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The upper layer of soil on the earth’s surface is called topsoil. It is also called A-horizon as it is the top-most layer where the earth’s essential organic activity takes place. This important layer of soil is usually about two to six inches in depth. It has the maximum amount of organic matter and microbes, and contains the highest level of nutrients needed for plants to grow. It is impossible for plant life to flourish without the nutrients provided by the topsoil.


[edit] Qualities of Good Topsoil

Good topsoil contains prime arable soil that is friable, with low stone content. It includes the right mixture of mineral particles, nutrients, organic matter, water, air and living organisms. The topsoil is the repository of all deposits of eroded material, along with dead and decaying organic matter and biomass. It is the layer where high biochemical activity takes place and is essential for the proper functioning of the ecosystem. It influences soil fertility, soil structure, drainage, root growth and aeration.

Topsoil contains essential nutrients for plants, including phosphorous, potassium, sulphur, magnesium and nitrogen that make for a balanced soil composition. Phosphorous is the nutrient that aids plant growth and development. Lack of phosphorous may lead to weak roots and underdeveloped growth, and dull and discoloured leaves. Potassium helps flower and fruit to develop, and is essential for photosynthetic function in plants. Magnesium is a constituent of chlorophyll, and is responsible for the green pigment of leaves. It also aids in photosynthesis activity in plants. Nitrogen is the main growth nutrient for the growth of stems and leaves. Good quality topsoil will need to contain electrical conductivity also in the expected range of soil-water ratio of 100-1,500uS/cm in good topsoil.

Alkalinity or pH value is also important for influencing microbe activity and mobility of soil pollutants in topsoil.

[edit] Commercial Topsoil

Topsoil is commercially sold as vital manure and soil composition for growing lawns and gardens as the soil mix can provide perfect conditions for potting plants. Nurseries and garden centres stock manufactured topsoil to be sold in bulk as an ingredient for soil mixes, raised beds, lawns and container gardens. Commercial topsoil is also used for landscaping, restoration, civil engineering projects and even sports ground construction.

To make commercial topsoil a sustainable venture, topsoil is manufactured whereby compost is mixed into regular soil to increase the humus or organic content by 2 per cent and this manufactured topsoil is culturally and environmentally healthier for use. Conservationists suggest that instead of gathering topsoil that can be used for essential farmland purposes, manufactured topsoil is used by mixing organic matter, reducing pesticides in existing garden patches, beds and lawns. Environment-friendly horticulturists also supply recycled soil for making topsoil to householders for their gardening purposes.

Livestock by-products, such as manure, are extensively used for commercial topsoil as this helps manure management, produces topsoil that is value added and environment friendly, helps the farmer to even market it wholesale. This can be used for seedings, gardening and lawn maintenance purposes and for general organic soil amendment.

[edit] Topsoil Erosion

It is estimated that 25 billion tonnes of topsoil lost each year across the earth’s surface, but it takes almost 500 years for one inch of topsoil deposit to develop. Hence topsoil erosion remains a major environmental concern. Toxic chemical deposits on topsoil and debris from weedy areas and contaminated soil areas can harm the organic goodness of the topsoil. Topsoil is usually eroded by water or blown away and this erosion can halt plant growth. Heavy rainfall and snowfall also cause extensive damage to top soil as also deforestation, construction activity such as mining, and poor agricultural practices. Topsoil erosion in agricultural lands is a growing cause for concern in farmlands all over the world. It affects productivity in farm lands and erosion leads to sediments, often containing pesticides that cause water pollution including silting-in of reservoirs, escalating costs of industrial and domestic water treatment, increased threat of flooding and even threatening survival of fish population. Erosion of topsoil has economic consequences for all, not just farmers.

[edit] Conservation Concerns

When topsoil is eroded of its organic content, its cohesiveness and capacity to hold water is reduced, leading to make the topsoil dry and barren, which in turn, increases the erosion rate. Top soil protection is of prime concern to environmentalists and agricultural practitioners. Soil that is high in organic matter can absorb water better and stay cohesive and thus prevent the top layer being washed off. Poor agricultural practices including harvesting, tilling, grazing by hoofed animals increases the depletion. Established practices for topsoil conservation effectively help control sedimentation rates. Soil protection measures in agricultural practices such as proper irrigation, terracing, field bunding help reduce the rate of sediment input and top soil protection of sediment and toxic elements help halt the deterioration that has the twin benefits for agriculture and environment.

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