By Stephen McAuliffe
SUSTAINABILITY has become
somewhat of a ‘buzz’ word in Irish agricultural circles in recent years, particularly as consumers place greater emphasis on the implications of how their food is produced.
However, as farmers are pro-ducers of internationally traded commodities, they are ‘price-takers’, and with little opportunity for gaining a significant premium for their produce they can only optimise efficiencies ‘inside the farmgate’.
So what does this mean for the modern day dairy farmer and can economic and environmental sustainability go hand in hand at farm level?
Greater use of white clover is one possible route to gaining a more sustainable credential for milk production and this current PhD study, which is part of the AFBI-Teagasc-QUB PhD programme foc-
using on improving grassland production in Ireland, has already provided some very positive results.
The objective was to measure the benefits, if any, of clover inclusion on milk and grass production over two growing seasons.
Three 7.3ha model farms (farm-lets) were set up within the Moorepark dairy research farm and each stocked with 20 cows (2.73 cows/ha).
All cows received the same concentrate input of 243kg/cow/year, fed mainly in the spring and autumn and each farmlet was required to sustain itself and fulfil its winter feed requirement by making sufficient silage.
Farmlet 1 – grass only swards receiving 250 kg N/ha/year.
Farmlet 2 – grass + clover swards receiving 250 kg N/ha/year.
Farmlet 3 – grass + clover sward receiving 150 kg N/ha/year.
The average yield over the three farmlets was 14 tonnes dry matter/hectare, with an average clover content of 24 per cent for the low N farmlet 3 and 20 per cent for the high N farmlet 2. Both these farmlets had increased production over the grass only farmlet. As can be seen from the table, the cows grazing the grass/clover sward at 250kg N had the highest milk production at 538kg milk solids per cow per year. The clover sward receiving 150kg N was next in line at 523kg milk solids/cow/year, with the lowest milk production from the cows grazing the grass only sward at 250kg N.
The difference between the cows grazing grass only swards and those grazing the grass clover swards at the same nitrogen level was 35kg/cow MS or 95.5kg/ha. Taking a milk price of €4/kg MS, the extra revenue generated would be a substantial €140/cow or €382/ha.
Similarly, the cows grazing the
lower 150kg N farmlet had increased milk output of 21kg/cow MS giving an additional revenue of over €84/cow or €229/ha. Part of this improved output was due to increased sward digestibility, especially in the aut-umn when the quality of grass begins to deteriorate. (See table)
Optimising the use of clover does require some management adjustments. For example, the reduced over-winter and spring growth of grass/clover swards can mean reduced grass availability in spring and a need for extra silage to be fed.
An average of 106kg DM/cow of extra silage was fed to the cows grazing clover swards each spring, though this was produced from the same farmlet swards in the previous growing season. Bloat can also be a cause of concern for farmers, however strategies such as adding oil to the water supply and not allowing cows to enter a clover sward when they are very hungry has helped to all but eliminate the risk of bloat.
This study has shown the ability of clover to convert significant quantities of atmospheric N into plant usable nitrogen, even on an intensively managed system.
As identified in the articles over the past two weeks. Clearly there is opportunity to use white clover to increase on-farm milk production from the same land area.
Alternatively it is possible to reduce nitrogen use, increase the sustainability credentials of the farm and maintain the same or better levels of production.
This PhD study has added to the existing evidence that greater use of white clover offers the potential to significantly improve both the environmental and economic sus-
tainability of grass based pro-duction systems in Ireland.