Replenish Rebuilder: Phosphorus Fertility Built Around Soil Biology

A soil can contain a considerable reserve of phosphorus and still struggle to supply enough of it to a growing crop. The challenge is not simply how much phosphorus is in the soil, but how soil chemistry, roots and microorganisms influence its availability.

Replenish Rebuilder brings together mineral-sourced phosphorus and sulphur with activated compost in a granulated product. It is designed to contribute to fertility while working within the biological processes responsible for nutrient cycling.

Supporting the processes behind nutrient availability

Phosphorus is essential for root development and energy transfer, yet its availability is strongly influenced by soil pH, mineral reactions and the activity of roots and microorganisms. Fungi and bacteria participate in organic matter decomposition and phosphorus transformations; living roots contribute exudates that help shape those microbial communities.

Rebuilder combines micronized rock phosphate and sulphur with activated compost. The mineral fraction contributes nutrients, while the compost brings organic material and a diverse microbial component. The long-term interest is the interaction between those ingredients and the biology already functioning in the field—not simply the fertilizer analysis.

Inside Rebuilder: Biome Makers microbial analysis

The manufacturer’s Biome Makers BeCrop analysis detected 1,017 microbial species in Rebuilder, including a range of fungal and bacterial groups. Reported fungal groups included Ascomycota (70%) and Mucoromycota (14%); prominent bacterial groups included Firmicutes (47%) and Proteobacteria (19%).

That diversity makes the product interesting from a biological perspective. But DNA-based profiling identifies organisms detected in the sampled material; it does not measure how many are alive, how well they establish after application or whether they will change crop performance. Those questions need field-level evidence.

Read Replenish’s explanation of the microbial analysis. The full report is embedded below.

What has been measured in the field?

Replenish and Biome Makers also evaluated Rebuilder in a barley study near Strathmore, Alberta. The comparison followed microbial indicators over the growing season under different fertility treatments. The manufacturer reports changes in indicators associated with nutrient cycling, phytohormone production and stress adaptation.

These are useful observations, but they describe the conditions and treatments of that study. A change in a biological indicator is not the same as proof of a repeatable yield increase. We see the trial as a reason to investigate carefully, not as a universal prediction for every field.

Review the Alberta barley BeCrop field study.

A Mineral Multivitamin for the Soil

One of the reasons I like Rebuilder is that we’re not simply adding phosphorus. The rock phosphate brings calcium and a broader mineral package along with it. Calcium is a major part of the phosphate rock itself, and depending on the source it can be the largest mineral constituent listed in a product analysis.

Zinc, Boron, Iron, Copper and Other Trace Minerals

Along with its phosphorus, calcium and sulphur, Rebuilder contains a range of naturally occurring micronutrients, including zinc, boron, iron, manganese, copper and molybdenum. These elements play important roles in plant nutrition, from enzyme activity and chlorophyll formation to reproductive development and nitrogen metabolism.

I like the fact that we’re adding more than one mineral to the soil. The precise amounts and plant availability of these trace elements depend on the mineral source and soil conditions, so I wouldn’t use Rebuilder to replace a targeted zinc, boron or copper recommendation where a soil or tissue test shows a deficiency. But that wider mineral profile is part of what makes it interesting as a soil-building fertilizer.

When I talk to growers, I describe that broader mineral package as a multivitamin for the soil. We still have to address the nutrients a soil test says are limiting, but I like the idea of adding a wider range of minerals alongside activated compost and the biological processes that help cycle nutrients.

Rebuilder’s Ultra-Low Salt Index: About 10× Lower Than MAP

There’s another feature of Rebuilder that deserves more attention: its very low-salt formulation. When fertilizers dissolve around the seed, soluble salts increase the concentration of the soil solution. At sufficient concentrations, that makes it harder for a seedling to take up water. Fertilizer salt index is one way to compare that effect.

A Replenish technical comparison sheet supplied to us lists a salt index of 3.4 for the Rebuilder formulation. New Mexico State University and FAO references list conventional MAP (11-52-0) at 34.2. That’s about ten times the salt index of Rebuilder on an equal-weight-of-product basis, or approximately 90% lower for Rebuilder.

What interests me is the opportunity to bring calcium-rich mineral phosphate, naturally occurring trace elements and active compost into a fertility program without the same soluble salt load as conventional MAP. For crops establishing in dry or challenging seedbeds, understanding the salt load in the seed zone matters.

There are two things to keep separate. MAP is a highly water-soluble, concentrated phosphorus source and remains a valuable starter fertilizer. Rebuilder carries only 17% P₂O₅ compared with MAP’s 52%, and its rock-derived phosphorus follows a different release pattern. A lower salt index does not automatically mean any rate can safely be placed with any crop seed. Soil moisture, opener width, seedbed utilization, crop sensitivity and the complete fertilizer blend still determine placement limits.

The Rebuilder salt-index figure of 3.4 was supplied directly to Peace Soil Works by Replenish. The MAP value of 34.2 comes from published salt-index reference tables. These numbers compare equal weights of fertilizer material, not equal amounts of available phosphorus.

Published MAP salt-index comparison · FAO fertilizer salt-index table · Rebuilder technical sheet

Where mineral nutrition fits

Rebuilder has a guaranteed analysis of 0-17-0-12 (N–P₂O₅–K₂O–S). Its rock-derived phosphorus and sulphur sources do not necessarily behave like highly water-soluble starter fertilizers. Release and crop access depend on soil chemistry, moisture, temperature and biological activity.

In cold spring soils, early phosphorus demand may still justify a readily available starter source. Rebuilder is best evaluated within the full fertility plan, with soil-test results and placement safety considered before any change to seed-row fertilizer.

Building soil health is a management process

Microbial diversity alone does not rebuild soil. Crops, living roots, residue management, organic inputs, appropriate nutrient supply and workable moisture conditions all shape the biological system. Rebuilder can be assessed as one input within that wider strategy.

At Peace Soil Works, our aim is to understand whether a product contributes to improved nutrient cycling and stronger soil function over time. Consistent soil testing, biological measurements where appropriate and paired field strips are more informative than a single-season promise.

What the Crop Trials Have Shown

Rebuilder is interesting because it tackles phosphorus and sulphur from a different direction. That makes field research important: we need to know whether the crop gets the nutrition it needs while we work on the biological side of soil fertility.

In a 2022 irrigated canola comparison near Strathmore, Replenish reported 24 bu/ac where no phosphorus was applied, 45 bu/ac with MAP, 47 bu/ac with broadcast Rebuilder and 49 bu/ac with side-banded Rebuilder. That result gives us a useful reason to study mineral phosphorus sources, placement and nutrient cycling together.

The multi-year Farming Smarter project adds perspective. Here are the reported results against the grower-standard program:

The 2022 wheat crop finished 7.4 bu/ac ahead with Rebuilder, but the 2023 wheat result went the other way. Rebuilder matched the 2022 canola grower-standard yield and was higher in 2023. That’s why I don’t believe in picking one trial number and turning it into a blanket product claim.

For me, the important question is whether Rebuilder can fit the nutrient requirement of a specific field while supporting better long-term biological function. Its BeCrop research looks at microbial indicators; the field trials look at crop performance. Both are worth examining, but they’re measuring different things.

2022 Strathmore canola study · Farming Smarter 2022 report · 2023 report

Further reading

Rebuilder product information (PDF) · Compare Replenish fertilizers · Soil health and nutrient testing.

If you want to explore Rebuilder as part of your soil fertility program, get in touch with Peace Soil Works to discuss the field and your objectives.