0610 · 20.1Food supply

Food production and yield

0:00Imagine a farmer trying to supply more food without simply doubling the size of the farm. They could grow more grain in each field, lose less of it to insects, or produce more milk from their cattle. But methods that increase production can also create problems. By the end of this video, you will understand how modern farming increases food supply, and why greater efficiency can come with environmental and animal welfare costs.

0:23First, we need to distinguish total production from yield. Total production is the whole amount produced, while crop yield commonly means the amount harvested per unit area of land. Farming a larger area can increase total production without increasing yield. Improving plant growth or preventing crop damage can increase yield, because the farmer harvests more from the same area. Remember that plants make sugars by photosynthesis, but they also need mineral ions from the soil for healthy growth.

0:51Animals need food for respiration, growth and producing substances such as milk. Farmers increase production by improving growing conditions, reducing losses, and breeding organisms with useful inherited characteristics. Let us follow those ideas from a field to a livestock shed.

Increasing crop production

1:06Agricultural machinery allows farmers to work larger areas of land and improve efficiency. A tractor can prepare soil and sow seeds much faster than people working by hand. Harvesting machines can collect crops quickly when they are ready, reducing losses caused by delays. Machinery does not automatically make each plant grow better, but it allows more land to be managed with less labour per unit of food produced. Chemical fertilisers improve yields by supplying mineral ions that may be in short supply in the soil.

1:35For example, plants absorb nitrate ions and use them to make amino acids, which are built into proteins needed for growth. If a crop lacks these ions, supplying them can improve growth and increase the harvest. Fertilisers are not food for plants, and adding more does not guarantee improvement if another requirement is limiting growth. Insecticides kill insect pests that damage crops. A caterpillar eating leaves reduces the leaf area available for photosynthesis, while insects feeding on fruits can make them unsuitable for sale.

2:05Reducing this damage improves both the quantity harvested and its quality. However, some insecticides also kill non-target insects, including pollinators and predators of pests, so their effects are not always limited to the organisms the farmer wants to remove. Herbicides kill weeds, which are unwanted plants growing among crops. Weeds compete with crop plants for light, water and mineral ions, so fewer of these resources may be available to the crop.

2:30Removing weeds reduces competition and allows the crop to grow better. Notice the distinction. Insecticides reduce damage by insect pests, while herbicides reduce competition from unwanted plants. Selective breeding changes the inherited characteristics of crops and livestock over successive generations. Farmers choose parents with desirable characteristics, breed them, and select suitable offspring to breed again. Wheat plants might be selected for high grain yield, while dairy cattle might be selected for high milk production.

3:00The improvement depends on offspring inheriting useful characteristics, rather than an individual organism changing because the farmer wants it to. These methods are often used in large-scale monocultures. A monoculture is the cultivation of a single crop species in an area, rather than a mixture of different crops. Imagine a large field containing only wheat. Because the crop has similar requirements across the field, the farmer can organise planting, treatment and harvesting in a consistent way.

3:28That uniformity makes machinery easier to use and allows efficient production on a large scale. The same equipment can sow and harvest the whole field, and fertilisers can be applied according to the needs of one crop. Large-scale production can reduce the cost of producing each unit of food. But growing one species over a large area also means that the field offers a limited range of habitats and food sources.

3:51This can reduce biodiversity, which is the number of different species that live in an area. A pest that feeds on wheat encounters a large, continuous food supply, so it can spread through the crop readily. Diseases can also spread between nearby susceptible plants, especially when the plants are genetically similar. Greater reliance on fertilisers and pesticides can create pollution, with consequences for organisms beyond the field.

Intensive livestock production

4:14Now consider intensive livestock production, in which many animals are kept in a relatively small area under closely managed conditions. Food, water and temperature can be controlled, and the animals can be monitored regularly. This can produce a large amount of meat, milk or eggs using relatively little land. Keeping animals together can also make feeding, cleaning and collecting products more efficient. One important advantage concerns how animals use energy.

4:39If animals move less, less energy is transferred through respiration to support muscular activity. Keeping them at a suitable temperature can also reduce the energy needed to maintain body temperature. With an appropriate diet, more of the energy supplied in food can therefore support growth or production, although animals must still respire to stay alive. The same close grouping creates disadvantages. Infectious diseases can spread rapidly between animals kept near one another.

5:06Restricted space may prevent normal behaviours, creating animal welfare problems even if the animals are well fed. Large quantities of waste also accumulate in a small area, and poorly managed waste can pollute water. Buildings, feed and environmental control can be expensive too.

Applying food production methods

5:23Let us work through a farming problem rather than just repeat the advantages. A farmer grows wheat in a large monoculture and finds that caterpillars are eating the leaves. The farmer wants to know whether a herbicide would solve the problem, and whether an insecticide could increase the yield. Start by identifying the cause of the loss. An insect is removing leaf tissue, not a weed competing for resources. A herbicide would therefore target the wrong organism.

5:47An appropriate insecticide could reduce caterpillar numbers, so less leaf tissue would be eaten. More leaf area would remain available for photosynthesis, helping the plants produce materials needed for growth and grain production. The possible disadvantage is that non-target insects could also be killed, so the decision involves both a production benefit and an environmental cost. This example also shows why the phrase chemicals make crops grow better is too vague.

6:14Fertilisers supply mineral ions, insecticides reduce damage, and herbicides reduce competition. Each method addresses a different obstacle to production. Similarly, neither monoculture nor intensive livestock production means that nothing can go wrong. Both can increase efficiency while also increasing particular risks. In an examination, you might be asked to describe how a named method increases food production, or to describe advantages and disadvantages of a farming system. For example, consider the question, describe two advantages and two disadvantages of intensive livestock production.

6:49First separate production benefits from costs or risks, then choose distinct points. Give a clear biological connection rather than simply calling the system good or bad. Restricting movement reduces energy expenditure on muscular activity, so more energy from food can be available for growth. Controlled feeding supplies the nutrients needed for high production. Close contact between animals allows infectious diseases to spread rapidly. Restricted space can prevent normal behaviour and cause animal welfare problems.

7:17Each sentence gives a separate point connected directly to the conditions in intensive production. Let us recap the central idea. Increasing food supply means growing or rearing more successfully, working more efficiently, and losing less of what is produced. Machinery allows larger areas to be managed, fertilisers supply mineral ions, insecticides reduce insect damage, herbicides reduce weed competition, and selective breeding improves inherited production characteristics. Monocultures simplify crop management but can reduce biodiversity and allow pests or diseases to spread.

7:51Intensive livestock production improves control and efficiency, but can increase disease, pollution and welfare problems.