Meeting a nitrogen loss limit on a Waikato milking platform

Frame the test first. The limit is applied through a model, so a pathway must be defensible in that model, not merely good in reality. Both pathways below assume the modelled loss responds roughly proportionally to nitrogen inputs and to the time animals spend on pasture in the high-risk autumn/winter period.

Pathway A - capital (standoff pad, N to 150)

• Capex of $1.35m exceeds the $600,000 borrowing cap, so this option is not currently fundable without restructuring.
• Annualised cost: interest at 6.8% = $91,800; 20-year depreciation = $67,500; running and effluent management = $25,000. Total ≈ $184,300/yr, about $1.58/kg MS on 116,850 kg MS.
• Modelled effect: standoff for ~60 winter days might deliver 8–12 kg N/ha and the 30 kg N cut another 3–5 kg, taking 58 to roughly 42–46. It meets the limit with almost no margin.

Pathway B - system change (2.1 cows/ha, N to 130, plantain at 30%)

• Revenue falls from 285 × 410 × $8.60 = $1,005,150 to 240 × 410 × $8.60 = $846,240, a loss of $158,910.
• Costs saved: 50 kg N/ha on 112 ha = $7,000; supplements and animal health at about $350/cow = $15,750; reduced winter crop ≈ $12,000. Total ≈ $34,750.
• Net cost ≈ $124,200/yr, or $1.19/kg MS.
• Modelled effect: lower stocking (−8 to −10 kg), lower N (−5 to −7 kg) and plantain displacing urine nitrogen in autumn (−4 to −6 kg) gives roughly 37–41 kg N/ha.

Recommendation. Pathway B: cheaper per kilogram of milksolids, inside the borrowing cap, and leaves 4–8 kg N/ha of headroom for a dry season or a model reversion. Conditions: plantain established by autumn 2026, monitored pasture composition, and a review trigger if modelled loss exceeds 43 kg N/ha.

The claim is too strong, but the option is not without merit.

Mechanism. Plantain reduces the nitrogen concentration and volume of urine, and possibly slows nitrification in the urine patch. The effect is therefore greatest where plantain makes up a large share of diet dry matter during the highest-leaching period, typically late autumn and winter. It is not a property of the sward merely containing plantain.

Where the claim is weakest.

• The response in trials depends on the proportion of plantain in the diet (commonly cited threshold is around 30% of dry matter) and on cultivar. At 30% of the platform, achieving 30% of diet across the risky months requires deliberate grazing management, not just sowing.
• Plantain establishes slowly and persists poorly under set stocking and dry summers. Cattle graze it selectively, so the proportion in the diet can fall sharply in the second and third years.
• Establishment costs seed, spray and lost grazing, likely $400–$700/ha all up in the first year, and the stand may need resowing within four to five years.
• The model may represent plantain as a fixed percentage reduction, which may overstate the effect on this farm or may be rejected by the consent authority if not supported by evidence.

Fair assessment. Plantain is a low-cost, low-regret measure worth perhaps 4–6 kg N/ha here, but banking the entire 13 kg N/ha gap on it is imprudent. It should sit alongside a reduction in nitrogen fertiliser and stocking rate, and be supported by pasture dry matter sampling so the actual dietary proportion can be demonstrated to the regulator.

At $5.80/kg MS, revenue on 285 cows × 410 kg MS is $677,730; under Pathway B it is 240 × 410 × $5.80 = $570,720. Fixed costs do not fall with the milk price, and a 2.5 cow/ha system on this debt load would likely be at or below breakeven, so the question shifts from 'which compliance pathway' to 'which system survives'.

Implications.

• Pathway A is ruled out outright. A $1.35 million asset with $184,000/yr of annualised cost cannot be serviced at $5.80, and the bank will not extend.
• Pathway B becomes more attractive, not less: it is the lower-cost, lower-input system, and its net cost falls proportionally with milk price because much of it is forgone revenue rather than cash.
• Additional low-cost levers: once-a-day milking for part of the season, reduced replacement rate, selling surplus rising two-year-olds, wintering cows off the platform to a support block, and reducing the winter crop area further.

Decision. Proceed with Pathway B immediately but stage the plantain and destocking over two seasons, and hold the standoff pad as a later option only if the limit tightens or the model changes. Simultaneously test the debt structure: extend the term or seek a interest-only period.

Strategic point. The low-price scenario is the reason to choose the reversible, low-capital pathway now. A farm that meets the limit with system change retains the option to intensify later; a farm locked into a standoff barn does not. If $5.80 persists beyond three seasons with no recovery, a partial land-use change, such as retiring a runoff block or leasing land, should be modelled seriously.