(a) Define soil erosion. [2 marks] (b) List four factors that influence nutrient availability in the soil. [4 marks] (c) Explain two roles of each of the following factors in soil formation: (i) climate; (ii) living organisms; (iii) topography. [6 marks] (d) State four problems associated with overhead irrigation [4 marks]
Explanation
(a)Definition of soil erosion: This is the wearing away of soil by means of natural agents such as water, ice/ glacier, and wind. (b) Factors that influence nutrient availability in the soil: Soil pH, Concentration of other nutrients, Leaching, Crop removal/overgrazing, Oxidation and Reduction, Burning, Erosion, Soil moisture content, Level of organic matter/microorganisms in the soil (c) of roles of factors of soil formation (i)Climate - Abrassive action of rock particles blown by wind - Rain may be severe enough to cause erosion - Rain water causes chemical change of rock minerals' aids chemical weathering - Temperature causes the expansion and contraction of rocks alternately leading to minerals with low expansitivity breaking away to form soil. (ii) Living organisms - Soil organisms like termites, earthworms eat deep into the soil and mix the mineral and organic matter together resulting in the formation of soil - Activities of man during farming operation help to break rocks into tiny particles to form soil - Roots of plants grow into openings in the rocks, physically forcing the rocks apart into smaller particles, - Human activities can also cause erosion which result both in soil destruction and formation. - Living organisms produce carbon dioxide which forms carbonic acid with water and enhances rock weathering, (iii) Topography -The shape of the land influences the movement and amount of water in the soil - Hilly and slopy surfaces support erosion and encourage soil formation - A flat and exposes the whole surface to equal environmental factors and therefor delays soil formation - The topography of the land affects the distribution 0,i, plants and animals which influence the process of 01 formation - More soil formation in the valleys than at the top of the hills (d) Problems associated with overhead irrigation - Wind distorts sprinkler patterns and causes uneven distribution of water - The spray force can damage ripening soft fruits. - A stable water supply is required for economic use of the equipment - The water must be clean and free of sand, debris and large amounts of dissolved salts - The initial investment is usually high - Power requirements for pumping water is high - Requires technical know-how - Can spread diseases - Lateral pipes hinder movement of farm machines - High cost of maintenance/repairs/spare parts not readily available.
