At the time of writing, there was rain in many parts of the country last week, yet soil moisture deficits have not improved for most parts of the country, writes Martina Harrington, Teagasc.
Little has changed for much of the country since last Wednesday, with the exception of the south-west. It could be said, things have got worse as last Wednesday there was the hope of a few days rain on the horizon.
While it did come, it only held the deficits in most places at between 44 and 55mm, which from last week’s note we know will significantly reduce growth rates.
The lucky south-west has fared better, with more rain they have seen a fall in the soil moisture deficit to <20mm, this will allow an increase in their growth rates for the coming weeks.
While there is still growth and fields are green, fertiliser should be applied as soon as possible, at a rate of 20 units of nitrogen per acre.
If permitted under your allowances, Phosphorous and Potassium should be applied to help push on growth to have a bank of grass available if we do not see rain for a couple of weeks.
Within your farm, you may also need to take into consideration if you have heavier land or reseeds that could be pushed harder than very dry or older swards etc.
So, what about second cut silage?
We have seen many crops of first cut silage being taken over the last week and will see further cuts this week.
The reports are of mixed yields and many farmers will want to try and make up for any lighter cuts by getting fertiliser out quickly onto second cuts, this is where beef farmers can learn from the summer of 2018.
Apply 27 units of nitrogen to the second cut; if possible, apply this fertiliser in the form of a compound e.g. one and a half bags to two bags of 15-3-20 as the P & K will really help to boost growth.
This will supply enough fertiliser to get the crop growing and give you options.
If rain does come, the bag and a half to two bags of 15-3-20 can be topped up to the recommended fertiliser rates as shown in the table below.
However, if we do not get rain, the second cut silage can be grazed without wasting fertiliser.
In most cases in 2018, the full complement of fertiliser was applied for second cut silage and many farmers didn’t get a return.
Slurry
The preferred choice is to get slurry which is high in potassium onto these silage fields to replace the large quantities removed in the silage crop.
However, applying slurry currently under the very dry weather conditions increases the risk of N loss through volatilization. It also presents a possible risk of burning of re-emerging grass especially if the slurry is very high in Dry matter.
It is possibly best to hold slurry applications until rain is definitely forecast to increase N recovery and reduce losses.
Fertiliser rates for second cut.
Second cut grass silage should be fertilised based on crop yield potential. The table below shows the fertiliser requirements based on a grass dry matter yield of 2 to 4t DM /ha (4 to 8t fresh grass/ac).
Suggested fertiliser programmes are shown with and without cattle slurry at various rates depending on grass yield;( units per acre are in brackets). Don’t forget the sulphur – for 2nd cut grass silage crops, apply 10 to 15kg S/ha per cut.
|
Second cut silage N, P & K Requirement based on grass yield & fertiliser programme |
||||||
|
Grass yield (Tonne DM/ha) |
N kg/ha (units/ac) |
P kg/ha (units/ac) |
K kg/ha (units/ac) |
S kg/ha (units/ac) |
Fertiliser options |
|
|
No slurry |
Cattle slurry gal/ac |
|||||
|
4t/ac fresh grass |
50 (40) |
8 (6) |
50 (40) |
8 (6) |
2 bags/ac 15-3-20+ S, 0.2 bag/ac ProUrea 46 |
1,500gal/ac, 0.8 bags/ac ProUrea + S |
|
6t/ac fresh grass |
75 (60) |
12 (10) |
75 (60) |
12 (10) |
3 bags/ac 15-3-20+ S, 0.3 bag/ac ProUrea 46 |
2,000gal/ac, 1.2 bags/ac ProUrea + S |
|
8t/ac fresh grass |
100 (80) |
16 (13) |
100 (80) |
15 (12) |
4 bags/ac 15-3-20+ S, 0.45 bag/ac ProUrea 46 |
2,500gal/ac, 1.6 bags/ac ProUrea + S |
