[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
http://www.energybulletin.net/node/47740
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.


Phosphorus Molecules

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 
cars.

     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 
forever.

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, 
isn’t it?


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 
degraded soils?

References:

(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 
15.09.2008.

(6) Ibidem, p. 116 - 117.

(7) Production and International Trade Statistics, International 
Fertilizer Industry Association (IFA), 
http://www.fertilizer.org/ifa/statistics/pit_public/pit_public_statistic..., 
accessed 14.09.2008.

(8) S. M. Jasinski, Phosphate Rock, Mineral Commodity Summaries, January 
2008, p. 124, (available at: 
minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/).

(9) Ibidem.

(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, 
http://www.theecologist.co.uk/pages/archive_detail.asp?content_id=424.

(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. 
http://www.feasta-multimedia.org/2008/seminars/Bruce_Darrell.mov

(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
http://www.energybulletin.net/node/47474
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Original article available here:
http://permaculture.org.au/2009/01/14/phosphorus-matters



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