Phosphorous scarcity?

Phosphorus is an essential nutrient for all plants and animals. We get our P through the food we eat, which has been fertilized by mineral or organic P fertilizers. Indeed, 90% of the P society uses is for food production. Modern agricultural systems are dependent on continual inputs of P fertilizers processed from phosphate rock. Phosphate rock is mined in only a few countries, including China, the US and Western Sahara/Morocco. Yet these P reserves are becoming increasingly scarce. Studies suggest current reserves will be depleted within 50-100 years. Further, a global peak in P reserves could occur by 2040. While the exact timing might be disputed, it is widely accepted that the quality of P rock is decreasing and cost increasing. The price of phosphate rock has risen seven-fold in the last 14 months alone.The P situation has many similarities with oil, yet worse than oil, there is no substitute for P in food production.

http://www.phosphorusfutures.net/
Yet another argument for sustainable agriuclture, that recycles nutrients as much as possible within the farm.