Root therapy
Root therapy
Might root stimulants help those waterlogged crop roots? From seaweed to soil conditioners, Julia Knights finds out whats on offer.
ENCOURAGING tap roots to go deeper will be crucial for many late drilled crops, which have been water-sodden for weeks. The root structures of these plants are likely to be shallow and flat, leading to weak anchorage and poor nutrient uptake.
Conventional solutions would be rolling, if practicable, or judicious use of plant growth regulator to reduce tillering. But the difficult season has raised the profile of alternative solutions, involving bio-products, claiming to enhance or stimulate root growth. Do they work? And if so, are they cost-effective?
John Spink of ADAS Rosemaund is a firm sceptic: "Trials with these bioproducts often measure root mass. This is meaningless; root extension is the important factor and this should be measured instead," he says.
His logic is that wheat roots already possess 12 times the root mass they actually need, in order to extract nutrients. So an increase in root mass would therefore have little effect.
Not surprisingly, the manufacturers of root stimulants are not going to take such assertions lying down. Certainly, some independent trials do indicate some lodging reduction and yield increases for cereals, oilseed rape and root crops for some products. However, results are often inconsistent. And there are few trials which compare competing products side by side.
There are two main types of root stimulant products: first, growth hormones, namely cytokinins, auxins and gibberellins, which can be synthetic or natural; and second, soil conditioners.
1. Growth hormone products
THE theory is that growth hormones induce crop roots to produce more of their own natural growth hormones. In turn root development, nutrient uptake and ultimately yields will be improved. Application rates vary depending on the hormone concentration in each product.
Synthetic formulations
Axis foliar spray, formulated by Mandops, and marketed by Dalgety increases cereal yields by 6%, according to trials conducted at Sparsholt and Shuttleworth colleges. The product also acts as a crop "safener" when tank-mixed with herbicides, claims the company.
At £37.50 for a 5-litre pack, recommended rate for cereals is 1 litre/ha, applied between 2.5 leaves and the end of tillering.
Also from Mandops, Axon is for oilseed rape and includes zinc, which boosts root auxin production, claims the company. Independent trials apparently indicate yield increases of 6-8%. Price is £40 for a 5-litre pack from Dalgety, and recommendation is for a 1.25 litres/ha treatment as soon as possible after the crop has two fully expanded leaves.
"The product is particularly useful on backward crops and small-scale patch emergence," says Mandops managing director, Peter Harding.
Route by Loveland Industries is a soluble liquid formulation of nitrogen and zinc complexes, combined with an alkyl polyglycoside wetting agent. Suitable for use on cereals, pulses and oilseed rape, it retails at £54 for a 5-litre pack. Recommended rate for spring and winter cereals is 0.8 litres/ha, applied between GS14 to mid-tillering and again between GS12 and GS30.
Procams Dr David Ellerton is impressed by Route and reckons it could be particularly beneficial for stressed crops. Average yield responses of 0.4t/ha on winter cereals have been shown in trials carried out by Crop Technology and the Scott Abbott Arable Crop Station. And on late drilled, stressed winter wheat, savings of £27.26/ha are indicated. Care needs to be taken when spraying with Route to avoid contaminating surface waters or ditches.
Natural formulations
There are numerous natural products containing seaweed extracts, which are also rich in growth hormones. Many are approved by the Soil Association for organic crops.
Exact formulations tend to be secret, and seaweed variety, preparation and concentration of active ingredients may vary considerably between products.
Maxicrop Triple by Maxicrop is a viscous black liquid made from a particular brown Norwegian seaweed. Yield increases of up to 10% in cereal and root crops have been reported in trials. The product is £35 for a 10-litre pack, and recommended rate on cereals is 1.5 litres/ha.
University research on this seaweed product does show benefits other than yield: beneficial microbes such as pseudomonas bacteria are stimulated, which in turn increases nutrient availability. Leaf chlorophyll is also increased which improves growth potential. Enhanced tolerance towards stress such as frosts down to -20íC has also been identified.
"For more backward crops with just 1-2 tillers, the product is also useful to aid tiller survival," says a Maxicrop spokesman.
The company has two products approved for the organic market – Maxicrop Original , a seaweed meal, and Maxicrop Concentrate, a pure seaweed extract.
Root Boost, by Omex Agriculture, is a water-based inverse emulsion which is coated with a fine layer of oil to protect it from breakdown when mixed with a fertiliser, or when in contact with the soil. Recommended at 5 litres/ha on potatoes and 2.5 litres/ha on cereals, the product retails at £6/litre.
The best responses using Root Boost appear to be on potatoes: yield increases of 15t/ha have been achieved from Harper Adams trials. A reduction in take-all in cereals has also been found, claims Omexs Andy Eccles. However, Root Boost is only supplied with Omexs suspension fertilisers.
Kelpak is an Omex product which is approved by the Soil Association, and comes from seaweed collected from the African coast. The only trials data comes from South Africa where cereal yield benefits are recorded.
Application rate and timing are critical: recommendation is for 1.25 litres/ha to cereals between GS13-15. Kelpack retails at £6/litre.
Headland Lion by Headland Agriculture is also Soil Association approved. This is a powder product made from Irish seaweed. It is water soluble, and is recommended for use on a wide range of crops. Seamac is the liquid formulation. A 10-30% yield increase on ware potatoes has been shown in trials, claims the company. No data is available for cereals.
Premier N, launched this year for cereals by Dalgety, is a nutrient rather than a growth stimulant, says the company (see Crops, Jan 20 p25). The claim is that it encourages the plant to produce more root mass, which can explore a larger area of soil for water and nutrients. Yield boosts have been shown in trials. Cost is about £10/ha.
2. Soil conditioners
These are entirely different from root hormone/stimulants. Conditioners improve the physical soil structure, so helping aeration and drainage. The idea is that as soil/root contact improves, nutrient uptake increases, which in turn boosts yield.
New product Agri-gate by Interagro contains surfactants, which make soil particles aggregate. Suitable for soils with cereals and root crops, limited quantities are available this year. Price is £75 for a 3-litre pack, but a little goes a long way – recommended rate is 0.75-1 litre/ha.
CSC Cropcares Dr Keith Dawson has been impressed by it in Scottish trials. "Most of the bio-stimulants were disappointing and the economics didnt stack up. However, Agri-gate improved soil drainage and rooting and we saw yield benefits of between 5-10% in both cereals and root crops."
Eco-Ag from the Kings Lynn based company of the same name is also described as a soil conditioner, which improves soil structure and reduces waterlogging.
It has recently been reformulated to improve product performance and make it more cost effective, claims the company. At £6/litre, recommended rate 1 litre/ha, followed by a further application of 1-1.5 litres/ha with the first N top dressing.