The average weather conditions over a long period of time and any change in these average weather conditions can be regarded as climate change. Climate is one of the most important factor in the agricultural productivity. Key Climatic Changes at a glance 30 and 150 % rise in the concentration of carbon dioxide and methane respectively over 250 years. The Temperature, 0.6 C˚ rise in global temperature in 20th century with 1990s is the warmest decade and 1998 is the warmest year. More global warming is due to continuous increase in concentration of green house gases.
Expected climatic changes
It is expected that average global temperature will rise somewhere between 1. to 6.4 Degree centigrade within Twentieth century. 30-35% increase in the release of nitrous oxide by 2030 due to injudicious use of nitrogenous fertilizer. Melting of the glaciers by the effect of the global warming. Decrease in SOC pool having negative impact on soil health.
Adverse Effects of Climate Change
- Higher temperature
- Drought and Floods
- Increasing carbon dioxide concentration
- Soil fertility
Effects of Higher Temperature
Rising global temperature is becoming a major threat to agriculture and food security especially when coupled with drought. Crop responses at present are poorly understood. Crop response to high temperature usually depends upon moisture availability. High temperature cause various morphological and physiological changes resulting in decreased yield 5% decrease in wheat and maize yield with every 1C˚rise in temperature 10% decline in rice productivity with 1% rise in minimum temperature. Decrease in starch concentration and an increase in protein and micro nutrient concentration has been observed under high temperature. High temperature cause hastened maturity.
Drought and Floods
Shift in precipitation patterns due to global warming. In Asia and Africa Increase the frequency and severity of drought. Agricultural productivity expected to decline significantly in Asia and Africa in coming decades. Significant effect on seed germination, seedling establishment and yield observed under water deficit conditions. intensity of the water cycle causing extreme weather events as floods and droughts. Worst floods had been observed in Pakistan in last few years. 500000 tons according to an estimate of stocked wheat, Standing cotton 28340 ha, fodder 121000 ha and rice 81000 ha and sugarcane destroyed in 2010 in Pakistan as a result of Climate change.
Higher concentration of Atmospheric Carbon dioxide
C3 plants are generally more responsive to higher concentrations of atmospheric carbon dioxide as compared to C4. Under ideal condition elevated carbon dioxide levels cause up to 15% rise in wheat and 28% rise in tomato production. Under nutrient limiting conditions only 7 % increase in wheat yield. Elevated carbon dioxide levels can also compensate the yield reduction caused by water shortage
Soil fertility and plant nutrition
Climate change is having a very negative impact on soil fertility and plant nutrition. Here we shall discuss 3 basic concepts
- Drought and nutrient acquisition
- Intense precipitation and nutrient acquisition
- Higher temperature and nutrient acquisition
Drought and Nutrient acquisition
Plants uptake nutrients like nitrates, Ca, Mg and Si via mass flow or diffusion. Drought can influence there uptake. Drought greatly affects the growth of the roots and thus results in least uptake of less mobile nutrients like phosphorus. Affect the microbial colonies
Excessive precipitation and Nutrition Acquisition
Intense rainfall results in loss of nutrients via soil erosion. Very intense rainfall can result in nitrate leaching. In poorly drained soils intense rainfall can result in hypoxia condition resulting in elemental toxicity of Mn, Fe, Al and B.
Higher Temperature and Nutrient Acquisition
Absorption and subsequent assimilation of nutrients reduction causes by High temperature stress. At the temperature of 280C in Maize Absorption of calcium is reduced. Both soil and air temperature in rice are affected Nutrient uptake.
Ali Usman, Dr. Shakeel Ahmad Anjum, Abdul Shakoor, Ali Zohaib, Ali Raza Asif
Agro-biology Laboratory, Department of Agronomy, University of Agriculture, Faisalabad 38040, Pakistan