Farming and the environment

In today's western world, farming practices have evolved in line with economic developments, to favour an increase in productivity above all other factors. Whether this is right or wrong is another argument entirely. The intended aim of this node is to discuss fairly the advantages and disadvantages of modern farming techniques. It is however inevitable that some bias on the part of the author will be introduced. I'll try and keep this to a minimum, but be aware that this is a divisive issue and difficult to not become opinionated on.

Types of farming

A distinction must be made between arable and livestock farming - with the prior having undergone rapid change in the last 30 years and the latter a more gradual change. I intend to focus on arable farming as it has seen both the greatest change to date, and faces further upheaval and modernisation over the next few decades.

Arable farming is the growing of food crops on a large scale and is a term usually applied to 'food' crops (maize, wheat and corn) as opposed to cash crops (tobacco, coffee or almonds). Economic factors are gradually reducing the total number of arable farms, favouring large scale, highly mechanized operations due to their higher efficiency. Whilst this has notable social implications, these are not unique to agriculture and are discussed at length elsewhere on everything.

Changes in arable crops

Most large scale farms now specialise exclusively in the three staple grain crops of oats, maize and wheat. Barley is grown to a lesser extent as a side crop, mainly due to its lack of hardiness and the risk of economic ruin by depending too heavily on it. The only other major arable crop besides the three grains is Oilseed Rape, grown mainly for the oils it contains which have a plethora of potential uses.

This movement towards fewer crops eventually leads to the contentious issue of monoculture - the singular cultivation of a single crop over large areas of cleared pasture land. The economic advantages of this are immediate - the purchase of specialist machinery is now viable and conditions and practices can be optimized to benefit the growth of this particular crop. Monoculture as a result has increased rapidly in popularity amongst large scale arable operations for these reasons.

Monoculture and its effects

Monoculture is made increasingly popular by the rise of the biotechnology industry, producing better and faster growing species of the common three grain crops; making the sole cultivation of one species advantageous due to the high levels of production achievable. It is however not without its problems.

Firstly monoculture is not an environmentally friendly practice and this cannot be ignored or largely disputed. It places a heavy dependance on inorganic fertilisers, pesticides and other artificial chemicals. Whilst other objections to monoculture exist this is the major argument used by environmental groups.

Monoculture requires the use of fertilisers as growing a single crop year in year out depletes rapidly the natural fertility of a given area of land. This is because each year the roots will grow to the same depth and remove essential minerals from the same level of soil as a result. This loss of materials must be replaced accordingly or subsuquent crops will be severely stunted in growth or fail entirely.

Soil fertility

The two most important minerals present in the soil are nitrates and phosphates. To a lesser extent potassium and it's varying compounds are also required, but in low enough levels to not to be a problem. Naturally occuring aerobic bacteria each year decompose the leftover of a crop and by a complex process of interactions turn plant proteins first to their component amino acids, then to urea and finally to ammonia by deammination. Since ammonia is highly toxic to most life, this would initially seem a very negative outcome.

Nitrifying bacteria however thrive on ammonia and convert it throught to nitrites and finally to usable nitrates. The soil has now been said to be replenished and next years crop should thrive.

The chemistry for this in case you're interested is NH₄⁺ --> NO₂^- --> NO₃^- and requires many species of bacteria.

Fallowing and legumes

The above process is helped by the fact that in conventional farming fields are either left fallow (without a crop) or a nitrogen replenishing crop is grown and then ploughed in to the soil - this important factor is discusses later.

Phosphates (PO₄^3-) are however only replaced over a period of many years - with normal culture this is not a problem as varying crops remove minerals from varying depths, always ensuring a constant and balanced supply for each sucessive crop. With monoculture this is of course not the case. As such phosphate heavy fertilisers are required.

Application of fertilisers damages the balance of bacteria in the soil. In a cycle of positive feedback this will increase requirements for fertilisers the next year - to the point where soil fertility cannot be maintained without them.

Avoiding fertilisers

Traditional farming methods, without understanding such mechanisms, made use of them through fallow fields and leguminous crops. Ploughing a field fallow allows time for restoration of nutrients at the cost of a years production. Typically taking place in a cycle of four years, with one fallow year, this gave a bumper crop the year after fallowing. This larger crop reduced but did not eliminate any economic penalties of the system.

Leguminous crops such as mustard could be grown instead during the winter season. Here rhizobium and other nitrogen scavenging species living symbiotically in the leguminous plant roots (inside special nodules) replenish minerals rapidly. The leguminous plants are then ploughed in to the soil, decomposing and providing nutrition to the next growing crop in the cycle.

