12 December 1998


A prototype spoke wheel system could turn attitudes to fertiliser injection around, reports Debbie Beaton.

THE potential savings and environmental benefits of injecting fertiliser in the root zone where the plant needs it most have been well known for a number of years – the basic principle being to improve the efficiency of fertiliser usage. When nitrogen fertilisers are applied as surface dressings they are subject to gaseous losses or at risk from leaching, so about half the amount applied is often not recovered by the plant.

Fertiliser injection helps to overcome those problems, but it has not been widely adopted largely due to the crop damage and soil disturbance that current knife systems inflict when fertiliser is applied into a growing crop. Such systems commonly have a large draft requirement too.

Those drawbacks are not found in a new spoke wheel system currently being used in the US and Canada, says its importers, Regent Fertiliser.

The company are trialling the prototype on farm colleges this season. Maize, sugar beet, potatoes and grass are the main crops being targeted. Maize in particular, says Regents consultant John Denyer, responds very well to a post-emergent application of fertiliser nitrogen.

"Research has shown that maize responds well to fertiliser N at the 6-8 leaf stage, but broadcast applications at that time are risky because granules can lodge in the leaf joins resulting in scorch damage. Consequently growers compromise and go on at the 4-leaf stage. The spoke wheel system will allow them to apply the fertiliser at the optimum timing," he explains.

The spoke wheel applicator is essentially a series of wheels with projecting spokes mounted on a tool bar. As the wheels revolve, the spokes penetrate the soil and inject a metered amount of fertiliser into the soil about 8-10cms below the surface.

Fully adjustable injector wheels are mounted on a 6m tool bar so that they can be placed within 15cms of the plants, to ensure maximum fertiliser uptake, according to the crop. Tank capacities of 1,000 litres can be fitted to the unit itself with an optional additional 1,000-litre tank mounted at the front of the tractor.

Benefits of fertiliser injection

&#8226 eliminates surface gaseous losses

&#8226 negates surface run-off

&#8226 avoids crop scorch

&#8226 places fertiliser directly into the plant rooting zone

Scandanavian cereal growers have long recognised the advantage of putting fertiliser where the plant needs it most. Vaderstaad is among several companies offering drills equipped to put fertiliser and seed down the same spout. The companys Rapid-30 is being trialled in Scotland for such use in spring barley.

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