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Fertiliser options after first cut silageMany farmers have closed off paddocks for first cut silage, as it will take 6 to 8 weeks for the grass to reach its optimum maturity. The target harvest date is usually May and will be very dependent on the closing date and the amount of fertiliser applied. If your Phosphorus (P), Potassium (K) and lime were corrected, you will have applied up to 100 units/acre of Nitrogen (N) on a typical ryegrass sward. Under normal, good growing conditions, it takes 50 days for the crop to take up N and transfer it into protein in the crop.

Before harvesting, it is good practice to test a grass sample to ensure good fermentation is optimised. It is recommended to test for water-soluble carbohydrate (WSC) and nitrate N levels. The WSC value should be in the region of 3% for lactic acid bacteria to rapidly multiply and drop the pH ensuring unwanted microorganisms multiplying. Ideally, the nitrate N level should be below 0.1%.  A sugar reading of over 3% will allow the crop to ferment quickly, reducing pH and quick crop preservation.  Midday mowing on a dry day is advantageous, to ensure higher grass sugars.


As your silage crop will be your main feed source for the winter months ahead, great care should be given to the area closed, closing date, fertiliser treatment, harvesting and ensiling programme. The quantity and quality of silage needed for your livestock should be calculated and it’s advisable to factor in a buffer of 20% to cater for unforeseen circumstances. Plan ahead, book a contractor in good time and aim to wilt for a maximum of 24 hours if possible, to approx. 30% DM and this will reduce losses through effluent.  Harvest your crop before the heading date to ensure reaching a high DMD of 72% to 75%. Silage of this quality will save on expensive meal supplementation over the winter. Once grass goes to seed, it will drop 1% DMD every two days, thus reducing the quality of your silage. Pack the pit firmly to eliminate air pockets, seal with two sheets of plastic, cover with tyres placed close together and sandbags at the edges.


This must be the top priority. The movement of silage machinery will start in early May and extend up to October. All machinery operators must drive with care and have respect for other road users. Children should not be in the vicinity of machinery at any time. Make sure silage pit walls are not defective, do not overfill the pit and insert safety rails to indicate the location of sidewalls.

Preparation for Second Cut Silage

It’s important to note that large quantities of P and K are removed in your first cut and the amount will depend on the yield of the harvested crop. Plan now for your second cut and calculate possible offtakes which will be the requirement for the second cut. Note a typical second crop of grass silage yielding 3 tonnes DM/ha will require the following:

Soil Index N Kg/ha (units/ac) P kg/ha  (units/ac) * K kg/ha  (units/ac)
1 100 (80) 30 (24)  * 75 (60)
2 100 (80) 20 (16)  * 75 (60)
3 100 (80) 10 (8) 75 (60)
4 100 (80) 0 0

*If build up rates of P were applied for the first cut,  then revert to Index 3 rates for the second cut. Source: Teagasc

Check your most recent soil analysis results to establish your soil index rate. Consult your adviser to interpret the results and make the necessary recommendations.

It is good practice to recycle slurry onto silage ground for two reasons, firstly because silage removes large quantities of P and K and secondly its ratio of P:K of 1:6 is ideal to replace removal rates. Use slurry analysis to determine its value. Take a representative sample following agitation and send it to an accredited laboratory to determine the DM percentage and P and K content.

The typical value of cattle slurry of 7% DM spread at 1000 gallons/ac is 5N 5P 30K. This N will only be 3 units at best if spread in dry conditions on bare ground. However, by using Low Emission Slurry Spreading (LESS) rather than a splash plate you can increase the N by a further 3 units.

From Teagasc research over many years, sulphur is identified as being deficient in up to 30% of grassland soils. It is recommended to apply S at 20 kg/ha for each cut. For this reason, many of the Target Fertilisers range carry sulphur as standard.

Target Fertilisers products most frequently used :

  • 24-2.2-4.5 + S
  • 27-2.5-5 + S
  • 24-2.5-10 + S
  • 21-2.2-10 + S
  • SuperCAN
  • UreaMAX + S

Baled Silage

Where there is surplus grass during the season, baled silage is often harvested. On high stocked farms this should be harvested without delay so the paddock can be brought back into rotation as soon as possible. To replace nutrients taken from the soil, a good rule of thumb is for every four bales removed, 1000 gallons of good quality slurry or one bag of Target 0-7-30 should be applied.


To view Target Fertilisers’ full range of grassland fertilisers, click here

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