Soil Science Module 1

Soil Science Module 1

• Soil components include mineral matter, air, water, soil microorganisms, and soil organic matter (SOM).
• Ideal soil proportions are 25% air, 25% water, 5% SOM, and 45% mineral matter.
• Key soil properties are texture, mineralogy, and SOM.
• Minerals are solid crystalline materials; rocks are naturally occurring mixtures of two or more minerals.
• Mechanical weathering breaks down rocks into smaller pieces without changing chemical composition.
• Biogeochemical weathering changes the chemical composition of rocks and minerals.
• Soil separates are sand (0.2-0.05mm), silt (0.05-0.002mm), and clay (<0.002mm), ranked largest to smallest.
• Soil texture refers to the proportion of each soil separate in a soil.
• Texture impacts soil environment factors like water-holding capacity, decomposition rates, and permeability.
• Specific surface area is the surface area per unit mass of particles.
• Primary minerals have little to no change in composition, while secondary minerals form from the breakdown and weathering of minerals.

Soil Science Module 2

• Common soil minerals include iron oxides, calcium carbonates, sodium carbonates, and clay minerals.
• Clay's negative charge attracts positive molecules, increasing water-holding capacity and nutrient storage.
• Soil organic matter (SOM) forms from decaying plant and animal matter.
• SOM impacts water-holding capacity, plasticity, infiltration, nutrient availability, and soil organism diversity.
• Agricultural management affects SOM through ploughing and tilling, impacting its composition and function.
• Physical characteristics like soil texture—and structure—affect water movement and availability (infiltration, permeability, and water-holding capacity).
• Soil structure describes how soil particles are arranged (e.g., granular, blocky, platy, massive).
• Good soil structure enhances erosion resistance, root penetration, and water infiltration/retention.
• Bulk density is the mass of a unit volume of dry soil.
• Soil porosity is the percentage of pore space in a soil.

Soil Science Module 3

• Soil compaction reduces pore space, increasing bulk density and decreasing porosity.
• Adhesive forces attract different molecules; cohesive forces attract like molecules.
• Saturation is when all available pore spaces are filled with water.
• Field capacity is the amount of water held against gravity.
• Permanent wilting point is when a soil cannot hold any more water.
• Gravitational flow moves water through larger pores due to gravity.
• Capillary flow moves water through smaller pores due to adhesive and cohesive forces.
• Soil texture impacts water storage and flow rates.

Soil Science Module 4

• Important trophic interactions in soil involve trophic levels that occupy similar positions in a food web.
• Soil organisms use metabolic strategies like autotrophy (obtaining carbon from CO2) and heterotrophy (obtaining carbon from organic compounds), and phototrophy (using sunlight) and chemotrophy (using inorganic chemicals) to obtain energy.
• Major soil microorganisms include bacteria, archaea, and eukaryotes (animals, plants, protists, and fungi).
• The rhizosphere is the zone of soil influenced by plant roots, impacting soil microorganism populations.
• Biological diversity and functional diversity are measures of the variety of species and roles in a soil community.
• Soil biota play critical roles in decomposition and nutrient cycling, soil structure, and plant-microbial relationships (e.g., legume-rhizobium and mycorrhizal symbiosis).

Soil Science Module 5

• Biological nitrogen fixation converts atmospheric nitrogen to a usable form for plants.
• Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with plant roots. plant growth promoting rhizo organisms improve plant performance.
• Essential nutrients for plants include macro- and micronutrients (e.g. C, H, O, N, P, K, macro- and micronutrients).
• Essential nutrients are necessary for plant growth. They have specific functions, and deficiencies cannot be substituted with other nutrients.
• N, P, and K are critical nutrients; plants use specific forms of these nutrients.

Soil ScienceModule 6

• Different factors influence how soil nutrients are taken up by plant roots (diffusion, mass flow, and root interception).
• Liebig's Law of the Minimum states that crop growth is limited by the scarcest nutrient.
• Nutrient cycling involves the movement of nutrients between living and nonliving parts of an ecosystem.
• Key nitrogen processes include nitrogen fixation, mineralization, immobilization, nitrification, denitrification, volatilization, and leaching.
• Key phosphorus processes include phosphorus fixation, organic P mineralization, and leaching.

Soil Science Module 7

• Inputs, transformations, and losses of potassium (K) in soil.
• The definition of fertilizer as natural or artificial substances that enhance plant growth.
• The concepts of fertilizer grade as the % of total N, available P2O5, and soluble K2O.
• The 4R's of nutrient management emphasize applying nutrients in right source, rate, time, and place.

Explore the fundamental components and properties of soil in this quiz covering Soil Science Module 1. Understand soil texture, weathering processes, and the significance of soil organic matter. Test your knowledge on the ideal soil composition and the distinctions between minerals and rocks.