Climate change is a serious issue throughout the world. Impact of climate change is determined by its various factors, namely, temperature, CO2 concentration, precipitation, solar radiations and wind etc.
By Warda Mustafa and Kiran Tariq
What is climate change?
Due to human activities mainly emission of green house gases and deforestation, ozone layer is depleting that leads to global warming, increase in CO2 concentration and melting of ice caps and glaciers which causes flooding and precipitation. According to IPCC and NASA, CO2 concentration was below 300ppm before 1950 but after that it reached to 412ppm. Due to heat trapping nature of CO2 Earth’s temperature has been increased by 1ᵒC and will increase by 5.8ᵒC by the end of this century. Land sliding and soil erosion is also occurring due to melting of glaciers and excessive flooding.
Effects of climate change on soybean:
All these climatic changes are affecting the lives of the people around the world. Agriculture represents the core part of various countries’ economy and provides food to the people wherever they live. Different climatic factors have negative as well as positive effects on plants, among them Carbon dioxide concentration, rise in temperature and precipitation have detrimental effects on crop growth. Soybean (Glycine max L.) is one of the most important oilseed crop that is being affected by climate change. Its seed contains 18-22 % oil and 40-42% good quality protein that is healthy to use. So, soybean can truly be claimed a meat growing plant on earth and golden bean. It is of great importance at commercial level as lecithin, margarine, flour, cookies, oil, candy, vegetable cheese, biscuits, soymilk and many other products are being manufactured.
Producers of soybean:
Brazil is the largest producer of soybean with total annual production of 123 million metric tons and United States of America ranked second with production of 96.62 million metric tons. Indonesia, Peoples Republic of China, Japan, Argentina and Korea are among the other top producers.
Soybean production in Pakistan:
Soybean production in Pakistan is limited to small area and have lower yield as it is an ignored crop due to adaptability issues that are not being solved by plant breeders and policy makers. Breeding potential is the maximum rate of increase in number of individuals of population under optimum condition. Different characters of soybean are observed to determine its breeding potential namely adaptability, germination, maturity and yield. These characters are greatly influenced by CO2 concentration, temperature and water.
Climatic conditions for soybean cultivation:
As soybean crop can be grown in wide latitude from 20-50 ͦN and 10-40 ͦS but it is well adapted to the region having suitable combination of climatic factors as it is the quality of being to adjust to new conditions. Under changing climate the degree of adaptability is not enough.
Temperature is the key factor for adaptation of soybean to any climatic region as only 1ᵒC change in temperature has great impact on soybean growth. It can be grown in wide range of temperature from 5ᵒC to 40ᵒC but 30ᵒC is the optimum temperature for its growth. Its germination is greatly affected and days to germination vary from 3 to 14 in response to the change in temperature. Apart from germination, many other characters are also influenced by rise in temperature. This change is positive till 30ᵒC, after 36ᵒC growth of soybean growth starts decreasing and after 40ᵒC it does not even germinate. Maturity of crop is also being affected by elevated temperature, as every 1ᵒC rise accelerates the maturity till 40ᵒC and every 1ᵒC increase after that delays the maturity. Rise in temperature also have positive correlation with growth rate, number of flowers, number of nodes and number of pods that ultimately increase the yield while many other characters like flower initiation, seed formation and dry matter accumulation are negatively correlated that ultimately affect the yield.
Carbon dioxide concentration is another important factor that influences the growth of soybean. Increase in CO2 concentration accelerates the germination and flowering that result in early maturity and reduction of the total duration (70 days) of crop and to get more generation in one year under controlled chamber. Various yield related traits are affected by rise in CO2 concentration. There is a positive correlation between rise in CO2 concentration and yield as its increase leads to the increment in total plant height, leaf area, length of branches, dry leaf weight, number of seed/plant and average seed weight. All these characters increase the yield of the crop.
Global warming causes the increase in temperature that results in the rapid melting of glaciers and ice caps. Due to which more flooding and precipitation occur which helps to fulfill the water requirements of the crop. Planting to emergence is one of the critical stage at which crop needs water as, at germination 80% to 85% moisture should be available to get high germination percentage so precipitation would be helpful in this scenario. Second critical stage of water requirement is pod filling stage that has direct relation with yield because at this stage plant needs more water due to rapid growth rate.
Although any climatic factor separately or in combination do not have much adverse effect on soybean growth yet, but continuously changing climate needs serious action in this regard. Adaptability of soybean needs to be improved to meet the changing climate, for this purpose wild soybean are a good source of variation that are need to be explored in depth so as to find required genetic resource to overcome this problem. Development of climate ready cultivars of soybean by using conventional and modern breeding tools are dire need of the hour. Changing planting dates and intercropping are also possible solution to some extent. Policy makers, plant breeders and biotechnologists have to do serious efforts to mitigate the negative impacts of climate change on soybean crop so as to meet the increasing demand of oil and food of ever increasing population because it has immense potential to fulfill the oil requirements around the world.