Dear Master Gardeners,

Some MGs might find interesting an article that I’ve just co-written on “Peak Phosphorus” and what it means for agriculture.

Also at The Oil Drum (which has 102 comments)

Background reading (may be easier to start with):

As we know from our MG training, phosphorus is one of the three macro-nutrients required by plants. Farmers (both organic and non-organic) use the phosphorus from rock phosphates as fertilizer to replenish the amount used up by crops.

The main points of the article are widely accepted:

  • Phosphates suitable for mining are limited.

  • Modern agriculture needs large amounts of phosphorus to raise enough food for the world population.
  • World demand for phosphorus has grown dramatically during the past decades and shows no sign of declining.
  • There is no substitute for phosphorus.
  • Phosphate production will probably follow a bell-shaped curve, with the most accessible deposits mined first.
  • We currently waste a heck of a lot of phosphorus.

What is new and controversial in the article is the assertion that we have passed the point of “Peak phosphorus” – the point of maximum production and consumption of phosphorus. This would mean that over time phosphorus will become more difficult to obtain, and more expensive. This would be a major problem for society, since without sufficient supplies of phosphorus we will have difficulty feeding ourselves.

My co-author Patrick Déry came to the conclusion that we have passed peak phosphorus by running statistical analyses on data from the US Geological Survey (estimates of phosphate reserves and production). The specific dates for peak phosphorus are what are controversial. The fact that we will run out of phospate deposits is not in dispute. At some point, we will inevitably face a phosphorus problem.

Bottom line for Master Gardeners:

  • Growing food will become much more important than it is now. Our skills and knowledge will be in even greater demand.

  • Recycling nutrients, e.g. through composting, will become more important. Expect to hear more about schemes like “urine diversion” and “humanure.” .
  • If I remember correctly, we in Santa Clara are blessed with soils that are abundant in phosphorus. Perhaps an MG expert can verify.