The Potash Development Association (PDA) has reviewed the role of plant nutrition in mitigating the impact of extreme weather events on crops.
This comes after the driest and warmest spring weather conditions experienced in the UK and Ireland.
According to the PDA, limitations to root development will exacerbate the impact of weather extremes.
As soils dry from the top down in spring, deeper-rooted crops will be able to better access water and nutrients.
So phosphate’s role in root growth is clearly important in the early stages of crop development, in order to cope with periods of dry conditions – whether temporary within the season, or more extreme in nature.
Stress levels within crops
Extremes of temperature, light intensity and water availability cause stresses on plants, which can have negative impacts on their growth and development, and restrict yield and/or quality.
Nutrition plays an important role both in terms of management of crops where these stresses may occur, and to a lesser extent, but still important, alleviating the extremes.
Potash is the nutrient that is often seen to have the greatest impact, but it is certainly not the only one, with sulphur, calcium, and magnesium all also playing a role.
Potassium
Photosynthesis is the process by which plants capture light energy to convert carbon dioxide and water into carbohydrates, such as sugars, required for growth and building yield.
The rate of photosynthesis therefore dictates the efficiency of the production of sugars and ultimately crop yield and quality.
Plants subjected to stresses – such as moisture stress – considerably reduce their photosynthetic rates, reducing the efficiency of carbohydrate production resulting in lower yield.
Photosynthetic rates are maintained in plants through efficient activity of the stomata (tiny apertures on the underside of leaves surrounded by guard cells).
The stomata are important for allowing the movement of carbon dioxide into the plant, whilst releasing oxygen and transpired water.
The plant regulates the opening and closing of the stomata through movement of potassium into or out of the guard cells.
When potassium moves into these cells, they accumulate water as a result of their higher salt concentrations (through osmosis) and therefore swell, opening the pores.
If potassium levels within the plant are low, the stomata become slow to respond and do not close as quickly, resulting in the loss of water vapour and a reduced photosynthetic rate.
Magnesium
Magnesium is required to help plants capture the sun’s energy for growth and production through photosynthesis.
Photosynthesis takes place in chlorophyll, the green pigment in plants, and magnesium is the central atom of the chlorophyll molecule, with each chlorophyll molecule containing 6.7% magnesium.
Magnesium facilitates the translocation of carbohydrates (sugars and starches), enhances the production of oils and fats, and is necessary for cell division and growth.
The mineral also plays a significant role in activating enzymes involved in respiration and photosynthesis.
Calcium
Calcium is an essential crop nutrient vital for many aspects of crop development. It plays an extremely important role in the production of plant tissue and in improving plant growth.
Calcium is required for plant cell walls and membranes, contributing to the structure of cells and holding together the cell walls of plants.
Plant roots also require calcium, which is essential for the normal development of a healthy root system to ensure crops can take up the air, water, and nutrients they need from the soil.
Sulphur
Sulphur is an essential plant nutrient necessary for protein synthesis and maintaining the balance of amino and sulphur-containing compounds.
Due to the central role of both sulphur and nitrogen in the synthesis of proteins, the supplies of these nutrients in plants are highly inter-related.
A shortage in the availability of sulphur will reduce the efficiency of nitrogen use.
As well as protein synthesis, sulphur is essential for plants to form enzymes, vitamins, and chlorophyll. In legumes, it is crucial in nodule development and efficient nitrogen fixation and is critical for determining the nutritional quality of foods.
Its role in mitigating crop stress relates to its ability to improve the plants’ tolerance through the synthesis of essential amino acids, proteins, and other compounds that help plants cope with stressful conditions.
Regarding drought stress, sulphur influences the production of compounds that enable the plant to better conserve water, thereby maintaining cellular activity and photosynthetic rate.
