John KempfRegenerative Agriculture Entrepreneur

Whiteboard: Cover Crop in a Jug

17 Sept 2025 · 3 min

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2:43

John Kempf explains the origin and effects of a product called Rejuvenate, originally developed as a residue digester for corn residue. He reports that Rejuvenate markedly increases nutrient availability by releasing nutrients from the soil mineral matrix—examples include calcium increases up to ~40%, and phosphorus and potassium increases of ~20–30% (potassium sometimes rising from ~60–70 ppm to ~150 ppm). He notes the product was developed ~15 years ago, provided strong ‘cover crop–like’ benefits (growers called it a “cover crop in a jug”), but its input costs have risen over time, reducing its previous cost advantage.

Questions this video answers

In extreme cases, available calcium increased by about 40%.

Available phosphorus and potassium increased by about 20–30%.

Potassium increased from about 60–70 ppm up to approximately 150 ppm in some cases.

About 15 years ago.

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The question that we should ask ourselves is what can we do to produce this similar type of response even in very difficult conditions? And when we want to experiment and try this approach on new soils that don't have a history of COVID crop applications, but where we need a strong fertilizer and nutrient response immediately in this coming year, what is it that we can do quickly that has very strong economic benefits? And so to. To replicate what a cover crop can do with root exudates in, in releasing these soil nutrients. Years ago, we developed a product called Rejuvenate that was developed initially. The, the initial purpose for developing it was as a residue digester to speed up residue decomposition for corn residue in particular. And we discovered to our surprise, that rejuvenate had a marked effect on increasing nutrient availability to such a degree. We have a number of soil analysis of treated and untreated side by side field split field applications where available calcium levels would jump by, in extreme cases as much as 40%. Available phosphorus and potassium levels would jump by 20 to 30%. You might take a soil from 60 or 70 parts per million, all the way up to 150 parts per million potassium. So there's these tremendous increases in nutrient availability that showed up in soil as nutrients were extracted and were released from the soil mineral matrix. But the challenge with rejuvenate, as time has gone by, the materials that go into it have inflated in cost, as has everything else. And rejuvenate, 15 years ago, when we first developed it was a very inexpensive material to apply. And today it's no longer as inexpensive as it was. So Rejuvenate had a lot of horsepower in the context of releasing nutrients. So much so that we had a group of growers in the New England states and in various areas where they had very challenging soils and challenging fall conditions for establishing a cover crop. And their nickname for Rejuvenate became a cover crop in a jug because they saw the same types of soil aggregation benefits, the same types of nutrient release benefits, the same types of benefits that they were getting from a cover crop, but just resulting from a single application to the soil.