-- home -- soil index -- environment -- issues --Rev 20051120,20070708,

History As can be seen from the diagram, the human race has grown very suddenly at an enormously accelerating rate after the year 1850 when the industrial revolution began. Before it, the human population curve stayed steady at 500 million people since year zero, with a few dips caused by plagues. From 10,000 years ago, there have been several rapid increases, each co-inciding with an invention of some kind. The number of births and deaths per 1000 population stayed close to 40. But since the 1850s, the death rate declined suddenly, and even more steeply since 1950. The gap between births and deaths has led to the rapid increase in world population. Since about 1950 the birth rate had been declining suddenly but not as fast as the decline in deaths.

Before 8000BC, there must have been some 5 million people in the entire world, just at the end of the first stone age and the beginning of the new stone age, which brought the very first beginnings of agriculture. Before that, humans had to forage and gather food by walking long distances. This kind of life could sustain a family of ten on an area of ten square km. Large aggregations of people were simply not possible.

Even while foraging, people did influence their environment by removing noxious or useless plant species and helping advantageous ones. This meddling with nature, eventually led to agriculture.
Agriculture went through pastoralism, by which herds of grazing animals were herded over natural pastures, to shifting-farming and finally to traditional farming. Farming required people to stay in one place and farm the earth there, now and then supplemented by hunting and fishing. The new ways of farming, made possible by the invention of the plough and domesticated animals for ploughing and transport, also enabled the development of better tools and weapons from metals. Industry, boats and trade developed.

From 3000BC to 2000BC was the bronze age, followed by the iron age to about 500AD. During that time several civilisations rose and fell, like Babylon, Egypt, Greece, Rome. Although scientists today differ about the causes of the rise and fall of these civilisations, Plato clearly identified the demise of the Greek power from loss of the land, not being able to sustain its civilisation any longer:

"The consequence is, that in comparison of what [Attica, central Greece] then was, there are remaining only the bones of the wasted body, as they may be called, as in the case of small islands, all richer and softer parts of the soil having fallen away, and the mere skeleton of the land being left". Plato, 360BC.

• Foraging: 0.5 people per square km. Nomadic people move large distances, eating what they encounter.
• Pastoralism: 5 people per square km. Nomadic people move with their herds.
• Shifting farming: 50 people per square km. People burn forest, plant until fertility is lost, then move on.
• Traditional farming: 500 people per square km. People stay on the land, with their herds. They maintain a mix of pasture, arable land, gardens and stabled animals. Animal wastes are cycled onto the land.
• Modern farming: 1500-2000 people per square km. Assisted by the enormous power of fossil fuel, farming is highly mechanised, requiring little labour. Lavish use is made of fertilisers. Agricultural products are shipped vast distances.
• Genetic engineering: ?

The connection between agriculture and civilisation is not a trivial one. In order to be able to maintain a bureaucracy, an army, a legislature (the law), engineers, artisans, and so on, the farmers must produce not only enough food for themselves, but also enough to spare for those  who do not produce their own. The more efficient farming, the richer and stronger is society. This has unfortunately, over the ages, also depressed farm wages, for the less one needs to pay for food, the more is left over to spend on culture. When farmers are put under unnecessary strain, they will farm to survive, taking ecological shortcuts that will inevitably lead to ecological disaster. It is society's responsibility to avoid this happening. Society would indeed be foolish in not assisting its farming communities.

Ironically, on the scale of farming success, the extremes on either end are hard to control: at the lower end, subsistence farming  will exceed nature's carrying capacity in order to survive. Farming for greed at the other end of the scale, will have the resources and the motivation to exceed nature's carrying capacity for short-term profits. In the middle, where farming is just profitable, will it be possible to farm sustainably.

