[permaculture] Phosphorus matters: soil erosion & contamination | Energy Bulletin
Lawrence F. London, Jr.
venaurafarm at bellsouth.net
Tue Dec 8 17:29:52 EST 2009
Phosphorus matters: soil erosion & contamination | Energy Bulletin
Published Jan 14 2009 by Permaculture Research Institute of Australia,
Archived Jan 15 2009
Phosphorus matters: soil erosion & contamination
by Marcin Gerwin
Part One: Closing the Phosphorus Cycle
Phosphate mine on Nauru island.
Currently part of it is reforested.
Photo: Jon Harald Søby
It might sound ridiculous, but for every container of bananas, coffee,
tea or cocoa imported, we should send back a shipment of a fluffy,
earth-like smelling compost. Why is that? With each container of food we
import nutrients taken up by plants from the soil. We import calcium,
potassium, magnesium, boron, iron, zinc, molybdenum, copper and many
others. One of the essential elements imported in food is phosphorus.
For every ton of bananas we import 0.3 kg of phosphorus, for every ton
of cocoa it’s 5 kg and for ton of coffee it’s 3.3 kg of phosphorus. Tea
is a bit more complicated, because the amount of phosphorus depends on
the origin of tea - for example in 1 ton of tea leaves harvested in Sri
Lanka there are some 3.5 kg of phosphorus, while tea from South India
contains 6.6 kg of phosphorus (1).
Each year some 13.5 million tons of bananas alone are exported around
the world (2), containing 4,000,000 kg of elemental phosphorus up taken
by the plants from tropical soils. And most of this phosphorus never
comes back to the soil it was removed from. Yes, but can’t the farmers
replace the nutrients lost using fertilizers? That’s what the
fertilizers are used for, are they not? Sure they can. Farmers can buy a
bag of ground phosphate rocks or guano (bird or bat droppings) or even a
bag of artificial fertilizer such as superphosphate if they don’t farm
organically. No problem. They can replace every kilogram of phosphorus
taken from the soil by plants and sent overseas with their produce.
So, why should we send compost back on ships? This would add extra cost
to the imported food and make it much more expensive! We should start
closing nutrients cycle soon, because the world reserves of phosphate
rocks, which are used for the production of phosphate fertilizers, are
declining. They can be depleted even this century (3).
The problem with the lack of phosphate fertilizers does not start,
however, when all phosphate rock reserves are gone. It starts as soon as
the demand for phosphate fertilizers exceeds the supply of phosphate
rocks available for export, meaning: farmers living in countries that do
not have a local source of phosphate rocks would like to buy phosphate
fertilizers, but there are not enough bags for everyone. And this
situation may appear within the next 10-20 years.
This short timeframe is based upon the assumption that the demand for
phosphate fertilizers will continue to grow and that within 10-20 years
US reserves of phosphate rocks available for mining will be considerably
depleted and USA will have to rely on imported phosphorus. It is unclear
whether the phosphate exporting countries will be able to respond
adequately to keep up with the rising demand by opening new mines or
increasing production in the existing ones, which otherwise could lead
to lack of sufficient amount of phosphate fertilizers on the market. A
50% rise in the US imports would require 50% rise of present world
phosphate rock exports. A similar situation may exist in countries other
than USA, but it was not taken into consideration due to lack of
sufficient data. Demand for phosphate fertilizers in the USA may drop,
however, owing to fall of agricultural production caused by droughts,
depletion of water resources or by other climate related events. This
could slow down domestic production of phosphate rocks and conserve
these resources for a longer period of time.
What plants need Phosphorus for?
