Better use of
clover for natural N
By Jessica Buss
Clover and its role in boosting the protein content of home-grown forage is the focus of part two of our Grassland 96 report
IMPROVED use of clover would eliminate the need for bag nitrogen while maintaining production on 40% of dairy farms. Speaking at Grassland 96, Scottish Agricult- ural College forage specialist John Bax said clover was more relevant now than it ever had been.
"Input costs are rising, there is a downward pressure on milk price, and an increased interest in natural systems."
He estimated that 40% of milk producers that use less than 200kg/ha (160 units/acre) of nitrogen could use clover without fertiliser Nand maintain production.
Clover sward silage yields are 85 to 97% of a sward that receives 350kg/ha (280 units/acre) of artificial N applied a year. This clover silage is also better quality as excessive nitrogen was not brought into the clamp.
However, Mr Bax stressed that bag fertiliser could be used and in the recent MMB/Milk Development Council clover study of five farms up to 70kg/ha (56 units/acre) of N was applied. Using clover these herds achieved an average of 3500 litres from forage. But when fertiliser was applied swards must not be under-grazed, he warned.
"The most important point is to use good white clover varieties," he said. "These outperform older varieties and are more nitrogen tolerant."
Heavy soils were worst for clover which performed best when sown in soils that warmed up quickly in spring.
Winter grazing by sheep was also essential to maintain high clover contents. Clover should comprise 15-20% of the sward in May and 45-50% by mid-late autumn.
"Bloat has never been a problem at the SAC or on the trial farms," he said. "The secret is to set-stock to avoid giving hungry cows access to lush herbage that causes bloat."
Clover also allowed extended grazing in the autumn. At the SACs low input Acrehead dairy unit clover swards were grazed until early December. Spring turnout was only two days later than fields that had received 100kg/ha (80 units/acre) of N.
How to manage clover swards for profitable milk production is summarised in the latest Milk Development Council report Use of Clover on Dairy Farms. It is based on results of three years MMB-funded work on five commercial dairy units.
John Bax:New white clover varieties out-perform older ones and are more nitrogen-tolerant.