1. PLANT NUTRITION
AND FERTILIZERS
Green Industry Training
Spring 2013
Dr. Heidi Kratsch

2. Overview
•Nutrient availability to plants
•Plant Nutrient Requirements
•Fertilizer Types
•Tree Fertilization
•Lawn Fertilization

3. Cation exchange capacity (CEC)
The degree to which cations can be held by
soil particles and exchanged with soil water.
Cation Anion
positively charged negatively charged
ex. Mg 2+ ex. SO4 2-
Positive ions attract negative ions.

5. The pH scale
• Reflects the acidity or
alkalinity of a solution.
• Each step of the pH
scale represents a 10-
fold change in
concentration.

7. Essential Nutrients
Chemical elements involved in the
metabolism of the tree or necessary for
the plant to complete its life cycle

8. Essential Nutrients (17 Elements)
Carbon
Oxygen
Hydrogen
Available from the air or water
(Carbon from CO2 made available by photosynthesis)

9. Essential Nutrients (Elements)
Macronutrients: Micronutrients:
• Nitrogen (N) •Boron (B)
• Phosphorus (P) •Chloride (Cl)
• Potassium (K) •Copper (Cu)
•Iron (Fe)
• Sulfur (S)
•Manganese (Mn)
• Calcium (Ca)
•Molybdenum (Mo)
• Magnesium (Mg) •Zinc (Zn)
•Nickel (Ni)

10. Soil Organic Matter
• Originates from living organisms, consisting
mostly of carbon and nitrogen.
• Includes living organisms (bacteria, fungi,
earthworms) and decaying plant matter.
• Soil organisms use decaying plant matter as a
food source.

12. Humus
• An organic component of soil, formed by the
decomposition of leaves and other plant material by
soil microorganisms.
• Stable vs. effective
• Stable humus does not add nutrients, but it does
bind and store nutrients.
• Presence of stable humus can prevent leaching of
nutrients from the soil.

13. Nitrogen
• Often the most limiting nutrient for plant growth
• Proteins and chlorophyll
• Necessary for photosynthesis
• Absorbed mostly in NO3 − form

14. Nitrogen Deficiency
• Reduced growth
• Smaller leaves
• Chlorosis (yellowing)
greater in older leaves
• Common in sandy soils
low in organic matter
• Over-irrigation
• Easily leached from the
root zone.

15. Phosphorus
• Deficiency seen as
purpling of leaf veins.
• Important in root and
seed development.
• More efficient in the
presence of nitrogen.
• Rarely deficient in
western soils, except
P-deficiency in pepper planted
when soils are cold.
too early in the season

16. Phosphorus Deficiency

17. Potassium
• Many functions
including movement of
sugars in plants.
• Increases size and
quality of fruits and
vegetables.
• Leaches readily when
over-applied as
fertilizer.
• Deficiency causes
marginal leaf chlorosis
of older leaves. Potassium deficiency

18. Potassium Deficiency

19. Secondary macronutrients
•Calcium – lack of availability causes blossom-
end rot in tomatoes
•Magnesium – deficiency causes
interveinal chlorosis in older
leaves
Ca deficiency
•Sulfur – deficiency rare; released
with decomposition of organic
matter
Mg deficiency

20. Micronutrients
Iron deficiency on silver maple
Zinc deficiency on apple
Manganese deficiency on red maple

21. Iron Deficiency

22. Diagnosing nutritional problems
•Collect as much information as you can:
• Visual symptoms
• Water quality issues
• Evaluate condition of the soil
• pH and EC meters are now portable and inexpensive
• Soil test – accurate for P, K, micronutrients
• Foliar analysis – accurate for micronutrient
deficiencies (must be used in conjunction with soil
test analysis)

24. Complete Fertilizer
10% soluble
Potassium (K2O)
32% Nitrogen
10% available
Phosphorus (P2O5)

25. Fertilizers
Inorganic Organic
• Release elements • Release inorganic ions
quickly in water slowly
• Excess can “burn” Examples:
plants • Urea formaldehyde
• Urea is treated as • Isobutylidene diurea
inorganic because of (IBDU)
“quick release” of N • Manures
• Solubility not affected • Sewage sludge
by temperature
• Blood
• May leach from soil
• Bone meal

26. Slow-release fertilizers
• Release nutrients over an extended period
• Higher cost
• Reduce leaching and burn problems
• Release rate may be affected by soil moisture and
temperature

27. Urea aldehydes
• Urea formaldehyde
• 36-38% nitrogen
• Slowly released
• Relies on microbial breakdown
• IBDU – isobutylidene diurea
• Slowly released
• Not dependent on microbial
activity.

