Meals, not myths – The future of global food production

The stakes are high in the future of agriculture. If we are to feed nine billion people by 2050, myths about the right ways forward in agricultural production need to be replaced by policies based on scientific evidence.

The global population is expected to exceed nine billion people by 2050. This will more than double the demand for food and put unprecedented pressure on our ecosystem. Views on what this means for the future of agriculture differ strongly. Many otherwise well-informed people have acquired perceptions about agriculture that are not based on scientific evidence. Interestingly, most of these people live in rich urban centres such as San Francisco, Sydney or Paris. This is in sharp contrast to prevailing views in urban areas in developing countries, such as Lima or Nairobi, where many people still have links to agriculture or have relatives living in rural areas.

There are five main myths about agriculture that need to be dispelled. And there are five terms crucial to understanding these myths. To start with, all substances are chemical, because they are composed of atoms and molecules. Molecules of organic substances contain carbon, while the molecules of mineral substances do not. Both are chemical in the sense that they are composed of atoms and molecules. Humans, plants and animals are all organic.

Natural compounds are those produced without human interventions, such as petroleum, water, natural gas (methane) and rock phosphate. Synthetic compounds are those transformed through human intervention to produce compounds different from their natural state.

To give an example of how this all works, gasoline, nitrogen fertilizers and phosphorus fertilizers are synthetic products. The first two are transformed from petroleum or natural gas, while superphosphates and other phosphorus fertilizers are transformed from rock phosphate. Thus, petroleum and natural gas are organic and natural, while gasoline is organic and synthetic.

Rock phosphate is mineral and natural, while mineral fertilizers such as ammonium nitrate and triple superphosphate are mineral and synthetic. Cattle manure is organic and natural. Biofuels such as ethanol are organic and synthetic.

Mineral fertilizers are bad

The first myth is that mineral fertilizers are bad. But plants do not care whether the nitrate or phosphate ions they absorb from soils come from a bag of fertilizer, a piece of manure or a decomposing leaf. It is the ionic form that matters. The same goes for other plant nutrients.

Mineral fertilizers do not cause environmental harm when the recommended application rates are followed (100 kg N/ha for maize in the Midwestern United States, for example) because most of the nutrient ions are either taken up by the plants or incorporated into soil organic matter. But if nitrogen fertilizers are applied at excessive rates, nitrate leaches into ground water, and nitrous oxide gas is emitted into the atmosphere. The same happens if organic sources of nitrogen are applied at excessive rates.

Nitrate in water can be toxic to humans, particularly children, if concentrations exceed 10 parts per million. Phosphate anions are held tightly by most soils so they seldom leach, but they can enter surface waters by runoff and soil erosion, attached to soil particles. High nitrate levels combined with phosphates cause eutrophication (enrichment of water bodies with nutrients), which in turn produces excessive aquatic plant and algal growth.

This in turn reduces the dissolved oxygen content of water, killing fish and other organisms, resulting in ‘dead zones’, such as those commonly found in the Gulf of Mexico and other large estuaries around the world. Eutrophication is also caused by inflows of nutrients from organic sources, such as municipal waste, and organic fertilizers.

Nitrous oxide is a potent greenhouse gas, having 310 times the atmospheric warming power of carbon dioxide. The main source of human-made N20 emissions is fertilizers, either mineral or organic, when nitrate ions produced from either source are transformed in the soil into gaseous nitrous oxide under wet conditions.

Mineral fertilizers, when in contact with seeds, can cause ‘salt burns’ to emerging seedlings, because most of them are soluble salts. Farmers know this very well and place mineral fertilizers a few centimetres away from the seeds to prevent this problem. Organic fertilizers do not have this effect on seeds.

Another difference between organic and mineral fertilizers is nutrient concentration. Urea, for example, contains 46% nitrogen, while most organic fertilizers contain 2-4% nitrogen (both dry weight). This translates into high transport costs of organic inputs produced outside the field. A farmer will need 10 to 20 50-kg bags of dry manure to equal the nitrogen contained in one 50-kg bag of urea.

While plants do not care about the source of the nutrient ions they absorb, soil does, and it needs the carbon provided by organic fertilizers, which mineral fertilizers do not contain. Organic carbon improves soil porosity and water-holding capacity, and provides a substrate for soil micro-organisms to grow and enhance nutrient cycling. Also, since organic fertilizers originally derive from plants, they contain all essential nutrient elements (macro- and micronutrients), while mineral fertilizers contain only a few.

These positive effects occur when organic fertilizers are applied in appropriate quantities. But some organic fertilizers have very low phosphorus concentrations. Crop residues, as well as leaves from leguminous nitrogen-fixing trees or cover crops, do not contain sufficient phosphorus to satisfy crop needs. At the other extreme, some animal manure, particularly poultry manure, may provide too much phosphorus. Sewage sludge and other municipal waste may often contain toxic heavy metals such as cadmium and lead.