White sweetclover. Photo: Kristian Peters
Phosphorus is one of the key mineral nutrients that are necessary for
plants growth. Phosphorus stimulates root growth, flowers blooming and
seed development. It is an essential component of DNA, RNA, cell
membranes, sugars and carbohydrates (4). Without phosphorus plants just
don’t grow and there is no substitute for it. Although in many soils
there are large reserves of phosphorus, it is often present in the form
that cannot be used by plants (such as insoluble calcium or aluminum
phosphate salts). Some plants, however, like white or yellow sweet
clover for example (5), can mobilize phosphate by secreting organic
acids (when harvested they can be used as a green manure with high
phosphorus content), but far more efficient for this job are mycorrhizal
fungi and microbes that secrete enzymes, various acids and chelating
agents that turn organic and inorganic phosphate into a solution that
can be taken up by plants (6). Nevertheless, when the content of
phosphorus in the soil is low, all that farmer can do is to bring in
some kind of phosphate fertilizer.
How much phosphate rocks is available for export?
Worldwide approximately 30 millions tons of phosphate rocks are exported
every year, mainly from Africa (62.8% in 2006) (7). It sounds like a
lot, but it is less than is needed for the consumption of a single
country - the USA - the largest consumer, producer and supplier of
phosphate fertilizers in the world. In 2006 the USA consumed 32.6
millions tons of phosphate rocks (8). Fortunately, USA is currently
almost self-sufficient in production of phosphate rocks. In 2007 US
imports accounted only for 2.8 millions ton of phosphate rocks (8.6%)
and 99% of it came from just one origin - Morocco.
Phosphate rocks mine in Togo.
Photo: Alexandra Pugachevskaya
However, the reserves of phosphate rocks in USA are limited. In 2007
there were only about 1,200 millions tons left (9). As soon as USA runs
out of its phosphorus there will be a huge demand for the phosphate
rocks. When might this happen? If the consumption in the USA continues
to grow, the US domestic reserves could be gone in 25 years (10). At the
current rate of production this could be in around 40 years. Most of the
phosphate rocks in USA are mined in Florida and according to Stephen
Jasinski from the U.S. Geological Survey “production in Florida could
begin to drop in about 5 years or imports will be needed if the new
mines are not opened (11).”
Demand for fertilizers is growing at the rate of 2.8% per year (12). It
is expected to continue to grow, because fertilizers are needed to feed
the increasing human population and to satisfy the need for biofuels.
The acreage of industrial farms around the world which rely on
artificial fertilizers may still increase in the years to come (e.g. in
Russia, Brazil or even Madagascar) and in consequence the overall demand
for phosphate fertilizers will rise. Certified organic farms can also
use phosphate rocks (in unprocessed form), when phosphorus is deficient
in the soil.
There are many countries like India, Australia, Poland and most of the
Western European countries which are completely dependent on imports of
phosphate rocks for fertilizing soils and growing food. And we import it
mainly from Morocco as well. Without phosphate fertilizers yields of
wheat, maize, tomatoes, strawberries, potatoes and many other crops will
drop and eventually they could even fail. In Poland we have huge
reserves of phosphate rocks. The problem is that the content of
elemental phosphate in these rocks is low, they are located under
villages, forests or farmlands or there is too much water in the mines
to continue extraction.
However, if we manage to close the phosphorus cycle, there’s no need to
worry about phosphate rock reserves. What we have mined so far can
circulate from farm to table and back again, without depleting the
soils. Let’s have a closer look where the phosphorus is leaking now.
Where does the phosphorus go?
In tropical climate phosphorus can be lost as soon as the farmer burns
the rainforest to clear the site. Most tropical soils are poor in
nutrients, and phosphorus is stored not in the soil, but in the
vegetation. When rainforest is burnt phosphorus is left in the remaining
ashes, but these ashes can be washed away by rains very quickly. There
may be some old branches or unburnt leaves left on the ground and
microbes can feed on them releasing phosphorus to the crops for some two
years. But later on, when there are no more sources of phosphorus for
the microbes to feed on and to release for plants, the land becomes
infertile. And the farmer? If he cannot afford to buy commercial
fertilizers he burns down another patch of the rainforest or he is
forced to move to the city. There are more than 300 million
slash-and-burn farmers worldwide, each one clearing about a hectare of
forest a year (13).
