Question

How much soil will be needed to cover the area of water on the earth surface with fertile land..........​

Answer 1

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Explanation:

Soil covers most of the land surface of the earth in a thin layer, ranging in thickness from a few centimetres to several metres. It is composed of inorganic matter (rock and mineral particles), organic matter (decaying plants and animals), living plants and animals (many of them microscopic), water and air.

Basically, soil forms as rocks slowly crumble away. Air and water collect between the particles, and chemical changes occur. Plants take root, binding the particles together, shielding the surface from the elements, drawing up minerals from lower layers and attracting animal life. Bacteria and fungi break down plant and animal remains into fertile humus.

The speed of this process varies. In prairie regions with ample rain and organic inputs, it may take 50 years to build up a few centimetres of soil; in mountainous areas it can take thousands of years. The process of destruction as a result of misuse or erosion is much quicker. Once completely destroyed, soil is for all practical purposes lost for ever.

Fertile soils teem with life. Porous loamy soils are the richest of all, laced with organic matter which retains water and provides the nutrients needed by crops. Sand and clay soils tend to have less organic matter and have drainage problems: sand is very porous and clay is impermeable. Only 11 percent of the earth's soils have no inherent limitations for agriculture. The rest are either too wet, too dry, too shallow, chemically unsuitable or permanently frozen.

To grow, plants need nitrogen, phosphorus, potassium and a range of other elements. However fertile the soil, growing crops will use up its nutrients. Farmers once compensated for this by spreading animal manure and plant waste on their fields. Increasingly, these have been replaced by manmade fertilizers.

Organic matter maintains the soil structure. It also acts as a buffer for chemical fertilizers, adding to their beneficial effects and reducing possible harm. In fact, the organic content and structure of the soil has to be managed as carefully as the nutrient content.

As agriculture has become more intensive and extensive, mineral fertilizer use has increased. Between 1981 and 1991, the world's annual use of fertilizers rose from 81 to 96 kilograms per hectare of cropland. This average, however, conceals huge differences in usage Zimbabwe, one of Africa's higher users, used only 56 kilograms per hectare a year in 1989-91.

When fertilizer levels correspond to the needs of specific soils and crops and the structure of soil is conserved, yields can be sustained indefinitely. Overuse or under-use of fertilizer can lead to crop failures. Over-application can also cause pollution: excess nutrients leach out of the soil into groundwater, streams, rivers and lakes, making their water unfit for consumption or boosting the growth of algae, which can suffocate entire aquatic ecosystems.

The production of food depends on healthy agricultural systems. These in turn depend on healthy soils.

Answer 2

Answer:

Loamy-textured soils are commonly described as medium textured with functionally-equal contributions of sand, silt, and clay. These medium-textured soils are often considered ideal for agriculture as they are easily cultivated by farmers and can be highly productive for crop growth....................!