Grassland management for Spring 2024

The weather finally looks like improving and we will be heading to grass with cattle soon. Hopefully we can finally call an end to the winter, writes Martina Harrington.

We therefore have to put a plan in place and while we can have rules of thumb, every farmer will have to make their own plan.

So what are the decisions?

Area to be grazed?

Put a start day of the 6^st of March on grazing, say you want to have the whole farm grazed by the 21^st of April, that is 46 days of grazing. For simplicity, say you are going to graze it in equal amounts and have 60 acres (24.2ha) that’s 1.3 acres or 0.5ha per day or 9acres / 3.7ha per week.

Simply put, you have to let out enough stock to graze this area.

How much stock to let out?

This is a key question and we often have a fear around this

If you want to go to the next level, you can say you have 900 Kg DM per ha, so you have to eat (900 kg DM x 0.5ha) 450 Kg DM per day. Most animals will eat 2% of their body weight, e.g.

• Suckler cow will eat 15 Kg DM,
• 2yr old steer (550 Kg)  will eat 11 Kg DM,
• Yearling (400 Kg) will eat 8 Kg DM
• Lighter yearling steer (350 Kg) will eat 7 Kg DM

So to graze 450 Kg /15 Kg = Let out 30 suckler cows or 41 two year olds or 56 – 64 yearlings. This is not an exact science, let out some cattle and then gauge it week by week thereafter.

Again more decisions come into play now,

• What cattle do you let out first?
• Have you enough animals to cover the area in the dates set?
• If not, do you close low cover fields (with no butt) as silage now, not graze, apply full rate fertiliser and cut early May or do you close fields with heavy covers, add a little fertiliser and cut late April early May.

Monitor your plan

If you are not grazing the 9 acres or 3.7 ha per week, let out more stock, or graze lighter covers.

If you are grazing more than 9 acres or 3.7 ha per week – graze the heaviest covers, if this doesn’t slow you down re-house some cattle or supplement with hay/silage (this is a last resort)

Where to graze?

Your decision may change based on the year, your stocking rate or the silage quality you require.

Start on some low covers to allow the cattle to settle back into grazing, you don’t want them to walk heavier covers into the ground and this will only take a few days.

Then move into heavier covers, on your driest ground.

Grazing area v’s silage ground

The table below shows our typical year; graze 30% of your grazing ground, then go into your silage ground and then back into your grazing ground. The reason for this is to have grass back on the first field grazed, so you can go back in and graze on the 21^st of April. As you can see below what is grazed on the 6-13^th of March has 39 days to grow before cattle are back in grazing and to have adequate covers, you will need to have a growth rate of 36Kg DM/ha/day to achieve this.

In the example below you start closing silage on the 21^st of March and have it all closed by the 10^th of April. The planned cutting date should be the 15 -25^th of May to achieve good quality - the earlier in May you cut, the better quality you will get. The DMD of silage reduces by 3% per week in delayed cutting.

If you have lower demand in spring and a requirement for all top quality silage, you should consider trying to increase the area of silage ground grazed first, perhaps by letting out two groups, one on grazing and one on silage ground.

To have enough bulk in mid-May, you need to get slurry out as you graze and follow closely with your top up of Nitrogen, recommendations are further on in this article.

Remember, you do not have to cut all your silage at once when you have baled silage, you can go in on the 15^th of May, cut the silage for your growing stock at 76% DMD, then leave the rest to “bulk” up and cut two/three weeks later at 65 -70% DMD.

The earlier silage is cut, means that it allows for a better second cut, and can help mitigate against drought conditions later in the year.

Fertiliser

We are now in March and have estimated that 1200 Kg of grass DM will be grown between now and the 15^th of April. To grow this much grass you need 36 Kg of N/ha or 29 units per acre. A little over a half bag per acre of protected urea will supply this; it’s cheaper than CAN per unit of nitrogen, you can cover ground faster with a full spreader and it is better for the environment.

Remember you also need to have all conditions right to minimise loss of expensive fertiliser

• Soil temp > 6^oC
• Ground needs to be trafficable
• The forecast needs to be dry

This first application should be followed by a further 27 units of Nitrogen 3-4 weeks later as a compound like 1.5 bags of 18-6-12 per acre, depending on your demand. Always check your soil samples and nutrient management plan for allowances.

Fertiliser For Silage

The recommendation for first cut silage on older permanent is 80 units of Nitrogen, 16 units of Phosphorous and 100 units of Potassium plus Sulphur at 15 units per acre. On newer more productive ryegrass swards, you could increase the Nitrogen by 20 units per acre, just remember your cutting date. Silage takes up 2 units of nitrogen per day, so at 80 units you need 40 days between application and cutting.

The P and K requirement can be made up from 3,000 gallons of slurry per acre and then topped up with 1.9 bags protected urea (38% N + 7%Sulphur) per acre. 

If not applying slurry look at 3.5 bags of 13-6-20 per acre and 1.6 bags protected Urea (38% N +7% sulphur) per acre.

Sulphur is closely associated with nitrogen uptake and efficiency. As the rate of nitrogen fertiliser applied increases, the response to sulphur fertiliser also increases, therefore we must pay particular attention to sulphur requirements on heavily stocked farms and when fertilising silage crops.

Potassium (K) is as important as nitrogen in producing silage, it is the K that produces the bulk, therefore you need to have soil tests for silage ground and if you need to build potassium, do so after your first cut silage. Muriate of potash is 50% K, or 50 units of K per bag. If you are index one or two for K on silage ground, apply a bag per acre and watch your yields grow.

Take Home messages

Walk your farm - spring grass is worth over €2.LU/ day i.e. 20 cattle = €40 saving per day

Get cattle to grass as soon as possible

Train them in on low covers and move to high covers

Graze some grazing ground first, move into silage ground and then back to grazing ground – area depends on your farm

Do a plan & monitor the plan

Prepare to be flexible /do not graze tight if ground conditions are soft/move cattle on

Apply 25 -30 units of Nitrogen per acre as protected urea

Start closing silage ground by St. Patrick’s Day by applying 2500-3000 gals of slurry/acre

Follow with 80 units of N + Sulphur per acre on the silage ground by 1^st April

Apply correct fertiliser amounts

You don’t have to cut all your silage the same day – get top quality silage for your growing animals