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Overview of Soil Properties for Crop Production

Overview of Soil Properties for Crop Production. By J.G. Mexal Department of Agronomy & Horticulture New Mexico State University. Soil Properties Important Soil Properties. Physical Texture Structure Chemical pH C.E.C. W.H.C. Organic Matter. Soil Properties Chemical Properties. pH

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Overview of Soil Properties for Crop Production

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  1. Overview of Soil Propertiesfor Crop Production By J.G. Mexal Department of Agronomy & Horticulture New Mexico State University

  2. Soil PropertiesImportant Soil Properties • Physical • Texture • Structure • Chemical • pH • C.E.C. • W.H.C. • Organic Matter

  3. Soil PropertiesChemical Properties • pH • Measure of acidity (hydrogen ions - H+) • Range = 0 -- 14 • Based on acidity of pure water • 0.0000001 g H+ / liter water • 10 -7 g H+ / liter water • pH = 7

  4. Soil PropertiesChemical Properties

  5. Cu, Zn Manganese Phosphorus Boron Iron 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Soil PropertiespH vs Plant Nutrients Relative Nutrient Availability vs pH

  6. Soil PropertiesChemical Properties • Cation Exchange Capacity (CEC) • ability of soil to hold positively charged ions e.g. ammonium (NH4+), calcium Ca++, sodium (Na+) • Function of Texture and Organic Matter • finer texture and O.M. increase CEC • Soils have little ability to hold negatively charged ions (e.g. nitrate (NO3-))

  7. Soil PropertiesChemical Properties • Organic Matter • Living and dead plant and animal matter present in and on soil • Can be added (e.g. manure & waste) • Other terms: • litter • humus

  8. Soil PropertiesOM Distribution

  9. Soil PropertiesChemical Properties • Benefits of Organic Matter • Increases CEC (fertility) of soil • Increases infiltration of water • Increases water holding capacity • Provides nutrients for plants • Reduces root diseases

  10. Soil PropertiesChemical Properties • Organic Matter Additions: • A biologically active soil can sustain OM additions of 15-30 t/ha/yr. • A ‘strong’ wastewater (TOC = 300 mg/L) could supply about 6 t OM/ha/yr. • Total nitrogen would limit loading rate before OM loading becomes problematic

  11. Soil PropertiesWater Holding Capacity • Water Holding Capacity (WHC): amount a water held by a soil; a function of texture. • Field Capacity (FC): amount of water held against the force of gravity after irrigation. • Permanent Wilting Point (PWP): amount a water at which the plant wilts permanently. (Does not hold well for desert plants) • Available Water (AW): FC - PWP = AW

  12. Soil PropertiesWater Holding Capacity

  13. Soil PropertiesPorosity & WHC of Soils and Soil Mixes/ Craul ‘99 Pore Space (%) Key: c=coarse, f=fine, S=sand, Sl=silt, C=clay, P =Peatmoss

  14. Soil PropertiesPorosity & WHC of Soils and Soil Mixes/ Craul ‘99 Pore Space (%) Key: c=coarse, f=fine, S=sand, Sl=silt, C=clay, P =Peatmoss

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