21 November 1997

HOW RAC DAIRY UNIT DEFEATS DROUGHT

MIXED forages and treated straw are the keys to tackling drought on the Royal Agricultural Colleges dairy unit.

Two years of dry weather, and the likelihood of a third, is concentrating the mind of Mike Limb, farms director at the college.

"Our Cotswold limestone soils are particularly drought-prone, and we have no water to irrigate. Two consecutive years of low rainfall meant we ran out of any slack in the system last summer."

Carried-over silage supplies were used to buffer feed the summer calving 165-cow dairy herd while at grass last year, but those supplies were soon used up, and cows were then fed first-cut silage.

That meant that a significant proportion of first-cut had been used by the end of summer. "We grow two-year Italian ryegrass leys for silage and usually get a reliable first cut, and a reasonable second cut. Only in a wet summer will we manage a third cut."

"Some would argue that summer calving, and a reliance on buffer-fed silage, is silly on such dry land, but we like it because it helps quota management. The herd average is 6360 litres, so it is difficult to justify a high level of buffer-fed concentrate at that level," explains Mr Limb.

Zero grazed lucerne is also fed during the summer. "We started growing lucerne six years ago when we became concerned about dry summers. It gives three reliable cuts. However, it can struggle to establish in an extremely dry summer so we are looking at undersowing in maize."

Caustic treated straw was also introduced in mid-July, and fed at 1-1.5kg with lucerne, rolled barley and a 21% protein dairy cake.

The drought, and lack of silage, meant that treated straw was fed at higher than usual levels during the winter – 3-4 kg a cow. "The dependence on straw meant we had to balance it with a suitable concentrate. That means we probably lost some margin, but we had no other option."

As an experiment, kale was strip grazed, zero grazed and baled last year. It was hoped it would provide some mid-summer forage. But dry weather meant it was late to start growing and matured later than required, so it was not grown again this year, says Mr Limb.

Maize silage is grown on the farm, but drought means it is unreliable too, he says. "We grow 20ha of maize, but find we cant rely on it. We are 450ft above sea level and on thinnish soils, so we are in a marginal area. Yields vary between 30t/ha at their best to only 18t/ha in 1995 when it was very dry. It is no insurance crop."n

Mike Limb of the RAC… using mixed forages and treated straw to tackle poor summer grass growth.

SUMMER RAINFALL

1992400mm

1993465mm

1994312mm

1995205mm

1996247mm

DROUGHT POLICY

&#8226 Mixture of forage crops.

&#8226 Treated straw.

&#8226 Emergency cropping.