As can be deduced from the summary of advantages and disadvantages of the green revolution, it is not at all certain that it is sustainable and that it will deliver what is needed for 11 billion people. For instance, the amount of cereals (wheat, rice, etc.) per person has not increased since 1975, staying steady (even decreasing) at 350 kg/yr each, despite the fact that grain yields have been increasing from 1.5 tonne/ha to 2.5 in the same period. Simply by more people having to share the same land, the available cropland per capita was 0.3 ha in 1986 and is now 0.23 ha, decreasing further to 0.15 ha by 2050. It is estimated that 0.5 ha per person will just give an adequate amount of food and cooking fuel (Americans have 0.68 ha each). Not knowing that the world's arable soils would become so scarce, people have built their cities over the most valuable and productive soils. In the USA 0.8 ha per person has been paved by cities and roads.

To compound the situation, due to our increasing affluence, more soil is needed for: water collection, stock fodder, domestic fuel, paper, energy farming (windmills, trees, etc.), rubber, wine, beer, coffee, tea and so on.

Modern agriculture is characterised by large industrialised monocultures. Where pigs or broilers (young chickens) are reared, they are reared in closed confinement in very large numbers, producing large amounts of wastes that are difficult to recycle because of transport costs. Large fields in monoculture are very sensitive to pests, requiring excessive amounts of chemical pesticides. There's little scope for land cycling (alternating crops), green manuring (alternating fertility crops like legumes) and fallowing (leaving land unused). To reach the highest possible yields (and profit), even small losses to birds, mice, insects, are fought with chemical overkill. Pesticides and fertiliser leach into groundwater and aquifers and into streams and the ocean, where they cause measurable harm. A safe limit of 50ppm (parts per million) nitrate is in place for our aquifers, but this amount kills marine fish and other organisms in a marine aquarium. In many cropland areas, such as in Holland, groundwater is polluted by concentrations of nitrates exceeding 100ppm. The amount of nitrate raining down from the sky, in many places in Europe and the USA, exceeds the equivalent of 100kg/ha fertiliser application. It fertilises dunes and changes their ecology.

For optimal productivity, farm animals are fed growth hormones and antibiotics, which end up in their meat, causing endocrine disruption in people who eat a lot of it (excessive growth, obesity and early start of menstruation in girls are known to have been caused by better diets, but may be linked to the use of hormones in food as well).

Although much environmental harm has been caused already, the good news is that both consumers and farmers are becoming more aware and more cautious in embracing new technologies for profit only. We are obviously entering an era where we need to be smarter and eat smarter.

The main food components people need are (with daily pure amounts per kg body weight):

• water to maintain respiration, perspiration and urination.
• carbohydrates and fat for energy. Depending on work 30-60 kcal/kg/day.
• proteins for growth, body functioning and cell repair (mammals can't make 9 amino acids). 1g/kg=140g beef.
• fibre as roughage for smooth digestion and substrate for digestive bacteria
• minerals to maintain mineral concentrations in body fluids
• vitamins and trace minerals for health

Typical energy expenditures (approximately):
500kcal - 8 hours sleep (Basal Metabolic Rate BMR is 1500 kcal/day)
750kcal - 8 hour office job (1.5 x BMR)
1200kcal - 8 hour medium job, gardening, teaching, (2.4 x BMR)
2000kcal - 8 hours tree cutting, digging (4 x BMR)
3000kcal - 8 hours truck loading, pit sawing (6 x BMR)
1500kcal - 1 kg potatoes, 0.5 kg meat, 100 g plant oil.

From the amount of energy spent in an office job, it is difficult to compose a diet that does not overfeed, yet provides everything one needs. A few greasy chips, a bar of chocolate and similar delights, can easily tip the scale, resulting in preventable disease. The more energy one spends, the easier it is to eat healthily. It is not surprising then, that many diseases are linked to poor eating habits, or rather poor exercising habits, diseases that were uncommon before the automobile became commonplace:
 

Meat or vegetarian? Agriculture does not escape the principles of physics and ecology. One of these is the food or energy pyramid, shown here. Solar energy is converted by grass (primary producer) and is eaten by grazers (primary consumers). They use the food for growing , moving and living. But only a small amount is used for growing, usually between 5 and 20%. It is called the conversion efficiency or conversion rate. For quick ecological estimates, often the figure 10 is used, meaning that 10kg food is required to grow one kg. It corresponds to 10% efficiency. If wheat was grown instead of grass, humans could eat the wheat direct, and thus attain a ten times better usage of the soil. So if people went vegetarian, we would get up to ten times more food, solving the world's food shortage in one step. We will see that this is not that simple.

