Sustainable Soil Use

1. Overuse of Insecticides and Herbicides

The use of chemical sprays to reduce weed and insect populations has increased yield and prevented food loss during storage. Overuse, however, can result in issues with output going forward.

When an insecticide chemical is used frequently, the pest population may develop resistance to it. This implies that not every target pest is now killed by harmful chemicals. Herbicide resistance is caused by the same principle.

The image below demonstrates how resistance develops. A pest must go through several generations before developing complete resistance. Yet, many pests, like insects, have exceptionally short life cycles, meaning several generations can happen in as little as a few weeks.

How resistance to an insecticide occurs

Farmers typically apply a higher dose to improve the effect if an insect can no longer be efficiently controlled by an insecticide. While it might be effective in the short run, this can hasten the development of pesticide resistance. The best course of action for farmers is to employ a variety of pesticides so that, in the event that pest resistance develops to one product, another chemical will likely still be toxic to the pest.

Herbicides and insecticides can potentially have unanticipated negative effects on the ecosystem. In the case of pesticides, their use has the potential to kill beneficial insects like bees, which will have an impact on plant pollination. Due to the fact that many animals eat insects, a change in the availability of insects may also have an effect on the larger food web.

Spray drift can be a problem with pesticides and herbicides, as the chemical may hit a target it wasn't meant for and harm the environment. Herbicides can linger in the soil for a long enough time to impede the development of other plants. Insecticides and herbicides can leak into rivers and lakes during periods of heavy rainfall, harming other organisms. There is some proof that herbicides can affect soil organisms like fungi and microscopic animals, which affects the food chain.

These issues do not only affect plants. In many countries, routine medication is provided to livestock – not because the animals are ill, but rather to stop infections from happening. If done properly, this is a good technique, but if done excessively, issues may arise. Antibiotics are frequently administered to animals as part of their treatment. Humans are given the same products or ones that are fairly similar. These antibiotics run the same danger of developing resistance as insecticides, making them less likely to control disease and putting both humans and livestock at higher risk of illness or death. 2. Misuse of Fertilisers

It is common knowledge that adding fertilisers to soils lacking in mineral nutrients will accelerate plant growth. So, it is simple to assume that adding fertiliser to any soil will cause plants to grow larger and produce more. As the soil reaches its optimum amount of mineral nutrients, however, the addition of additional mineral nutrients ceases to be advantageous. Each further application after that is a waste of time and resources. The environment will also be negatively affected.

It might be most economical for farmers to apply a lot of fertiliser all at once, but heavy rain can dissolve the mineral nutrients and carry them away when there is run-off. In addition water can soak through the soil if the weather or soil conditions are not ideal, which can result in a significant amount of the nutrient content being wasted (leaching). The roots will take up fewer mineral nutrients if the weather does not permit quick plant growth, and again there is a possibility that they will be washed away before they are needed.

The natural equilibrium of mineral nutrients in rivers and lakes is disturbed when excess water carrying dissolved fertilisers drains into them. Eutrophication can result from too much nitrogen and phosphorus in the environment.

Using too much fertiliser might have further negative effects on the ecosystem. Excessive amounts can change the soil's pH, which has an impact on the organisms that dwell there and – more importantly – on a plant's capacity to absorb nutrients. It is possible for the addition of fertiliser to reduce the availability of nutrients by changing the pH of the soil.

There are several mineral nutrients that plants only need a tiny amount of (these are called trace elements): too much of them in the soil can have the opposite effect from what was intended by making plants toxic.

The ability of a plant to absorb water might be impacted by the overapplication of fertilisers. Osmosis is the mechanism by which water passes through a membrane from an area of higher (water) concentration to an area of lower (water) concentration in order for roots to absorb water. The solution within a plant's cells is typically more concentrated (solutes) than the solution in the soil. When the concentration of solutes in the soil solution is too high, it might cause water to run out of the plant due to overfertilisation. This makes the plant dry (often called scorching). This can happen when fertiliser is applied incorrectly to a field, but it can also happen when manure (dung) heaps are nearby. In these situations, plants fail to thrive and there is a higher danger of nutrients draining into the nearby soil.

