Spring Grazing Management

Early spring grass is extremely digestible and high in crude protein. To capitalise on the benefits of grazed grass, animals should be turned out to pasture directly early-mid February ground conditions permitting. The main objectives of spring grazing management are to increase the proportion of grazed grass in the diet and to condition swards for subsequent grazing rotations.

When To Apply Early Nitrogen

Lack of nitrogen (N) supply in the soil can limit spring grass growth. The timing and rate of fertiliser N and slurry application are key decisions for every livestock farmer. Research has shown a large range in grass response to early N (between 5 to 18 kg DM/kg N applied). While the appropriate application of early N is beneficial, the incorrect application of early N is wasteful, costly, pollutes water and increases greenhouse gas emissions.

• Always check the weather forecast (www.met.ie) prior to making slurry or fertiliser N applications – do not spread slurry or fertiliser if rain or very cold weather is forecast.
• Only apply fertiliser N when soil temperature is greater than 5°C and rising.
• Check the soil trafficability before spreading to avoid damage to soil.
• Measure farm cover and use the grass growth predictions (Grass10 Newsletter, PastureBase Ireland, Farming Forecast on Sunday on RTÉ 1) to inform decision making around slurry and N fertiliser application.
• Target the areas of the farm most likely to respond to early application of N, these include fields with a high perennial ryegrass content or those recently reseeded, drier areas of the farm, fields with a grass cover of greater than 400 kg DM/ha or 6 cm grass, and fields with optimum soil fertility, i.e. good P and K status, pH > 6.2.

Apply slurry to approx. 40% of the farm as soon as permitted (depending on slurry opening date), targeting high demand areas where possible, e.g. silage ground and low P and K grazing ground.

In February, slurry can be applied to grazed areas (up to 30% of the farm). Apply all slurry using LESS (low emissions slurry spreading) methods. 2,000 gals/ac applied using LESS will supply ~20 kg/ha (16 units/ac) of available N and 2,500 gals/ac will supply ~25 kg/ha (20 units/ac) of available N. Manage slurry application to ensure that no more than 2,500 gal/ac are applied in each application.

In February, fertiliser N should be applied to the areas of the farm that received no slurry in January. Don’t apply more than 29 kg N/ha (23 units N/ac) chemical N fertiliser in February. The whole farm should receive fertiliser N in March (29-50 kg N/ha; 23-40 units N/ac). No more than 75 kg N/ha (Slurry N + Chemical N) in total up to early April (Table 1).

Table 1. Nitrogen fertiliser and slurry application plan for the early spring period on well-drained soil

¹Application of N for February/March grazing
²Assumes slurry at 6% DM, adjust application rates based on slurry DM%
³Some of this area will be silage ground
⁴Combination of Protected Urea and cattle slurry

Table 2. Nitrogen fertiliser and slurry application plan for the early spring period on heavy soil, less intensive and/or later turnout farms (flexibility in application is essential on heavy land)

¹Assumes slurry at 6% DM, adjust application rates based on slurry DM%
²Some of this area will be silage ground
³Combination of Protected Urea and cattle slurry

Table 3. Closed Periods for the application of organic & chemical fertilisers

Difficult Spring Grazing Conditions

Three daily objectives for grazing in wet weather are:

1. Feed the cow
2. Minimise damage
3. Residuals (if possible)

The only way a farmer knows if a paddock is fit for grazing is to walk it. If there are 30 paddocks on the farm and 29 are waterlogged, we should expect cows to be grazing the 1 paddock that’s fit for grazing.That’s the lengths we need to go to the achieve days at grass this spring.

• Farmers should stay focused & alert to weather. Take opportunities when they present themselves.
• Make an effort to get cows out with an appetite. Take cows off the paddock if they are finished grazing or if they are poaching
• Hold cows in the shed/yard after milking time with no access to silage. Cows need to be miked at 3pm for a farmer to have any chance of achieving a 2nd grazing bout following evening milking.
• If grazing, the paddock should be very dry, have multiple access points, low cover (allocate larger area than heavy cover), ideally the paddock to be reseeded this year/ underperforming paddock
• If feeding silage by night, make sure that it has ran out by the following morning if planning to put cows out grazing the next day. Silage is a bulky feed and will inhibit grass intake
• If you walk the farm and there are no paddocks available for grazing (waterlogged/snow etc.), unfortunately cows will have to be housed.
• Make sure to get cows out grazing at the 1st opportunity again!