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Complete organic fertiliser, rebuilt for New Zealand

by Seacliff Organics in Information

Yes, Steve Solomon's complete organic fertiliser can be rebuilt from inputs sold in New Zealand: flaxseed meal and mussel meal for nitrogen, ag lime and gypsum for calcium, BioPhos for phosphorus, kelp meal, and a little potassium sulphate. The starting recipe below is for a garden bed that has not been soil tested. Solomon himself says a soil test beats any fixed recipe, and we agree.

One recipe, three versions

Solomon founded Territorial Seed Company and now lives in Tasmania (Solomon 2006a; Bee 2014). His dry mix, complete organic fertiliser or COF, has been printed in his books and in Mother Earth News, and republished with his permission by a garden group there. It has also changed each time he published it. The volumes below are converted from US measures, and the 2012 quantities are per 10 square metres.

Version Nitrogen Lime Phosphorus and kelp Extras Rate per 10 square metres
1993, Organic Gardener's Composting 4 parts seed meal 1 part lime, dolomite preferred on most soils 1 part bone meal or rock phosphate, half a part kelp meal None About 4 litres
2006, Mother Earth News 4 parts seed meal One third of a part each of ag lime, gypsum and dolomite 1 part bone meal, rock phosphate or guano, half to 1 part kelp meal Optional borax, half a teaspoon per 3.8 litres of seed meal 4 to 6 litres, once a year
2012, The Intelligent Gardener About 3 litres oilseed meal 0.5 litre ag lime plus 0.5 litre gypsum, or 1 litre gypsum alone on prairie and desert soils 1 litre soft rock phosphate or bone meal, 1 litre kelp meal About 85 ml potassium sulphate, and optional teaspoons of borax and zinc, manganese and copper sulphates The whole batch, about 6 litres

The 1993 book preferred dolomite on most soils (Solomon 1993). The free copy in the Soil and Health Library now carries his own correction: "This recipe for COF is out of date."

By 2006, the year Gardening When It Counts came out (Solomon 2006c), dolomite was down to a third of the lime (Solomon 2006b). In the companion article he argued that repeated dolomite had left many organic gardens hard and compacted (Solomon 2006a).

By 2012 dolomite was gone, the lime had become a regional choice, and potassium sulphate was added for gardens outside Cascadia, the Pacific Northwest of North America (Solomon 2012). His Tasmanian version of June 2012 keeps dolomite only for very coarse sand with no clay subsoil (Bee 2014).

What stayed the same: five slots

  • A nitrogen meal as the body of the mix. Solomon treats most seed meals as about 6 percent nitrogen and says they take around two months to break down in warm, moist soil (Solomon 2006b; Solomon 2006a).
  • Lime and gypsum as calcium, not as pH correction. He sized the lime to supply calcium, magnesium and sulphur as nutrients without shifting pH much (Solomon 2006a). Lime raises pH. Gypsum usually does not (Chalker-Scott n.d.).
  • A phosphorus source. Bone meal or rock phosphate, with soft rock phosphate his first choice by 2012 (Solomon 2012).
  • Kelp meal for trace elements. In 1993 it was the first thing he would drop if money was short, then the phosphate (Solomon 1993).
  • Optional trace elements, kept small. The 2012 mix is designed to avoid excesses, because a shortage is easy to fix and an excess is not (Solomon 2012). Boron has a very narrow gap between too little and too much (Brdar-Jokanović 2020).

We would not carry over his 2006 target of about 7 parts calcium to 1 part magnesium (Solomon 2006a). A review of the trial evidence found that, within the ranges commonly found in soils, these ratios do not generally affect fertility (Kopittke and Menzies 2007). The workable range is wide: correct the ratio when a test shows it is out, and do not chase a single number.

Why the overseas recipes do not transfer

The published versions call for cottonseed, soybean or canola meal, feather meal, Azomite and guano (Solomon 2012; Bee 2014). Local products differ in strength and in weight per litre, so swapping litre for litre goes wrong.

BioPhos shows why. Its product page gives 1 kg as about 0.5 litre. Solomon's 1 litre of soft rock phosphate per 10 square metres would become 2 kg of BioPhos, or 200 g per square metre. That is four times the top rate printed on the same page (25 to 50 g per square metre). The recipe has to be rebuilt by weight and analysis, then converted back to scoops.

The lime choice needs a local answer too. Solomon uses lime plus gypsum where the land once grew forest, and gypsum alone on prairie or desert soils (Solomon 2012). Forest is thought to have covered more than 80 percent of New Zealand before people arrived (Stats NZ 2015), so the forest option is the default here.

A New Zealand starting recipe

[DAN SIGN-OFF NEEDED: the proportions in this table are a proposal. The reasoning and assumptions are listed in decisions_for_dan.]

One batch covers 10 square metres, once a year, worked into the topsoil before planting. Weights come from the volume and weight figures printed on each product page.

