Soil and Climate - Soil: Reflections on the Basis of our Existence - page 129

prices rose seven-fold in just 14 months in 2007 and 2008 and a major headache
is likely when phosphorus runs out. We must develop agricultural methods that are
much less phosphorus-intensive if we are to feed the world in the future.
Constant development is driving new solutions and approaches. To reduce
fossil fuel use, nitrogen fertiliser factories can run on biofuel or, as in the case
of a plant currently being built in Minnesota, on wind power. This facility will
produce only a fraction of the fertiliser that could be produced in an oil-powered
plant, but when oil eventually runs out this may well become a preferred method.
Technology exists today for extracting phosphorus and other minerals from sew-
age sludge, but the question is whether this will be enough. Or, to put it another
way: for how many people will it be enough?
Perhaps the use of mycorrhizal fungi will catch on in the future. The fungi are
disadvantaged in modern agriculture not only by artificial fertiliser but also by
heavy machinery, which destroys their intricate hyphal networks. Plough-free crop
growing systems are best for mycorrhizal fungi. Organic farming requires inten-
sive mechanical intervention to keep weeds at bay, which is also deleterious to
mycorrhizal fungi. On the other hand, phosphorus content is low in organically
farmed soil and organic crops often have superior mycorrhizal fungi networks
compared to conventional crops. Trials in Canada have shown that wheat and lentil
harvest volumes can be increased by 6 and 26 % respectively if mycorrhizal fungi
are added to the soil and use of phosphorus-based fertiliser is reduced by a third.
Lentil yields benefit more than wheat because the latter is a grass with an intricate
root system that enables the plant to fare relatively well even without fungal help.
Legumes such as lentils have coarse roots that rely on fungi to absorb enough
phosphorus. Estimates indicate that mycorrhizal fungi can grow hyphae whose
combined length can stretch to several hundred metres in just a single gram of soil.
What mycorrhizal fungi cannot do is create new phosphorus, so we have to
learn to use this resource more wisely than we do today. In Sweden, large quanti-
ties are lost in agricultural runoff into the Baltic Sea, where it causes toxic algal
blooms. Farmers in south-east Asia have long used human faeces and urine as fer-
tiliser. These are resources we will not be able to afford to ignore in the future.
Only time will tell whether technological progress can enable phosphorus separa-
tion during wastewater treatment or even in our toilets. The phosphorus contained
in a person's urine is sufficient to produce at least half of the food that person eats.
Urine also contains nitrogen and potassium, both essential elements for plants.
Perhaps we will succeed in squaring the circle to ensure enough phosphorus to
guarantee our future food supply. But only if we change our habits.
Do Rainforests Hold the Key?
One of the most harmful actions from a climate perspective is to clear tropical rain-
forest and replace it with soybean fields or grazing land for cattle. Growing biofuels
like sugar cane or palm oil is little better. Rainforests contain vast amounts of carbon
that sooner or later will enter the atmosphere as carbon dioxide if the forest is felled.