ISA Arborist Certification Chapter 3 - Soil Science Exam with Complete Solutions

organic layer - ANSWER 0 Horizon, an unaltered soil, thin layer of decomposing organic matter Loam - ANSWER A mix of three different particle sizes and is often considered an ideal soil texture because of the favorable characteristics for plant growth. Not made up of equal mix of sand, silt, clay. Contains less clay Topsoil - ANSWER commonly known as the uppermost layers (O,A,E, and sometimes the upperpart of B horizon) C Horizon - ANSWER Deepest Soil layer composed of partially weathered parent material. Soil in this horizon is continually forming. A Horizon - ANSWER Contains most of the fine absorbing roots of trees and is very biologically active. Rich in organic matter. E Horizon - ANSWER Between the A and B Horizon, lacks the organic matter as in A, has lighter color due to this. Absorbing Roots - ANSWER Roots found in the upper 6-10 inches of soil Roots - ANSWER Few_____ grow deeper than 3 to 4 ft. Soil Structure - ANSWER Shape, size, strength, and arrangement of soil aggregates form ____. Micropores - ANSWER Soil pores that retain water and are the source of available water to plants between rainfalls. Macropores - ANSWER Soil pores too large to hold water against the force of gravity and become filled with air as water drains from the soil. Bulk Density - ANSWER Mass of dried soil per unit of undisturbed soil volume. Can be used to assess whether adequate pore space exists. Sand - ANSWER Soils with a high percentage of _________ are less prone to compaction. Clay - ANSWER Soils with a high percentage of ______ are easily compacted. pH - ANSWER The measure of the acidity or alkalinity of soil. pH 7 - ANSWER pH neutrality pH 0-6.5 - ANSWER Acidic pH 7.5-14 - ANSWER Alkaline pH 6.0 to 6.5 - ANSWER Generally favorable pH for most trees Highly Alkaline soils - ANSWER iron, zinc, and manganese may be unavailable. calcium, magnesium, and potassium may become more available. Highly acidic soils - ANSWER Phosphorus may be unavailable. Micronutrients - ANSWER iron, manganese, ... Temporaliy lower pH - ANSWER Add Sulphur Raise pH - ANSWER Add Lime Buffering Capacity - ANSWER resistance to change in pH, especially in soils high in clay or organic matter. Essential elements - ANSWER Minerals required for tree growth, dissolve in water then become available for absorption by tree roots ions - ANSWER Essential Elements/ Minerals in solution, are charged particles called ____. anions - ANSWER Negatively charged ions. cations - ANSWER Positively charged ions. cation exchange capacity - ANSWER A measure of the soils capacity to attract, retain, and exchange positively charged cations. This may be used to gauge soil fertility. Negative - ANSWER Soils typically have a net __________ charge. High negative charge - ANSWER Organic matter and clay particles normally have a _________density. this charge attracts and holds cations giving soils high in clay and organic matter a high cation exchange capacity. Sandy Soil - ANSWER ____ soil has a greater possibility of leaching due to its low CEC and may have to use a slow release fertilizer with a high water-insoluble nitrogen content.