1How to read these tables
Where a value is uncertain it is shown as a nominative value with its minimum and maximum in brackets, like 0.35 (0.15–0.75). The central run uses the nominative value; the uncertainty run draws from a triangular distribution across all three. A value shown as a single number is treated as exact.
Everything here is a national-typical starting point assembled from published sources, not a measurement from anyone's site. Two things follow. First, replace any of it you can with your own data — the model is built to make that easy. Second, where you cannot, the ranges are the honest statement of what is not known, and they are wide for good reason.
The ranges are not decorative. The decay constant for mineral-associated organic matter spans a factor of about six from minimum to maximum, and it is the parameter that dominates any prediction beyond a decade. That is the state of the published literature, not a shortcoming of this compilation.
2Climate
Monthly temperature, rainfall and potential evapotranspiration for 27 locations, summarised here as annual totals. The full monthly series are in data/climate-nz.js and are editable in the model's Climate panel.
The monthly values are smoothed normals reconstructed from published NIWA 1991–2020 station statistics — annual mean temperature and its seasonal amplitude, annual rainfall and its seasonal distribution, and annual PET. They are representative of a district rather than an exact station series. Where a result matters, substitute the real station data.
The surplus column is rainfall minus potential evapotranspiration. A negative value means the site is potentially water-limited for part of the year, which suppresses respiration as well as production.
Each site also carries an uncertainty entry describing year-to-year and within-district variation: temperature ±1.2 °C, rainfall ×0.70 to ×1.30, PET ×0.90 to ×1.10. These are sampled by the uncertainty run.
3Texture and drainage
Texture classes
Specific surface area is estimated from texture, because it is almost never measured. The ranges span the usual spread of nitrogen-BET and EGME values for temperate soils. The MAOM capacity column applies the Hassink (1997) relation to the fine fraction, with a multiplier for the mineralogies his temperate data set does not cover.
Two classes deserve comment. Allophanic materials have specific surface areas an order of magnitude above what their particle size implies, because short-range-order aluminosilicates dominate their surface chemistry — this is why Waikato and Taranaki ash soils hold so much carbon. Peat carries two extra multipliers, applied to the particulate and mineral-associated decay constants, because its organic matter is millennia-old humified plant material rather than this season's residue. Without that correction a drained peat is predicted to lose about ten times more carbon than is actually measured.
Drainage classes
The drainage class sets where the water table sits, and therefore whether a horizon respires aerobically or produces methane. On a wet site it changes the answer more than any rate constant in the model.
4Soil orders
The 15 orders of the New Zealand Soil Classification, each carrying a default three-horizon profile. The table below shows the topsoil; the B and C horizons are in data/soils.js and in the model's Soil panel.
The protection factor multiplies the mineral-associated decay constant. Values below 1 mean the mineralogy holds carbon more strongly than an average temperate soil: allophane and ferrihydrite in the Allophanic and Pumice orders, iron and aluminium oxides in the Oxidic order, calcium bridging in the Melanic order.
What each order is
5Plants
Twenty-five plants and land covers. Above-ground net primary production is total annual growth in tonnes of dry matter, not harvested yield: a maize silage crop cutting 20 t DM/ha has an ANPP of about 22, the difference being stubble and senesced leaf.
The wood fraction is the share of above-ground production laid down as long-lived woody biomass, which does not reach the soil within the year. It is zero for herbaceous covers and 0.62 for a radiata pine rotation, where most growth becomes stem wood that leaves at harvest. The model reports that carbon separately so the account still balances.
Lignin:N is the ratio that controls decomposition rate. Pasture at about 2 decomposes fast; cereal straw at about 24 and pine litter at about 40 do not.
Crop coefficients
Monthly Kc, multiplied by reference evapotranspiration to give crop water demand. Values follow FAO-56 adapted to New Zealand growing seasons. A value near zero means the ground is bare or the crop is out of the ground.
Growth distribution
The percentage of the year's above-ground production made in each month. This sets when residues are returned and when the crop is drawing water, and it is what makes a spring-sown crop behave differently from an autumn-sown one on the same soil.
