Research snippets: silage conditioners for legumes, chicory establishment and fertiliser formulation

Published 11 September 15

Earlier this week, researchers from across the UK and Ireland met to present and discuss the latest grass and forage related research at the biennial British Grassland Society Conference at Aberystwyth University. Dr Debbie McConnell, AHDB Dairy R&D manager, shares some of the key highlights from the research conference.

Minimising forage legumes at harvesting

Forage legumes have fragile leaves that are prone to shattering during conditioning. In crops such as lucerne, as much as 70% of the plant protein resides in the leaf, making it important to try and minimise any leaf shatter at harvesting. However, to improve silage fermentation, forage legumes require higher dry matter contents (>30%). Researchers at Aberystwyth University investigated how different mower conditioners can be used to minimise crop losses at harvesting while maintaining high wilting rates. In the experiment, individual stands of perennial ryegrass, white clover, red clover and lucerne were harvested using:

  1. Mower + no conditioner
  2. Mower + steel tine conditioner
  3. Mower + rubber roller conditioner

All crops were harvested using a round baler and the total amount of crop DM and protein loss measured.  

Forage type 1

Forage type 2

In the study, crop loss was significantly higher from the legumes than perennial ryegrass (Figure 1), which resulted in a higher proportion of N being lost from the legumes (5.83% of total N offtake) than from perennial ryegrass (2.47% of total N offtake).

Although steel-tined mower conditioners achieved higher crop dry matter content (37.8%) than rubber roller conditioner (35.5%) or mowing without a conditioner (32.7%), crop losses were also higher (Figure 2). Consequently, using rubber roller conditioners when harvesting legumes can reduce forage losses, while achieving an acceptable dry matter content.

Establishing chicory-ryegrass swards

Chicory is a deep rooted, perennial herb with good growth through the summer months and relatively high nutritive characteristics. Though currently not extensively used for dairy cows in the UK, in NZ its deep tap root and drought tolerance characteristics provide farmers on light soils with an alternative forage options. Chicory can be established as a pure stand or in a mixture with perennial ryegrass and other herbs. Researchers at Aberystwyth have been investigating the best method and time of year to establish chicory-perennial ryegrass swards. They compared:

  1. Ploughing vs. direct drill (with and without herbicide)
  2. Sowing after first or second cut silage

Plots were sown following an existing perennial ryegrass ley at a rate of 2.5kg chicory and 30kg perennial ryegrass per hectare. Plots received 270kg N/ha.

In the study, the most successful method to establish a chicory-PRG sward was by ploughing after first cut silage (Figure 3). Direct drilling of chicory-ryegrass swards can be successful, however, herbicide needs to be used to reduce competition from the existing sward.



Fertiliser formulation affects nitrogen (N) recovery on poor-draining soils

Spreading N-based fertilisers on grassland can increase greenhouse gas emissions (GHG) such as nitrous oxide (NO2) and ammonia (NH3-N) resulting in lower amounts of N available for uptake by the plant. The project, which is a joint collaboration between Teagascin Southern Ireland and the Agrifood and the Bioscience Institute in Northern Ireland, is investigating how N fertiliser formulations can affect GHG emissions and grass yield. Across three sites of differing soil types, researchers examined GHG emissions and grass yield response to calcium ammonium nitrate (CAN), urea and urea treated with urease or nitrification inhibitors.

In wet conditions, switching from CAN to urea resulted in a dramatic reduction in NO2 emissions but this increased NH3-N loss, with 25% of nitrogen applied being lost as NH3-N. This rise in NH3-N, however, was mitigated by the use of a urease inhibitor. Across the three sites and multiple years there was limited effects of fertiliser formulation on grass yield, however, on poorly-draining soil in wet conditions, the use of urea with an inhibitor resulted in a greater proportion of N being recovered by the sward (Figure 4).



Fychan et al. (2015) British Grassland Society 12th Research Conference Proceedings p. 89 - 90

Marley et al. (2015) British Grassland Society 12th Research Conference Proceedings p. 23 – 24

Harty et al. (2015) British Grassland Society 12th Research Conference Proceedings p. 53 - 54