Soil Erosion - Fundametnals of Biology - Lecture Slides, Slides of Biology

Download Soil Erosion - Fundametnals of Biology - Lecture Slides and more Slides Biology in PDF only on Docsity! Definition : soil erosion is the removal of the top-soil by the wearing action of rain and wind . Reason : a. Deforestation b. Over-grazing c. Poor farming methods Docsity.com A. Deforestation : • The removal of trees exposes the top-soil which is then no longer protected by the leafy canopy of the forest . • The thin layer of top-soil will be easily washed away by heavy rain . Docsity.com •Erosion and soil loss is the end member of a variety of physical, vegetative and nutrient factors that lead to soil degradation . •Using heavy machinery on soil rapidly compacts it into a hard layer which can hardly absorb any water . Eventually the soil become dry and easily be blown away . •Soil fertility is a complex issue and nutrient loss is not necessarily nor always a consequence of erosion. Docsity.com Soil conservation • Soil conservation is to take steps to prevent soil erosion . A. Crop rotation i. Definition Crop rotation is growing of different crops on a field from year to year to prevent the soil from lacking of one particular type of material due to the withdrawal by one type of crop . Docsity.com ii . method 1st and 2nd year : ~ Crop with a high nutritional demand can be followed by the crop which have lower nutritional demands . ~ long-rooted plants crop can be followed by short-rooted crops so that the minerals are removal from different soil level . Docsity.com B. Other methods ~ Steep slope are grown with tree to provide canopy to protect the top-soil from washing away by heavy rain . ~ Adequate number of animals is reared on the grassland to avoid the over-grazing of grasses . ~ Gypsum can reduce erosion on heavy clay soils by improving soil structure and increasing water infiltration. Docsity.com ~ Lime and other calcium sources. Agricultural lime, chemically described as the oxide, hydroxide, or carbonate of calcium and/or magnesium, is used to correct soil pH. Docsity.com • Use of pesticide to the kill the pest . • Common weed control practices : herbicide (weed - killer)applications and cultivation . Docsity.com • Pesticides kill the pests which are animals (insect) that consume the crops in the fields . •The amount aphid and thrips populations decreased . •Prevent the pest population from reduces yield. Docsity.com • cause crop and environmental damage. • Cause environmental contamination, and adverse side effects . • Some weed control may tie up soil nitrogen . • Pesticide contain toxic substance . Docsity.com • Pesticides , particular DDT , is very poisonous and cannot be easily degraded by natural process . • The toxic chemicals such as pesticide and herbicide may be leached into the river . It can toxic to human by pass through the food chain . It would also kill the aquatic animals and plants . • It also cause water pollution . Docsity.com B. Accumulation of DDT concentration along food chain . ~ DDT sprayed into crop fields may be absorbed by the surrounding plants . Though the initial concentration in plant is very small , DDT will be accumulated in the herbivores when they eat the contaminated plants . ~ when secondary consumer eat the contaminated herbivores, they also accumulate DDT to a higher concentration . ~ So that DDT is concentrated along the food chain to higher levels in the final predators . As a result , predators are eliminated . Docsity.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Losses through respiration and excretion . . . . . . DDT blomass . . . . . . Secondary carnivores (predatory bird) Primary carnivores (blowfish) herbivores (mud small) plant (aquatic plant) Docsity.com C. Development of resistant population of pests . ~ The prolonged use of DDT causes immune populations of the pests to emerge . ~ Therefore greater does of insecticides are required to kill these resistant strains . It aggravates the problem of pesticide pollution . Docsity.com A. Introduction ~They are mainly composed of nitrogenous , phosphorus and potassium(NPK) compounds . ~ They are water soluble and can be absorbed by plants immediately i.e. quick action . ~ They contain no humus so that they cannot improve the soil texture . Docsity.com B. Undesirable effects of excessive use Excessive use of fertilizer would cause pollution : i. Eutrophication ~ The leaching of excessive chemical fertilizers to river or lake will cause eutrophication (nutritional enrich- ment of water that promotes the growth of aquatic plants) . ~ As a result , algal bloom (excessive growth algae) will occur and cause the following effects : 1 . Blue-green algae unsuitable for fish food and may be harmful to them . Docsity.com 2 . Algae reduce the penetration of light to the submerged plants . 3. On a cloudy day or at night they will compete with fish for dissolved oxygen . 4. Decomposition of the dead algae further deplete the dissolved oxygen . As a result , fish and submerged plants may be killed . ii. Disease ~ Drink water with high nitrate content may cause anaemia in child . Docsity.com Twenty five events showed peak concentrations over 10 micrograms/litre and 48 events had a mean concentration of 1-10 micrograms/litre. The remaining 50 events were below 1 micrograms/litre. The highest recorded pesticide concentration in streamwater was 68 micrograms/litre. Even pesticides traditionally thought to be strongly soil-adsorbed (e.g. deltamethrin) were found in the stream. Docsity.com solution Solutions involve finding sustainable ways for the agricultural area to reduce both its dependence on pollutants and the amount of pollutants it produces, and to properly recycle or dispose of pollutants before they contaminate soil, water, or air. Organic farming avoids the use of pesticides and fertilizers. Efficient irrigation can slow salt buildup in soil and drainage water. Avoiding large concentrations of animals can reduce nutrient pollution, and their waste can be used as fertilizer for crops. Certain cropping methods can reduce the erosion of sediment from the land. Docsity.com