Soil and Water Kelly Young UA Cooperative Extension

1. Soil and WaterKelly YoungUA Cooperative Extension

2. Objectives: • Discuss soil components, texture, chemistry • Consider relationships between soil, water, plants and air • Learn about the properties of water • Compare and contrast fertilizers • Suggest soil amendments

3. Ideal Soil Composition Desert soils have significantly less than 5% organic matter. Why?

5. Maricopa County soils: • Mineral • Alkaline • Arid • Probably some caliche • May be rocky and shallow, particularly in foothills • May be saline • May be heavy

6. Soil Texture frisbee beachball dime

7. Soil texture affects water movement

8. Determine your soil texture

9. Soil Texture Triangle

11. Soil Compaction • Compaction reduces pore space: • Restricts H2O and O2 • Poor root development

14. Capillary Action • Cohesion – “like sticking to like” • Water molecules stick together • Adhesion – “sticking to unlike” • Water molecules stick to certain surfaces • Capillary action – drawing of water in a narrow tube

16. Soil-Plant-Air Continuum

17. Stomata Factors affecting opening and closing: • Light, especially blue light • Water • Temperature • CO2

18. Water moves down its concentration gradient • Concentration of water is • Highest in soil • High in plant • Low in air

19. When transpiration > water uptake by roots, wilting occurs.

20. Water loss • Evaporation – change of water phase from liquid to gas • Transpiration – evaporation of water from leaves • Evapotranspiration (Et) – combined loss of water directly from soil evaporation and transpiration

21. Factors that affect Et • Temperature • Relative humidity • Wind speed • Light intensity • Type of plant

22. Terry’s 1-2-3 Rule Watering depth • 1 ft - Flowers, vegetables and other small annuals • 2 ft – Shrubs • 3 ft – Trees

23. Root volume • V = ½( 4/3 π r3) Π ≈ 3.14 r = ½ diameter If a tree has a 12’ diameter: r = 6’ The root volume would occupy approximately 452 cubic feet.

24. Root volume • V = ½( 4/3 π r3) Π ≈ 3.14 r = ½ diameter Assume 5 years later the tree has a 20’ canopy: r = 10’ Now, the root volume would occupy approximately 2093 cubic feet!

25. Soil Chemistry atom

26. Cation Exchange Capacity • Cations: • NH4+, K+, Fe++, Ca++ • Anions: • NO3-, SO42- Clay particle Organic matter and clay carry a negative charge

27. Plant Nutrients Macronutrients Micronutrients Fe Zn Mn B Mo Cu • C • H • O • N • P • K • Ca • Mg • S

28. Nitrogen deficiency

29. Phosphorus deficiency

30. pH is a measure of acidity/alkalinity

32. Zn deficiency Fe deficiency

33. Fertilizers • Add nutrients to the soil • Organic and inorganic forms • Usually salts • Can burn plants • Must be watered in

34. Fertilizer analysis N-P2O5-K2O (nitrogen-phosphate-potash) Complete fertilizer Incomplete fertilizer Slow release fertilizers

35. “Organic” versus “Chemical” fertilizers Organic Chemical Ammonium nitrate, urea, superphosphate, etc. Can be energy intensive to make Lighter weight Salt Must be purchased Salt Manure, compost, fish emulsion, etc. Sometimes recycles waste May be resource intensive Can be bulky, heavy Micronutrients Pathogens, weeds Salt

36. Salinity Na, Ca, K and other salts accumulate in soils

37. How does soil become saline? • Shallow watering • Fertilizers • Irrigation water quality • Application of other salty substances to soil.

38. Soil Amendments • Used to modify soil chemistry • Gypsum (Calcium sulfate) – temporarily removes Na from soil • Soil sulfur – may eventually reduce pH after many yearly applications • Organic matter

39. What should be added to the native soil when planting trees and shrubs in the landscape? • Organic matter • Fertilizer • Organic matter and fertilizer • Nothing, only native soil should be backfilled into the planting hole.

40. Possible causes of “unthriftiness” • High soil salinity • Root diseases • Root parasitic nematodes

41. Questions? Contact me at kyoung@arizona.edu.