Friday 20 April 2018

Graze fields before closing for silage

Kevin O'Sullivan

To achieve high quality silage the optimum time for harvesting is around the early June period.

Most farms will close silage fields off in April for cutting towards the end of May or early June.

It is important that silage fields are grazed prior to this in order to remove dead material off these fields in order to make good quality highly digestible silage.

It will also result in higher yields of silage if they are grazed before closing. This may be a problem this spring on cattle farms where poor growth and ground conditions have pushed back the date of cattle going to grass.

However this is not always practical and where silage ground is not grazed in the spring good quality silage can be obtained by cutting earlier.

It is important that as ground conditions improve that higher stocking rates are applied on these fields over a short period in order to graze them out in preparation for silage conservation.

Fertiliser application rates depend on a number of factors. Nitrogen demand will depend on sward quality with newer reseeds with high levels of perennial ryegrass having higher demands of 125kh/ha (100 units/acre or 4 bags CAN/acre).

These reseeds will produce higher yields to correspond with this. For older pastures the nitrogen application can be reduced by 25%.

Nitrogen should be applied at least 50 days prior to the intended time of cutting to ensure full utilisation. Phosphorous and potassium (P & K) are essential for maximum yields but their requirement can only be accurately assessed by soil analysis. Cattle slurry that is not to diluted can supply sufficient P & K levels if the soil has already adequate Index 3 P and K levels.

Slurry should only be applied on bare pastures as it can cause contamination if applied to leafier swards resulting in poor silage quality.

It is probably a good idea to apply slurry after fertilizer in case the slurry cakes on the field surface and affects the absorption of the fertilizer to the soil.

If P and K levels are less than Index 3 -on soil analysis - P and K will have to be supplied by bag.

Where slurry is applied top-up fertiliser applications should be delayed by 1 week.

In wet conditions N fertiliser applications may be split 50:50 in two applications but allowing sufficient time for utilisation by the crop of the second N application.

Finally, it may be worthwhile to apply sulphur with the nitrogen on sandy or gravel soils where deficiencies may occur. This won't be necessary on more organic type soils.