Such systems however are labour intensive, and often cost more to implement than comparitively cheap inorganic fertilisers.

How are fertilisers a problem?

The watch word for fertiliser usage is eutrophication - the mineral enrichment of aquatic ecosystems. Run off from the soil caries away fertiliser in to freshwater systems where the minerals cause rapid growth of algae which cover the water surface in an algal bloom. This stops any photosynthetic activity of other aquatic plants by blocking light, causing their death and decomposition. Again nitrifying bacteria come in to action, but this time their metabolism causes further damage by consuming all the oxygen in the water as they reproduce rapidly due to many available food sources. This kills almost all aerobic organisms in the water, the end product being the death of fish and shrimps.

Futher decomposition of these dead organisms propagates the cycle and ultimately the freshwater body stagnates as anaerobes (bacteria not requiring oxygen) dominate and produce toxic H₂S gas and methane. This flammable methane produces the jack-o-lantern effects seen over stagnant bogs and is an undesirable outcome for a once thriving freshwater body.

The loss of freshwater bodies in turn requires complex systems of irrigation to feed water back over the land as naturally occuring water sources are now polluted and useless.

Reducing harm from fertilisers

These problems can be reduced in severity by careful application of inorganic fertilisers at suitable times where the minerals will be used for growth rather than leached from the land and in to freshwater. Spring is a good time to apply fertilisers as the growing crop will utilise the minerals rapidly. Ploughing of straw in to the land when applying can also help as the carbon provided from the straw helps microbes grow and consume excess fertiliser.

Despite these preventative measures, unexpected weather patterns can still cause heavy rainfall at unusual times; resulting in leaching of minerals. The main problem here being inorganic fertilisers are very water soluble and more likely to wash off than remain embedded in the soil.

Organic fertilisers (read: animal slurry) have benefits in that they have reduced risks of leaching due to their more...solid nature. However where monoculture is taking place their is by definition no available animal slurry. This is one of the reasons why combined arable/livestock farms are being encouraged as part of new EU agricultural policy and the Single land payment (UK).

Soil erosion

Is another common problem where monoculture takes places as removal of hedgerows is required to move large machinery around. Sowing, ploughing, spraying and harvesting equipment has difficulty manouvering around small gaps in hedges. Hedgerow removal also makes economic sense as rather than the continual cost of maintaining such passing points, for a one of investment a landowner can remove the problem forever.

Soil binding by hedges

Hedgerow roots however help to bind the soil and act as natural windbreaks to reduce wind-sweeping of the top layer. Without them again soil fertility decreases as minerals are continually lost to lower lying areas and ultimately fresh (and sometimes saline) water bodies.

Advantages of hedgerow removal

However, removal of hedgerows also help to improve crop growth as roots of the hedges may outcompete crops at the edge of fields for nutritents and water. Additionally hedges shade crops at the edges of fields from light. Without hedges more crops can be grown in a given area - allowing the landowner to then leave headlands and maintain the same level of production. These headlands help to reduce eutrophication risks as leached minerals pass over the headland and are scavenged by natural plants growing there.

Maintaining Biodiversity

Biodiversity can be maintained providing headlands are left, so the environmental argument that removal of hedgerows damages ecological sustainability is largely void. It is not advantageous for a farmer to lower biodiversity as many natural predators of crop pests may be damaged, increasing the requirement for expensive pesticides.

Monoculture and pesticides

Inspite of natural predators large amounts of pesticides are still required by monoculture as any large area of crops is vulnerable to a single thriving pest population. The centre of large areas of crops are most vulnerable as they are most distant from predator species. Recently banning of the most lethal pesticides has become necessary as there is evidence that DDT and like chemicals are becoming concentrated in animal and human tissues and causing birth defects and a variety of cancers.

This concentrating effect is known as bioaccumulation - a pest absorbing sufficient pesticide to kill it is often consumed by a higher order predator at a higher trophic level. By definition pesticides are not organic molecules and therefore impossible to excrete by an organism. They are more fat soluble and than water soluble and so tend to concentrate in tissues. Since progression up a food chain dictates fewer number of predators eating a continually greater amount of prey, the top species tend to accumulate very high amounts of pesticide in their tissues.

Bioaccumulation as a problem

This presents a problem - deceased top trophic predators now either decay in the soil releasing large quantities of insoluble poisons which are unlikely to leave the soil, or worse, they are consumed by humans with inevitable consequences. Premature death of predators may also adversely affect food chains, possibly even causing an increase in pest population.

