Edibles fertilisers - Specialist formulas

Fertiliser manufacturers are targeting particular market sectors with formulations to improve crop quality and yield, Jack Shamash reports.

Recent years have seen a shift from generic fertilisers to making crop-specific products for growers - image: HW
Recent years have seen a shift from generic fertilisers to making crop-specific products for growers - image: HW

Over the past few years there has been a marked shift in fertiliser use. Instead of simply using generic fertilisers for all kinds of edible plants, producers have been making crop-specific products, designed to meet the needs of the various different market sectors.

Solufeed is one of the firms that has opted for the more specialised approach. "About two years ago, we introduced a Blueberry Special - a fertiliser for blueberries. It's really starting to catch on," says Bob Greensmith, who is responsible for communications and business development at the firm.

Blueberries benefit from an acidic soil. The specialised product contains PeKacid, a new, highly-acidic (it has a pH of 2.2), fully-soluble phosphorus and potassium fertiliser formulation. It is specially designed for use in calcareous soils where the water has a high bicarbonate content. The use of PeKacid replaces the conventional application of technical and agricultural grade phosphoric acid to produce an easier, safer and more effective fertilisation process.

The product also contains iron chelates - organic compounds containing iron, which is essential for blueberry growth. The mixture is also specially formulated to increase uptake of nitrates. This results in better growth and fewer problems with runoff and contamination of surface water.

Additives in the mix

Most fertilisers contain a mix of nitrogen, phosphate and potassium (NPK). However, there are different ways of delivering these elements and the fertilisers can also have different additives and trace elements.

Solufeed also produces a variety of fertilisers for the growing market in strawberries. "We do a Strawberry Special, a Strawberry Starter for use in the early season and a product called Stout, which is aimed at outdoor strawberries and for people with pick-your-own farms," says Greensmith. Stout contains NPK but also magnesium and, importantly, is non-hazardous. The Strawberry Starter has the high levels of nitrogen that are required early in the growth cycle.

Solufeed is also promoting its iron chelates. This year, it has produced a formulation of Fe DTPA with iron levels of 11 per cent. These are particularly useful for tomatoes, cucumbers and peppers. The products also have extremely low levels of sodium, which means that they can be recirculated in closed systems without excessive build-up of salts. "These specialised products are becoming recognised by growers. They are striving for better qualities and yields," says Greensmith.

This year, German-based firm Compo has been concentrating on making products for very arid conditions, which are not generally suitable for crops in Britain. However, the firm is still heavily promoting Novatec - a stabilised ammonium product containing nitrification inhibitor DMPP that improves the uptake of nutrients.

The company believes that the product is ideal for field vegetables, particularly because it slowly releases nitrates over a period of up to 12 weeks. "It doesn't leach nitrates into the soil so it is much more environmentally friendly," says British representative Mike Butler. Compo is also investing heavily in biodegradable coatings for controlledrelease fertilisers, although these are more applicable for ornamentals than edible plants.

Ilex EnviroSciences has also been developing fertilisers tailored to the needs of growers. Over the past year, the firm has released five new products - three of which contain phosphites, nutrients and trace elements.

Its PK Maxx is a ready-to-go product that reduces mixing time, while PK Veg is a highly-concentrated NPK fertiliser based on plant-available phosphorus in both phosphite and phosphate forms, specifically formulated to promote strong root development. Ilex has also produced the foliar feed CaPITAL, which contains high levels of soluble calcium plus boron and zinc.

Also new is AdvoCate, a new-generation calcium formulation. Unlike traditional calcium chloride and calcium nitrate products, AdvoCate is made more complex with natural sugars and amino acids to increase calcium mobility and improve nutrient uptake. Ilex sales manager Andy Varney explains: "We point out that AdvoCate can help correct physiological disorders and increase storage qualities for plants."

Agronomist Don Vaughan, who works for advisory firm Fast Products, says growers are spending an increasing amount of time and money analysing their crops to ensure that they are properly nourished and to avoid waste.

"We always recommend a full soil analysis and tell people to feed to need. Most people will want a fairly basic NPK fertiliser, but then might need mixes to address a lack of trace elements. We suggest a full analysis of the soil every three years. We also recommend regular leaf and sap analysis," he adds.

Most tomatoes in the UK are grown hydroponically and all nutrients have to come from fertilisers. "Most growers will buy commercial fertilisers and mix them up to meet their individual needs," says independent agronomist Gwyn Roberts. He explains that hydroponic growers are always looking for very pure products to avoid insoluble sediment clogging up their tanks and build-ups of salts. "Fertilisers have definitely improved in quality over the past few years," he says. But soil testing has to be done regularly and there has to be constant monitoring of pH, he advises.

Testing for quality

Norwegian manufacturer Yara is also stressing the importance of testing. It advocates the use of tractor-mounted computerised system N Sensor ALS, which tests nitrogen levels by shining a light at crops and testing the wavelength of the reflected light. Head of agronomy Mark Tucker says farmers are increasingly concerned about the quality of the crop. "We recommend our calcium nitrate product Tropicote, rather than urea, which is cheaper. Tropicote will give a better colour and skin finish on most plants."

The manufacturer is another that produces a wide range of products for specialist purposes. Not only are fertilisers formulated for particular crops, but they are also special formulations for drip-feeding and solid application.

Tucker believes that the environmental credentials of fertilisers will become increasingly important. "If you have a retailer who wants a low carbon footprint, you have to be able to show that your fertilisers are responsibly sourced," he says. All Yara products are produced with low-carbon input, he adds.

The interest in organic products is also growing. Solufeed has just launched a range of organic fertilisers that has been approved by the Soil Association. Greensmith explains: "We did a lot of research and we found that people wanted three basic types of fertiliser - balanced, high nitrogen or high potassium." The range is all made from animal and vegetable products such as rice husks or sugar beet waste.

PP Products has recently produced a foliar fertiliser based on natural limestone. Lithovit contains trace elements designed to improve plant vitality and tolerance to stress conditions. The product is intended to improve crop yields, quality and storage properties. It is applied by spray and absorbed through the leaf stomata.

Some more old-fashioned products are starting to come back into favour. PP has increased sales of calcium cyanamide product Perlka, which has been manufactured in Germany since 1895. Over the past five years, sales have more than doubled to around 2,000 tonnes a year. The product suppresses the bacteria that lead to nitrogen loss. It decays to leave 50 per cent residual lime.

PP proprietor Paul Corfield explains: "It's very popular for brassica growers. We recommend around 500kg per hectare. It isn't a cheap product, but it stimulates the health of the plants and their resistance to disease such as club root.

"We also recommend potassium phosphite Farm-Fos44 to strengthen leaves and roots," he adds. "These older techniques are proving very useful. When we first started importing this product, people thought we were mad, but all the scientific evidence shows that it works."

Foliar feed caveat

Most manufacturers offer foliar feeds, but agronomists reckon that they should not be used routinely. Roberts says: "They don't last very long and get washed off quickly. We only use them as a last resort if the roots aren't working very efficiently." Many of the foliar feeds are seaweedbased and can be used to improve leaf colour.

Getting the right sort of fertilisers in place is set to become increasingly important. Efficient use will save growers money and ensure that they produce high-quality crops. Efficiency will also keep the environmental lobby happy by minimising the carbon footprint of various crops, while avoiding runoff will ensure that growers meet likely Government legislation as part of the latest nitrate directive. All of which means that growers must choose carefully from the products on offer to ensure that they get ones best suited to their needs.

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