Soil erosion

Soil erosion and conservation
Main causes of soil erosion
Removal of natural vegetation cover to leave the grounnd exposed to the elements; most serious- deforestationàin Ethiopia:heavy rains are no more inetrupted by vegetation, water has not enough time toinfiltrate the soil. If this water evaporates, a hard crust may form,making the surf.less porous.Or the heavy rain may accc. the leaching and remove nutriens and organic matter.

Ploughingàdeep ploughing destroy soil by breaking up peds and burying orgaic material too deep for plant use. farm machinery-produce platy peds-reduction of infiltration capacity
Overgrazing (african savannas)àaccelerates soil erosion-reduction of grass surface-increase in exposed surface
Monocultureàcultivating the same crop on the same piece of land-uses up always the same nutriens;
Overuse of wateràsalinisation and reduction of soil quality
Fertilisers and pesticidesànot good if used repeatedly over long periods; chem.fert.-doesn't provide humus and Nitrogen may go into groung water
Nitrate and phosphate runoff causes eutrophication(enriched nutrient content in rivers and lakes)
DDT-kills soil organisms,slows down the decomposition of organic matter
Law of minimum-there is an optimum minimum level for all nutrients

Conesrving and upgrading soil:
If removal of vegetation cover-addition of vegetation; afforestation
growing of cover crops-reduses runoff,protect newly ploughed land from exposure(marram grass anchors,gulleys with brush wood),improving farming methods-rotation of crops,tropical soils-5-15 years recovery,areas with 12O -ploughing,steeper slopes-terracing-slow down runoff-increase infiltration,strip cropping-planting 2 or more crops in the same field,where lateric soils-ploughing,where evaporation exceeds precipitaion-dry farming- covering of soil by straw or weeds to reduce misture loss and lomit erosion,soils suffering from shortage fo water-Eatern Africa-constructing wells(pramene),building small dams(hradza)- increase the infiltration,irrigated areas-water flushed; areas of heavy rains-dams-to control flooding,building of shelter-belts and addition of humus-reduce wind erosion,lime adding to acid soils-to improve soil structure and texture

Loess plateau- North China
Most rapid soil loss in the world; during and after Ice age,large amount of LOESS(yellow) was deposited to a depth of 200m in the Huang-He basin. After deforestation because of farmin, this material is being washed away by the heavy summer monsoons, every year by 1cm. This material is carried by the Huang He river and this is the reason why is this river called the yellow river.

Burkina fasso-overgazing

Stone lines to prevent runoff afforestation in Nepal

There was defoestation , so villagers agreed to stall-feed they animals.It means that they ate what they were given not enything they wanted.and also their manure(hnoj) could be collected, and spread on the land instead of eing deposited on the forest floor.