Like most nourishing substances, fertilizers, whether mineral or organic, are effective when used in the appropriate quantities, but can cause harm if used excessively. Just as a glass of milk can be nutritious, too much milk can make people sick.

Most successful farmers therefore use a combination of mineral and organic fertilizers, taking advantage of their pluses and minuses. There is probably not a single successful sustainable farmer in a rich country that uses only mineral fertilizers. Is that the case for the opposite, organic farming, as well?

Rich countries need organic farming

The second myth holds that organic is the only way to go in rich countries. There is nothing conceptually wrong with organic farming, as long as it can provide crops with the necessary plant nutrients at the right application rates and at an economically viable cost.

The shift from conventional to organic farming usually temporarily reduces yield (one to three years in the United States). This is because nutrients held in the soil are needed for the organic material to grow. Soil nutrient reserves begin to deplete since no more mineral fertilizer is added. This is possible in soils with high nutrient capital reserves, the product of decades of mineral fertilization.

After that transition period, organic agriculture really begins to function with proper nutrient cycling. The crop yields do not differ much at this point from those of conventional agriculture, which in this context is agriculture that uses both mineral and organic fertilizers.

Organic farming, however, usually requires additional space and additional time to grow the organic fertilizers. The latter can be anything from green manure, which is then incorporated into the soil, to hay that is cut and fed to animals in confinement. There are few comparisons between conventional farming versus organic farming that take into account the extra land or time needed.

Pests, diseases and weeds are more of a challenge to control without the use of insecticides, fungicides and herbicides in organic farming. But pesticides also destroy beneficial organisms. If used solely in conventional systems, they can create an increasing dependency, as the pathogens themselves mutate and develop tolerance. This is already happening with some weed species developing tolerance to glyphosate, the key ingredient in the practice known as ‘no-till’ Roundup-ready soybeans.

Purely organic pest, disease and weed control is carried out by using tolerant crop varieties, crop rotations and conserving natural enemies. It is more difficult to control weeds without herbicides in organic farming, but it is still possible. The best approach is integrated pest management, which is based on the sound principles of organic agriculture with strategic applications of insecticides and herbicides.

Food safety is a concern in both organic and conventional agriculture. Most of the recent vegetable-related E. coli outbreaks were the result of contaminated liquid manure spread on fields. This can happen in either system, but organic farming is more vulnerable because it depends solely on organic inputs.

Certified organic agriculture as practiced in the United States prohibits the use of mineral fertilizers and (mostly organic) pesticides. It has become a maze of regulations for farmers. In the end, farmers and organic inspectors spend more time examining the farmer’s books than the crops or cattle in the fields.

Some of these regulations are clearly illogical. For example rock phosphate is considered organic, yet its main constituent is calcium phosphate (which does not contain carbon). The same is true of potassium nitrate, because it occurs naturally. Furthermore, organic certification prohibits the use of genetically engineered seeds, which are also organic. Some of them, such as transgenic maize and cotton, can decrease or eliminate the need for insecticide applications. This has the environmentally positive effect of allowing beneficial insects to persist.

The question of whether to practice organic or conventional agriculture in rich countries boils down to whether the premium prices organic products receive are sufficiently high to compensate for the harder work organic agriculture requires. Organic farming is one way to go in rich countries, but certainly not the only one.

Poor countries need organic farming

The third myth holds that organic is the way to go in poor countries. Some consider organic farming to be the best sustainable option for smallholder farmers in poor countries, including most of Africa. This view is usually advocated, sometimes vehemently, by non-governmental organizations (NGOs) in rich countries as an alternative to mineral fertilizers. Actually, most African farmers are organic farmers by default, because they use only low-quality manures and compost.

But what happens with organic farming when most soils of smallholder farmers are depleted of nutrients, and cereal yields an average of one ton/ha, as opposed to 10 tons/ha in the United States and Europe? How can nitrogen-fixing cover crops or trees grow when phosphorus supplies are near zero?

Also, the quantity and quality of cattle manure depends on the quantity and quality of the fodder they ingest, which in turn depends on the nutrient capital of the soil. Because of this, much of the manure in Africa is low quality and produced in small quantities. It has few nutrients to offer crops. It is extremely difficult to understand how nutrient-depleted soils can grow organic inputs in sufficient quantities for crop production.

The problem would diminish if organic inputs were brought from outside the farm. But high transport costs and low nutrient concentrations make this a very expensive endeavour, especially in Africa, where the infrastructure is poor.

The last thing that is needed is more bureaucracy with illogical rules or maintaining an ideology for the sake of it. Rather, a more sensible agriculture is needed, based on the wise combination of both organic and inorganic inputs called ‘integrated soil fertility management’.

For example, in nutrient-depleted African soils, the initial application of mineral fertilizers is a sensible and often necessary way to start. Soil organic carbon increases when there are high crop yields and crop residue returns, and organic inputs become more effective as more carbon becomes available for micro-organisms.

