The work was done after an earlier trial suggested kikuyu-dominant pastures could be more profitable than those with a large proportion of ryegrass. The work, from June 2008 to May 2012, showed mulched and non-mulched kikuyu farmlets grew and harvested more grass per hectare – at 12.6 and 13 tonnes drymatter (DM)/ha respectively – than a ryegrass farmlet at 10.9t DM/ha. The cows on the ryegrass farmlet needed more supplements and were grazed off more often.
Milk produced, at 1169kg milksolids (MS)/ha for the mulched and 1101kg MS/ha for the non-mulched kikuyu pastures, was also higher than the ryegrass farmlet’s production of 1086kg MS/ha.
The trial results challenged Northland perceptions that kikuyu pasture systems were less productive and profitable than those based on ryegrass. Despite having twice the pasture management costs the mulched kikuyu farmlet was the most profitable at $3147/ha averaged over four years.
However, there was a suspicion the trial set-up could have affected the result, with the ryegrass farmlet situated on a wetter and less developed area of the farm. It was decided to try comparing the pasture systems in a more balanced way, to see if productive and profitable dairy farm systems in Northland could be achieved on different pasture types if they were well-managed.
The new trial was set up in June 2012 with a kikuyu farmlet of 44ha with 3.2 cows/ha during the first two seasons. The ryegrass farmlet was 40ha and stocked at three cows/ha, the same rate as the kikuyu farmlet in the third year of the trial.
In the first two seasons all the kikuyu-based pastures on that farmlet were mulched and drilled with Tabu Italian ryegrass in autumn, but in the third season the seed was broadcast before grazing and mulching. Grazing alone was used to manage kikuyu on the ryegrass farmlet.
Weekly farm walks and monthly pasture samples were collected and analysed from the next four paddocks to be grazed on each farmlet. Pasture quality averaged 0.3 megajoules of metabolisable energy higher on the kikuyu farmlet during early spring and summer, which was probably because of the higher-quality Italian ryegrass component and Poa lowering pasture quality on the ryegrass farmlet as it flowered and died in spring. The situation was reversed in autumn when the ryegrass farmlet showed higher pasture quality.
While spring and summer pasture growth was similar on both farmlets, pasture growth rates were higher on the ryegrass farmlet during June, July and August in all three years. From February to May the kikuyu farmlet showed higher growth rates.
Ryegrass farmlet covers were higher during winter but similar to the kikuyu farmlet from September to December. However, from January to May covers were higher on the kikuyu farmlet.
Milk production averaged over the three years was the same for both farmlets at 1154kg MS/ha. The high milk price meant feeding high levels of supplements was profitable, but in the final season, when this was not the case, production was similar to the ryegrass farmlet. Production per cow was higher on the ryegrass farmlet in the first two seasons, but in the third year it was identical to the kikuyu farmlet.
When it came to profitability, adjustments were made to wages, regrassing costs and administration to reflect a commercial farm situation. The ryegrass farmlet was almost twice as profitable as the kikuyu farmlet in the first season, mainly because of lower FWE but also because of slightly higher milk production in summer from feeding turnips.
Expenses per kg MS were 19% higher on the kikuyu farmlet because of mulching, regrassing and using more supplement over summer and dry cow grazing over winter.
In the past two seasons the ryegrass farmlet’s profitability was only marginally ahead because of lower FWE, showing regrassing was the only factor reducing kikuyu’s profitability.