6Amendments and livestock
Organic materials
The column that matters most is carbon per tonne as applied. Dairy effluent at 4% dry matter carries 0.015 t C per tonne, so 100 t/ha delivers about 1.5 t C. Biochar at 90% dry matter and 75% carbon carries 0.675 t C per tonne, forty-five times as much, and four-fifths of it is effectively permanent.
The stable fraction is the share that behaves as already-humified material and joins the mineral-associated pool directly, subject to that pool's saturation limit. The inert fraction is pyrogenic carbon, which bypasses the limit entirely.
What each material is
Livestock partitioning of intake carbon
Grazing removes carbon from the paddock as intake and returns part of it as dung. The rest leaves as animal product, as enteric methane, or as animal respiration. Fractions are of intake carbon and follow the New Zealand agricultural greenhouse gas inventory methodology together with standard digestibility assumptions. Animal respiration is the balance.
7Fertiliser and lime
What the model needs in order to read a fertiliser and liming programme, from data/fertiliser.js. Soil carbon is oxidised by microorganisms, and two of the strongest controls on what they manage to oxidise are the nitrogen supply and the pH; both are set by what is spread on the block, so these three tables sit alongside the soils and the plants rather than outside the model.
Nitrogen sources
The acidity column is the mass of pure calcium carbonate needed to neutralise the acid generated per kilogram of nitrogen applied — the standard agronomic form of the number. Nitrification of one mole of ammonium releases two moles of H+, and taking the resulting nitrate back up consumes one mole of OH−, so the net load runs from nothing, where the plant recovers every nitrate ion, to about 7.1, where every one of them leaches. The values below are the conventional New Zealand and Australian field figures, which sit between those limits; the Fertiliser panel exposes the number directly so it can be moved for a leaky soil or a well-timed dressing.
Liming materials
The calcium carbonate equivalent includes both the neutralising value of the compound and the effectiveness of the usual New Zealand grind, so a tonne of agricultural limestone is worth about 0.9 t of pure carbonate. The carbon column is the carbonate carbon in the product itself, released as carbon dioxide as it dissolves; it is reported beside the organic carbon account rather than inside it, because it is not soil organic carbon and never was. Burnt and hydrated lime carry none: their carbon dioxide was released in the kiln, upstream of this model.
Nitrogen responsiveness of each plant
A multiplier on the production response curve (Eq. 15). One means the plant gives the full published response to fertiliser nitrogen; zero means none. Legumes fix their own and respond hardly at all, established forest is nitrogen-conservative, and a bare fallow grows nothing to respond with. A plant absent from this table takes the default of .
8Process parameters
Every rate constant and response coefficient in the model. The decay constants are potential rates: what the pool would do at 10 °C, optimal moisture and pH 6.5. Every environmental modifier scales them downward, so realised turnover in the field is always slower.
"Sampled" indicates whether the parameter is resampled by the uncertainty run. A few structural constants — the optimum pH, the critical C:N ratio, particle density, the depth lime is mixed through and the methane global warming potential — are held fixed because varying them would confuse the interpretation rather than inform it. Their nominative values are still read by the model and are still editable in the Advanced panel; only their minima and maxima are inert, and the panel greys those out rather than offering boxes that discard what is typed into them.
9Scenarios
The twenty ready-made land uses. Each is a partial state object in data/scenarios.js: anything it does not specify falls back to the model defaults. They are starting points to be edited, not fixed cases.
Three pairs are built for direct comparison. Canterbury irrigated arable against Canterbury no-till separates the effect of cultivation from the effect of residue removal. Drained peat pasture against restored wetland shows the trade of a large carbon dioxide loss for a large methane emission. Pasture with annual compost against pasture with a single biochar application contrasts a recurring labile input with a one-off permanent one.
Every table on this page is generated at load time from the arrays in data/. To add a district, a soil, a crop or a scenario, copy an existing object in the relevant file, change the values and give it a new id. It will appear here and in the model's dropdowns the next time the page loads.