Compared to peak oil, climate change, or the water crisis, it's a relatively under reported issue. But the fact is that the world's food production could be severely hit by a global shortage of phosphorus—a key nutrient that is needed to grow crops. And because phosphorus comes from rocks, and is cycled over tens of thousands of years—once it is gone from our soils, it is effectively gone forever, as far as humans are concerned.

So what can we do to prevent this crisis? On the macro-level, we can campaign for more sustainable agriculture, we can eat less grain-fed meat (and campaign for an end to subsidies for livestock), and we can buy organic. We can even support municipal efforts to recycle urine (which is very high in phosphorus). But we can also make changes in our own gardens. Here's how:

Top 5 Tips for Preserving Phosphorus in the Garden

1. Garden Organically: Pretty much everything that makes for good organic gardening, also makes for good stewardship of phosphorus in our soils. Especially recycling animal and plant waste to make compost, and avoiding chemical fertilizers. (Which are, you guessed it, chock full of mined phosphorus!)

2. Give Up Digging: When we till the soil, phosphorus and other nutrients are exposed to the elements and can get washed away. To add insult to injury, while there is a global shortage of phosphorus, we are also seeing water ways that are suffering from an excess due to agricultural run-off. So why not try no-dig gardening for your backyard vegetables? You could even explore edible perennial crops as a means to cut down on digging.

3. Mulch, Mulch, Mulch, Mulch, Mulch: Mulch is good. Need we say more?

4. Garden With Urine: Yes, some people still find this icky—but urine is an incredible fertilizer. Not sure how to do it hygienically? Check out JOsh's post on how to garden with pee, or check out my DIY biochar experiment that may just help prevent nutrient leaching.

5. Homemade Bonemeal: OK, I'll admit, I haven't tried this one, and there's little advice on the internet about how to do it. But given the fact that bonemeal is a phosphorus rich commercial fertilizer, why can't we use the bones from homemade chicken broth to make fertilizer? I have posted on homemade bonemeal over at TreeHugger, and the consensus seems to be burn, bake or dry the bones thoroughly, crush them as best you can, and then add them to the compost pile. We'll see how that works out.

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Salivating over sustainable eats? Learn how to make your own with help from Emeril Lagasse in Planet Green TV's organic cooking show, Emeril Green.