Physical Properties of Soil - Crop and Soil Science - Lecture Slides, Slides of Botany and Agronomy

Download Physical Properties of Soil - Crop and Soil Science - Lecture Slides and more Slides Botany and Agronomy in PDF only on Docsity! Physical Properties of Soil Docsity.com Soil Texture • What is Soil Texture? – It is the proportion of three sizes of soil particles. • Which are: – Sand (Large) – Silt (Medium) – Clay (Small) Docsity.com Soil Texture • Pore size and number: – this depends on the particle size. – So there are more pores that are found between the larger particles. – See page 34 for example. Docsity.com Soil Texture • What is a Soil Separates? – They are categories that scientist have divided up into three groups – The three groups are: • Sand • Silt • Clay Docsity.com Soil Texture • What is Sand? – It is the largest and is further divided into four subcategories. – They are: • Very coarse sand • Coarse sand • Medium sand • Fine Sand Docsity.com Soil Texture • Silt – is the medium sized soil separated. – Silt particles are silky or powdery to the touch – Silt grains will not stick to one another just like sand grains. – Silt is the best soil as it has the ability to hold large amounts of water in a form plants can use. Docsity.com Soil Texture • Clay – is the smallest size soil separate. – It is composed of tiny crystals – Clay is formed by chemical reactions between weathered minerals to form tiny particle of new minerals. – Clay will hold more plant nutrients than any other separate. – Clay grains will stick to one another. Docsity.com Soil Texture • There are 12 textural classes which can be seen in the next slide. Docsity.com Soil Texture • 1. – 40% sand 22% clay and 38% silt – What is the soil classified as? Docsity.com Soil Texture • 2. – 90% sand 10 % clay and 25 % silt – What is it? Docsity.com Soil Texture • 3. – 30% sand 50 % clay and 15% silt – What is it? Docsity.com Soil Density and Permeability • What is Particle Density? – it is the density of solid particles only. Docsity.com Soil Density and Permeability • What is Bulk Density? – It is the mass of a volume of undisturbed oven dry soil – BD= Weight dry soil ___________= __G__ Volume dry soil cm3 Docsity.com Soil Density and Permeability • Example BD: • The core is 500 cubic cm that weighs 650 grams • What is the answer? Docsity.com Soil Density and Permeability • Example: – The soil core before had a volume of 500 cubic centimeters and weighed 650 grams when dry. When wet the same core weighed 900 grams. – Calculate Porosity. Docsity.com Soil Density and Permeability • Answer: 900-650 _________x100 =50% 500 Docsity.com Soil Density and Permeability • What is Permeability? – is the ease of which air, water, and roots move through the soil Docsity.com Types of Soil Structures • Before we discuss these turn to pg 43. • There are four types of soil structures. • They are: – Granular structure – Platy structure – Blocky structure – Prismatic structure Docsity.com Types of Soil Structures • What is Granular structure? – It is commonly found in A horizons – Peds are small usually between 1to 10 millimeters Docsity.com Types of Soil Structures • What is Platy Structures? – Usually found in E horizons – Peds are large but tin, platelike and arranged in overlapping horizontal layers. Docsity.com Soil Tilth • What is Soil Tilth? – is a general term for the physical conditions of a tilled soil. Docsity.com Soil Tilth • What is compaction? – It is the result when pressure is applied to the soil surface. Docsity.com Soil Tilth • Now you will read pages 45-50 and will take notes over these pages Docsity.com Soil Pans • Fragipans: – results from clay accumulation – Clay will bind soil particles into hard brittle layer Docsity.com Soil Pans • Plinthite – Layers are cemented by a special type of clay common to the tropics – These soils are very poor for Agriculture uses. Docsity.com Soil Pans • Caliche and Duripans – Has chemicals cement soil particles together Docsity.com Soil Colors • Light brown, Yellow to Red: – These are the colors of oxidized iron minerals, chemically similar to rust – Red indicates good drainage Docsity.com Soil Colors • Bluish Gray – this is the color of less oxidized iron and indicates a lack of oxygen in the soil – So this is an indication of poor drainage Docsity.com Soil Colors • Mottled Colors: – Will show different colors often spots of rust, yellow, and gray. Docsity.com