On many farms, however, fertilizers are applied and farmers continue to
grow crops. Some minimal amounts of phosphorus may leach from farm to
groundwater, especially when artificial soluble fertilizer is used (such
as superphosphate) (14). Most phosphorus losses occur through surface
soil erosion, when soil is washed away by strong rain, or through
harvesting of plants. Runoff of the nutrient rich water from the fields
into the streams, lakes and oceans often causes explosion of the algae
population and can lead to depletion of oxygen, seriously affecting
aquatic animals and even coral reefs.
And what was the former one? Harvesting of plants? That’s right. With
each apple, carrot, cucumber, coffee, cherry or watermelon a small bit
of phosphorus is taken away from the soil. It can be eaten by the farmer
and his family or loaded on truck and transported to the market. It can
be also shipped overseas to the foreign supermarkets. So long nutrients!
Have a good time in Italy or France! Please come back… one day.
Phosphate processing plant in
Soda Springs, USA, operated by Monsanto.
Source: The Center for Land Use Interpretation
Before food reaches the table many crops are processed and there are
various residues left which contain phosphorus, e.g. orange peels or
rice husks. They are either composted or sent to landfill. Then,
finally, the consumer prepares a meal from the food that farmers
harvested, and then leftovers with the precious phosphorus are thrown
into the garbage or on the compost pile. The meal is eaten and out of
the pizzas, spaghettis and apple pies only less than 1% of phosphorus is
absorbed by our bodies (15) and remaining 99% is, in industrialized
countries, flushed down the toilet. The content goes to a wastewater
treatment plant. Treated biosolids from the treatment plants are reused
as soil amendments or sent to the landfills. Part of the phosphorus from
the wastewater treatment plant is discharged with treated water into the
rivers or the sea.
Not all phosphate rocks are used for production of fertilizers. Around
5% are used as animal feed supplements and another 5% for industrial
applications, e.g. for the manufacture of detergents. Some of us (like
the author) are allergic to phosphates in soaps or washing powders and
are a living proof that we do not need to use them at all. There are
plenty of natural soaps and washing powders without phosphates we can
buy or we can make our own.
Phosphate is used also for production of glyphosate, a herbicide which
is known under a trade name Roundup. The manufacturer of Roundup,
Monsanto, owns even a whole phosphate mine and rock processing plant in
Idaho, USA. Luckily, organic gardeners don’t have to spray any of these.
A much better idea would be to use the remaining phosphate rock reserves
to restore degraded lands, rather than to produce herbicides or detergents.
Closing the nutrients cycle
Ideally the same amount of nutrients that left the farm should come back
to it. To achieve this goal we should compost or ferment all residues
from farms, food processing plants and households and make them
available for farmers. And yes, we need to compost urine and feces as
well. There are many types of compost toilets, including the simplest
sawdust toilet to the commercial types with electric fans. If handled
properly they don’t smell badly and the final product of the compost
toilet is just a plain ordinary compost. It can be collected in the city
in special containers, standing along the curb near the containers for
recycling glass and plastics. Joseph Jenkins’ “Humanure Handbook” is a
great resource on the subject.
All organic waste can be collected as a part of a municipality recycling
program and leftovers from the kitchen can be picked up weekly from the
separate curbside container. For backyard gardeners and farmers who eat
their own food there are many methods of composting to choose from –
buckets, triangle cages, compost tumblers, worm composting, loose heaps
or classic wooden containers. There are even composters which can be
kept directly in the kitchen without any suspicious smells.
It seems also a good idea to extract carbon and hydrogen from the food
residues in the form of biogas which is primarily methane (CH4). It can
be used for cooking, heating, electricity generation or for powering
vehicles. The exciting thing about biogas is that we don’t waste any of
the minerals from the organic matter - carbon is taken by plants from
the air in the form of carbon dioxide and hydrogen comes from water.
After fermentation process in a biodigester the organic matter is still
perfectly useful as a fertilizer.
If the resources of phosphate rocks become depleted this organic waste
recycling program will be crucial for farmers. They will be able to buy
or receive finished compost according to the amount of food they sold.
