Grass advice: Can't afford to take your foot off the pedal

Despite the exceptionally dry weather and the soil moisture deficits (SMDs) in some parts of the country, we must remember not to take our foot of the pedal on applying fertiliser.

Ground conditions are excellent and now is an ideal time for spreading because you are getting the maximum benefit out of your fertiliser.

Fertiliser advice mid-season

By now, you should have ceased the use of urea and switched to CAN, protected urea or a compound fertiliser.

A good rule of thumb to go by when calculating nitrogen (N) requirements in mid-season is that grass uses a unit of N/day during mid-season growth. So, if your rotation is 21 days, apply 21 units/ac or 26kg/ha post-grazing.

Soils low in phosphorus (P) or potassium (K) will need a compound fertiliser, such as 18-6-12 or 27-25-5 in every second round.

However, for build up, P is best applied in the spring and K is best applied in the autumn.

Sulphur (S) should be included in alternative rounds and balance N with S at a ratio of 12:1.

After first-cut silage

Applying fertiliser after first-cut silage is critical if you want to achieve high-quality yields for your second cut and to avoid a drop in soil indexes.

For every 1,000kg/ha of grass DM that is taken off for silage – rather than grazed – will add approximately 2.5kg/ha of P and 25kg/ha of K to the overall P and K requirements for maintenance to a paddock across the year.

Slurry is a very valuable resource for replacing nutrients where paddocks are cut for silage.

According to Grassland Agro’s Dr. Stan Lawlor, if you were to spread 700gals/ac of thick slurry or 1,500 gals/ac or watery slurry; this would replace the P and K off-takes for 1,000kg/ha of grass DM.

Ideally, slurry should be spread straight away after cutting before the grass begins to build up on the paddock again.