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Description
Flashcards by Hlengiwe Zondi, updated more than 1 year ago
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Created by Hlengiwe Zondi
over 9 years ago
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| Question | Answer |
| 3 main resources agriculture depend on | Soil, water, sunlight |
| How soil is formed | Soil is formed at a rate of 1cm every 100 to 400 years and takes 3000 to 12000 years to build enough to form into productive land . Soil is non-renewable and once destroyed is will be gone forever. Soil is necessary growth medium for plants. Soil is one of the most valuable resources |
| Soil is origin | It is a continuous process. It takes an enormous amount of time to produce a small amount of soil. By the process of weathering(breaking up or frocks by water, wind or ice) and decay(decomposition of dead plants and animals and their wastes) over thousands of years, our soil has formed |
| Humus | Partially decomposed plants and animals |
| Loam | It is the better soil for plant growth because it has the average water capacity and average air spaces |
| The amount of time soil takes to form | The exact amount of time taken depends upon the speed at which the parent rock weathers. Weathering occurs through chemical, physical and biological processes |
| Soil structure: Organic particles | Humus and living organisms |
| Inorganic particles | A mixture of different sized particles or sand, silt or clay, air spaces(pores) between soil particles, water(from forms of precipitation, minerals(plate food) |
| Organic material/humus | It is the glue that binds the soil particles together and plays an important part in preventing soil erosion. Organic matter is the main source of energy for soil organisms such as bacteria and warms. Humus also affects the filtration capacity of the soil, therefore reduces water runoff |
| Sand | - has the largest size of particles - has large spaces between the particles allowing water to slip through - you would find it on a beach side |
| Silt | - particles are mid-sized - spaces are smaller and will hold water and nutrients fairly well - you would find it along a riverbank - the smaller particles hold water and nutrients better than sand |
| Clay | -smallest size of particles - spaces are very small and will trap water -you would find it at the bottom of the river -lots of water but not as much room for air. Plants in clay could suffocate |
| Waterlogged | It means soil can't hold anymore water |
| Why do plants need air | It is essential for healthy soil to have air in it so that micro- organisms(small insects, worms etc) are able to breathe and respire |
| What do plants need to grow | In order for plants to grow they need Light Water Gases (oxygen and carbon dioxide) Minerals |
| In a teaspoon of soil you can expect to find | 100 million - 1 billion bacteria Several km of fungi depending on whether you have agricultural or forest soil Several thousand Protozoa From 10 to several 100 nematodes |
| Earthworms | They help to aerate the soil (add air) by constructing tunnels through soil. They also circulate the soil by removing soil from the lower layers and depositing it on the soil surface. They assist in the breaking down of organic material by feeding on humus |
| Dung beetles | They collect dung from the surface of the soil and roll it up into balls. Some bacteria play a role in adding nitrogen to the soil. Plants need nitrogen in order to grow. |
| Bacteria and fungi | Both bacteria and fungi help to break down dead organic materials. Some bacteria play a role in adding nitrogen to the soil. Plants need nitrogen to grow |
| Termites and ants | They assist in decomposition. They also take small pieces of grass down into the mounds, thus helping to fertilise the soil. |
| Soil erosion | Soil erosion Is due to wind and water. The amount of soil these non-living things can carry away is influenced by 2 factors: Speed - the faster either moves the more soil it can erode Plant cover - plants protect the soil and in their absence wind and water can do so much more damage |
| Plants prevent soil erosion for the following reasons | - plants slow down water as it flows over the land (runoff) and this allows much of the rain to soak into the ground - plants roots hold the soil in position and prevent it from being washed away |
| More reasons | Plants break the impact of a raindrop before it hits the soil, thus reducing its ability to erode Plants in wetlands and on the banks of rivers are of particular importance as they slow down the flow of water and their roots bind the soil, thus preventing erosion |
| Ways to prevent soil erosion | Contour ploughing Windbreaks Unplugged grass strips between ploughed lands ( strip cropping) Make sure that there are always plants growing on soil Make sure that the soil is rich in humus Avoid overgrazing |
| More ways to prevent soil erosion | Allow indigenous plants to grow along riverbanks Conserve wetlands Ensure soil fertility by using a crip rotation system Minimum or no tillage Encourage water infiltration and reduce water runoff with mulching |
| Why is soil erosion bad | Soil erosion means a loss of topsoil. Planting can't occur. Loss of vegetation |
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