28. Sulfur-coated fertilizers
• Prills of various
fertilizers (urea, triple Sulfur-coated urea
superphosphate,
potassium sulfate,
potassium chloride)
• Coated with sulfur and
wax-like sealant
• Not dependent on
microbial activity

29. Forms of Nitrogen
• Ammonium (NH4+)
• Potential toxicity
• Acidifying
• Should be no more than
40% of total N for
container plants
• Urea – broken down to
ammonium
• Nitrate – less chance of Ammonium toxicity symptoms
toxicity but greater
chance of leaching

30. Water-Insoluble Nitrogen (WIN)
GUARANTEED MINIMUM ANALYSIS
Total Nitrogen (N) 12.0 %
Water Insoluble Nitrogen (N) 10.8%
Iron (Fe) 0.2%
Organic Matter 80.0%
Look for WIN that is at least 50% of total Nitrogen.

31. Tree Fertilization
•Age
•Health
•Species
•Form of fertilizer
•Method of application
•Site conditions

32. For woody plants:
Most soils supply adequate amounts of
nutrients other than nitrogen.
Exception:
• Iron and manganese might not be
available in alkaline soils.

33. Determining the need for fertilization
• Fertilizer applications are not the solution for “urban
stress.”
• Soil testing – before planting and every 3 to 5 years
• Shoot growth
• Over 6 inches per year- no fertilization needed
• Under 2 inches per year- fertilize with N
• Foliage off color- take a soil sample
• History of the landscape

34. Fertilizing a newly planted tree

35. Prescription Fertilization
• Excess N fertilization can
harm trees.
• Energy put toward
growth rather than
defense.
• Trees stressed by
drought, poor soil
aeration, and some
diseases may not
Sucking insects such as
spider mites are attracted
respond to fertilization.
to excess N in leaf juices.

36. Soil Samples
• Take soil cores from 5
to 20 locations.
• Sample down 6 to 12
inches from the
surface.
• Mix the cores and
remove 3 cups.

37. Soil Analysis
•Phosphorus
•Potassium
•Texture
•pH
•(Nitrogen testing is meaningless because it
can change on a daily basis due to N cycling
by soil microbes.)

38. Foliar Analysis
• Collect leaves from
healthy and
symptomatic trees of
the same species
• Take samples from
different areas of the
tree

39. Nitrogen for trees
• Trees respond best to
surface applications of N.
• In turfgrass areas,
provide 1-2 inches
irrigation to move N
below turf roots.
• Do not mix quick-release
N fertilizers with backfill
soil at time of planting.

40. N Fertilization Guidelines for Trees
• Slow-Release: 2-4 lb. actual N per 1,000 square feet
of root area
• Quick-Release: 1-3 lb. actual N per 1,000 square feet
• Thoroughly water the area after application.
• May use liquid injection or drill-hole method to
provide > 1 lb. actual N per 1000 sq. ft. for trees in
turfgrass.

41. Trees in turfgrass areas
• No more than 1 lb. N per 1,000 square feet from
quick-release source per application.
• High temperatures and low humidity increase burn
potential.

42. Subsurface: liquid injection
• Fertilizer dissolved in
water
• Hydraulic pressure
• Hole spacing
• Advantage: provides
water
• May combine with
broadcast fertilization

43. Subsurface: drill-hole method

44. Drill-hole method
• Granular fertilizer
1 – 2 inches
• Calculate amount
required
• Distribute uniformly
among holes
12 inches
• Do not fill within 2
inches of the surface
• Backfill with soil
amendment

45. Causes of iron chlorosis
• High lime soils common in arid, western U.S.
• pH in 7.8-8.0+ range – low solubility of Fe
• Planting acid-loving plants in Nevada
Aggravating factors:
• Cold soils
• Over-irrigation
• Soil compaction
• Over-fertilization (growth too vigorous)
• Other stresses (disease, pests, injury…)

46. Soil application of iron + sulfur
• Iron (ferrous) sulfate is a
soluble iron form, but will
not remain available on its
own.
• Place a 50:50 mixture of
iron sulfate : elemental
sulfur in holes around the
drip line of trees and
shrubs.
• Chelated iron can be
applied dry or as a liquid
around trees.

48. Chelated micronutrients
• “Chelate” means “claw”
• Nutrients not affected by soil
pH in their chelated form
• Used to deliver iron,
manganese, zinc, and copper
• Has revolutionized rose
production (poor iron
accumulators, yet grow
better at higher pH)
• More expensive than sulfate
forms

49. Soil application of iron chelates
• The only chelate stable in alkaline soils is FeEDDHA
(Sequestrene 138, Millers Ferriplus) - this is
expensive!
• Broadcast chelate within the drip line of tree or place
in holes 1 foot deep around the drip line.
• Treat in early spring, before leaf emergence.

50. Foliar Application
•Used for micronutrients
•Rapid but temporary
•Example: chelated Fe
•1-2 applications per year
•Ineffective for nitrogen
•Difficult to get uniform
application
•May stain paved areas

51. Implants/injections
• Useful only for micronutrients
• Apply early in spring during
budbreak
• Place injection into first xylem
rings (follow label instructions)
• Do not use more than once
every 2 years
• Not for trees < 4 in. diameter
• Do not use on drought-stressed
trees!