In studying how animals spend their energy, Kleiber discovered that there is a fixed relationship between body weight and basal metabolic rate, the energy spent when at rest. In mammals, this energy is mainly used for staying warm, but part of it also for breathing and pumping the blood round. It is known that the weight of an animal is related to its length to the power of three and its surface area likewise to the power of two. So, bigger animals need to spend more energy to stay warm, but proportionally less than small ones. A human baby spends proportionally more energy staying warm, than an adult. If heat loss were the only expenditure, Kleiber's law should be:

BMR = 3.4 x weight ^0.67  rather than BMR = 3.4 x weight ^0.75 , but this is a fine detail.

It is important to know that some farm animals spend more of their energy growing than living, and pigs and broilers appear to be very effective at gaining body mass, particularly when young. Like humans, mature animals no longer grow. They spend their energies in living and reproducing instead. If one wants to rear lots of young animals for the production of meat, it can only be a species that reproduces profusely, like pigs (1-15 per litter, 3 litters/year), chickens (200-300 eggs/ year), rabbits (?). The traditional grassland animals like cattle, sheep, goat, deer are most unsuitable.

Kept in confinement, animals will, out of necessity, spend little energy in moving around. So the conversion rates are optimal. When also fed the right diet, their conversion rates can be astounding:
Piglets are weaned after 3-5 weeks, reach slaughter weights of 90-100 kg in 100-160 days. It means that many pigs are now marketed in less than 5 months after birth. Weaned piglets start with a conversion rate of 1.3, rising to 3.5 at 90 kg body weight.
Chicken broilers do even better, perhaps because of their higher body temperature and being non-mammals. In 9 weeks they reach 2-3 kg for conversion rates starting at 1.5 and ending at 2.0. (Ducks 2.5-2.9 and turkeys 2.5-3.2).
Compare these conversion rates with cattle (8-19), eggs (2-3), fish (1.4-2), milk (1.0). The table below , compares efficiencies of animal food production:
 
 

From this table we can see that food production from milk, eggs, chicken and pork is far more efficient than from grazing animals like sheep and cattle, but fish are most productive. In Asia and china, fish aquaculture in freshwater ponds has almost reached the same volume as all ocean fisheries, supplying well over 15% of all dietary protein. Carp ponds can produce 100-300kg/ha (50kg/ha protein) without any fertilisation or feeding, but with extra feeding, polycultures of multiple fish species yield 15-40t/ha. Compare this with 80t/ha for  vegetables and 20-30t/ha for fruits, all yielding much less protein per ha.
 

With milk, eggs, chicken and pork being such efficient protein converters, the world would not be helped very much by exclusively vegetarian diets. Besides, much of their food is considered unsuitable for humans, such as fish meal made from by-catches, and crop wastes. Whereas fish ponds and milk cows may compete with good cropland, beef cattle and sheep roam on grasslands that are not suitable for cropping, so they remain efficient sources of meat, hides and wool. So, neither cropland nor harvest can be saved by shifting our appetites to vegetable matter.

Why do we need soil? Why would we need soil in the first place? Can't we rely more on using hydroponics to feed the world? Hydroponic cultivation is the pinnacle of technological cropping, where most of the climatic conditions are controlled: temperature, CO2 concentration, moisture, nutrient levels. Usually done in temperate climates inside modern glasshouses, this method of high intensity cropping has found widespread use.  In the glasshouse the temperature is kept under control. Often carbon dioxide gas is added to the atmosphere inside. Chemical sprays can easily be contained inside a closed environment, resulting in savings. But best of all is the controlled application of nutrients, while water is copiously available because it is circulated.

