23 May 1997

Keep gap between silaging & slurry

APPLY slurry as soon as possible after silaging – but not within six weeks of second cut – and dilute to minimise scorch risk.

That is the recommendation of SAC grassland specialist John Weddell. He advises adhering to the six-week gap between slurry or dirty water application and silaging must be adhered to in order to minimise contamination, and the risk of high nitrate silage.

"Diluting slurry with water will help avoid scorch and aid uptake, particularly in dry conditions."

According to ADAS fertiliser consultant Brian Chambers, applying slurry or dirty water before regrowth starts after first cut will also help to minimise scorch. "Contamination will also be reduced as the slurry hits the ground rather than grass."

When planning second-cut fertiliser regimes, producers should take slurry and dirty water nutrient values into account, he advises.

"Nitrogen input from slurry can be low, because two-thirds can be lost to the atmosphere – typical efficiency is only 20%."

However, inputs from P and K in slurry are likely to be higher, he says. Applied at 25cu m/ha (2200 gal/acre), typical dairy slurry contains 30kg/ha (24 units/acre).

of phosphate, half of which will be available now with the rest in the following crop, he says.

"Slurry applied at that rate will supply about 90kg/ha potash – of which 80kg/ha will be available in the current crop. "