52. Soil Additives
• Mycorrhizae fungal
inoculants
• Symbiotic relationship
• Inoculation of
landscape soils has not
been successful
• Native mycorrhizal
species quickly
overtake inoculant
species.

53. Turfgrass Fertilization
Considerations:
• Minerals required for growth
• Natural soil fertility
• Fertilizer selection
• Turfgrass species, desired
quality and use
• Application schedule.

54. pH adjustment for turfgrass?
• Use of regular sulfur applications can deteriorate soil
structure and cause build-up of soluble salts.
• Hard water used for irrigation can negative the
acidifying effects.
• Acidifying fertilizers are a better option for western
soils
• Offset alkalinity of irrigation water
• Temporarily low soil pH at time of fertilization.

55. N is most important for turfgrass fertility
• Elicits the strongest growth response
• Enhances green color
• Absorbed primarily in NO3 − form
• Can be translocated to leaf tissue within 24 hours.

56. Analysis of quick-release N fertilizers
N carrier Analysis Burn potential Soil reaction
Ammonium 33-0-0 High Acidic
nitrate
Potassium nitrate 13-0-44 High Basic
Ammonium 21-0-0 High Acidic
sulfate
Urea 45-0-0 High Slightly acidic
Monoammonium 11-50-0 Moderate Slightly acidic
phosphate
Diammonium 20-50-0 Moderate Basic
phosphate

57. Analysis of slow-release N fertilizers
Activity at low
N carrier Analysis Burn potential temperatures
IBDU 31-0-0 Moderately Moderate
low
Sulfur-coated 22 to 38-0-0 Low Moderate
Urea (SCU)
Resin-coated 24 to 35-0-0 Low Moderate
urea
Urea 36 to 38-0-0 Low Very low
formaldehyde
Manures Variable Very low Very low
Activated 4 to 6-4-0 Very low Very low
sewage sludge

58. Turfgrass N requirements by species
Grass species Lbs. N per 1,000 sq. ft. per year
Creeping bentgrass 3 to 8
Kentucky bluegrass 2 to 4
Perennial ryegrass 2 to 4
Red fescue 1 to 3
Chewings fescue 1 to 3
Tall fescue 1 to 2
Dwarf fescue 1 to 2

59. Phosphorus requirements of turf
• Greatest response to phosphorus seen with turfgrass
seedlings.
• Deficiencies rarely observed in established turf
• Exceptions include low soil P levels or pH above 7.8
• Applications should be based on soil tests.
• High soil P levels increase potential for annual
bluegrass (weed) infestation.

60. Recommended P2O5 application based on soil
test (Bray P1 Extractable Phosphorus)
P1 soil test (lbs./acre) P2O5 (lbs./1,000 sq. ft.)
Less than 25 4
26 to 50 2
51 to 75 1
More than 75 0
- One application per year is usually sufficient.
- If recommendation exceeds 2 lbs. P2O5/1,000 sq. ft.,
split applications between spring and fall.

61. Potassium requirements of turf
•K involved stress resistance, wear tolerance,
disease resistance
•Factors that affect requirements:
• Clipping removal, irrigation, soil texture
•Application should be based on soil tests.
•High potash “winterizers”

62. Recommended K2O application based on soil test
K soil test (lbs./acre) P2O (lbs./1,000 sq. ft.)
Less than 50 6
51 to 100 4
101 to 150 2
151 to 200 1
More than 200 0
- Potash applied as 0-0-60 (muriate of potash) or as
part of a complete fertilizer.
- More than 1.5 lbs./1,000 sq. ft. may cause burning.

63. Iron deficiency
• Most common micronutrient deficiency for turfgrass
• Intervienal chlorosis of leaf blades and thinning of
turf
• More serious problem when pH above 7.5 or high soil
phosphorus.
• Spray every two weeks with 1 to 2 ounces ferrous
sulfate per 1,000 sq. ft. until corrected.

64. Fertilizer calculations
• You have a 50-lb bag of 26-5-10 fertilizer that you
want to apply to a lawn at a rate of 1.0 lb nitrogen per
1000 sq ft. How much of the 26-5-10 fertilizer will you
need to apply per 1000 sq ft?
• Ignore the weight of the fertilizer bag and divide the
amount of nitrogen desired (1.0 lb nitrogen per 1000
sq ft) by the percentage of nitrogen in the bag (26%).
26% = 0.26.
• (1.0 lb nitrogen per 1000 sq ft) 0.26 = 3.8 lb of a 26-
5-10 fertilizer is needed to supply 1.0 lb nitrogen per
1000 sq ft.

65. Leaching and Uptake Problems
• Limit fertilizer
application to as-
needed basis.
• Avoid over-cast onto
hard surfaces.
• Use organic or slow
release.
• Avoid over-irrigating
sandy soils.

66. Questions?
Contact:
Heidi Kratsch
University of Nevada Cooperative
Extension
Phone: 775-784-4848
Email: KratschH@unce.unr.edu