Physical Properties of soil SAQ's Q & A.docx

What is the primary characteristic of colloidal clay particles, despite being the smallest type of clay particles? ANSWER: They have the greatest capacity for ion exchange. What type of water is available for plant uptake, and where is it typically held in the soil? ANSWER: Capillary water, held...

What is the primary characteristic of colloidal clay particles, despite being the smallest type of clay particles? ANSWER: They have the greatest capacity for ion exchange. What type of water is available for plant uptake, and where is it typically held in the soil? ANSWER: Capillary water, held in large pores between the soil aggregates. What is the ratio of pore space to soil volume in a typical soil? ANSWER: 50% pore space (air and water) and 50% soil volume. What type of soil has intermediate characteristics of clay and sandy soils, and what is its composition? ANSWER: Loam soil, containing amounts of sand, silt, and clay in a ratio of 40%:40%:20% What is the product of the breakdown of organic matter, and what are its characteristics? ANSWER: Humus, a dark sticky material that absorbs water and improves soil quality. What is the primary difference between gravitational water and capillary water in soil? ANSWER: Gravitational water is moved through the soil by gravity and is only available temporarily, while capillary water is held in pores and is available for plant uptake. What are the primary characteristics of clay soils, and how do they affect plant growth? ANSWER: Clay soils hold water easily, have poor drainage, and can lead to waterlogging, but are fertile and protect minerals. What is the primary advantage of loam soil over sandy and clay soils? ANSWER: It has more advantages than both sandy and clay soils alone, with good drainage and nutrient retention. What is the significance of soil texture in determining soil properties? ANSWER: Soil texture, which is a fixed property, affects drainage, aeration, and fertility due to the different properties of sand, silt, and clay particles. Describe the importance of good soil structure for healthy plant growth. ANSWER: Good soil structure provides aeration, water drainage, and root penetration, which are essential for healthy plant growth and nutrient availability. Explain the effects of soil compaction on soil structure and plant growth. ANSWER: Soil compaction destroys soil structure, reduces pore space, and lowers drainage and aeration, making it difficult for plant roots to penetrate and grow. How does organic matter loss affect soil structure and fertility? ANSWER: Organic matter loss leads to poorer soil structure, lower nutrient availability, and lower water retention, resulting in lower soil fertility. Describe the types of water held in soil and their availability to plants. ANSWER: Soil holds hygroscopic water, capillary water (available and unavailable), and gravitational water (temporary availability), which are affected by soil texture and structure. Explain the significance of soil colour in determining soil fertility. ANSWER: Soil colour is an indicator of soil fertility, with dark brown or black colours indicating high fertility and nutrient richness, and light or grey colours indicating low fertility. Describe the impact of soil temperature on plant growth and development. ANSWER: Lower soil temperatures result in lower germination rates, water uptake, and mineral uptake, affecting plant growth and development. How does erosion, sedimentation, and weathering affect soil structure and fertility? ANSWER: Erosion, sedimentation, and weathering lead to loss of topsoil, organic matter, and nutrient-rich sediments, resulting in poorer soil structure and lower fertility.