Job Product By volume By weight Grams per square metre
Nitrogen Flaxseed Meal 2 litres 1.25 kg 125
Nitrogen Mussel Meal 1 litre 600 g 60
Calcium Superfine AgLime 500 ml 520 g 52
Calcium and sulphur Gypsum 500 ml 450 g 45
Phosphorus BioPhos 250 ml 500 g 50
Trace elements Acadian Kelp Meal 600 ml 240 g 24
Potassium Potassium Sulphate 85 ml (one third of a cup) 120 g 12
Total About 4.9 litres 3.68 kg 368

Notes on the choices:

  • Two parts seed meal to one part of a stronger animal meal follows the blend Solomon thought probably best, which used feather and fish meal (Solomon 2012). We do not sell feather meal, so mussel meal fills that slot.
  • Mussel meal alone is an option: about 2.2 litres (1.3 kg) carries the same nitrogen, with more sodium (3.6 percent on its product page).
  • Karanja or neem seed meal can replace part of the flaxseed meal. Lucerne meal (an estimated 3 percent nitrogen) is too weak to carry the mix.
  • Colloidal Soft Rock Phosphate can replace BioPhos at Solomon's own measure of 1 litre (1.3 kg).
  • The potassium sulphate rate is Solomon's. Its product page prints no analysis [LAB RESULT NEEDED: potassium and sulphur percent for Potassium Sulphate].
  • No dolomite, borax or metal sulphates. Those come from a soil test, not a recipe.

For hungry crops, side-dress with flaxseed or mussel meal alone. Do not repeat the full mix in the same year, because it carries lime (Solomon 2006a).

Worked example: what 10 square metres receives

Nitrogen. Using the percentages printed on the product pages:

  • Flaxseed meal: 1,250 g x 4.8 percent = 60.0 g
  • Mussel meal: 600 g x 8.6 percent = 51.6 g
  • Kelp meal: 240 g x 0.8 percent = 1.9 g
  • Total: 113.5 g of nitrogen, or 11.4 g per square metre

Solomon's 3 US quarts per 100 square feet is 2.84 litres over 9.29 square metres, or 3.06 litres per 10 square metres. If his seed meal weighs the same as our flaxseed meal (0.63 kg per litre) and holds 6 percent nitrogen, that is 3.06 x 630 g x 6 percent = 116 g. The two mixes carry about the same nitrogen.

Not all of it is available at once. Oregon State University's model predicts that 75 percent of the nitrogen becomes plant available within 10 weeks when a product holds 6 percent nitrogen or more, and less below that: for 4.8 percent, (15 x 4.8) minus 15 = 57 percent (Sullivan et al. 2019). That gives 60.0 x 0.57 = 34.2 g from the flaxseed meal and 51.6 x 0.75 = 38.7 g from the mussel meal: 72.9 g, or about 7.3 g per square metre. The model was built on Pacific Northwest trials of manures and of seed, fish and animal by-product meals, not mussel meal, so treat that figure as an estimate.

Boron. Kelp meal: 240 g at 90 parts per million = 21.6 mg. Mussel meal: 600 g at 32 parts per million = 19.2 mg. Total 40.8 mg, or about 4 mg per square metre. Solomon's optional borax dose is half a gram of boron per 100 square feet, or 54 mg per square metre. Kelp is a light top-up, under a tenth of that, not a boron correction.

When a fixed recipe is the wrong tool

A recipe is a set of guesses about your soil. Solomon lists where his own fail:

  • After about three years of use. He recommends a full soil test at that point, because the mix can build calcium, magnesium or phosphorus too high (Solomon 2006a).
  • Where pH is already 7.0 or higher (Solomon 2006b).
  • In dry climates, where soils can already be high in calcium, magnesium or sodium and extra lime can do harm (Solomon 2006a).
  • Whenever the garden matters to the household budget. His advice is to test first and buy only what the soil needs (Solomon 2012).

We would add three more. This recipe is for garden beds in mineral soil, not for pots or a living soil that was amended when it was made. Licensed medical cannabis cultivators should work from tests of their own media. And gypsum is only worth adding where calcium or sulphur is short: a Washington State University extension fact sheet concludes that most urban soils are not improved by it (Chalker-Scott n.d.). If your test shows plenty of both, leave it out.

With a Hill Laboratories report in hand, use the soil planner, which works from your numbers. For rates per square metre by crop, use the fertiliser calculator.

What to do

  1. Small garden, no soil test: spread one batch per 10 square metres once a year and work it in before planting.
  2. Add a thin layer of compost. Solomon pairs the mix with about 6 mm a year (Solomon 2006b).
  3. Side-dress hungry crops with a nitrogen meal only, never a second dose of the full mix.
  4. Within three years, or sooner for a market garden, get a soil test and move to the soil planner.
  5. Solomon's books, including the free library copy of Organic Gardener's Composting, are on our Books page.

References

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