With the end of the closed period for spreading slurries and material with high availability of nitrogen (N) either approaching or having passed, it is worth reviewing your fertiliser policy. The NVZ regulations allows those with shallow soils to spread from the 1st January, with a few limitations in that until the end of February, the maximum volume is 30M3/application of slurry or 8 tonnes of poultry manure and three weeks between applications.
The NVZ regulations states that the crop available nitrogen (N) from cattle slurry is 40%, irrespective of the time of year. The Fertiliser Manual (RB209) states that the crop available N is 25% when applied in the January to grassland and 35% in April. Therefore your crops might be getting 25 kg less of N less than you thought.
On the other hand, applications of slurry to grazing land could be increasing the risk of Staggers if the soil has a potassium index greater than 2. The recommendation in RB209 would be for a zero application of potassium. A dressing of 30M3 of slurry will apply 87 kg of potassium.
Sulphur on the other hand may be short especially on sandy and shallow soils where a recommendation is for 40Kg/cut. An 30M3 application slurry will only provide 21 kg of sulphur leaving the crop short of half its sulphur needs.
With rising fertiliser prices and dairy margins under constant pressure making best use of slurries and manures is critically important.
For help with your fertiliser planning, consult your nearest FACT qualified FCG consultant or contact William Waterfield w.waterfield@fcgagric.com in the Andover Office.