We are heading towards the end of May and, thankfully, we are looking at fertilising second-cut silage relatively early as many first cuts have already been harvested due to the good weather.
Many farmers across the country have secured their first-cut silage about a week to 10 days earlier to what they are accustomed to.
This was due to brilliant growth rates in the last three weeks, followed by a dry, sunny period which played into the hands for many to secure their first cut.
It meant that many farmers got their silage harvested before or around the middle of May which means silage of a 75% dry matter digestibility (DMD) would have been harvested for many.
As the weather has broken, with showers over the weekend expected to continue into next week, a bit of moisture in the soil along with high soil temperatures may present a perfect opportunity to spread fertiliser for second-cut silage.
Fertilising second-cut silage
Teagasc research has shown that there is a high grass growth rate response to nitrogen (N) in second-cut silage and a balanced nutrient supply is vital, along with appropriate applications of phosphorus (P) and potassium (K) and sulphur (S).
A good second-cut silage crop is vital to build a good silage reserve for a potentially long winter ahead, which has to be budgeted for, and so the second-cut silage should be fertilised according to the crop yield potential.
The table below is a fertiliser requirement provided by Teagasc and is based on a grass dry matter (DM) yield of 2-4t DM/ha, which is the equivalent to 3-6.5 bales/ac.
The table below outlines guideline nutrient requirements for second-cut silage:
Grass yield (t DM/ha)
N kg/ha (units/ac)
P kg/ha (units/ac)
K kg/ha (units/ac)
No slurry
Cattle slurry gal/ac
2
(4t/ac fresh grass)50 (40)
8 (6)
50 (40)
2 bags/ac 15-3-20 + S
0.2 bags/ac of Pro. Urea1,500 gal/ac
0.8 bags/ac of Pro. Urea + S
3
(6t/ac fresh grass)75 (60)
12 (10)
75 (60)
3 bags/ac 15-3-20 +S
0.3 bags/ac of Pro. Urea2,000 gal/ac
1.2 bags/ac of Pro. Urea + S
4
(8t/ac fresh grass)100 (80)
16 (13)
100 (80)
4 bags/ac 15-3-20 + S
0.4 bags/ac of Pro. Urea2,500 gal/ac
1.6 bags/ac of Pro. Urea + S
The protected urea used in this scenario is 38% N + sulphur (S) and the value of this cattle slurry with a 6% DM, when using low emission slurry spreading (LESS), is six units of N, five units of P, and 32 units of K for every 1,000gal.
For second cut, it is important to include sulphur (S) in your application, as it is linked to N uptake and N use efficiency (NUE), as the response to S increases with the rate of N applied.
Not applying S can have a negative impact on your silage quality as low protein silage is the result of a lack of S in the grass.
Fertilising and slurry application should be done as soon as possible after first cut to try and have your second ready for mid to late July.
The amount of fertiliser you should spread on your silage ground should be discussed with your adviser as increased or reduced levels of P and K may have to be spread, depending on your soil indexes, land type, or allowances.
The table above should be used as a guideline only, as it will not suit every farm scenario.
