Environmental Requirements for Good Plant Growth

1. Environmental Requirements for Good Plant Growth

2. Soil • composed of sand, silt, and clay, organic matter, living organisms, and pore spaces • classified according to percentage of sand, silt, and clay they contain.

3. Ideal Soil Composition • 45% Mineral Matter • 25% Water • 25% Air • 5% Organic Matter

4. Soil Particles • vary greatly in size • sand is the largest • silt - medium • clay - smallest

5. Soil Profile • Consists of 3 basic layers • Topsoil • represents depth normally plowed • Subsoil • deep rooting plants send roots down into subsoil • soil bedrock

6. Water in Soil • Gravitational Water • Soil is unable to hold against the force of gravity • Of little value to plant as it drains away quickly • Seen more in soils with large pore space

7. Water in Soil • Capillary Water • Free moving capillary water • Moves in all directions • Available capillary water (field capacity) • Remaining water after capillary movement stops • Soil surface is dry and water is a thin film around soil • Most important water for plants (half available) • Unavailable capillary water • Not available to plants • Held tightly by soil particles and moved as vapor

8. Types of Soil • Sandy • Clay • Loamy

9. Sandy Soil • Silt and clay make up less than 20% by weight • Drain well • Little water holding capacity

10. Clay Soil • Must contain at least 30% clay • Holds more moisture than is good for plants • Poor drainage

11. Loamy Soil • Most desirable soil • Equal parts sand, silt and clay • If more sand, it is sandy loam • If more clay, clay loam • If more silt, silty loam

12. Soil less Planting Media Mixes • Many greenhouses and nurseries use soil less mixes • Advantages of soil less planting media • Sterile • Lightweight • Easier to handle and ship • Good moisture retention and drainage • Free of weed seeds

13. Soil less Planting Media Mixes • Disadvantages • Light weight - pots tip in strong wind • Minor elements are missing • Iron • Sulfur • Manganese • Zinc • Calcium • Transplants may not adjust well to new media

14. Soil less Media Options • Perlite • Gray-white material of volcanic origin • Improve aeration • Larger particles provide better drainage and aeration • Vermiculite • Exploded Mica • Improves aeration • Neutral pH

15. Plant food and fertilizers • divided into two groups • Major elements (macro) • Nitrogen - N • Phosphorus - P • Potassium - K

16. Plant requirements • large amounts of major elements • relatively small amounts of minor elements

17. Commercial fertilizers • shows % or pounds per cwt. (100#) of the three major elements in large numbers on the container or bag.

18. Commercial fertilizers • 5-10-5 • 5% N, 10% P, 5% K • remaining 80% is filler • NP&K are always listed in that order.

19. Soil tests • determine amount of elements needed for various plants.

20. Nitrogen • has most noticeable effect on plants • encourages above ground vegetative growth • regulates use of other elements

21. Phosphorous • held tightly by soil particles • not easily leached • effects plants in several ways • encourage cell division

22. Phosphorous • flowers and seeds don’t form without it • hastens maturity, offsetting quick growth caused by N. • encourage root growth • makes K more available

23. Phosphorous • increase disease resistance • improves quality of grain, root and fruit crops • container plants can be damaged by excess P • increases soluble salt content of medium • causes dehydration of roots

24. Potassium • modifies both fast soft growth of N and early maturity of P • is essential

25. Potassium • increase disease resistance • encourages healthy root systems • essential for starch formation • development of chlorophyll • efficient use of CO2

26. pH • measure of acidity or alkalinity • pH scale - runs from 0 - 14 • most plants grow best from 5.6-7.0

27. pH • 7.0 is neutral • pH of 7 or above is alkaline or basic • pH below 7 is acidic

28. pH • as numbers decrease, solution becomes more acidic. • As numbers increase, solution becomes more basic or alkaline

29. pH • if soil is too acidic, lime is added to raise the pH • if soil is too alkaline, sulfur is added

30. Above ground environment • temperature • some plants prefer cool weather • some plants prefer warm weather

31. Temperature • there are temperatures above and below which plants stop growth • generally, plant growth rate increases as temps increase up to about 90 degrees

32. Light • must be present before plants can manufacture food • plants vary in light requirement • effects flowering

33. Photoperiodism • response to different periods of day and night in terms of growth and maturity

34. Photoperiodism • short day plants • chrysanthemum and Christmas Cactus • bloom when days are short and nights are long

35. Photoperiodism • long day plants • lettuce and radishes • bloom when days are long and nights are short

36. Photoperiodism • day length indifferent • do not depend on length of light or darkness • African Violet and tomato

37. Phototropism • plants appear to grow towards the sun or light source

38. Humidity • moisture level of the air • most plants grow best in 40-80% RH • Relative Humidity

39. Humidity • too high humidity may cause the spread of fungus diseases

40. Plant diseases and Insects • reduce production • lower fruit and vegetable quality

41. Gases and Air Particles • CO2 is vital to plants for Ps • Air pollutants can cause damage

42. Air Pollutants • Sulfur Dioxide - SO2 - from burning coal • Carbon Monoxide - CO - exhaust from cars

43. Carbon Monoxide • reduces plant growth • can kill plants