Massey Organic Trial

August 2007
Two dairy farms, two small herds being studied side by side on the same property, one organic and one conventional. After 6 years what are the results?

The Massey University Organic-Conventional Dairy Systems Trial began in August 2001 and the organic farmlet was certified in 2003. The trial is the only comparative grassland based grazing dairy study in the world.

The organic herd of 43 cows is milked off 20.6 ha while the conventional herd of 48 cows is milked off 21.3 ha. Both herds comprise of average New Zealand Holstein/Friesian cows.

Both herds produce milk from grass so production was a question of how much feed they received and its quality, as well as the health of the animals.


1. To develop farm and herd management systems that optimise performance;

2. To compare the impacts of organically and conventionally managed dairy systems on soil health & water quality, pasture and forage crop productivity, and animal production and health;

3. To identify management practices that improve the biological activity of soils, optimize clover content and best maintain biological N fixation, and best control mastitis and other health issues in organic milk production systems; and

4. To determine the stability and sustainability of high biodiversity organic dairy pastures, including the control of weeds.

The project

Each of the two farmlets is managed individually according to best practice for its particular type of management system and environmental conditions. For the organic farm, best practice is guided by the certifying agency, Agriquality, and by an organic farmer advisory group. Comparisons between the two systems are made through regular intensive monitoring, and economic costing methods are used to determine the differences in cost of production under the two systems and to influence management decision-making.

Pasture is monitored on both farms twice a year. These surveys include herbage accumulation in all paddocks, botanical composition etc. Soil properties are measured and a range of indicators of soil micro activity. Soil nitrogen is also being studied in detail.

Animal Health

Animal health issues did not appear to differ significantly between the two units and there were no significant issues recorded on either unit during the first two seasons. That has changed during the latter seasons with somatic cell count challenges in the organic herd. Homeopathic remedies, tonics and drenches were used on the organic herd.


During first season of full certification in 2003, the organic farmlet consistently grew less pasture than did the conventional farmlet, so that less pasture was consumed and more supplements were fed on the organic farmlet. In particular, the conventional farmlet produced more pasture in early spring due to the application of urea fertiliser.

By the 2005- 2006 season species composition of the pastures on the two farms had started to diverge, with a lower ryegrass % and higher white clover % of herbs and other grass species on the organic farm.

There have been two approaches to increasing the clover percentage on the organic farm. First, grazing management objectives that include maintaining pasture masses in the 1500-2600 kg DM/ha range, particularly in spring, and grazing the poorer pastures hard (

Second, the worst pastures on the organic farm are being renewed by cultivation and sown with a mix of perennial ryegrass, white clover, red clover, chicory and plantain. One half of a paddock was established in September 2004 and the other half was established in late February 2005 to compare establishment and weed ingress in spring and autumn.


Soil monitoring up to autumn of the third season revealed no differences between the conventional and organically managed paddocks for ammonium-N, nitrate-N or mineralisable-N. Likewise, there is no difference in earthworm populations between the two systems.

Preliminary results suggest that nitrate-N concentrations in drainage water are lower on the organically managed areas, but further monitoring is required to have confidence in this result. Some differences in soil nutrient status may be beginning to emerge between the systems there is a hint that a gap in Olsen P, sulphate-S and potassium values may be developing between the conventionally and organically managed areas. These values are slightly greater under conventional management, presumably as a result of fertiliser inputs to this system.

Overall Results

In the initial season of the trial the conventional and organic farms produced similar amounts of milksolids per cow and per hectare, and somatic cell counts were low for both herds.

In the first season, milksolids per hectare were 959 and 993 and per cow were 436 and 451 for the organic and conventional farms respectively. These compare favourably with the district average of 314 kgMS/cow that year.

In the second season, with a very dry summer, milk production again was similar on both farmlets (723 kgMS/ha and 745 kgMS/ha respectively for conventional and organic). However, the cost per kg of milksolids produced was 23% higher on the organic farmlet, due mainly to the fact that it was a very dry summer and organic feed had to be brought in from off farm.

The 2005-06 season deteriorated in October with a prolonged summer dry spell. On the conventional farm Palm Kernel Extract meal was fed in March and early April, enabling them to be milked through into May, with their last 8 weeks on once-daily milking and their last four weeks on pasture only.

The lack of a cost effective organic supplement for the organic herd meant an early dry-off in March. It is unclear if this was good farming decision or not. The net result was a 40% difference in production for the two herds for that season.

Preliminary Conclusions

Pasture production, and hence milk production, is less on the organic farmlet, most likely due to the inability to cost-effectively apply nitrogen fertilisers at critical periods in the spring.

Mastitis, though more of a challenge on the organic farm, is manageable and has remained below tolerance levels; other animal health issues have not been a problem under organic management.

The trial so far has demonstrated that organically rearing young stock is feasible, and in fact may be a very viable option for dairy farmers.

Impacts on the environment in the form of nitrate-N contamination to ground and surface water may be less under organic management, but further monitoring is needed to be able to conclude this with any confidence.

Finally, putting aside last seasons results, the organic dairy system seems to be an economically viable option for dairy farmers, given the price premium for organic milk..