Given last year's balmy December temperatures and the springtime downpours that have no doubt drenched their crops, few ornamentals growers would argue with Compo Expert UK director Jerry McHoul's observation: "It has been a real topsy-turvy season thus far with many species that broke dormancy in the mild winter now slowing up from cool spring temperatures, both day and night."
Andrew Wilson, technical manager for ICL Professional Horticulture, also notes that hardy nursery stock growers in particular have had a lot of "climatic anomalies" with which to contend. "While temperatures since the autumn have been very mild, the rainfall has been high in many areas of the country. Extreme rainfall events, where an inch of rain can fall in an hour, are more common."
Fortunately for these growers, fertiliser manufacturers and distributors are aware of the UK's increasingly extreme weather and have a large amount of advice and products on hand to help their plants thrive. McHoul, for instance, suggests that growers should not apply the first nitrogen (N) requirement until the soil has warmed sufficiently for plants to take up this key nutrient.
"One way to ensure that N is not leached if plants are slow to take it up from early-applied granular dressings in field situations is the use of stabilised NPK products," he says. "These fertilisers contain the (nitrification inhibitor) DMPP, which prevents the nitrogen from being quickly transformed into nitrate, which can be easily lost in sandy soils and wet springs."
McHoul points out that the NovaTec range of products, originally used by fruit and vegetable growers, helps tackle this issue and is now becoming increasingly popular for field-grown ornamentals and trees.
Meanwhile, ICL's Wilson adds that the long, wet winter has the potential to flush through any available nutrition left in the plants' root area. "This could render some stock impoverished until the controlled-release fertiliser (CRF) within the compost gets to a temperature where it is releasing (nutrients) sufficiently for the plant to grow. Many of these overwintered crops were potted the previous spring and the CRF is coming to the end of its release period."
He notes that one way to ensure there is enough fertiliser in the correct balance is to top dress pots with a shorter-release product to "fill in the gap."
Andrea Marshall, technical business development manager for Sinclair Professional, agrees that in areas of high rainfall some nutrients may have leached out so will need to be replenished. "As daytime temperatures rise and plant nutritional requirements increase, additional feeding can be applied as a water-soluble fertiliser (WSF) or top dressing," she explains.
For overwintered plants, Marshall recommends that growers could get their growing media analysed to enable them to apply the correct feed. "It's always advisable to get your water source checked too."
Evidently, many fertiliser suppliers concur that top dressings are particularly helpful this season. Wilson reveals that ICL sells two products specifically designed to help growers redress the fertiliser balance in their plants' growing media. "OsmoTop will give a quick green-up, releasing NPK along with a full trace element package over a twoto three-month period," he says.
He adds that Osmocote with Fusion Technology, which sticks the granules to the surface, is similar to OsmoTop but has a longer release period of four-to-five months. Wilson also notes that these products are suitable for protected crops as well as hardy nursery stock.
Marshall adds that Sinclair Professional's Sincron + Top Dressing helps to green-up overwintered plants while providing additional feed for up to four months without the need for repotting. "We are just launching a new formula, Sincron + Top Dressing 16-7-15 + TE, which is ideal for containerand field-grown nursery stock plants.
"It has a nutrient release of up to four months with two slow-release nitrogen sources for a longer and more consistent supply of nitrogen. The granules are sticky so bind to the compost, which means the product doesn't fall off if the plants fall over."
McHoul points out that Compo Expert's Floranid Permanent continues to be a bestseller for the company thanks to what he describes as its "steady and reliable release profile over three months". He also notes that its ultra-low salt index of the crop-safe IBDU form of slow-release nitrogen means that it is "kind to sensitive plants" because it poses little risk of causing scorch. "With a balanced formula of 16-7-15, the product can be used year-round as a general top-dressing fertiliser on any nursery."
CRFs are continuing to help by providing a base level of steady feeding. As Marshall reminds growers: "CRFs such as Sincrocell in the growing media not only provide nutrition on the nursery but also provide additional shelf life while the plant is in the store and for the end consumer."
Many such fertilisers are also being formulated (or reformulated) to better suit the specific needs of particular crop types and peat-free growing media. ICL, for example, is selling several improved CRF products such as Osmocote Exact Standard High K with a new NPK ratio of 12-7-19. This product, which is recommended when potting and growing pot plants such as cyclamen, perennials and hanging baskets, features double-coating technology - a second waxy coating that delays the start of release by two-to-three months.
Limited volumes of two other new Osmocote formulations - Osmocote-coated CalMag and Osmocote Iron - that are currently being trialled are available to growers this season. Osmocote-coated CalMag has been developed for container nursery stock and pot plants that have a high requirement for calcium and magnesium. It is also handy for growing media that have a high level of structural mix.
