As part of their assesment of this farm a group of students from Greenmount College of Agriculture and Horticulture carried out a sward analysis. I have used material from their project elsewhere on these pages but in the subjects of farm policy I have re-edited it to include a little personal background to the reasons for our management style and updated. Since this subject is a purely statistical one and we ourseleves had never before undertaken such an analysis (although the results can be attributed to various aspects of our policy) I have decided copy this chapter from the project "verbatim". This is entirely the students work I place no editorial claim on it at all.
Grass is on of Northern Ireland's most valuable resources. The botanical composition of a sward can have strong influence on its productivity especially under intensive management regimes. Preferred grasses, consisiting mainly of ryegrass and Timothy, are much more productive and have a higher nutritive value for livestock when compared to the less preferred grasses such as meadow grasses, bents fescue and Yorkshire fog. Swards dominant in ryegrass and Timothy do not naturally occur in Northern Ireland, and must be sown. Less-preferred grass species which occur naturally in our soils gradually invade reseeded grassland, especially when management is not of a high standard or soil fertility status is low, causing deterioration in the yield and nutritive value of the sward.
Initially the fields were grouped according to soil type, location and sward composition. In total fourteen groups were selected and assessment of ward composition at ten stops throughout each group of fields was made. It was necessary to get a representative sample of the whole area, yet the actual pin-point position of the area to be examined was determined randomly. This was done by throwing a quadrat measuring 0.25 square meters and making an assessment from that spot.
Once the position of the quadrat had been established, the sward composition within the quadrat area was assessed visually. The plant species present were identified and the area covered by each species was recorded as a percentage of the total area of the quadrant. After carrying out the ten stops, an average species composition for the sward was determined.
Perennial ryegrass dominated in both grazing and silage swards but it was possible to see that the other species present varied slightly in both the silage and grazing areas.
Grazing swards were found to contain nearly ninety four percent perennial ryegrass. Thus the swards had a high production potential. The preferred species cocksfoot and clover, in addition to meadow grass, an unpreferred grass species were also present, although in small amounts. As previously outlined, perennial ryegrasses are more productive palatable and therefore acceptable to stock, in addition to being of higher nutritive value when compared to the unpreferred of weed grasses indigenous to Northern Ireland. The high soil fertility status maintained on this farm coupled with effective sward management practices are likely to be significant contributors to the maintenance of a high proportion of perennial ryegrass within the sown swards.
The silage swards consist of mainly perennial ryegrass (88%), with small quantities of bents, meadow grasses and clover (Figure 9). The ryegrasses used in these swards are mainly intermediate types (c.v. Morenne and Talbot). These are better suited to conditions on this farm as rainfall is low during the grazing season. Intermediate varieties are generally not as high yielding in spring, are less likely to develope unplatable stemmy growth after April grazing and are also capable of producing similar total annual yields when compared to early varieties. The relatively high proportion of chickweed found to be present within the silage swards reflects a high incidence of the weed being present in the reseeds. However in older swards chickweed was not seen to be a problem reflecting the annual growth cycle of the weed and the effective management regime imposed upon the swards.
Th epolicy for the grazing swards is only to reseed when it is necessary to do so through sward deterioration. The objective on the farm is to minimise the frequency with which reseeding is necessary through maintaining a very high standard of sward management and avoiding physical damage to swards. In addition to the economic considerations associated with aiming to minimise the frequency with which swards are reseeded, there is the added consideration on the farm of practical difficulties with cultivation work. The shallow nature of the soils and preponderance of rocky outcrops makes ploughing the land almost impossible. This is significant as direct drilling/mineral cultivation approaches to reseeding are generally much less reliable under Northern Ireland conditions when compared to conventional plough-based methods. The results obtained from the assessment of sward composition demonstrate that this policy is justified. For example, paddock number 15 has not been reseeded for 25 years, and this was recorded as having 98.8% perennial ryegrass. This is only one example, however, it shows the effectiveness of Mr Rankin's grazing management policy in terms of minimising sward deterioration. Reseeding the grazing swards with the frequency of once each five to seven years, which is typical of Northern Ireland would be completely unnecessary. Howver, some paddocks have been reseeded recently, aftre drainage work was carried out and also because of poaching damage caused by cattle during the winter. Poaching, however, is not a persistant problem as careful grazing management is practised which aims to minimise the extent of physical damage to the swards.
In the silage area, however, a more strategical approach to reseeding is taken. Swards intensively managed for silage production tend to deteriorate more rapidly compared to those used for grazing. While the land has also fairly shallow soils there are little or no rock outcrops. This land is very intensively manageed and each year one of the five fields in normally reseeded. This leads to weed problems in the reseeds which usually have to be chemically controlled, yields also tend to be lower during the first year. However, to maintain a a high proportion of highly productive grasses in silage swards we think this policy pays good dividends.
Dock infestations are an occasional problem in the silage swards as in the case of many Northern Ireland farms. Mr Rankin usually sprays the docks prior to the second cut of silage. This work is usually carried out by a contractor. No spraying has been necessary so far this year.
Page created on 28th January 1996