One of the system changes was the decision to shrink the effective milking platform from 120ha to 64ha – the balance largely being used for perennial forage crops, harvested either through cut and carry or tightly regimented on-off grazing. The policy was designed to minimise the risk of nitrate leaching.
The farm is located on the banks of the Manawatu River, sandwiched between the main university campus and Palmerston North city. The free draining, naturally fertile soils generally translate into a feast-or-famine pasture situation, dependent on seasonal rainfall patterns.
About 32ha – part of the retained milking platform – has spray irrigation via a sprinkler system.
Along with a ryegrass-clover mix, the perennial forage crops planted are lucerne and a herb sward of chicory, plantain, and red and white clover.
The longer-term forages have been selected over short-term alternatives to minimise repeat cultivation and the associated potential loss of soil nutrients during cultivation, said Professor Peter Kemp, pasture scientist and head of the university’s Institute of Agriculture and Environment.
Lucerne and the herb mix made the cut because of their resilience under dry conditions, if managed appropriately, combined with their high summer feed quality.
In spring 2013, 10ha of the herb mix was established along with 9.5ha of lucerne.
The herb mixes were break-fed by No 1 Dairy Farm manager Jolanda Amoore with the 235 cows allocated about 0.5ha a break, and breaks back-fenced to prevent over-grazing.
After two hours’ grazing, the cows were shifted back to their day paddock on the milking platform. This on-off grazing strategy was adopted to minimise deposition of urinary nitrogen on the forage area.
The herbs were grazed once they reached a height of between 20-25cm, targeting a post-grazing residual of not less than 7cm, corresponding to a grazing interval over spring and early summer of about four weeks.
The grazing rules were designed to optimise yields – both plant and milk – while preserving plant reserves to maximise longevity and persistence. In mid-summer and autumn a prolonged dry period developed, and the herb mix was spelled from grazing until April.
“A big feature of the plantain and chicory is that as long as you look after it – maintain its taproot health – it recovers spectacularly well when it does rain,” Kemp said.
For Peter Kemp, integrating the different forages under a practical management system is where gains can be made.
As the new system beds in, more data will be collected. Pilot sites monitoring nitrate leaching are already in place and applications for funding a more extensive monitoring network are under consideration.
While pasture scientist Peter Kemp acknowledges the forages are not exactly cutting edge, it is the farming system that develops around them, the integration of the patchwork of forages and the ryegrass-clover mixes on the milking platform that will be the focus of the developing story.
The ultimate aim is that this data will be able to be incorporated into nutrient budgeting software Overseer.
The herd will form another research focus. Split evenly between Friesian, Jersey and crossbreds, the results from the first season on OAD milking are muddied somewhat by the impact of part of the herd transitioning from autumn to spring calving. More data will be collected this season.
