Abstract SYMPHOS 2011

PHOSPHORUS, CROPS AND FOOD
Agriculture & fertilization CP6
Dr. Donald L. Smith
Plant Science Department, McGill University, Macdonald Campus
Ste. Anne de Bellevue, Quebec, Canada H9X 3V9
Phosphorus is one of the three crop plant macronutrients contained in almost all fertilizers applied to agricultural
lands. In plants large pools of phosphorus reside in DNA and RNA and in the phospholipids of membranes.
A smaller pool is in ATP, where phosphorus plays a pivotal role in energy metabolism, including photosynthesis.
Finally, phosphorylating and dephosphorylating proteins is a key mechanism for regulating protein conformation
and enzyme activity, including the enzymes that regulate the cell cycle. When other growth requirements are not
limiting crops have a very clear pattern of yield response to phosphorus fertilizer additions.
This has been a very important contributing factor in increased global food production over the last six decades, and
has allowed food production to keep pace with population growth during that time.
However, application of large amounts of fertilizer phosphorus has also been an important contributor to
agricultural pollution of water, contributing to eutrophication of rivers and lakes and even, in some cases, the
development of “dead zones” in the open ocean.
Agricultural phosphorus utilization has continued to expand in response to food requirements, however, there is
now concern that we will reach “peak phosphorus” extraction sometime in the reasonably near future (perhaps
only a few decades from now).
If this is so it poses an important challenge to global food security. The thinking on peak phosphorus has paralleled
that of peak oil and assumes a more or less bell shaped curve of extraction rate.
Clearly, there are things that can be done to mitigate this, and phosphorus recycling is the most obvious. It may
well be possible to integrate a biogas biofuel approach whereby municipal sewage treatment plants produce and
sell biogas into energy markets and use the returns to extract and recycle phosphorus from the remaining sludge,
selling this back to the agricultural sector.
Food prices are already rising, in part because of higher energy prices and diversion of food material into biofuels.
If we are going to avoid a potentially serious problem with world phosphorus and global food production levels we
should begin broader and more integrated phosphorus management activities quite soon.
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