Other nutrients may also have a direct impact on plant development. An excessive amount of fertiliser might result in lush, rapid growth that the plant cannot support. Pest and disease attacks are more likely to occur in dense growth. If the crop is fruit, a nutritional imbalance (such as a high nitrogen-to-potassium ratio) may lead a plant to develop a lot of foliage and be less likely to blossom.

When nutrients leak into drinking water supplies, water quality can be damaged and this can also have an effect on humans. The development of 'blue baby syndrome' is linked to excessive levels of fertiliser in the water supply. Newborns with this condition have oxygen-deficient skin tissues, which gives them a faintly blue or purplish hue.

Users of both organic and inorganic fertilisers run the danger of overapplying the fertiliser. Because they are more likely to dissolve in water, inorganic fertilisers carry a risk. Farmers will benefit from the early availability of the crop, but they also run the danger of leaching if there is a lot of rain or irrigation. There is a risk of overapplication with bulky organic fertilisers since it is more difficult to establish the precise nutrient content and the nutrients are released over a longer period of time.

Laws are in place in certain industrialised countries to lessen the potential effects of excessive fertiliser use. Nitrate vulnerable zones (NVZs) have been established by the UK government in places where nitrogen concentrations are already high. To avoid the risk of leaching, there are severe restrictions on when fertilisers can be administered in particular locations. The farmer must also keep meticulous records to demonstrate how much fertiliser has been applied. Large fines may apply if the records are not kept.

3. Misuse of Irrigation

Everyone who is alive needs water. Many countries are experiencing water shortages as a result of the demand for water. Agriculture is under pressure to conserve water and recycle as much as it can. Water shortages for people or cattle may occur as a result of water waste. Irrigation done in excess can have a number of detrimental impacts.

• Damage to the soil structure: when wet, air pockets are lost and the soil is compacted.

• Death of plant roots: waterlogged soils prevent plant roots from getting sufficient oxygen to respire and cells start to die.

• Loss of nutrients: nutrients dissolve in the water in the soil, and as water drains away nutrients are taken away with it.

• Soil erosion: large amounts of water run-off will take some of the soil particles with it.

• Soil capping: the surface of the soil can become hard and compact, which makes it harder for plants to grow through the soil.

• Salinisation: the salt content of the soil can increase. Scientists have estimated that around 20% of irrigated land has become saline in the last 20 years. Salts dissolve into the water within the soil but are normally at their highest concentrations deeper in the soil. Over-irrigated soils become waterlogged and therefore the salts are able to move throughout the soil. When the sun causes the evaporation of water from the soil, the salts are left behind. If the salt levels become too high, plants will have difficulty taking up water (by osmosis) and water supplies may also become unsuitable for drinking.

• Preventing soil cultivation: if the water content is too high, the soil can be too heavy to cultivate. Machines can get stuck because the soil structure cannot support their weight.

Pesticides, fertilisers, and excessive water consumption can all have negative effects on both humans and the environment. The difficulty is that simply using them less also results in issues, including decreased yield and even fewer resources for subsequent crops. Not applying any of these innovations is a bad idea. If additional mineral nutrients aren't added to the soil, plant growth will be slowed because there won't be enough nutrients for building plant proteins or making fibres for support, for example. Plants may produce a crop that is of worse quality in terms of nutrient content or the ability to be stored for an extended period of time, as well as growing more slowly and having smaller yields.

Less yield from the soil means less food for farmers and their families as well as less grazing for livestock. If the land is unable to offer enough food for the farmers to subsist, they may need to relocate.

Desertification, or the process of turning rich land into a desert, can be caused by poor soil management. Soil erosion is a potential cause of desertification of formerly fertile land, and agricultural practices have a significant impact on erosion risk.