It may sound absurd, but the content of phosphorus or other nutrients in
crops may eventually be counted in the future, so that we can determine
how much compost the farmer should receive. Ideally local food should be
involved in this scheme to minimize transport needs. And what about the
food from overseas farms like coffee or tea? Well, things get much more
complicated here. Theoretically, we could exchange nutrients in the form
of food, so that for every kilogram of coffee would send back wheat or
barley with the equal content of phosphorus. What farmers can do now is
to bring compost from the cities, where people eat imported food. The
other option is sending compost back. Hmm… Wouldn’t it be just perfect
to have a village scale economy where all nutrients would circulate
without cars, trucks, cargo ships and complex municipality programs?
Growing food security
Trees in bloom in the Hunza
Valley. Photo: bongo vongo
In places like the Hunza Valley (currently northern Pakistan) and many
others around the world, people have grown food in one place for
hundreds of years without depleting the soil. As Rob Hopkins writes in
his Transition Handbook about the Hunza Valley:
Here was a society which lived within its limits and had evolved a
dazzlingly sophisticated yet simple way of doing so. All the waste,
including human waste, was carefully composted and returned to the land.
The terraces which had been built into the mountainsides over centuries
were irrigated through a network of channels that brought mineral-rich
water from the glacier above down to the fields with astonishing precision.
Apricot trees were everywhere, as well as cherry, apple, almond and
other fruit and nut trees. Around and beneath the trees grew potatoes,
barley, wheat and other vegetables. The fields were orderly but not
regimented. Plants grew in small blocks, rather than in huge
monocultures. Being on the side of a mountain, I invariably had to walk
up and down hills a great deal, and soon began to feel some of the
fitness for which the people of Hunza are famed. The paths were lined
with dry stone walls, and were designed for people and animals, not for
People always seemed to have time to stop and talk to each other
and spend time with the children who ran barefoot and dusty through the
fields. Apricots were harvested and spread out to dry on the rooftops of
the houses, a dazzling sight in the bright mountain sun. Buildings were
built from locally-made mud bricks, warm in the winter and cool in the
summer. And there was always the majestic splendour of the mountains
towering above. Hunza is quite simply the most beautiful, tranquil,
happy and abundant place I have ever visited, before or since (16).
Rakaposhi mountain near the
town of Gilgit, Hunza Valley.
Photo: bongo vongo
Villages can provide a good life and it is easy to design a local food
system that ensures food security there. Food security means that all
people have access to safe, nutritious and affordable food, at all
times, without degrading the supporting systems (17). No matter if your
food comes from the grocery store or the backyard garden, it contains
some amount of nutrients it has taken up from the soil where it was
grown. If we wish to sustain fertility of our soils, and thus food
security, we need to return these nutrients to the soil, so that our
tomatoes, corn and apple trees will be able to grow and produce crops
In a natural environment this nutrients cycle is supported by a myriad
tiny creatures. There are bacteria and fungi in the soil that hold the
nutrients and extract them from rocks or the air. There are nematodes,
protozoa, arthropods and earthworms that cycle these nutrients and make
them available for plants (18). We, humans, are also a part of the soil
food web. Our job is to return the wastes to the soil. We can design our
farms so that they will work just like natural systems, cycling the
nutrients over and over again. A good example of such a system in an old
growth forest. It doesn’t need fertilizing, weeding or irrigating. It
grows by itself and it is always productive. That’s a clever system,
Beach in Sopot, Poland. Photo: Marcin Gerwin
We can design for food security in cities as well, but it’s not as easy
as in villages. Most people living in the cities buy food rather than
grow it on their own, so the whole economic system must be working
properly, so that they will be able to afford it. The food shortages in
2008 around the world were not caused by a lack of food, but because
people didn’t have money to buy it. The first thing to do would be to
start growing food right in the city. On vacant parking lots, on roofs,
in backyards. But what if there is not enough space? I live in a small
city on the coast of the Baltic sea. Sopot is a summer resort bordered
by the sea, a landscape park and two large cities. The land here is
among the most expensive in Poland. There is no way one could buy a
vacant lot for a vegetable garden, it would cost a fortune. We do have
many allotments, but there’s not enough for everyone. So, what can we do?
