The effects of climate change have following consequences such as-
(i) On crop yield:
Decrease in potential yields is likely to be caused by shortening of the growing periods, decrease in water availability. An increase in temperature beyond 22% causes sterility in rice, resulting in reduced grain yield.
The combination of decrease in soil moisture and increase in heat stress is likely to result in lower wheat yields. In cooler regions, the yields of most crops are expected to increase with increasing temperature. In winter dry land corps, C02 enrichment and temperature could probably result in depletion of soil, water, leading to moisture stress during grain filling and consequently poor harvest.
(ii) On duration of Crop:
Duration of crop growth cycles are related to temperature. Due to change in temperature pattern, there is possibility of reduced duration of crops growing and there by will be reduction in yield in some of the areas of the world in case of major food crops. In case of an annual crop, the duration between sowing and harvesting will shorten the cycle and would have adverse effect on productivity.
So, late mature varieties of paddy which require high temperature for cultivation would be better suited to exploits new environmental conditions. Similarly, switch over to winter sown cereals eg- wheat, barley, oats would take advantage of longer growing season.
(iii) Soil fertility:
The increase in temperature would induce a greater mineralisation, lessen the soil organic matter. Thus, soil fertility would probably be modified because soil degradation is more likely to occur.
Most corps weeds being C3 plants, they are likely to compete even more than crops such as corn. However, some killers would gain in effectiveness with the temperature increase.
(v) Disease and insect pests:
The increase in rainfall is likely to lead to an increase of atmospheric humidity combined with higher temperatures; these could favour the fungal diseases, in seats, and pests. The increase in temperature will have significant effect on the distribution, development over pests and insects and their interaction with the agricultural crops.
The losses due to insects, pests in wheat have been estimated as high as 12-20% in the new environment. There will be increase in density of ‘Helicoverpa’ armiger that leads to damage to cotton.
(vi) Cropping pattern:
The area which at present is judged to be most suited to a given crop or combination of crops, May no longer remain as such after a climatic shift. Wheat belts may be replaced by barley and maize by soya bean and soon. The reduction in the length of growing season of cotton will make this crop even more suitable in double copping system in Indo-genetic plains of India.