(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) Explanation 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.