Plantain Case Study - High profit, low nitrogen leaching

Richard runs Chlorofield Ltd, a rolling dairy farm on well-drained pumice soils at around 400 metres elevation on the Mamaku Plateau within the Rotorua lakes catchment.

It's classic Rotorua country with 1900 to 2200mm of rainfall each year, cool winters, and the kind of reliable grass growth that can make a simple system work well.

When Richard and Amy Fowler took over their Rotorua dairy farm in 2019, they knew environmental regulations were coming. Farming in the Lake Rotorua catchment meant they would need to reduce nitrogen leaching significantly, an average 31% reduction by 2032 for dairy farmers in the area.

This farm achieved N leaching 25% below the catchment average (40 vs 53 kg N/ha) while maintaining operating profit at 142-159% of the district benchmark. The system combines plantain, tactical N fertiliser use, low imported supplement, and a simple low-cost structure.

Farm details

Location

Mamaku Plateau, Rotorua Lake catchment

Elevation

400m above sea level

Soil type

Pumice (well-drained)

Contour

Rolling

Farm size

Milking platform plus support block off-farm

Stocking rate

2.6-2.9 cows/ha (2024/25 = 2.7 cows/ha)

Milking frequency

Twice daily

Wintering

Approximately one-third of herd wintered off-farm

Rainfall

1,400-1,750mm annually

Simple system, good cost control

Richard and Amy’s success comes from three key elements working together.

1. Low-cost structure

Operating expenses have consistently been well below the regional benchmark. In 2021/22, farm operating expenses were $4,224/ha compared to the benchmark of $6,861/ha – just 62% of the average. Even in more challenging years, expenses remained at 67-70% of the benchmark. This low-cost approach flows through to strong profitability. Operating profit has ranged from 142% to 159% of the regional benchmark over the period measured.

2. Strategic nitrogen fertiliser use

Rather than applying a set amount of N fertiliser each year, Richard uses a tactical approach, applying only when needed to achieve specific pasture cover targets.

Season	2019/20	2020/21	2021/22	2024/25
Farm (kg N/ha)	40	28	25	0
Benchmark (kg N/ha)	112	80	85	87

N fertiliser use compared to regional benchmark over time.

At the start, small amounts of N fertiliser (25-40 kg/ha) were used tactically in late winter to achieve target pasture covers, and occasionally in autumn to build winter feed. By removing the autumn application, N use dropped to 24-30 kg/ha. By 2024/25, with a slightly lower stocking rate and good pasture growth conditions coming out of winter, Richard eliminated N fertiliser entirely while maintaining milk production. For comparison, the regional benchmark farms were applying 80-112 kg N/ha over the same period.

3. Low imported supplement

Chlorofield operates with minimal reliance on imported feed. In 2023/24, imported supplement was just 0.4 t DM/ha compared to the benchmark of 2.1 t DM/ha, less than 20% of what comparable farms were using. This is enabled by:

Matching stocking rate to pasture growth (2.6-2.9 cows/ha).
Wintering approximately one-third of the herd off-farm.
Making supplement on-farm when conditions allow (0.2-0.4 t DM).
Strong pasture utilisation (11.7-12.2 t DM/ha eaten in most years).

"One of the other changes we made to meet N reduction target is to aggressively pull Nitrogen from the system, so for the last 2 years we haven’t put any N on at all, and maintained production - it went hand in hand with using plantain."

Introducing plantain

Plantain was introduced to the system in 2022/23 as part of the DairyNZ Plantain Potency and Practice Programme. Richard and Amy achieved 19-22% plantain content across the whole farm through annual broadcasting.

Establishment approach

Season	Area broadcast	Seed rate	Plantain achieved
2022/23	100% of farm	8 kg/ha (4 kg/ha BSE)	19%
2023/24	80% of farm	2-4 kg/ha (1-2 kg/ha BSE)	22%
2024/25	100% of farm	4 kg/ha (2 kg/ha BSE)	21%

Plantain establishment details by year (BSE = bare seed environment)

Richard broadcasts Prillcote (coated) Ecotain plantain seed with the annual phosphorus fertiliser application in spring (November). The initial application in 2022/23 used a higher rate (4 kg/ha bare seed equivalent) to establish plantain across the farm, with lower maintenance rates (1-2 kg/ha) in subsequent years.

In 2023/24, a trial compared seeding rates of 0, 1, and 2 kg/ha across different paddocks. The results showed no significant difference in plantain content the following year, suggesting that once established, plantain may persist for 2-3 years on this soil type without annual reseeding. However, Richard continues annual broadcasting to maintain consistent levels.

