Slurry on grass lowers need for fertiliser

MAKING EFFECTIVE use of slurry and manure in the next few months could eliminate the need for many livestock units to buy in phosphate and potash fertilisers this year.

Devon-based Creedy Associates consultant John Morgan suggests using slurry or manure on silage grass early in the season to boost early growth, reducing the need for artificial fertiliser. “Now is the ideal time to apply manures to grassland as it is just starting to grow, so it will make best use of the available nutrients,” he says.

But Mr Morgan warns against over-applying manures in the early season, because there is still a risk of leaching occurring after heavy rainfall. “The chances of leaching are reducing as the year progresses, but it”s better to be cautious than have a pollution problem,” he says.

“Application methods such as trailing shoe tankers or injection are the best way of applying slurry as they place slurry in or near the surface of the soil, helping improve nutrient use and reduce pollution risks.”

Later in spring, Mr Morgan says maize ground is an ideal place to apply manures, but once again caution is needed to avoid over-applications. “Many people treat maize ground almost as sacrifice ground and spread up to three or four times too much manure or slurry.

“This creates a big pollution risk, particularly with slurry. The maximum that should be applied according to the Code of Good Agricultural Practice is 50t/ha.

“Better value can be gained by spreading the right amount on maize ground and then using the rest elsewhere, such as on grass silage aftermaths.” Where slurry is spread on maize ground, it should be incorporated as soon as possible after application, ideally immediately. “Ploughing ground immediately after the slurry spreader would be the best solution, as ammonia starts being lost as soon as slurry is spread,” he adds.

But Mr Morgan cautions against relying on slurries and manures for all of a farm”s nitrogen requirement. “About 50-60% of nitrogen requirements can come from manures, but producers should use some bagged fertiliser to have a better idea of how much nitrogen has been applied to land.”

Even when manures are analysed, their make-up may change before application, either through more rainfall or drying out, so is difficult to apply them accurately, he adds.