Adaptation is an adjustment made within the crop production systems, in order to live successfully with changing climate (Matthews and Wassmann 2003). The probable adaptive responses need not to be new and they can include farm level practices, such as change of planting dates, altered water conservation practices, change to early maturing varieties to mitigate shortened growing season, change to drought tolerant crop varieties, and change to high yielding crop varieties to take advantage of unusually favorable weather. Other adaptation strategies, which can be considered, are application of irrigation and adoption of multiple cropping to take advantage of longer growing seasons. The policy makers require an assessment of the benefits derivable from the adoption of the various adaptation measures. The computation of such benefits would require knowledge of the pre- and the post-adoption yields in addition to the costs of the adaptation itself, in order to make the choice among potential adaptation options. The success in the assessment of impacts and adaptations does not depend on the accuracy of yield predictions as much as it depends on the extent to which the differences between pre impact (adaptation) and post impact (adaptation) yields are reflected. What is more needed for the assessment of impacts of climate variability is the difference between pre-and post-impact productivity and production. The performance of model could be adjudged satisfactory once the model truthfully indicated the differences between pre- and post-adoption yields, not necessarily the actual productivity or production. The adaptive responses could be facilitated by increased knowledge of weather patterns and climate-related variability through the use of climate forecast information.
To abate the shortening effect of temperatures on crop cycles, changed sowing dates and late-maturing genotypes of different crops could be used. But the winter cereals, whose cycle length is linked with cold temperature requirements (vernalization), will not able to avoid the climatic risk during warmer winters. Similarly, the late-maturing crops would face climatic risks in the early summer. The sowing dates of winter crops cannot be postponed to early fall because of much higher probability of experiencing low temperatures at sensitive stages and the cost of fungal disease control during the early fall. For summer crops, using earlier sowing dates or longer-maturing varieties would counteract the detrimental effects of climate change in all cases, as was demonstrated for sunflowers throughout Europe by Claire (1996), for spring wheat in Finland by Saarikko and Carter (1996), and for maize in Spain by Claire (1996). In the northern European regions, selecting adequate sowing dates could help to synchronize full canopy development and maximum radiation availability on maize-type crops (Delecolle et al. 1996), which would enhance final production. Many of the cropping mechanisms, such as shifting planting dates, choosing varieties with different growth duration, or changing crop rotations may result in lower yields. In the Indo-Gangetic plains, delayed planting is already one of the major causes of reduction in crop yields of rice and wheat. The rice-wheat cropping system is the economic backbone of this region and only a small gradual decrease in productivity in either rice or wheat crops will drastically imperil food security. Most studies project decreased yields in non-irrigated wheat and rice, and a loss in farm-level net revenue between 9 and 25% for a temperature increase of 2-3.5°C (Aggarwal and Mall 2002). Although the important mitigation and adaptation strategies required to cope with anticipated climate change impacts generally include adjustment in sowing dates, breeding of plants that are more resilient to variability of climate, and improvement in agronomic practices (Attri and Rathore 2003). The identification of suitable response strategies is key to sustainable agriculture. Likewise, Mall et al. (2004) suggested that delaying the sowing dates would be favorable for increased soybean yields at all the locations in India. Sowing in the second season would also be able to mitigate the detrimental effects of future increases in surface temperature due to global warming at some locations. However, the proposed shift in soybean production from the current main season to a second season may necessitate additional planning and change in management practices. Changing the sowing dates is a no-cost decision that can be taken at the farmer level, but a large shift in sowing dates probably would affect the agrotech-nological management of other crops to be grown during the remaining part of the year. Hence, there is a need to identify district or agroclimatic regions vulnerable to climate change and to find out suitable adaptation practices to be followed in order to sustain the productivity of these regions to some extent. It is most likely that at least in the short run, the effects of climatic variability are much larger than the projected impact of global climatic change. Therefore, evolving strategies for managing climatic variability in agricultural production will take care of adaptation required for climatic change (Aggarwal 2003).
Sowing date adjustments are a simple and powerful tool for mitigating the effects of a potential global warming (Baker and Allen 1993). Krishnan et al. (2007) demonstrated the potential outcomes by adjusting the sowing time of rice at two sites (Cuttack and Jorhat) and simulating the crop growth under different climate change scenarios (Fig. 3.1). Under the GCMs scenarios, temperature at the time of flowering for the main season was found to be high, and there were considerable variations when simulated for different climate change scenarios under different sowing dates. Among the different sowing dates tested, the sowing on July 15th at Cuttack led to the yield changes of +6.6, +4.1 and -9.8%, respectively under the GFDL, GISS and UKMO model scenarios. Interestingly, the sowing on July 1st at Jorhat resulted in yield increases at +27.1, +24.3 and +13.4% respectively, for the corresponding scenarios. Any further delay in sowing at both the sites, which had different dates for the maximum response, was not beneficial in terms of crop yield.
Fig. 3.1 Adaptation to climate change by adjusting the sowing dates under different GCMs scenarios of the rice variety IR 36 grown during the kharif season at Cuttack (A) and at Jorhat (B) using ORYZA1 model (Source: Krishnan et al. (2007))
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