Edible Landscaping

Charlie says… Find Alternatives to Rock Phosphate Fertilizer

Phosphate fertilizers may become more scarce and expensive in the future, so consider using alternatives, such as cover crops and animal manures, to boost low phosphorous soils.

Edible gardeners know that phosphorous is a key nutrient for vegetable, fruit, and berry production. Phosphorous is essential for root crops such as beets, carrots, and potatoes. It also helps with flower and fruit production and shoot and leaf growth. Most commercial phosphorous fertilizer is derived from mined phosphate rock extracted from China, the United States, and the western Sahara in Africa. We're all familiar with forms such as super phosphate, triple super phosphate, and rock phosphate. Whether it be rock powder or a conventional fertilizer, it's from this mined rock that phosphorous fertilizer comes.

Now concern is arising that we may be coming to the end of cheap phosphorous fertilizer (similar to the end of cheap oil). Peak phosphorous may occur as soon as 20 years from now, making the existing quarries of phosphorous very precious and the fertilizer very expensive. Sensing a potential shortage, the U.S. no longer exports rock phosphate, and China has severely restricted their exports.

This may severely affect yields of many crops on farms and in gardens. The solution is to use the natural phosphorous in the soil more efficiently. Adding animal manures, growing tap-rooted cover crops such field peas that mine phosphorous from the subsoil, and considering using human manures are all ways to maximize the preservation of phosphorous in your garden. While you may not be ready to install a composting toilet, cover cropping and using animal manures could be good practices to use to wean us off their dependence on commercial phosphate fertilizer.

For the complete report, go to the Soil Association.

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