Agroforestry systems promote soil health by fusing the advantages of trees, crops, and other vegetation, encouraging long-term sustainability and resilience in agricultural landscapes. When trees and shrubs are planted alongside other crops in agroforestry systems, the resulting buildup of leaves, branches, and other plant remnants results in the soil being more organically rich. The structure, water-holding capacity, and nutritional supply of the soil are all improved by this organic matter. Additionally, nutrients are drawn out of deeper soil layers by trees and shrubs and brought to the surface by litterfall and root turnover. The associated crops can now access these nutrients, hence requiring fewer additional fertilizers.

According to the FAO report on desertification and land degradation, a total estimate of about 2 billion hectares of land worldwide is affected by land degradation. 24 billion tons of fertile soils are lost annually due to erosion, and 12 million hectares of land are degraded each year – this is 23 hectares per minute.

Certain factors, including human activity and natural processes, contribute to the decline of soil quality and productivity. Soil degradation involves several aspects, such as loss of soil fertility, erosion, desertification, soil pollution, and a decline in biodiversity. Unsustainable agricultural practices, urbanization, industrial activity, excessive grazing, poor land management, climate change, and other factors are major causes of soil degradation. The impacts of degraded soils are felt in various ecosystems, food production, water resources, and human lifestyles. It has negative effects on biodiversity, decreases agricultural output, and may have long-term effects on environmental sustainability and food security.

Sustainable land management techniques, such as agroforestry, are necessary to address the poor state of soils. Also, effective measures to stop soil degradation must be put into place in order to preserve the long-term sustainability of land resources. This requires both international cooperation and local community involvement.

How does the soil degrade?

Poor vegetation cover and rising soil temperatures can cause higher evaporation and lower soil moisture levels. This may cause the soil to dry out, lower the amount of water available to plants, and raise the possibility of a drought. Additionally, increased rainfall and severe weather occurrences like storms and floods can exacerbate soil erosion. As a result, topsoil is lost, which affects soil fertility and productivity since it is depleted of nutrients and organic matter.

Intensive farming methods like deforestation, overgrazing, intensive cultivation, and forest fires have all contributed to soil degradation. These practices destabilize the soil, making it susceptible to wind and water erosion, which affects the complex processes below. Chemical degradation of soil can also result from the overuse of chemical fertilizers and pesticides as well as poor treatment of industrial waste. These compounds have the ability to pollute the soil, lower nutrient availability, and change the pH of the soil. Also, when soil particles are compressed, pore spaces are reduced, which can result in soil compaction. Compaction can prevent water and air from moving freely through the soil and hinder plant growth. It can be caused by the use of large machinery, intensive farming, and excessive foot traffic. A compacted soil causes reduced rate of both water infiltration and drainage. It also implies that plant roots must work harder to break through the soil covering.

High salt content from irrigated water and fertilizers can build up in the soil and cause salinization. The excessive salts might make the soil unfit for farming and interfere with plant growth. Also, soil can become depleted of vital nutrients through continuous farming without proper nutrient replenishment. As nutrients are drawn out of the soil by plants for growth, crop yields fail if they are not replaced by organic matter or fertilizers. In addition, numerous contaminants, such as heavy metals, pesticides, industrial waste, or poor household chemical disposal, can contaminate soil. These contaminants can harm the ecosystem and human health while deteriorating the quality of the soil.

Restoring soil health through agroforestry

“Agroforestry is a suitable tool for landscape restoration because it can enhance physical, chemical and biological soil characteristics, thereby increasing soil fertility, controlling erosion and improving water availability.” (FAO, 2017 – Agroforestry for landscape restoration)

The fertility and structure of the soil depend heavily on organic matter. Reduced organic matter content, due to factors like excessive tillage, inadequate land management techniques, and a lack of organic inputs, can affect the soil’s capacity to hold onto moisture and nutrients. The ability of soil to hold moisture is crucial for plants to grow and survive. However, this quality is lacking in degraded soils. They have very little organic matter; therefore, they cannot hold water due to their larger pore spaces. Fallen leaves, wood twigs, animal wastes, and the remains serve as organic matter in an agroforestry system. They help enrich the topsoil, improve the water holding capacity of the soil, and prevent water loss through evaporation and deep seepage.

Also, trees and other perennial plants in an agroforestry system help to reduce soil erosion. Their roots hold the soil’s particles together, preventing runoff and water and wind erosion. By doing this, topsoil is kept in place and nutrients are kept in the rooting zone. Also, effective water management in agricultural landscapes is achieved through agroforestry practices. In order to reduce evaporation and stop water loss, trees and other plants serve as windbreaks. They increase the soil’s ability to retain water and decrease runoff by forming pathways for water infiltration.

In comparison to typical monoculture practices, agroforestry systems maintain a higher amount of biodiversity. Insects, birds, and other creatures can all find a habitat among the variety of plant species. These organisms promote soil health by enhancing nutrient cycling, natural pest control, and crop pollination. They also serve functional roles in loosening or aerating the topsoil to improve drainage and the water-holding capacity of the soil. Also, less chemical inputs, such as synthetic fertilizers and pesticides, are needed in agroforestry systems. This is because of the variety of plant species and beneficial interactions that exist within the system.