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Clay (fine particles): <2 micrometers. Soil Texture: Proportion of Sand, Silt, & Clay
Loam: Roughly equal
sand, silt, & clay
Agriculturally ideal (p. 689) 20 % 80 S Si Cl
% 20 lt Clay
S-Clay S-C-Loam Clay Loam 50 SiCL 80
Loam Silt Loam
0 S LS
% Sand Soil Organic Matter:
Soil Organic component (p. 689-690; 650)
Living soil organisms: Invertebrates
Bacteria & fungi
Plant roots. Nonliving Organics: Decomposing dead
Gives dark colors to soil. Soil Pore Spaces (p. 689-690; p.. 652)
Approximately > 50% of soil volume.
Enables root penetration &Oxygen diffusion to
Air or water depending on conditions.
Clay soils: Small pores hold water tightly. Sandy soils. Large pores: rapid drainage, little remains.
Large Loam soils.
Loam intermediate Soil Water (p. 691; p.. 652, Fig. 29-7)
Saturation: (flooding, rain).
Field capacity: moisture content when excess has drained away. Permanent wilting point: soil is so dry plants cannot remove remaining water. Soil Chemical Factors
Cation Exchange Capacity
(p. 691; 653): Slight negative charge: holds +
ions (Ca++, Mg++, K+, NH4+, etc).
NH Many plant nutrients are cations. High CEC = fertile soil! Clays. Organic matter. Soil pH
Soil Acidity or alkalinity of soils.
Affects availability of nu...
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