Damage limitation and root support for flooded crops

Featuring John Haywood from Unium Bioscience

With rainfall totals reaching the highest recorded since the year 2000, many winter crops have been in standing water for prolonged periods. Research indicates that the longer winter crops are exposed to flooded conditions the more significant the impact, as one might anticipate.

According to experts, supporting roots in the early spring months will be crucial to mitigate the flood damage and encourage phosphorus and nitrogen uptake.

Flood damage to winter crops explained

The oxygen deficit caused by flooding can have multiple knock-on effects for winter wheat crops, according to John Haywood at Unium Bioscience. “Effects include impaired root growth (potential death), reduced metabolism, lower nutrient availability and absorption, higher risk of nutrient leaching, shoot growth impairment, compromised tillering and ultimate yield.

“The decrease in Photosynthesis (PS) will cause an increase in Reactive Oxygen Species (ROS). These are the main reason for reducing yields, which when out of balance will potentially cause irreparable cell damage further limiting growth and development and ultimately crop potential,” says John.

Malik et al reported reduction in tillers (bread variety) of 24, 45 and 62% depending upon water level below the surface 20, 10 and 0cm. “We can see at is stands we are likely to produce a lot fewer tillers – this also has implications on root production especially for wheat, which has a knock-on impact on leaf area, tillering, reduction in spikelet, grain numbers and grain weight – all the major plant processes,” says John.

Effects on the soil

“In terms of impacts on the soil, as the field capacity increases, and the soil becomes more waterlogged more pores become filled and the optimum moves from a 50:50 ratio (soil to air) to a 75:25 which is a reduction of 50% with severe implications on root growth. This impedes gas diffusion,” says John.

Oxygen Partial Pressure %Uptake of P (a)Uptake of K (a)
20 Field Capacity100100
5 Saturation7556
0.5 Waterlogged3730
Hopkins 1950
(a) Data represents relative values

“Plants tend to prefer nitrogen (N) in the nitrate form but under waterlogged conditions the balance in the soil favours ammonium levels due to a reduction in gas diffusion,” explains John.  

Effect of transient P stresses on nitrogen uptake, 2-day P stress

uM uptake/g DW roots/min  Sufficient P (+P)Deficient P (- P)
Ammoniacal N        NH41.8 *0.8 *
Nitrate           NO30.90.2

Megaheas et al 2000 Jnl. of Plt Nutrition, 23(2) 263-273

The pH of flooded soils tends to move towards neutral which can have implications on the nutrient solubility, soil movement and ultimate bioavailability (plant uptake – levels and rate of uptake). “Therefore, multiple effects can happen and impact growth and development depending upon your starting point.

“As the soil becomes more waterlogged the uptake of P and K is massively reduced, which then compounds the nitrogen stress,” he says.

“But all is not lost. It’s important to understand these impacts, so that you can take steps to support root growth and nutrient uptake in the late winter/early spring months.

“We know you cannot make a poor crop into a fantastic crop, but you can make a substantial difference with judicious and cost appropriate inputs,” adds John.

How can biologicals support flooded roots?

Biologicals have a part to play in general crop health and keeping them in the mix is important, but maximising root growth post waterlogging will aid recovery, as will supplying and making the critical nutrients available, including phosphorus.

“The most important aspect to consider with nutrients such as phosphorus, is availability. For phosphate, it exists in three pools in the soil but only the inorganic form dissolved in soil water is readily available to the plant,” explains Unium’s John Haywood.

John says that using the biostimulant Calife Extra acts as a ‘scavenging stimulant’ on the plant, designed to improve crop rooting and maximise nutrient uptake, whereas Luxor provides phosphate supply through maximising availability and reducing adsorption in the soil.

“The pidolic acid found in the biostimulant, Luxor (L-GPA) helps a crop to make the most of this availability while increasing nitrogen assimilation. Combining this with the calcium phosphite found in Calfite Extra tricks the plant into thinking it’s phosphorus deficient, so it increases its uptake,” he says.

Calfite Extra

“Calfite Extra from Unium Bioscience is a unique foliar nutrient complex designed to improve crop rooting and maximise nutrient uptake and utilisation from the soil,” explains John.

“It essentially improves the crop’s phosphorus use efficiency, delivering calcium through the leaf into the plant.

“It will encourage extra rooting, and extra root mass, so it’s better able to extract phosphate from the soil,” he says.


Luxor is a nutrient biostimulant that increases phosphorus delivery to the plant. It has a unique complex of ortho and polyphosphate in a humic/fulvic complex to maximise plant availability,” says John.

“Combined with a plant biostimulant (pidolic acid / L-PGA) to enhance nitrogen use efficiency, it increases photosynthesis and carbon fixation and can be applied close to the seed, in-furrow or as a foliar treatment,” says John.

John explains that in combination, the two products support a plant through the early stages of its lifecycle.

“Phosphite creates a healthier root system, more active in terms of exudations which means you improve scavenging and have a better acquisition of soil nutrients especially phosphorus.

“Following the recent high flooding pressure, it’s unlikely growers will want to compromise on cultural controls and IPM best practice, so an application of Calfite Extra and Luxor could help to provide the support that roots will need,” he adds.

Supporting roots in spring 2024

Agrovista’s technical manager for Scotland, John Murrie, is used to more rainfall than most parts of the UK and says applying biostimulants is a cost-effective way to encourage root biomass and nutrient uptake.

“We’ve had a very wet autumn and crops are struggling for rooting. It will be very important to get these crops going in the spring.”

John explains that interest in Calfite Extra alongside Luxor is increasing year on year on varying crops, winter and spring cereals, vegetables, even grassland. “It can be used on a range of crops and applying it in spring can really help get crops up and running, especially in cold soils.

“It will encourage extra rooting, and extra root mass, so it’s better able to extract phosphate from the soil,” he says.

“It can easily be added to tank mixes and compared to the cost of phosphate in fertiliser, it makes sense to use Luxor and Calfite,” adds John.

With impressive outcomes observed in cereals, oilseed rape, and potatoes, it’s evident that these products have become indispensable assets for both agronomists and farmers.

Cambridge-based arable farmer, Russ McKenzie, has been using Luxor to maximise the availability of P.

“Luxor provides phosphorus either through the soil or the foliage, with both forms complexed with humic and fulvic acid, ensuring the most accessible phosphorus source.

“When combined with Calfite Extra, it stimulates plants to enhance root development and root exudation, significantly increasing phosphorus uptake efficiency,” says Russ.

New biological research

Unium is working hard on biogenomics and how their products impact the regulation of genes – up or down. “We know that waterlogging down regulates ROS detoxification, nitrogen and amino acid metabolism, and anything that can upregulate the production of aerenchyma, photosynthesis, root / shoot biomass, chlorophyll content, and germination rates means that the plant is better able to tolerate the stress as it comes,” says John Haywood.

“We look forward to sharing this exciting development and how the technologies work and then carefully positioning them at the appropriate time to give the most reliable and robust results. It adds a new dimension to biological research and one we are utilising to its full potential,” adds John.

To learn more visit www.uniumbioscience.com.