantial change beyond farmer's means • low input technology, biophysical constraints & constraints to adoption of adaptation measures. • drought most important abiotic stress limiting crop productivity • Low adaptive capacity -- high level of uncertainty; low predictability • dearth of climate impact/adaptation studies & choice of technological options in the region • need to enhance research capacities in developing countries