Additionally, the new iron-coated product, Osmocote Iron, contains 17.8 per cent controlled-release iron. Wilson says: "Daily release of small portions of iron has been shown in trials over three years to promote better leaf colour because it helps optimise photosynthesis."
Many fertiliser producers and sellers are increasingly acknowledging the benefits that biostimulants can offer horticulture crops, including ornamentals, and are therefore incorporating them into their product range (see box, p39, for the EU's definition of biostimulants).
Wilson points out that ICL, for example, has introduced to its range the Lallemand Plant Care biostimulant product RISE P, which contains plant growth promoting rhizobacteria that help to increase the availability of phosphorous and metallic ions.
Meanwhile, Hortifeeds has released several biostimulant products to create a phenomenon it describes as "enhanced growth beyond fertiliser". Technical manager Bill Riley explains: "This concept combines the use of high-quality soluble fertilisers with enhanced uptake from incorporated biostimulants.
"The biostimulants are very diverse and include organic and inorganic chemical substances, such as organic silicate and complex micronutrients, amino acids, triacontanol (a fatty alcohol), micronised seaweed, and humic and fulvic acid complexes. We are also incorporating fungal and bacterial biostimulants into new products, to increase nutrient uptake and produce an environment similar to a natural healthy soil where microorganisms flourish alongside and within plant tissue for the mutual benefit of both higher plants and the fungi and bacteria."
Such products include:
- HortiHumic Complex An additive currently being incorporated into a range of root-applied fertilisers.
- HortiBoost Primarily used as a foliar fertiliser.
- HortiStar A fertiliser and biostimulant that adds silicate to plant leaves that Hortifeeds claims increases the physical strength of the leaf.
Other such products available include HortiChel Compound Trace Element Foliar Fertiliser and Hortifeed's HortiMix WSFs, of which Riley says: "Our crop-specific products are increasingly popular, for example the primrose and pansy mix, which is ideal for autumn and winter feeding."
Compo Expert has also recently launched a new biostimulant product, Basfoliar Kelp, into the ornamental sector. McHoul says this cold-pressed, liquid kelp extract is typically applied through fertigation systems or by overhead spray - and can also be used as an effective growth regulator at later vegetative growth stages.
"Used widely on the continent, Basfoliar Kelp will prove an invaluable tool to UK growers in initiating rooting establishment in ornamental production," he adds.
Growers may have noticed that many of the fertiliser and biostimulant products being introduced to the market are water-soluble, such as the two new MicroMax products sold by ICL. Wilson says: "MicroMax WS Iron is a fully water-soluble fertiliser, consisting of EDDHA-chelated iron plus X3, a specific biostimulant that enhances the absorption of the Fe-chelate compound into plant leaves resulting in optimum uptake by a large variety of crops." He adds that MicroMax WS TE is a water-soluble trace element mix, containing all major trace elements.
As well as these new additions, ICL has recently extended its Universol portfolio of WSF. "As a direct result of increased rainwater harvesting, we are seeing rising soft-water usage on UK nurseries," notes Wilson. "Soft water is very low in dissolved nutrients. While a standard WSF will add most nutrients, others such as calcium and magnesium are generally lacking or too low. We have therefore extended our Universol portfolio with new hardand soft-water options, making a complete range for all growing circumstances and water qualities."
Solufeed representative Clive Marlow asserts that liquid feeds can give more control of the rate of growth than relying solely on controlled-release technology. He also points out that Solufeed's products are all now made with "NonStop" technology, which greatly reduces the formation of scale deposits that block irrigation lines. "This is a major problem since a blocked drip line often results in plant death and is time-consuming to clean out."
Moreover, Solufeed has also released a soil conditioner named Fulvic 25, a Soil Association-approved product derived from the degradation of organic matter in the soil. Marlow says: "Fulvic 25 enhances rooting and growth by solubilising nutrients and feeding beneficial root zone microbes."
This spring the European Commission's Circular Economy Package officially classified plant biostimulants as fertilisers. It also gave them a concrete definition for the first time, describing them as "a product stimulating plant nutrition processes independently of the product's nutrient content with the sole aim of improving one or more of the following characteristics of the plant: (a) nutrient-use efficiency; (b) tolerance to abiotic stress; and (c) crop-quality traits".
Product advice - films
A series of 12 informative product films, each just two minutes long, has been recorded by ICL featuring advice and technical information on Osmocote controlled-release fertiliser, Peters Professional and Universol water-soluble fertilisers as well as Exemptor.
Adam Ferjani from ICL Professional Horticulture's marketing team says: "Packed with practical advice and technical information, the videos have been shot on location at nurseries where the products are used. The footage can also be found online at www.icl-sf.co.uk."