Foliar fertilizers for better blooms

Chrysanthemums. PHOTO: MUSTANG JOE/FLICKR

Cut flowers with greater marketable value

The benefits of foliar fertilization have been highlighted by a recent collaboration between Colombian flower farmers and the pioneering British ‘smart’ fertilizer company Levity Crop Science. Trials on chrysanthemums treated with foliar formulations showed significant improvements across a range of measurements, including stem length, numbers of stems and flowers, and shelf life. These improvements translated into greater marketable value for the produce from treated plants.

“Traditionally, fertilizer has been seen as a soil-applied product,” explains Dr David Marks, Levity’s founder and managing director. “Plants obtain the nutrients they need via the roots, and indeed that’s the route generally taken for most chrysanthemum production.

“Fertilizer is applied to the soil at the same time as the seeds are sown, a practice regarded as the easiest and most cost-effective.”

Yet Dr Marks says this may prove a false economy for many growers. Key nutrients such as nitrogen can be lost to the environment before the plant can take it up. Other nutrients, such as calcium, are only mobile in the plant’s xylem, which means they bypass areas of the plant that are calcium deficient.

“While a soil-applied fertilizer may display the correct nutrient analysis, it’s very difficult to guarantee that those nutrients will be available to the plant as it needs them: the right source, at the right time, in the right place, and in the right amounts,” Dr Marks points out.

He says there’s a large body of research that shows how soil fertilization can be supplemented, or even replaced, by foliar nutrition. “By choosing timings more carefully – during the growing season, rather than just at the start – and applying the fertilizer in the right place, to the leaf, it’s possible to make better use of crop inputs, while increasing yield.”

Chrysanthemum trials in Cundinamarca

In the trials, which were carried out at two separate farm sites in Cundinamarca state with varieties including Deliflor, Golden Polaris and Pink Atlantis, chrysanthemums were grown in glasshouses and subjected to foliar experimental treatments involving four liquid fertilizers developed by Levity. Each of the four ‘smart’ fertilizers contain specific ingredients designed to improve nutrient-use efficiency (NUE).

“Applying nutrient products at higher rates, in order to increase a crop’s uptake of a particular nutrient, is neither sustainable nor profitable,” says Dr Marks. “Levity’s ‘smart’ approach is to find compounds that either helps the plant make better use of those nutrients, or which stimulate the plant into absorbing greater quantities of them, or both.

“Often this results in an overall decrease in application rates, while seeing an increase in yield or other metrics such as quality, shelf life or number of blooms, and, in the case of fruit, improved firmness, colour and sweetness.”

Levity’s trials in Colombia – where it has been working with flower growers since 2020 – focused on four of Levity’s products. The first, Lono, contains nitrogen in the form of stabilised amine nitrogen (SAN) – co-formulated with either potassium (Lono K) or calcium (Lono Plus). As the name suggests, SAN allows nitrogen applications to be made without it being lost to the environment, as happens with nitrates or urea. SAN also encourages the plant to concentrate its resources on strong stem and flower development, rather than vegetative growth.

Another calcium-containing product in the trials was Albina formulated with LoCal, Levity’s specially developed calcium transport stimulant. LoCal encourages the plant to transport calcium to all parts – especially stem, leaf and root tips – rather than being limited to xylem transport. Levity says LoCal makes it easier for flowers and older leaves to absorb calcium.

The fourth product, Indra, contains nutrients that promote and enable the plant’s antioxidant production, helping to counter the accumulation of reactive oxygen species (ROS) caused by abiotic stresses, such as heat, cold, salinity, drought and high levels of UV light.

Rigorous methodology

Five treatments at different rates were made for each fertilizer, with four replicates. The foliar applications were made in addition to the grower’s standard programme using soil-applied, edaphic fertilization (EF).

Results were assessed for various metrics: stem length and diameter for all products, plus vase life and fresh weight (Albina); fresh and dry stem weight (Indra); number of buds and stem fresh weight (Lono K and Lono Plus).

Additionally, for each of the four fertilizer products in the trial, a cost-benefit analysis was conducted to determine which of the application rates, if any, gave the best return on investment. This was assessed by comparing the cost of buying the products against the value of any increase in saleable yield – based on a standard 0.5kg export-type bouquet achieving a Colombian peso (COP) sale price of COP8,000 (February 2022 prices, when the trial programme began).

Across the board economic boost

Results showed the four fertilizers each gave significant increases over a standard EF programme, with all metrics demonstrating improvement.

But it’s how that improvement translates into benefit for the grower, says Dr Marks, that makes these results significant.

“Our cost-benefit analysis showed that in all cases, apart from the very lowest application rates for Indra and Lono Plus, the grower would see an economic boost from the use of these products,” he notes.

“At the other end of the scale, the economic benefit was as much as COP175,000 from an application that costs just COP236 – in other words, a 740-fold return on investment.”

By analysing all the cost-benefit ratios, the research team was able to establish the right rate for each fertilizer, based on its economic value to the grower: Albina at 1 l/ha Albina; Indra at 0.75 l/ha; and Lono K and Lono Plus both at 1.5 l/ha.

“This work has reinforced our already extensive research work on the role of SAN in increasing crop yields,” says Dr Marks. “The applied nitrogen remains available to the crop rather than being lost to the environment.”

Levity chose Colombia for the trials as the world’s second-largest exporter of cut flowers – it’s the country’s fourth most valuable exported product.

“Giving growers the tools to improve their agronomic and economic performance, while also being able to demonstrate more sustainable and more efficient resource-use, should be of further benefit in raising margins and improving the already strong perception of Colombian-grown cut flowers amongst export buyers,” concludes Dr Marks.

Acknowledgment

Reporting by Adrian Bell of Agromavens.