4. Choice of Crops

The majority of farmers have some degree of control over the crops they grow. The decision for many subsistence farmers is likely to be the kind of plants that will best feed their families (either directly from the plant harvest or by feeding livestock).

Commercial crop producers, or farmers that grow crops for a living, may choose to grow a distinct selection of plants. The most lucrative product to expand in terms of revenue generation, however, might not be the best option for the larger community. One example of this conflict is the cultivation of poppies for the production of opium in nations like Afghanistan, either for the legal production of drugs or the illegal drug trade. Another example is the production of cut flowers for wealthy nations like those in Europe or North America on the most fertile terrain in nations like Kenya.

Even though using the fertile soil to grow food to feed the locals could benefit the entire community, it does not always result in huge incomes for the local farmers. If a country has commercial crops it can trade with other countries, which can be advantageous for the country as a whole. Foreign trade gives countries access to resources and technology that are not readily available to them locally, as well as the money to buy them.

The question of whether governments should impose dietary restrictions on their citizens is further complicated by this. Should the government restrict what farmers can grow? Should a government impose restrictions on what its citizens do, or should they be allowed to make their own decisions? Many countries (and political parties) have held varying perspectives on these issues over the years. In fact, there most likely isn't a right response. Nonetheless, bad choices made by governments can lead to a shift in power in the next election or, in extreme circumstances, a violent revolution.

5. Overproduction and Waste

Giving farmers the freedom to select the crops they want to plant in order to maximise their income may result in the overproduction of a specific crop. A farmer may charge more when selling a crop when there is a greater demand than there is a supply for that product. The contrary also occurs; when a commodity is widely accessible and there is an excess supply, farmers will receive less money for their harvest and perhaps some of it will be wasted. If a farmer doesn't earn a profit in a given year, he or she might start growing a crop that others did, which could lead to an excess or shortage of certain crops the following year. Thus allowing farmers the freedom to choose and manage their own land can lead to a waste of resources in a number of ways.

• Waste from overproduction: too much of a crop might mean that some will not be sold.

• Waste of storage space: it may take longer to sell a crop, so buildings are needed to store the spare harvest. Some crops need special conditions so they do not spoil.

• Waste of transportation: to sell all the crops, a farmer may need to travel larger distances, use more fuel, etc.

• Waste of quality produce: if a crop starts to decrease in quality because it has not been sold quickly enough, it will be worth less money.

• Waste of labour: the farmer may have to use staff to help grow and care for the crop, which is not an efficient use of time and labour if too much crop is produced.

Even if a farmer or grower sells their crop, the price will be poor if there is an oversupply. Does the farmer have enough cash left over after paying his expenses to purchase seeds for the upcoming harvest season?

5.1 Mechanisation

While the extensive rise in yields obtained over the past few decades has been aided by the use of machines, this does have a number of negative effects on the environment and the local population.

Fields have been expanded in order for the machinery to operate more effectively, and natural flora that might have served as a habitat for other organisms has been removed. Eliminating pests' natural predators could also directly affect the crop.

Tractors, for example, are powered by fossil fuels, a non-renewable resource. Moreover, their exhaust gases add to air pollution. For a farmer, large equipment (and its fuel) can be expensive. While mechanisation might enhance yield, the added costs may result in the farmer making little profit and making it difficult for him or her to repay bank loans, such as those required to pay for a new machine.Via their tyres, large machines apply a lot of pressure to the ground. The dirt is compressed and air spaces are eliminated, which might result in extremely compacted areas where these tyres move. This may limit the region where plant roots can spread out as well as the soil's normal drainage.

The use of machinery may affect employment and career opportunities. Many people can do their work more quickly with a large tractor equipped with a variety of agricultural attachments. As a result, locals have fewer options to work on the property. Some people might be forced to move if they can't find work or a way to support their families. People frequently move from rural to urban regions in search of employment, which can lead to more issues if there is a lack of affordable housing and competition for jobs. Causes and Impacts of Soil Erosion

Introduction

Soil erosion can be hazardous to farmers and can greatly affect agriculture. In this unit we unpack the various ways in which this can occur.

