CloverCheck 2009 – Monitoring white clover performance
Scott Laidlaw, AFBI-Crossnacreevy and Manus McHenry, CAFRE, Greenmount Campus
CloverCheck is an aid to the management of grass-clover swards run jointly by the Agri-Food and Biosciences Institute (AFBI) and CAFRE. The up-to-date information can be used as a bench mark to aid decision making in managing grass-white clover swards for farmers interested in exploiting white clover.
It provides regular updates on herbage growth and clover content on plots laid down on existing grass/clover swards on organic dairy and conventional beef or beef/sheep farms. Also, growth and clover content on the plots during the following two weeks are predicted and included in the fortnightly bulletins produced during the growing season.
Grass-clover growth and clover content 2009
The average growth and clover content of organic and conventional beef farms for 2009 are compared in Figs 1a and 1b, respectively.
From the start of the growing season to 5 October the organic plots produced 9.2 t DM/ha compared with 8.5 t/ha on the conventional beef farms. Clover content in the plots on the conventional farms was consistently lower than in organic plots (Fig. 1b).
However, even on the beef farms which had very low contents in spring maximum clover content reached 40% of the dry matter in late summer.
Year-to-year variation
In 2008 a pilot trial was run involving plots on the same organic farms as in 2009. The data for the two years is compared in Fig. 2. A combination of warm dry conditions in spring and high slurry rates resulted in particularly high growth rates in May 2008.
However by late June, growth rates were very similar for the two years although clover content was slightly lower in 2009 than 2008.
Testing the model
The CloverCheck model predicts growth and clover content two weeks ahead.
Weather forecast information (average daily air temperature, radiation and rainfall) and clover content of the swards early in the season are model inputs.
As it is now close to the end of the growing season the average actual data from the seven sites can be compared to the series of predicted estimates made in each of the 15 fortnightly bulletins issued during the growing season.
The comparisons for growth and clover content are presented in Figs. 3a and 3b.
The model has tended to over-predict growth in late spring and early summer while clover content prediction 2 weeks ahead has been very good except for early June when the model predicted a higher content than was recorded.
Plots and fields
When interpreting CloverCheck data it is important to remember that, although the plots are laid down on existing swards, the information is taken from plots cut regularly to a uniform height and free from grazing animals i.e. ideal conditions for clover to flourish. Clover content in fields containing the plots is consistently lower than in the plots.
Conclusion
- In conventional farms, N applied in spring and early summer will result in lower clover content than in organic farms. While the applied N will increase early spring growth, production later in spring and in summer is reduced.
- Other than in spring when higher slurry rates and early spring temperatures resulted in higher growth rates in 2008 than in 2009, growth and clover content were broadly similar for the two years.
- Grass-clover growth and clover content can be predicted on plots with some confidence; however, clover content in fields is over-predicted from plot estimates, the over-prediction is higher for conventional beef than organic dairy farms.
