Sunflowers are a hardy crop capable of producing viable yields even during hot, dry seasons, but as climate change continues to affect weather patterns, what does this mean for sunflower growers across the Black Sea region?
Background to climate change
Greenhouse gas (GHG) emissions
You might think that climate change and our understanding of the subject is relatively new, but it was the late 19th century when scientists first considered anthropogenic emissions of greenhouse gases could change the climate. Specifically, it was the French physicist Joseph Fourier, who described the Earth’s natural “greenhouse effect” in 1824 but it wasn’t until 1896 when a Swedish chemist, Svante Arrhenius, figured out that coal burning would enhance the natural greenhouse effect. There are several greenhouse gas emissions or GHG, that contribute to climate change, they work by absorbing infrared radiation emitted from Earth’s surface and reradiating it back to Earth. In other words, GHG trap incoming energy from the sun warming the Earth’s surface and the air above it, like a greenhouse. The greenhouse effect is a natural process, without GHG the average temperature of Earth would be about −18°C, rather than the present average of 15°C.
The difference today is that human activity has increased the amount of GHG in the atmosphere and now the greenhouse effect is getting stronger; we are making Earth’s atmosphere a more efficient greenhouse. The Earth’s surface temperature has risen by about 1°C since the pre-industrial period, 17 of the 18 warmest years on record have occurred in the current century, and each of the last three decades have been hotter than the previous one. The primary sources of GHG emissions are from producing electricity and heat, transportation, manufacturing, agriculture and forestry.
GHG in order of abundance;
- Carbon dioxide;
- Nitrous oxide;
Agriculture and climate change
Agriculture accounts for around 10% of the GHG in the EU*. It is also profoundly affected by climate change but, paradoxically, could also be part of the solution.
Sources of agricultural GHG include;
- Carbon dioxide from deforestation and burning fossil fuels;
- Methane from livestock during digestion;
- Nitrous oxide from the production and use of fertilisers.
Soil Carbon Sequestration
Agricultural soils contain less soil organic carbon (SOC) compared to natural vegetation due to the removal of plant material as the harvested part of the crop, which contains carbon. As a result, agricultural soils have about 30 to 40% less SOC than soils under natural vegetation. Clearly, we can’t convert all agricultural land back in to natural vegetation as we must produce food but changing agricultural practices could increase the amount of SOC contained in agricultural soils. This is known as soil carbon sequestration; taking carbon dioxide out of the atmosphere and holding it in the soil.
Crops absorb carbon dioxide while growing then release it after harvest but by returning plant material or biomass back to the soil allows carbon within the plants to be reduced to its elemental nature and stored in a stable state. Selecting farming methods that return biomass back to the soil will help mitigate against climate change. It’s estimated that soils could sequester more than 10% of the anthropogenic carbon dioxide emissions. Soils are estimated to contain 1,500 gigatons of organic carbon to a one metre depth, which is more than the amount found in vegetation and the atmosphere. At the same time reducing the amount of emissions released in the first place helps reduce the source of the problem. This can be achieved by increasing yields and efficiency to produce more food for the same or less GHG emissions.
Farming methods that help mitigate against climate change include;
- cover crops as temporary cover between crops to hold onto SOC;
- leave crop resides on the surface to protect the soil and increase the number of carbon capture microbes;
- reduced or no-till farming requires less machine use and less fuel;
- accurate and variable application of inputs according to need, particularly fertilisers;
- improved irrigation practices;
- grow perennial crops if possible as they have larger below ground biomass fraction;
- no burning of crop residues and stubbles;
- use animal manure as fertiliser;
- even and light grazing of livestock to encourage roots to grow deeper into the soil.
In addition to combatting climate change, soil carbon sequestration practices may improve soil, air, and water quality, be beneficial to wildlife, and increase food production.
Impact of climate change on sunflower crops
Changes in crop yield and productivity
Climate change is expected to affect agriculture across European regions, droughts will occur more often, and they will start earlier and last longer. In Southern Europe, higher temperatures and lower rainfall are expected to reduce crop yields, while in northern Europe growing conditions may improve allowing a greater range of crops to be grown, although more extreme weather events will likely increase volatility in crop yields. The net affect may balance each other out, possibly leading to small average yield increases
Changes to sunflower areas
Although rainfall levels are might decrease across southern Europe, this might result in more sunflower being grown as farmers are drawn to the drought tolerant nature of sunflowers compared to other alternatives. Indeed, this might be replicated across the globe as farmers look to adapt farming methods to combat drought conditions by choosing drought and heat tolerant crops such as sunflowers.
Changes to sunflower diseases
This is a difficult one to model as there are many variables that affect disease development, all of which will be influenced by climate change. It’s likely that regions where rainfall decreases, and temperature rise will see a fall in diseases that require free water to facilitate their lifecycle, such as downy mildew (Plasmopara halstedii), Sclerotinia head rot (Sclerotinia sclerotiorum), Phoma Black stem (Phoma macdonaldii) and Phomopsis stem canker (Diaporthe helianthin). Conversely some diseases will develop under hotter and dryer conditions such as Charcoal rot (Macrophomina phaseolina). Higher temperatures and reduced rainfall could also increase the incidence and spread of broomrape (Orobanche cumana) in sunflower. It’s thought that climate change may be involved in the recent development of Orobanche in France. On the plus side, if sunflower production moves north to be grown in regions where sunflowers haven’t been grown before, the lack of disease-causing inoculum may lead to less disease, at least initially.
Changes to sunflower pollinators
Sunflower rely heavily on insects to pollinate, especially honeybees and bumblebees, and there is clear evidence that pollination is already under threat from habitat loss, insecticides, pathogens and alien species. Climate change could further affect pollination by changing the activity of pollinators by reducing population sizes or by altering insect activity.
Nuseed conducts multiyear evaluations of each hybrid for self-compatibility, this is a measure of how well the plant can pollinate itself, reducing the impact of reduced pollinator activity.
How sunflowers help mitigate against climate change
It’s possible to alter planting dates so that the crop develops at a different time and avoids periods of water stress at key developmental stages such as flowering and grain filling.
Jeremy Klumper, a Nuseed Sunflower Breeder, said “If weather patterns change or shift, the growers will need to adjust with those weather patterns, so a normal planting in April, might have to be pushed back to May in order to match the rain fall. This could lead to producers having to select an earlier hybrid in fit within their growing window.” Nuseed are already developing hybrids that flower up to ten days earlier, providing the grower with options if their growing seasons get shorter.
Improved agricultural practices
Sunflowers can be grown effectively under minimum tillage or direct drilling systems, both of which conserve moisture, which will become vitally important in regions where it becomes drier. Also, worth noting that minimum tillage and direct drilling systems, use less fuel making them more economical while releasing less GHG.
The advantage sunflowers have over other crops
With a deep tap root that can access sub soil water and an ability to regulate plant leaf area according to available water, sunflowers can tolerate short periods of drought, and then recover better with less reductions in yield than other crops. Nuseed test and score their sunflower varieties tolerance to drought and publish this information in their hybrid catalogue, allowing growers to make an informed choice. Like all plant’s sunflowers will eventually succumb to prolonged periods of high temperatures but they are more tolerant of elevated temperatures. This ability to tolerate low water availability and high temperatures give sunflowers a greater advantage than other comparable combinable crops. They may also prove to be part of the solution; on average, the total emission of GHG for the production and transport of inputs in sunflowers is around 60% less per hectare than for other comparable crops**
In short, growing sunflower is an effective way to produce oilseeds with lower GHG emissions.