Hydroponics has taken the world by storm for the cultivation of specialty crops such as high quality and highly priced vegetables and fruits. Hydroponic cultivation requires a flat, slightly sloping floor and a capital-intensive structure. In most cases the energy content of the product is less than the energy put into the process. It is energy inefficient and unsuitable for the staple food of the world like cereals, tubers and pulses (beans), or for slow growing crops like tea or rubber. But it has proved that soil is not strictly needed for growing food. So what advantages does cropping in the open soil offer?

The idea of agriculture is to convert solar energy into food and products necessary for people, with the least amount of meddling (time, energy, fertiliser, chemicals). It ought to be like using the forces of nature to produce what we need. Since the only living organisms able to convert sunlight into something useful, are plants, agriculture will mainly be concerned with growing plants. Over the eons of time, plants and soil have been together, the one influencing the other. They form the most important part of the terrestrial ecosystem. Soils do naturally what has to be done artificially in hydroponics, like:

• a deep structure with low density and enough air space
• enables plants to root in, providing a hold-fast
• provides oxygen to roots
• retains moisture
• sponges up and drains excessive moisture
• soil micro organisms to assist its functioning
• to retain and exchange nutrients
• to cycle nutrients
• to transport moisture, nutrients, energy
• a cohesive structure that retains its potential
• minimises leaching losses downward
• minimises erosion and water run-off
• stabilises acidity levels (pH)

Before everything else, farming, like any other business, needs to be profitable in order to survive. That means that dollars earned must exceed dollars spent. Unlike most other businesses, farming operates under the vagaries of weather and climate. Unlike most other open air businesses, farms are hit hard by natural disasters, from frost and deluge to earthquakes. These are unpredictable and hit hard at a community's resilience, their damage erasing many years of profits. Farmers are extremely exposed to fluctuating and usually unfavourable market prices. In small markets, these are unduly influenced and controlled by the big buyers, resulting in underpayment for their produce. The farm cycle is controlled by the seasons, leaving little room for planning, marketing and stockpiling. Farmers live in remote areas, incurring high costs for their daily needs and the education of their children. The list goes on.

Farmers derive their resilience from nature's ability to repair, from being able to postpone costs a few years. But loan repayments do not fit into this category, hence their need for assistance in financing.
 
 

Above all else, farmers need to look after the soil that enables them to live, a soil 'borrowed from our children', a soil that must be bequeathed to them 'in as good or better state as we received'. With a renewal rate of tens of thousands of years and erosion risks far too high, this is no easy assignment. The American Society of Agronomy defined agricultural sustainability as summarised in the box on right. They go as far as saying that it should enhance environmental quality, the resource (soil) and the quality of life for all (not just the farmer), an even tougher mission. Mr Rutan has added another constraint, that of substituting biological technology for chemical technology. (Is any farmer reading this?)

Agricultural Sustainability: Enhances environmental quality  Enhances the agricultural resource base Provides for all our food & fiber needs Is economically viable Enhances the quality of life for all AND while improving plants, animals and production practices, facilitates the substitution of biological technology for chemical technology. (organic farming principles) [V W Rutan, 1989]

Large-scale farming is constrained too by having to be energy-efficient, which means that the amount of energy used must always be less than the amount of energy in the product. Many businesses exist, indeed the majority, where this is not true (all services, the bureaucracy, army, police and so on). Farmers use their tractor, which cost energy to make and fuel to run. They use fertilisers made or modified by factories and transported to the field. They use chemicals that were produced with large amounts of energy from fossil fuel. The list goes on.
As fossil fuel becomes more expensive, the drive behind farming efficiency using high yielding crops, will bend towards higher fuel efficiency (less fertiliser, chemicals, tilling, transport). So the question becomes 'how little fuel?' rather than 'how much yield?'.

Most of the chapters in this section on soil will focus on its sustainable use, and the understanding necessary to do so.