Cost of plantain

The initial establishment cost was approximately $91/ha (8 kg/ha Prillcote seed), reducing profitability by around 2%. In subsequent years, maintenance costs have been lower:

2023/24: Average $34/ha (mix of 2 and 4 kg/ha Prillcote across the farm).
2024/25: $45/ha (4 kg/ha Prillcote).

At maintenance rates, plantain represents less than 1% impact on operating profit.

High clover content

An interesting feature of Richard and Amy’s farm is its relatively high clover content - 17% in autumn 2025, compared to 12-14% on the other partner farms. This is likely due to the low nitrogen fertiliser use, which reduces competition between grass and clover.

The combination of plantain (21%) and clover (17%) means that nearly 40% of the pasture dry matter comes from species other than ryegrass. This diverse sward supports the low-input approach by providing biological nitrogen fixation from clover and nitrogen leaching reduction from plantain.

Environmental and financial performance

Nitrogen leaching

	2019/20	2020/21	2021/22	2023/24	2024/25
N leaching (kg N/ha)	52	49	47	40	42
Plantain %	0%	0%	0%	22%	21%
2032 NDA target	40	40	40	40	40

N leaching modelled in OverseerFM (version 6.5.10) over time.

Nitrogen leaching has progressively reduced from 52 kg N/ha in 2019/20 to 42 kg N/ha in 2024/25 – a 19% reduction. This compares favourably to the catchment average of 53 kg N/ha (2023/24 data from Bay of Plenty Regional Council). Chlorofield’s 2032 NDA target is 40 kg N/ha. At 42 kg N/ha in 2024/25, the farm is within 5% of its final target with 7 years still to go.

Financial performance

Metric	2021/22	2022/23	2023/24	2024/25
Production (kg MS/ha)	1,095	979	923	1,082
Benchmark production	1,111	1,144	1,094	1,077
Operating expenses ($/ha)	$4,224	$5,138	$4,224	$4,499
Benchmark expenses	$6,861	$7,669	$6,861	*$7,711
Operating profit ($/ha)	$5,549	$4,130	$4,342	$5,942
Benchmark profit	$3,583	$2,595	$3,049	*$2,911
Profit as % of benchmark	155%	159%	142%	201%

Financial performance compared to Rotorua District DairyBase benchmark. *Central North Island benchmark used for operating expenses and operating profit in 2024-25 due to insufficient data.

Despite the low-input approach, production has remained competitive at 90-100% of benchmark in most years. The 2022/23 season was challenging due to extremely wet conditions, affecting all farms in the district.

The key to profitability is the cost structure. With operating expenses consistently 30-40% below benchmark, Chlorofield converts a higher proportion of revenue to profit. Operating profit has ranged from $4,130 to $5,942/ha compared to benchmark figures of $2,595 to $3,583/ha.

Production maintained

A key question for farmers considering plantain is whether it affects production. At Chlorofield, the introduction of plantain in 2022/23 coincided with an extremely wet season, making it difficult to isolate the effect of plantain specifically. However, pasture and crop harvested has remained strong at 11.7-12.2 t DM/ha in most years, and milk production in 2024/25 (1,082 kg MS/ha) returned to levels achieved before the wet season. This suggests plantain has not negatively affected farm performance.

Success factors

1. Starting with a clear goal

Richard and Amy knew N limits were coming and designed the system from the start to meet them, rather than trying to retrofit an intensive system.

2. Matching inputs to the farm

Rather than chasing high production with high inputs, the system is matched to what the farm can sustainably support from pasture.

3. Cost discipline

Keeping operating expenses low provides a buffer against milk price volatility and allows profitability even at moderate production levels.

4. Tactical decision-making

Fertiliser and supplement are used when needed to achieve specific targets, not applied on a fixed schedule.

5. Embracing plantain early

By adopting plantain as part of the programme, Chlorofield gained an additional low-cost tool for N reduction.

6. Good pasture management

Strong pasture utilisation (11-12 t DM/ha eaten) reduces the need for imported feed and supports cow performance from home-grown feed.

You don't have to choose between profit and environmental performance. A well-designed low-input system can deliver both. Plantain is one tool in the toolkit; it works best as part of an overall approach that includes tactical N use, appropriate stocking rates, and good cost control.

This case study demonstrates that meeting NDA targets doesn't have to mean sacrificing profitability. However, the approach may not suit every farm. Key considerations:

System change takes time. This farm was set up as a low-input system from the start. Transitioning from a high-input system requires careful planning.
Soil and climate matter. This farm is on well-drained pumice soil at 400m elevation with 1,400-1,750mm rainfall. Results may differ on other soil types.
Off-farm grazing helps. Wintering one-third of the herd off-farm reduces pressure on the milking platform during the highest-risk period for N leaching.
Plantain is part of the solution. Plantain contributed to N reduction, but the biggest gains came from the overall system design including low N fertiliser and supplement use.