The rapid rate at which resistance to pesticides evolve means that many potential toxins are present in the food chain at once, each gradually increasing in concentration. Since man is the top predator, we receive the largest dose and the widest variety of toxins. This was recently highlighted in the (flawed) study in to PCB concentrations of scottish salmon. Whilst the study was too small to be conclusive it did highlight the important problem of bioaccumulation.

Differences with polyculture

With polyculture no individual pest is able to thrive, therefore total damage to crop populations are kept to a minimum. Biological control is possible, with more habitats due to more species of crop meaning more predators exist per unit area. This helps to control any pests present better and with less environmental damage than pesticides.

Compaction of the soil

The heavy mechanization of farming also presents a problem. Heavy machinery compacts the soil. This is initially a benefit as it reduces erosion, thereby improving soil fertility due to less run off of mineral containing material.

The necessity of ploughing is however increased as plant roots do poorly in compact, poorly oxygenated soil. Anyone that has ever said plant roots rot in contact with air has failed to consider that as respiring tissues, plant roots require oxygen, in appreciable quantities. This frequent ploughing harms natural populations of earthworms and spiders which would otherwise help to maintain soil air spaces.

Increasing emissions

Increased use of machinery also increases carbon dioxide and sulphur emissions (these are fuel driven machines remember) and also risks the contamination of lands with heavy metals and oils from the fuel. Fuel is of course an non-renewable resource and agriculture is one of the largest users, somewhat behind heavy industry though.

Water retention

The loss of earthworms and other natural flora and fauna reduces humus content of the soil. Humus is produced when organic fertilisers are decomposed and is a material with a high water retention ability. The increased use of inorganic fertiliser causes nitrate burns to these natural species, compounding the problem.

Without humus soil fertility falls (need I say positive feedback and an increased requirement for fertilisers) and most significantly irrigation of originally plentiful land is now required. Erosion risks increase as the soil is now less bound together (more particulate in nature) requiring costly erosion defenses and measures to prevent leaching and subsuquent eutrophication.

Benefits of modern methods

However modern methods have significant economic advantages too - more crops can be grown per unit acre of land, which in turn provides more food to feed a growing population. It is likely that without mechanisation, even greater food shortages would be seen (distribution of this food is a separate issue of course).

Modern techniques also reduce menial and dangerous jobs associated with farming, freeing up people resources and allowing better and more stimulating jobs to be undertaken. In the developing world this makes a lesser requirement to used child or forced labour to harvest crops from fields.

Produced crops are often of a higher standard than those produced by manual methods as conditions are more favourable. Additionally supplies are now sufficient to balance out seasonal variations in demand during the off-production seasons.

Human health risks

Despite these advantages there are serious problems modern farming has to human health. I will not consider social aspects as I feel these are beyond the scope of this node.

Blue baby syndrome is an increasing phenomena whereby eutrophicated water sources are used to source water for human consumption. Here the high nitrogen concentrations leads to conversion of nitrates (NO₃^-) to nitrites (NO₂^-) in the gut wall. These nitrites are highly toxic, binding with haemoglobin to produce methaemoglobin which is unable to carry oxygen. Particularly a problem in infants this results in stunted growth and bluing of membranes as oxygen saturation is too low to meet the demands of all respiring tissues.

Pesticides and mineral ions also damage human health, the former being commonly carcinogenic and the latter being converted to highly toxic nitrosamines by mammalian metabolisms. These could account partially for the seeming explosion in cancer cases of populations near major arable farming areas.

Take-away points

• Eutrophication is the mineral enrichment of an aquatic ecosystem, causing positive feedback of decomposition, increased biochemical oxygen demand and stagnation of water.


• Bioaccumulation is the concentration of pesticides and poisons up the food chain, with ultimate consumption by man.


• Erosion is a result of wind or water moving over poorly bound soil, reducing soil fertility.


• Inorganic fertilisers attempt to replace lost minerals by adding water soluble substitutes directly to the soil


• Monoculture is the growth of a single crop species over a large area

Conclusion

Economic factors must be made to balance environmental factors for sufficient food to be grown in an environmentally friendly and sustainable way. Without changes, both in the form of modernisation and tighter legislation on farming practices, we risk not being able to produce enough food to sustain a growing population (distributive issues aside).

Efficiency is a definite requirement but should not be a singular priority. Control of such issues should be placed beyond the control of companies marketing agricultural products, those using them and those with set agendas against them. Such impartial bodies could be very difficult to find, but are essential in maintaining production levels, biodiversity and human health.