GrowthWatch: Deciding on a grassland management plan for the current dry spell
By Teagasc’s Seán Cummins and James Fitzgerald
Levels of grass growth are varying greatly throughout the country based on the land type and levels of rainfall received, as well as the more usual factors such as: soil fertility; grassland management; and fertiliser use.
Before you can be sure of what course of action to take with regard to grassland management over the next few weeks, you must first be able to answer the following questions:
- What level of grass do I have on the farm right now?
- What rate is grass currently growing at on my farm?
- How much grass does it take each day to keep my stock fed?
By answering these questions you will be able to put yourself into one of the following categories and take the following steps to ensure you manage your grazing and grassland situation correctly.
High level of grass (700-1,000kg DM/ha) and growth less than demand
Keep your rotation length at circa 18-20 days and graze fields down to 4cm. There is no need to supplement with meal or silage currently, as grass availability is high.
Walk the farm regularly to keep up to speed with growth rates. Do not cut and bale surplus grass. Do not let the level of grass get depleted below an average farm cover of 500kg DM/ha (6cm).
High level of grass and growth greater than demand
Continue with a rotation length of 18-20 days, while also grazing down to 4cm. Cut and bale surplus grass when the opportunity arises.
Then, replace the nutrients removed in the surplus bales by spreading a light coat of slurry or one bag of a compound fertiliser such as 0-7-30.
Low level of grass (300-500kg DM/ha) and grass growth less than demand
Extend the rotation length to 25 days if not done so already. Again, graze grassland down to 4cm (do not waste grass).
Feed additional meal to finishing animals or silage/hay to other stock to fill the gap between what the grass can provide and what the herd’s appetite needs.
Alternatively, add some of the silage ground into the grazing rotation to increase grass availability. Continue to spread fertiliser to maximise grass growth. Do not spread straight urea and avoid topping paddocks.
Low level of grass and growth greater than demand
Continue with a rotation length of 18-20 days aiming for a residual of 4cm on grazing grassland. Additionally, do not cut bales from grazing ground until the average farm cover (AFC) is comfortably over 500kg DM/ha.
An AFC of 700-1,000kg DM/ha means that the average height of the grass across the farm is 7-8cm. There is 250kg of dry matter in each centimeter of grass above 4cm.
The bottom 4cm of grass are not counted as we aim to leave this amount of grass behind us after grazing, so that the grass plant is not overgrazed.
Similarly, an AFC of 300-500kg DM/ha equates to an average grass height across the farm of 5-6cm.
Due to the prolonged dry weather the grass growth rates haven’t reached the heights I would have expected for this time of the year.
Having said that, I am still relatively happy with how grass growth is going here when I hear about more extreme situations in other parts of the country.
I haven’t had to deviate from my normal grazing plan so far, as the farm’s growth rate (50kg DM/ha) still outstrips the demand for grass of 29kg DM/ha/day. Also the average farm cover is relatively stable at 846kg DM/ha which is no real change from the last time of writing six weeks ago.
I don’t have designated silage ground, but I did cut 15 paddocks of surplus grass over the course of the last month. This ground received slurry after cutting and the aftergrass regrowths seem to be doing well.
I am currently spreading one bag/ac of 18-6-12 after grazing, but when this rotation is over I will hold off on spreading again until August. I should have enough spread to carry me through until then.
I can see that the tops of hills and areas with lighter soil are beginning to burn a little, so I’m sure that if this dry spell continues growth will be reduced further, but for the moment the grass is doing enough to meet the appetite of the stock without running down the amount of grass on the farm.
I’m going to keep walking the farm weekly so that I stay up to date with the situation.
- Growth: 34kg DM/ha;
- Demand: 46kg DM/ha;
- Average farm cover: 1,166kg DM/ha;
- Stocking rate: 3.89LU/ha.
The Nire Valley hasn’t been as badly affected as other parts of the country in terms of the dry weather and it’s beginning to come into its own.
A grass growth rate of 34kg DM/ha was recorded over the last week. This is a little low for the time of year; but I’ve 23 days grass ahead and topped some of the heavier paddocks after grazing last week that were ‘woody’ at the base.
Grazed ground is being followed with 25kg/ac of Sul-CAN. The calves are currently out and weaned and are being offered 1kg/day of concentrates.
All of the second-cut silage ground has been closed and an early July cutting date is targeted. This ground received a mixture of slurry and straight nitrogen (N), or where slurry wasn’t available, compounds like 18-6-12 were applied.