Dairy Notes February 2010
This is the first year that all producers have had to observe the closed period for slurry application with no slurry spread from the 16 October to the 1 February. To reduce your fertiliser bill and maximise grass production, take time before spreading to plan how to make best use of the nutrients in slurry:
- Use soil analysis results to check what nutrients need to be applied.
- Take account of the nutrients available from slurry applied during February/March.
Soil analysis
Analysis results provide valuable information on what nutrients are available. Even if you have not applied compound fertiliser since the introduction of the Nitrates Action Programme in 2007, there should still be substantial reserves of phosphate (P) and potash (K) in your soils.
If you do not have a recent set of results, samples should be taken now before any slurry or fertiliser is applied. Information on how to take samples can be obtained from your local Agricultural Development Centre. As this is the fourth year of the Nitrates Action Programme, producers in a Derogation need to have analysis for the whole farm completed this year.
What fertiliser do you need to apply for first cut silage?
The analysis report will provide information on the available amounts of P and K in the soil – normally expressed as an index. You can use the Farm Nutrient Calculator on the Online Services section of the RURALni web site to calculate the fertiliser requirement for each field. You enter details of soil analysis results, proposed use of the field and slurry application rate, and the programme calculates the amount/type of fertiliser to be applied.
Efficient use of slurry
For slurry applied by splash-plate the efficiency of nitrogen (N) use increases from five percent in autumn to 20 percent in spring. Allow for the significant contribution to N supply from February/March slurry applications when working out how much bagged N to apply.
A splash-plate application of 45,000 litres per hectare of cow slurry in February/early March will provide the same N for grass growth as 2.5 small bags (50 kg bags) of 27 percent N. Using a trailing shoe or shallow injection system instead of splash-plate to apply the slurry will almost double the efficiency of N use, allowing a saving of another two bags of fertiliser per hectare.
Allow for this improved N availability when deciding how much fertiliser to apply for first cut. With the exception of fields reseeded last year, there is unlikely to be a yield response to applying a total of more than 120 kg N per hectare for first cut. The Farm Nutrient Calculator takes account of the time and method of slurry application when calculating how much fertiliser N to apply.
Sulphur deficiency
The use of Sulphur containing fertilisers for first cut silage is now recommended. Work by Agri Food Bioscience Institute (AFBI) researchers has identified Sulphur deficiency in over 50 percent of grass samples taken from fields just before first cut.
Maintaining good milk composition
Many herds suffer a decline in milk composition at this time of year which is likely to persist until turn-out. Consider the following action to prevent a sustained drop in quality:
- Resample forages being fed to see if changes in forage quality have occurred over the winter as you approach the back of the pit, for example, a higher proportion of the first ensiled grass is now being fed and this may not have been as well wilted.
- If new forage (for example, second cut) is being introduced into the ration, revise your winter feeding plan, to ensure the cow’s energy and protein needs are being met.
- Discuss the implications of any changes to your winter feeding plan with your nutritionist to ensure the concentrate being fed has the appropriate levels of digestible fibre and starch to maintain butter-fat and protein levels.
- Continue to monitor feed intake to ensure target intakes are being met.
