Climate change has begun to affect crop productivity negatively, necessitating suitable adjustments in cultivation practices as well as other adaptive measures. Sudden fluctuations in temperature and other weather abnormalities at different stages of crop growth, typical symptoms of climate change, reduce the final yield.
Wheat has been a major victim of climate change in the past few years though many other crops have also been affected. The above-normal mean temperature, especially in February-March, has lowered the production of wheat and some other rabi crops. The cold waves, especially ground frost, have become rather frequent in the past six years in the north-western agricultural belt of Punjab, Haryana and western Uttar Pradesh. They have been causing extensive damage to foodgrain, pulses, vegetables, fruits and even flowers. The crops include tomato, potato, winter maize, brinjal, peas, mustard, gram, papaya, amla, marigold and chrysanthemum.
In the case of wheat, the effect of climate change has been studied through various scientific techniques. The Karnal-based Central Soil Salinity Research Institute (CSSRI) has recently carried out an elaborate exercise to correlate the variations in minimum and maximum temperature with growth parameters and yield of different wheat varieties.
It has found that there is no longer any certainty that a particular wheat variety will perform to its potential every year. Its actual yield will differ from season to season, depending on the temperature and other weather conditions prevailing during each season, irrespective of its inherent productivity.
Explaining the effect of climate on wheat, CSSRI Director Gurbachan Singh says: “High temperature results in desiccation of the plants and disturbs the balance between photosynthesis and respiration. On the one hand, the photosynthesis activity in the plant declines at higher-than-optimum temperature due to loss of green matter of the leaves and inactivation of enzymes and other proteins; on the other hand, the respiration rate rises, resulting in rapid exhaustion of food reserves of seeds.”
The daily minimum and maximum temperatures recorded at the meteorological laboratory of the CSSRI reveal a significant correlation between temperature and wheat production. In the 2005-06 wheat-cropping season (November to April), the maximum and minimum temperatures remained 2 to 4 degree Celsius above the long-period average range. The maximum abnormality was noticed between January 15 and 18, and again between February 14 and 23, 2006. This proved unfavourable for wheat and, consequently, the output dwindled.
On the other hand, in the next cropping season (2006-07), the temperature showed a different trend. It remained more or less normal, being just 1 or 2 degrees higher or lower than the long-period average, for most of the time. The result was a bumper wheat harvest.
In 2007-08, too, the temperature remained conducive for good growth almost throughout the wheat-growing period. In fact, the mean daily temperature hovered between 0 to 3 degrees below the long-term average from January 20 to February 20. This helped in bagging a record wheat harvest of 78.4 million tonnes.
In the current wheat season, the observations recorded at the CSSRI meteorological station present a slightly worrisome picture. Both the maximum and minimum temperatures have ruled above normal levels on most days in January and February 2009. Scientists who are monitoring the impact of temperature on different wheat varieties feel such aberrations may have an adverse effect on wheat productivity during the current year. “However, it is yet to be seen how different varieties planted on different dates respond to such variations”, Singh points out. The wheat crop is currently being harvested.
Considering the critical role that temperature, especially in the final phases of crop growth — starting from flowering to grain-development (called terminal heat) — plays in determining crop output, the Indian Council of Agricultural Research (ICAR) has decided to launch an inter-institutional project to study this phenomenon. This will involve the ICAR institutes and state agricultural universities located in Punjab, Haryana, Delhi and Uttar Pradesh. It will focus on heat-tolerance among different crops, especially wheat, keeping recent climate aberrations in view.
Besides, it will also attempt to identify varieties of wheat and other crops which can withstand terminal heat without perceptible adverse impact on yield. Its success will obviously go a long way in mitigating, if not wholly averting, the ill-effects of climate change on wheat and other rabi crops.