1. Soil Erosion

All types of land are subject to the naturally occurring process of soil erosion, which has a significant impact on how the landscape around us is shaped. Soil erosion is often a rather slow process, except during natural disasters. However, the landscape can change dramatically and quickly as a result of human activities like agriculture, which can upset the natural balance.

The horizons (layers) of soil. Most plant roots are found in the topsoil.

Although soil is made up of several separate layers (or horizons), the topsoil, which is found immediately below dead leaves and plants, is the most fertile. Topsoil's structure, which both retains water and maintains air gaps, promotes the greatest amount of root growth. Because it contains organic materials and could have a lot of nutrients, topsoil is frequently a dark layer. The soil's fertility will be negatively impacted by the loss of this layer. The erosion of topsoil can happen in a variety of ways.

• Natural vegetation is being removed. Natural habitats have been severely impacted by the demand for land for grazing, crop cultivation, or timber production. Existing plants' roots aid in holding the soil together. The soil structure is not sturdy enough to endure heavy rainfall once these are gone. Topsoil is carried along by precipitation runoff, including flash flooding, and is dispersed from its original place. In addition to providing sites for any soil that is carried along to get lodged and deposited, tree roots are essential for slowing down the speed of rushing torrents of water. There might be nothing left to stop runoff and soil erosion when vegetation is gone. Due to the fact that the natural vegetation was the only thing holding the soil together, areas of rainforest that are destroyed for cultivation frequently experience significant erosion. Farmers regularly have to migrate because erosion makes it impossible to sow new crops.

• Overcultivation. Regular cultivation leads to the loss of soil structure because large clumps are broken up into smaller ones during plowing or digging. The mechanical disintegration of soil makes the smaller particles easier to move and more susceptible to erosion, which may be beneficial in the short term for even sowing and the growth of seedlings.

• Overgrazing. Due to pressure from cattle, vegetation in grazing areas may be reduced to almost ground level. The plants gradually deteriorate under continuous heavy grazing because they have little leaves for photosynthesis. Because there aren't any plant roots to hold the soil together due to a lack of vegetation, the soil is more susceptible to erosion. The plants will also be trampled on by a lot of animals in the region, harming them in the process. Animal hoofs compact the soil, which inhibits root growth and weakens plants further. Compaction also lessens the number of air spaces in the soil.

• Wind erosion. When vegetation is removed, the soil is far more likely to be blown around by the wind. The vegetation may be removed for a variety of reasons, including the need for additional room, excessive animal grazing, the development of arable crops, or the removal of hedges and barriers to make way for huge machinery.

• Water erosion. One of the more frequent causes of extensive erosion, as well as a factor in several of the other forms of erosion, is undoubtedly water. Soils can be eroded by water in a variety of ways.

• Heavy rainfall: The force of heavy rain (with huge droplets) knocks soil particles loose, allowing for more erosion.

• Rainwater run-off: Excessive water that the soil is unable to absorb will carry soil away from the area. If the soil surface has been capped (by huge water droplets) or compacted by humans or machines, water infiltration may also be reduced.

• Gulley erosion: Water flowing quickly through gullies and streams further erodes the local soil, creating deeper and deeper crevices. Gullies are initially created by the movement of rainfall run-off across the landscape. Where there is a natural slope in the soil, issues can become worse because rainwater moves faster and has a much stronger scouring effect.

2. The Impacts of Soil Erosion

While topsoil loss is one obvious indicator of severe soil erosion, other direct and indirect effects are much more difficult to understand. The topsoil is the soil's most productive layer, therefore losing it implies losing this productive layer. Due to a deficiency in nutrients, often insufficient air spaces, and problematic water availability, the subsurface is not able to support plant growth in the same way as topsoil. The subsoil's structure prevents plant roots from penetrating it easily, which is why there are so few of them depicted in the image above. The lack of fertility results in few plants surviving, and few plants surviving implies that little organic matter is reentering the soil and enhancing its fertility, which causes the area to become desertified.

