Topsoil disappearing

I previously posted water problem which talks about farmers in Tamil Nadu, cultivating water-intensive crops and indiscriminately exploiting groundwater for irrigation, thus leading to a steep fall in the water table. In this respect it is only in comparatively recent times that such water intensive crops as paddy (rice) started to be cultivated in Tiruvannamalai District. The proliferation of 'bore-wells' allowing individual farms, independent water access, is responsible for the intensive, inappropriate crop cultivation in this area. When all is said and done this is just not the right climate for yearly rice cultivation! In the above mentioned posting, it was also stated that by the juidicious planting of less water intensive crops the area would achieve a 10% reduction in the agricultural sector, thereby considerably easing the impending water shortage situation. At this time agriculture accounts for 85-90% of the total use of water in Tamil Nadu.

The current easy access of existing groundwater is also encouraging farmers to indulge in continuous crop rotation, never allowing the soil to rest and revitalize and exacerbating the disappearance of topsoil. In ths respect, the below abridged article from the U.S. investigates problems faced there with the gradual disappearance of topsoil.

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“Call it the thin brown line. Dirt. On average, the planet is covered with little more than 3 feet of topsoil; the shallow skin of nutrient-rich matter that sustains most of our food and appears to play a critical role in supporting life on Earth.

The estimate is that we are now losing about 1% of topsoil every year to erosion mostly caused by intensive agriculture. To combat this some farmers in the U.S. are beginning to adopt ‘no-till’ methods, which involves not tilling the land between plantings, leaving crop stubble to reduce erosion and planting new seeds between the stubble rows.

David Montgomery has written a book entitled, "Dirt" to call public attention to what he believes is a neglected environmental catastrophe. A geomorphologist who studies how landscapes form, Montgomery describes modern agricultural practices as ‘soil mining’ to emphasize that we are rapidly outstripping the Earth's natural rate of restoring topsoil. The National Academy of Sciences has determined that cropland in the U.S. is being eroded at least 10 times faster than the time it takes for lost soil to be replaced.

Healthy topsoil is a biological matrix, a housing complex for an incredibly diverse community of organisms; billions of beneficial microbes per handful, nitrogen-fixing fungi, nutrients and earthworms whose digestive tracts transform the fine grains of sterile rock and plant detritus into the fertile excrement that gave rise to the word itself ("drit," in Old Norse).

As such, true living topsoil cannot be made overnight and grows back, very slowly, at a rate of an inch or two over hundreds of years. Erosion rates in some U.S. regions have recently improved because of better conservation farming practices, including leaving some natural ground cover in areas of high erosion. Another way of losing soil is by paving it over with regards to urban development. But while some land is lost to development, pollution or changing weather patterns, it is believed that global soil loss is a crisis mostly rooted in agriculture. Soil tilling also seriously exacerbates mud and muddy runoff.

Every year fields are tilled and rains come, washing away the soil - which is just powder, brown dust. It's dead. There's no worms, no life in it. However in no-till fields the dirt is coarsely textured, darker and full of roots, debris and bacteria.

Switching to ‘no-till’ farming requires investment and learning new techniques and also depends more on herbicides because weeds are no longer controllable by ploughing them into the soil. Organic farming methods also can reduce soil loss and has been shown to increase soil health, water retention and regrowth when organic methods are used rather than the traditional methods.”

[Abridged from a report by Tom Paulson)