Wooden pier in Sopot. Photo: Marcin Gerwin
Right now access to food is not a problem. It is available in every
grocery store and in all supermarkets. It’s not an issue. With peak-oil
or unexpected weather events this could change. With the lack of
phosphate fertilizers it could change as well. A large portion of food
in Poland is grown in the conventional way and farmers apply artificial
fertilizers and spray pesticides. Some of them believe that plants
without fertilizers don’t grow, so I think it may be a little hard to
try to convince them to use compost instead of the factory-made fertilizers.
I also find it hard to believe that everyone in Sopot could easily
accept compost toilets. We would have to recover nutrients from the
treatment plant, which is located… er… I must admit I don’t know where
our sewage goes to. We will have to collect organic waste, however,
that’s what the European Union regulations will make us to do in the
years to come (you see, there are some positive aspects of our county
being an EU member). We could also start a co-operation program with the
farmers from the area, who could supply food directly to our city,
rather than through distributors. We could have long-term contracts with
them, just like in the Fairtrade scheme. We could set a guaranteed
minimum price for farmers, so that their security would improve as well.
And what if the economic system collapses? Then we need a land reform.
In the next part of the Phosphorus Matters: what can we do to restore
(1) Phosphorus content in food based upon: Organic Farming in the
Tropics and Subtropics: Exemplary Description of 20 Crops, Naturland,
second edition 2001.
(2) Calculated from: Banana facts, IITA Research for Development Review,
http://r4dreview.org/2008/09/banana-facts/, accessed on 14.09.2008.
(3) D. Cordell, S. White, The Australian Story of Phosphorus, 2008, p. 1.
(4) S. B. Carrol, S. D. Salt, Ecology for Gardeners, 2004, p. 149.
(5) Sweetclovers, UC SAREP, Online Cover Crop Database,
http://www.sarep.ucdavis.edu/cgi-bin/ccrop.EXE/show_crop_41, accessed on
(6) Ibidem, p. 116 - 117.
(7) Production and International Trade Statistics, International
Fertilizer Industry Association (IFA),
(8) S. M. Jasinski, Phosphate Rock, Mineral Commodity Summaries, January
2008, p. 124, (available at:
(10) D. Cordell, S. White, op. cit.
(11) S. Jasinski, Phosphate Rock (Advance Release), 2007 Minerals
Yearbook, p. 56.3.
(12) P. Heffer and M. Prud’homme, Summary Report “Medium-Term Outlook
for Global Fertilizer Demand, Supply and Trade: 2008-2012”, 76th IFA
Annual Conference, Vienna, May 2008, p. 4.
(13) D. Elkan, The Rainforest Saver, The Ecologist Magazine, 01.02.2005,
(14) S. B. Carrol, S. D. Salt, op. cit., 117.
(15) T. N. Neset, L. Andersson, Environmental impact of food production
and consumption, in: Water for Food, 2008, p. 102.
(16) R. Hopkins, The Transition Handbook, 2008, from the introduction.
(17) For more information on food security watch presentation given by
Bruce Darrel: Converging Crises, Policy Responses: Planning For Food
Security, Festa Seminar Series, June 19th, 2008.
(18) The soil food web is described in detail in the excellent book
Teaming with Microbes by Jeff Lowenfells and Wayne Lewis.
~~~~~~~~~~~~~~~ Editorial Notes ~~~~~~~~~~~~~~~~~~~
Marcin Gerwin graduated with a Ph.D. in political studies, from the
University of Gdansk, Poland, with his thesis: “The idea and practice of
sustainable development in the context of global challenges”. He is a
co-founder of "Earth Conservation", a small NGO from Poland working for
sustainable development. Please see his previous article on Energy
Bulletin here. KS
Original article available here:
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