The impact of wind erosion

Source: IGCSE Environmental Management textbook

Sand drifting over a farm in the 1930s as a result of severe erosion.

In the 1930s, the prairies of the USA and Canada experienced a significant instance of wind erosion. These regions had been transformed from grassland into cultivated cropland, utilizing tractor-drawn ploughs over vast areas. Severe drought hit the area, and without the stabilizing effect of deep-rooted grasses, the soil became vulnerable to wind erosion, resulting in massive dust clouds known as 'black blizzards.' These clouds not only affected humans and livestock but also impacted cities and shipping over 3000 kilometers away in the ocean. The consequences were disastrous, rendering entire farms unsuitable for use, and causing the loss of fertile topsoil, estimated to be up to 2 meters deep. The scale of the affected land was vast, reaching approximately 400,000 km2, leading to the displacement of around 500,000 people who lost their entire farms. Some estimates suggest that more than 75% of the topsoil was lost in the area. This environmental catastrophe had far-reaching effects, severely damaging the economies of both countries. In response, the US government acquired 45,000 km2 of land from farmers to prevent further arable production and allow it to revert to grassland.

Questions

Answers

1. What were the primary factors contributing to this severe soil erosion event?

2. What led to the authorization of farmers to adopt such cultivation practices?

3. Mention two significant consequences resulting from this extreme soil erosion.

4. How did the acquisition of land by the US government contribute to resolving the issue?

Many organisms in the area lose their habitats as a result of the loss of topsoil. Organisms that live in or eat topsoil will lose their environment. Animals that rely on the local flora have fewer options for food and shelter. Soil erosion, therefore, affects the entire ecosystem. Interference with the local ecosystem might also result in unanticipated issues, such as an increase in insect issues if enough natural predators can no longer exist in the new environment.

Even farther beyond the original place, soil erosion can have an impact. Rivers and lakes finally receive flowing water. The soil that is being carried by the water begins to settle as the flow of the water slows down, causing watercourses, rivers and lakes to become muddy. Due to the amount of silt deposited, there is nowhere for the water to collect after a strong rain, which might change the water bodies' ability to hold water and result in flooding in new locations. In other instances, rivers have become too shallow for boats to navigate, which has an impact on the way of life of those who depend on them for transportation or jobs.

Little lagoons created by silt deposits can serve as new breeding grounds for insects like malaria-carrying mosquitoes. Water availability and quality can both be impacted by silt. Silty water can have an adverse effect on aquatic species' health and viability by burying them at the bottom of the silty layer or obstructing light from reaching the leaves of aquatic plants. This has an impact on the water's oxygen content and its capacity to support healthy living conditions. Since the soil in the water might reduce fishes' ability to take oxygen from the water through their gills, fish populations may suffer.

Because of the desertification process, plants can no longer develop in the soil to their full potential. Both the cultivation of crops and the breeding of livestock (which feed on plant material) will be affected by this. Locals may need to relocate if the productivity of the land declines in order to survive. This may cause an entire town to leave in the event of a catastrophic drought. There may be a rise in emigration to cities, similar to the effects of mechanisation, but for many rural villages, this emigration may also involve their animals, which are prized belongings. The relocation of an entire farming community creates issues for the surrounding area, possibly leading to conflict (or even war) between the displaced farmers and the original farming communities.

Even if a family or group is able to find land to cultivate after being uprooted, it will take a long time before any crops they grow will produce any food. People and populations are at risk of hunger and starvation without a consistent source of food. The native vegetation in the new location may also be negatively impacted by foraging for food and fuel. When communities are displaced, the need for food and access to clean water becomes a top priority. As a result, foreign aid organisations concentrate on providing basic necessities like food and medical care to stop deaths and prevent crises from occurring.

Migration of communities frequently entails moving to a neighbouring country, which complicates international cooperation. The location of temporary encampments and the requirement for international approval can sometimes cause a delay in bringing the necessary resources to those in need.