11 August 1995

Drought-resistant lucerne is a useful source of nitrogen

By Rebecca Austin

OXON producer Mike Trevena has incorporated lucerne in his cropping pattern for six years as an insurance policy against dry summers and to save on nitrogen fertiliser.

In the "Swindon Triangle", 198ha (489-acre) Cote House Farm, Bampton, Witney, receives only 475mm (19in) of rain a year. But the long roots of the legume allow it to survive on land where grasses would be severely stressed in a dry season.

Lucerne is grown on 9ha (22 acres) of the mixed farm in a six-year rotation. Maize, lucerne and grass silage form the base of a total mixed ration for the 100 Holstein Friesians.

Cows eat an average 25.5kg of dry matter a day. "Forage variety in the diet increases intake," says Mr Trevena. "But the ingredients must balance each other and lucerne seems to fit in really well."

He reckons establishment is critical when growing lucerne. At Cote House Farm the crop is sown in early August after the barley has been harvested and included in the £111/ha (£45/acre) drilling cost is a bacterial culture which ensures the seed germinates and rhizomes develop. Because lucerne is a legume no nitrogen is applied, although 62.5kg/ha (50 units/acre) of potash and phosphate are needed in the spring and after second-cut silage.

The crop is never grazed, as it can cause bloat, says Mr Trevena. When fed from the field it is wilted for 36-48 hours before being offered to cows. It can be made into hay but the leaves tend to shatter when very dry, so it needs to be treated very gently, he adds.

The crop is cut for silage at about five to six weeks growth when it is 375-450mm (15-18in) high. It produces an annual total ensiled yield of 29t/ha (12t/acre). Generally, first cut starts in the first week of May and yields 12-20t/ha (5-8t/acre). Thereafter three cuts from the same crop average 7t/ha (3t/acre) each.

Once mown the cut lucerne is left to wilt for 48 hours. Sugars are activated by 2 litres/t (£1.80/t) of Biotals inoculant Axphast Profile II, which is added when the crop is picked up.

For the past six years Mr Trevena has ensiled lucerne in a clamp. But difficulties with mould at the clamp face led him to try big bales. Although lucerne bales well, round bales which couldnt be chopped properly caused trouble in the Keenan feeder. Bales made last year using a New Holland D1010 baler proved more successful.

Mr Trevena still fertilises any winter wheats which follow lucerne in the rotation but he believes there could be savings on nitrogen. However, producing lucerne silage, rather than more grass silage, cuts the forage fertiliser bill. "To get an equivalent yield of silage from grass, as we get from lucerne, we would need to apply 250 units/acre of nitrogen to the grass. That equates to a saving of £1000 a year."


Lucerne silage:

1994 analysis

Dry matter26%

Crude protein19.7%

NDF48.7%

D value67.5

ME MJ/kg DM10.7

pH4.56

The deep-rooted legume lucerne is grown as insurance against summer drought by Mike Trevena.