28 March 1997


By Rebecca Austin

TWO years ago Norman Light, who manages 486ha (1200 acres) at Lower Bisterne Farm, Ringwood, Hants, tried undersowing maize with Italian ryegrass.

He is now so pleased with the results he plans to undersow 20ha (50 acres) of his total 170ha (420 acres) of continuous maize this spring.

"We all need to be more careful in terms of pollution and soil erosion," says Mr Light. "At the end of maizes growing season there is always extra nitrogen available in the soil. Undersown grass will take up this, preventing run-off polluting watercourses, while the grasses root system reduces soil erosion."

The key to this techniques success lies in the grass variety. Mr Lights trials in previous years proved that the Italian ryegrass variety Bartissimo is the only contender from the three he tried on his farm.

"My trials were not replicated and merely based on observation, rather than scientific fact so the technique must be investigated on a scientific basis by the Maize Growers Association," he says.

Following his trials in 1995, Mr Light grew 4ha (10 acres) of undersown maize last year in three different fields. Bartissimo was broadcast in May at a rate of 10kg/ha – half that recommended for normal IRG establishment – three weeks after maize drilling.

The only extra cost was grass seed at £25/ha (£10/acre). Otherwise atrazine was applied at a rate of 2 litres/ha, as well as 1.5 litres/ha of bromotril-P once the grass seed had germinated. In the spring 160cu m of treated sewage sludge was injected 36cm (14in) below the surface and 250kg of MOP was also applied.

"It was difficult to tell whether the grass had suppressed yields compared with previous years because to notice any change by eye there must be a 10% difference in yield," says Mr Light.

"However, what was obvious was how rapidly the grass grew once the maize crop was cut. By Christmas the sward was taller than the maize stubble."

In the first week of March the ley received 75kg/ha (60 units/acre) nitrogen. It was due to be strip grazed two weeks later – weather dependent – by the farms 380 cows. Mr Light will then plough it up and plant another maize crop. He considers early grazing of the undersown grass more important than conserving it for silage which, on the farms light sandy soil over gravel, could be detrimental to the following crop of maize.

"It will be interesting to look at the grasss effect on the following years maize crop," says Mr Light.

"The idea makes so much sense and works," says Mr Light, who is keen to improve on his results. "We need to find out if any other IRG varieties grow as well as Bartissimo having been sprayed with atrazine first, as well as the grasss effect on the maize crop. An optimum grass seed rate must be established, as well as the ideal time to sow the grass. Once these points have been cleared up there is no reason why maize growers shouldnt be undersowing with grass," he adds.

Norman Light believes it makes sense to undersow maize with grass – both environmentally to reduce nitrate leaching and to provide extra grazing.