Grow Great Grass

Eamonn Patten, Drystock Advisor, Teagasc Ballinrobe.

Ireland is said to have a natural advantage to grow grass for our grazing animal production systems. This partly due to our location and climate. With all the focus now on climate change and environmental issues we want to retain these established benefits. Grass is the cheapest and most appropriate feed for cattle and sheep. However it is important that the farmer is enthusiastic about maximising the level of grass in the diet.

A good pasture has the potential to convert into about 250-400kg of animal live weight per acre/year or an equivalent of 25-30 round bales of silage for the year. A target for a grass based sheep farm is get 90-95% of annual energy requirements from grass. Not many farmers would be achieving this level of production from grass-the question is why not? 

The Variables

Taking an average year the main variables are:

Soil Type and Soil State

Fertiliser, Manures and Fertility

Grazing Infrastructure/Stocking rates

Sward Contents

Sward Quality/Palatability

There is a focus recently on soils and the levels of nutrients required/allowed for a certain stocking rate and rightly so. Phosphate (P) is important for root development and early growth, while Potash (K) has a key role in water regulation and nitrogen efficiency. If P, K and Liming are not correct, it is very wasteful applying chemical Nitrogen (N). Other factors to be monitored include levels of organic matter, earthworm activity, limited damage from compaction or poaching and having a good general soil health. Under the new nitrates restrictions there is now a requirement to prove a need to apply a certain amount of nutrients for a certain stocking rate e.g. for 2023 anyone with a stocking rate higher than 130kg/ha will require a soil sample to apply Phosphate from chemical fertiliser or off farm organic manures.(See Table 1)

Table 1 Annual maximum fertilisation rates of phosphorus on grassland

Nitrogen - Unfortunately there are different allowances for different schemes as in Table 2. 

Table 2 Nitrogen summary

Grass growth can be erratic and the challenge is to use it at its optimum growth stage, trying to graze the right animal at the right time on the right cover of grass. A good Grazing Infrastructure will lead to increased grass production and utilisation. It is easier to produce high quality leafy grass under a rotational regime and is a necessity with higher stocking rates. A minimum of 5 paddocks is required allowing animals 4/5 days a paddock resulting in a 20 day rotation.  Depending on circumstances paddocks can be temporary subdivided.

Sward content can vary from short term lays to permanent pasture with anything from 3 to 12 grass types plus clovers and weeds. In some farm situations the total yield of grass may not be as critical as when a grazing is available for use. The tolerance of swards to poaching and weather conditions can also be a consideration. A good permanent grassland sward, highly stocked should have at least 50-60% ryegrass and 20% white clover. Animal growth rates are higher with a clover mix in the sward plus the benefit of a lower chemical N requirement. A problem can be trying to retain the established levels of clovers in swards. Multi- species swards consisting of grasses, herbs, clovers and brassicas are now considered useful, especially in years of drought but again the question of persistency arises.

Reseeding can give a boost in sward performance especially for the first 5 years and it is a means of introducing more productive varieties and different species. Grass will go to seed and produce stem much faster if under stress or when nutrient levels are poor. This is more obvious in a reseed as it can be ‘hungrier’ for nutrients due to higher production capability. Stock need to consume what’s grown and occasionally when offered what looks like close to ideal grass covers animals can refuse  to graze it. If the soil nutrient levels are good, a different fertiliser strategy may help. The cultivars grown, slurry applications, cultivations and cropping history may come into play.   A nutrient that is often overlooked is Sulphur. It is an important nutrient for grassland, and is closely associated with N uptake and efficiency. Grass yield responses to Sulphur range from 1.0 to 3t/ha from heavy to light soil types. See map for potential areas of deficiency. 

In conclusion our old permanent pastures are often under rated due to poor management rather than the pasture itself. When farming at high stocking rates over a longer growth season and a requirement for more palatable pasture/fodder then a reseeding programme should be in place but the basics must be right.