Dairylink: Measure Grass to Manage

21st January 2016

Conail Keown reports on the variation in grass growth between and within some of the Dairylink farms and outlines methods to bridge the gap.

One of the key targets of the Dairylink Ireland project is to increase grass grown and utilised on the participating farms.

Every project farm situation is unique in terms of soil type, topography, rainfall, stocking rates and the management capabilities of the farmer. The impact these factors have on grass growth and the quantity of grass utilised can be seen in the grass growth information for each farm for 2015.

On average, only 7.5t of grass is utilised per hectare on Irish farms, but data from the best commercial and research dairy farms indicates that this can be increased significantly, and with grass clearly the cheapest feed available, increasing growth and utilisation will result in improved profitability.

Measure to manage

Research and analysis from Teagasc profit monitor and Pasturebase Ireland has illustrated that by increasing grass utilisation by 1t/ha, net profit can be increased by 190/ha (250/ha).

A key driver for increasing grass growth capacity on project farms is the weekly measurement of grass covers, and then inputting the information into grass measurement software and making decisions based on that information.

Reviewing two project farms (Charles Clarke and Robin Clements), grass growth for 2015 highlights a wide variation in growth, not only between farms but also within farms, with large variations between fields.

A full year of grass measurement provides each farmer with a clear picture of growth across all paddocks on each individual farm, which is essential.

Focus on two project farms

Charles Clarke, Bailieborough, Co Cavan

The grazing platform average growth for 2015 was 11.8t DM/ha and the variation in growth across the 38ha was 5.5t DM/ha, which is calculated by comparing the lowest-yielding paddock (9.4t DM/ha) with the best-performing paddock (14.9t DM/ha).

This information is illustrated in Figure 1. The horizontal black line illustrates average growth on the platform for 2015. The variation between paddocks is clear to see.

Robin Clements, Trillick, Co Tyrone

Robin had a much lower average growth on the farm than Charles. Grass growth throughout 2015 in this part of Ireland was approximately 20% lower than previous years as a result of wet and cold weather in summer.

Average growth on the Clements grazing platform was 9.02t DM/ha, with a big variation on farm of 8.4t DM/ha. The highest-yielding field produced 13.2t DM/ha, with the poorest paddock only managing 4.8t DM/ha.

While the variation between farms and the difference within each of these farms is significant, the challenge is to use this information to improve growth on each farm.

Two primary areas focused on are soil nutrients and reseeding paddocks. Other issues such as compaction and drainage will have an influence on growth, but using soil analysis to assess pH, P and K status of underperforming paddocks is a good starting point.

Soil fertility management essential on all farms

Soil fertility is critically important for grass growth. Approximately 90% of the soils sampled in Ireland are limited in one of the three major factors that affect soil fertility (pH, P and K). From soil samples taken as part of the Dairylink project, 55% of soils on project farms were found to be deficient in either pH, P or K. The ideal pH for grass growth is 6.3, as this maximises the availability of nitrogen, phosphorus and potassium.

Applying lime to increase soil pH will increase nutrient uptake and therefore DM yield, and it will also improve the long-term persistency of perennial ryegrass in the sward.

Recent research from Moorepark illustrates that lime applied at a rate of 5t/ha to soil with pH 5.3 increased grass production by 1.5t DM/ha in the following two years.

Research has also highlighted soils with P and K index 3 (index 2 based on NI soil analysis) will grow approximately 1.5t DM/ha per year more grass than soils with index 1.

Upgrading soils with poor fertility status is essential in order to allow farmers to fully capitalise on the cheapest feed available to them.

New reseeds

Newly reseeded areas on some Dairylink farms have been well established this year due to ideal growing conditions.

The key reason for reseeding was lack of productive perennial ryegrass in the old swards, which was illustrated in the grass measurement information.

Using the Agrinet tool, Charles and Robin were able to clearly identify paddocks that were underperforming especially at the start of the growing season when growth in these areas was slow to start.

Research clearly illustrates that swards with low proportions of perennial ryegrass are costing farmers up to 250/ha per year due to the loss of grass DM production and reduced nitrogen utilising efficiency.

If the cost of reseeding is estimated at 600/ha, the increased profitability of the reseed would cover the reseeding cost in just over two years. It is for this reason that reseeding is one of the most cost-effective investments farmers can make.

This article has been reproduced with the kind permission of the Irish Farmers Journal. Please click on the below Irish Farmers Journal logo to be brought to additional dairy articles

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