1. Overview of Soil Properties for Crop Production By J.G. Mexal Department of Plant & Environmental Sciences New Mexico State University

2. Soil Properties Outline –Definition –Classification –Physical Properties –Chemical Properties

3. Soil Properties Bottom Line Three most important characteristics: –Depth –Rock Content –Texture Water Storage = (Depth - Rock)Texture

4. Soil Properties Soil Definition Agricultural: “dynamic natural body… composed of mineral and organic materials and living forms.” Engineering: “fragmented mineral material at or near the surface … plus the air, water, organic matter, and other substances….”

5. Soil Properties Soil Definition Practical Definition: –Reservoir for water, oxygen, nutrients, and beneficial organisms –Provides physical support for plants

6. Soil Properties RoT Soil Composition ~50% ~25% 1-5%

7. Soil Properties Soil Classification Characteristics: –Texture –Structure –Horizon Development –Color Soils Maps Available

8. Soil Properties Arid Climate Deficit Utilization Recharge Temperature ( o C) PET or Ppt (mm)

9. Soil Properties Physical Properties Soil Texture –Particle Size Distribution (by weight) Sand Silt Clay –Soil Triangle

10. Soil Properties Soil Classification

11. Soil Properties Particle Size vs Area

12. Soil Properties Soil Triangle

13. Soil Properties Physical Properties

14. Compaction affects water availability Steinhardt et al. 1987 Soil Bulk Density (Mg/m 3 ) Moisture Content (kg H 2 O/kg soil) Unavailable Available Readily available Air space

15. Soil Properties Bulk Density Affects Growth Soil Bulk Density (g/cm 3 ) Root Penetration (%)

16. Soil Bulk Density & Hypoxia Reduce Growth/ Gilman et al. 1987 12 51 38 >51 25 Rooting Depth (cm) 2 4.1cm 3.2cm 1.8cm 1.8 g/cm 3 1.7 g/cm 3 + low O 2 Root Length (m) Gleditsia 14 26 36 1.2 g/cm 3

17. Soil Bulk Density Affects Growth/ Alberty, et al. J. Env. Hort. 2:48:84 1.05 1.21 1.23 1.31 Bulk Density (g/cm 3 ) Dry Weight (g) Puddled 20 15 10 5 0 5 15 20 25 30 35 Forsythia-shoot Forsythia-root Cornus-shoot Cornus-root

18. Soil Properties Important Soil Properties Physical –Texture –Structure Chemical –pH –C.E.C. –W.H.C. –Organic Matter

19. Soil Properties Physical Properties Structure –Natural organization of particles into units –“Peds” Platy Prismatic Columnar Blocky Granular