As the pressure on farmers to do their bit for the environment grows, clover is becoming more of an attractive option in trying to reduce the amount of chemical fertiliser applied on farms.
In light of this, an experiment is currently being undertaken in Clonakilty Agricultural College, to investigate the effect of sward type (grass only versus grass-clover) and nitrogen (N) fertiliser levels (150kg N/ha versus 250kg N/ha) on the productivity of spring milk production systems.
Teagasc’s Áine Murray discussed this study and its findings, to date, at the recent Moorepark ’19 Open Day.
The previous study
“A previous study in Clonakilty looked at the effect of tetraploid and diploid with and without clover – over the course of four years.
“The main discovery was that there was no difference between tetraploid and diploid varieties without clover on herbage production – for the whole grazing season – or on milk production.
“The only real difference was when you added clover. This resulted in an additional 1.2t DM/ha, 597kg/cow and 48kg of MS/cow produced.
This added up to €305/ha extra net profit per year.
The new study
It was from this previous study that the new Clonakilty study was developed. The new study now aims to see if the same results can be achieved by reducing the N input.
- Grass only with 150kg N/ha applied;
- Grass only with 250kg N/ha applied;
- Grass-clover with 150kg N/ha;
- Grass-clover with 250kg N/ha applied.
For the treatments on the lower rates of N, the reduction in N will be during the mid-grazing season. Only 9kg of N/ha will be applied in each round between the months of May and August and 12kg of N/ha in the last round in mid-September.
Touching on the performance of the experiment to date, Áine said: “At the minute, we are getting 1.5L/cow/day and 0.11kg of MS/cow/day more from the cows on the grass-clover with the lower N, than the grass only with the higher N.
“However, I expect there to be a much greater difference between the two groups over the next number of weeks as the amount of clover in the sward increases.”
Over-sowing
Since the beginning of the previous study (in 2014), none of the paddocks have been reseeded.
In some of the paddocks, the clover has not persisted as well as others; so in order to keep it at the optimum level (20-25%) they have over-sown some of the paddocks.
Explained their approach to this, she said: “We over-sowed the paddocks in April. First we grazed them really tight or took bales off.
We then mixed 2kg of clover/ac with 0-10-20 and broadcast it across the field. After this we spread parlour washings.
“The establishment can be hit or miss using this method; you need moist ground conditions and some paddocks take better than others.
“Following this, we grazed the paddocks at a cover of 1,200kg of DM/ha and tried to continue grazing them around this cover – to allow light to penetrate the bottom of the sward.”