But a purely mineral-based agriculture is not the perfect answer either. It may be the best option in the initial years, however, and can be gradually supplemented with more organic inputs, produced on site to minimize costs. Ideally, the bulk of the nitrogen could come from nitrogen-fixing trees and cover crops that also recycle other nutrients.

The overall effect would reduce but not eliminate the use of mineral fertilizers. Most of the phosphorus needs of crops, however, are likely to come from a fertilizer bag, containing high-reactivity rock phosphate, diammonium phosphate or superphosphate.

The evils of having to purchase seed every year

The fourth myth concerns the supposed evils of having to purchase seed every year. Many believe, especially in NGO circles, that multinationals are now forcing farmers all over the world to purchase seed every year instead of saving grain from the previous harvests to use as seed for the next one. Buying seed is actually nothing new. It has been the norm since the advent of hybrid maize over 70 years ago.

There are two main types of seed, varieties, and hybrids. Varieties were developed originally by early farmers, who selected and reproduced their best seeds. The result was what is now referred to as ‘landraces’, local varieties a crop species like maize or beans developed mainly by farmer selection.

Crop breeders have been practicing the same selection system for over two centuries, intentionally crossing two contrasting plant types of the same species. For example, they may cross a tall-statured but high-yielding rice variety with a short-statured but low-yielding rice variety, the objective being to develop a short-statured high-yielding rice variety.

Individual plants of the first generation (F1) are selected and crossed among themselves to produce the subsequent generation, F2. This generation of plants usually shows enormous variability in the desired traits. Subsequent generations are selected and crossed again until plants with the desired traits dominate. After further screening, by which time generation F6 or F8 had been reached, the traits are eventually stabilized and they are released as a new variety or cultivar. Seed from such varieties can be planted again for several years.

Hybrids are the F1 generation and possess the ‘hybrid vigour’. But this hybrid vigour is lost when one plants the F2s from these hybrids. Farmers usually prefer hybrids because the yield is 25-75% higher than varieties.

Large-scale production using complicated methods is needed to produce sufficient quantities of hybrids. In maize, for example, paper bags are placed over the tassel of one variety to prevent the pollen (male organ) from pollinating the ears below (the female organ). A row of the variety chosen to be the male partner is grown alongside the rows of another variety with paper bags covering their male organs, so the pollen from the first variety pollinates the female part of the ear, called pistil. Only those rows will be harvested for hybrid seed.

This technology was introduced in the 1940s. The hybrid vigour of the F1 seed and improved agronomic practices doubled maize yields in the United States and Europe in just a few years.

The benefits of hybrid seeds are well known globally. Smallholder farmers participating in a government subsidy programme in Malawi, for example, could choose between five kilograms of the country’s best maize varieties or three kilograms of the best hybrid maize suitable for use in Malawian agriculture. In both cases, they had to pay only a quarter of the market price. Over 70% of the one million or so farmers opted for the hybrids, knowing very well that they could not plant the seed they would harvest the following year.

Transgenic crops are bad

The fifth myth states that transgenic crops are bad for the environment and human health. Thanks to genomics, breeders can now select genes in their crossing programmes, instead of using the visible traits of individual plants. They can also transfer a gene from one species to another, eventually resulting in transgenic crops that can be either a variety or a hybrid.

A large number of transgenic hybrids or varieties of crops have been released in the last 20 years. Examples include maize, soybeans, cotton, canola and papaya, most of which are to provide resistance to insects and certain herbicides. Some are the result of genes being transferred from bacteria, for example Bacillus thuriegiensis to maize and cotton. This makes these transgenic plants – Bt corn and Bt cotton – resistant to insect attacks.

Their widespread use has saved millions of hectares of crops from insecticide applications that would have also killed beneficial insects. In Hawaii, a transgenic papaya resistant to the ring spot virus was developed about 10 years ago and currently covers most of the papaya growing areas of these islands.

Transgenic crops are now being developed for increased nutritional value as well. ‘Golden rice’, a seed with a precursor of vitamin A taken from a dandelion gene, is an example. It has the potential of eliminating vitamin A deficiency and blindness in millions of children in Asia. Transgenics are also being developed for drought tolerance. A drought-tolerant maize crop would provide a buffer to hunger for millions in Africa. Both are still works in progress.

Why the opposition?

So why is there so much opposition to this great use of science for the public good among well-informed people in Europe? Why are NGOs across the globe so resistant to using transgenic crops, while other countries, rich and poor alike, are rapidly planting more and more transgenic crops? The main claim against their use is that these human-made crops are harmful to our health and to the environment.

A series of major, peer-reviewed long-term studies and journal articles by scientists have shown that the transgenic crops currently being grown have absolutely no ill effects on human health or the environment. Good biosafety procedures continue to be extremely important to ensure that future transgenic crops meet the same standards.

The opposition to using transgenic crops in Europe remains a mystery. After all, the technology has been adopted in many other parts of the world. Faltering trust in science and scientists as a result of outbreaks such as mad cow disease has certainly played a part. But we must ensure that science and hard evidence are put back on policy-making agendas.

Footnotes