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Heat Stress in Potatoes
Extreme weather events pose a significant challenge to potato cultivation. Heat and drought stress reduces productivity, causes physiological defects in tubers, and damages crops.
However, recent studies have shown that natural technologies containing plant hormones and betaines can mitigate or control potato plants’ response to heat stress.
CS1: Field Trials
In the UK the top 10 warmest years since 1 884 have occurred in the last 2 decades. The highest temperature ever recorded in the UK is 40.3°C, set in Lincolnshire on 19th July last year, and on the same day 35°C was exceeded for the first time in Scotland. And whilst multiple records were broken in 2022, the Met Office is forecasting 2023 to be hotter still: (https://www.bbc.co.uk/news/science-environment-64032458).
Drought and heat stress are problematic in potato cultivation as modern varieties are adapted to grow at temperatures between 14°C and 22°C. Potato productivity is reduced at higher temperatures, typically whenever 25°C is exceeded during the day.
How Heat Affects Potato Yields
Potato plants under abiotic stress conditions suffer a disturbance in normal hormonal regulation, plant metabolism and photosynthesis. Reactive oxygen species (ROS) are generated and these cause membrane damage and cell death. As a consequence the rate of photosynthesis is reduced, the movement of assimilates from the leaves to the developing tubers is disrupted, and biomass accumulation is compromised.
The result is inhibition of tuberisation, secondary tuberisation, reduction in tuber bulking and ultimately loss of yield. Heat stress also causes physiological defects such as early skin set which is often followed by skin cracking and a loss of tuber quality. The earlier a heat wave occurs, and the longer it lasts, the more negative its impact. However, there are natural technologies which can minimise these losses to heat stress.
Field Trials In Norfolk & Lincolnshire
During 2022 independent, scientific trials were conducted in maincrop potato cv. ‘Melody’, a partially determinate variety, in Lincolnshire on loamy coastal soil. The trial was not irrigated.
The treatment was a simple programme of in-furrow application of our seaweed based biostimulant, CS1 , followed by 6 low volume foliar sprays of the same product at regular intervals throughout the life of the crop. The 2022 growing season in the UK experienced 3 heat waves, one in each month of June, July and August, which were crucial tuber formation and bulking periods for this crop. However the impact of the prolonged heat stress was minimised in the treated plants, resulting in a significant yield increase of 29.2%.
Interim investigation of the roots revealed that the untreated plants were at the hook stage, but the treated plants were beginning to form small tubers. This suggests that the treatment had advanced the physiological stage of the crop. In principle, this should lead to the development of more tubers that are larger and heavier as tuber development will occur over a longer period in the crop cycle. This was confirmed at harvest.
Additional trials in Norfolk with Russet Burbank delivered a similarly impressive yield increase of 40%. In this trial, regular applications of CS1 were used alongside microbial products.
A clear improvement in skin finish was observed where 43% of the untreated control was affected by black scurf (Rhizoctonia solani), but only 6% of the treated crop showed any symptoms.
The irregular black/brown masses on the surface of the tuber are the sclerotia, or resting bodies, of the disease. They are superficial and do not affect the tuber quality however, they do perpetuate the disease and inhibit plant establishment from the tuber if used as seed.
An interim assessment of foliage revealed a clear difference whereby the treated plants appeared darker and denser than the untreated plants. This suggests a higher leaf area index and an increased level of chlorophyll in the leaves of the treated plants. Numerous
studies have demonstrated increased photosythetic activity following seaweed extract
What does this tell us?
As with all field trials, these results were influenced by local climatic conditions and the biological, physical and chemical condition of the soil, meaning that results will differ from site to site. Soil-plant-climate interactions are complex. A deeper understanding of the effects of biostimulants on all aspects of the ecosystem is required in order to improve future methodologies in sustainable food production.
These results, from heat stressed trials in Lincolnshire and Norfolk in 2022, confirm that seaweed-based biostimulants can reduce potato yield losses to abiotic stress and improve crop quality. The frequency and magnitude of heat stress episodes are intensifying due to global climate change and we need to adapt. Understanding and implementing effective methods to mitigate stressful growing conditions is now a priority for farmers and growers across the UK.
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