III.Fertilizing Forages Dennis Hancock, PhD. Extension Forage Specialist UGA – Dept. of Crop and...

Preview:

Citation preview

III. Fertilizing Forages III. Fertilizing Forages

Dennis Hancock, PhD.Extension Forage Specialist

UGA – Dept. of Crop and Soil Sciences

Dennis Hancock, PhD.Extension Forage Specialist

UGA – Dept. of Crop and Soil Sciences

Plant NutrientsPlant Nutrients

Element Available Form

Oxygen O2, OH-

Carbon C03-2, HCO3 , CO2

Hydrogen H+, OH-

Nitrogen NO3- , NH4

+

Phosphorus HPO4-2, H2PO4

-

Potassium K+

Macro- (Primary)

Element Available Form

Calcium Ca+2

Magnesium Mg+2

Sulfur SO4-2

Meso- (Secondary)

Element Available Form

Iron Fe+2 , Fe+3

Copper Cu+2 , Cu+

Zinc Zn+2

Manganese Mn+2 , MnO4-

Molybdenum

HMoO4- , MoO4

-2

Boron H3BO3, B4O7-2

Chlorine Cl-

Micro- (Trace)

Nutrients in Forage PlantsNutrients in Forage Plants

• Nitrogen – Chlorophyll, proteins, nucleic acids (DNA, RNA)

• Phosphorus – Cell nuclear proteins, cell division, energy transfer, root growth, plant maturity, fruiting and seed production

• Potassium – Enzyme activity, stress tolerance, water balance, cell division, carbohydrate formation

Nutrients in Forage PlantsNutrients in Forage Plants

• Calcium – Critical to cell division, cell membranes

• Magnesium – Chlorophyll, enzyme activation

• Sulfur – Part of three amino acids (proteins)

• Boron – Cell growth, legume roots/nodule function

Liebig’s Law of the Minimum

Liebig’s Law of the Minimum

Fe

Cl

Ca N

Mg

K

P

MnMoS Zn

Cu

B

K is for PersistenceK is for Persistence

Potash also helps to ward off diseases and prepare for

dormancy

Potash also helps to ward off diseases and prepare for

dormancy

Leafspot and winterhardiness

K is the Key to a Good Stand

K is the Key to a Good Stand

“Lime is the cheapest fertilizer there is.”

“Lime is the cheapest fertilizer there is.”

How Soil pH Affects Availability of Plant Nutrients

Organic Matter

How Soil Holds Nutrients How Soil Holds Nutrients

Ca2+

Ca2+

K+

Mg2+Al3+

K+

Mg2+

Soil Particle

CEC = 10

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

Ca2+

Ca2+K+

Mg2+

K+

Mg2+

CEC = 200

Ca2+

Ca2+

K+

Ca2+

Mg2+

H+

Al3+

H+

Al3+

Al3+

CaCO3

CaCO3

pH = 4.5

Soil

Ca2+ + CO3

Soil

+

HCO3 + Al(OH)3

pH = 6.5

Low Soil pHLow Soil pH

Low Soil pH = Aluminum ToxicityLow Soil pH = Aluminum Toxicity

Lime QualityLime Quality

Sieve Size % of total

≤ 10 mesh 12

10-20 mesh 17

20-35 mesh 55

≥ 35 mesh 16

Rule: At least 90% must pass a 10 mesh sieve.

Lime Quality Affects Neutralizing TimeLime Quality Affects Neutralizing Time

Thou Shalt Soil TestThou Shalt Soil Test

Sample 1/3 of your pastures each year.Sample hayfields every year.

Thou Shalt Soil TestThou Shalt Soil Test

• Most common cause of poor establishment: Soil pH and/or fertility is too low.

• Most common cause of poor persistence: Soil pH and/or fertility is too low.

• Most common cause of poor drought tolerance: Soil pH and/or fertility is too low.

• Most common cause of poor establishment: Soil pH and/or fertility is too low.

• Most common cause of poor persistence: Soil pH and/or fertility is too low.

• Most common cause of poor drought tolerance: Soil pH and/or fertility is too low.

“Add only what is needed”“Add only what is needed”

Fertilizer BagFertilizer Bag

Guaranteed Analysis 19-19-19Total Nitrogen (N)………………………………………………………………… 19.00%

10.6% Ammoniacal Nitrogen 8.4% Urea nitrogen

Available Phosphoric Acid(P2O5) …………………………………………………. 19.00%Soluble Potash (K2O)……………………………………………………………….. 19.00%Sulphur (SO4) ………………………………………………………………………. 12.00%Calcium (Ca) ……………………………………………………………………….. 0.05%Magnesium (Mg) ………………………………………………………....…….…... 0.04%Boron (B)……………………………………………………………………………. 0.01%Copper (Cu)…………………………………………………………………………. 0.02%Iron (Fe)…………………………………………………………………………….. 0.10%Total Manganese (Mn)……………………………………………………………… 0.02%Molybdenum (Mo)……………………………………………………………….... 0.0005%Zinc (Zn)…………………………………………………………………………….. 0.05%

Hybrid Bermudagrass Yield Response to N Rate

Hybrid Bermudagrass Yield Response to N Rate

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 100 200 300 400 500 600 700 800

Nitrogen Rate (lbs N/A)

Forage Yield(tons/A)

@15% moisture

Average or “Normal” Response

Hybrid Bermudagrass Yield Response to N Rate

Hybrid Bermudagrass Yield Response to N Rate

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 100 200 300 400 500 600 700 800

Nitrogen Rate (lbs N/A)

Forage Yield(tons/A)

@15% moisture Yield Limitations - Drought, low fertility, etc.- Inefficient application timing- Less effective N source

Hybrid Bermudagrass Yield Response to N Rate

Hybrid Bermudagrass Yield Response to N Rate

SPLIT YOUR NITROGEN APPLICATIONS!SPLIT YOUR NITROGEN APPLICATIONS!

• Long-term, this can increase yields by 1200-2400 lbs/acre and increase NUE by 25-30% Especially important under extremes

Leaching Volatilization (in the case of urea-based products) Late freeze Drought

Other Common Nitrogen Sources

Other Common Nitrogen Sources

Nitrogen Source Content Approx. CCE*

Ammonium Nitrate 34-0-0 -61

Amm. Sulfate 21-0-0-24 -110

Anhyd. Ammonia** 82-0-0 -148

UAN Solution 32% (35% U + 45% AN) 32-0-0 -55

28% (30% U + 40% AN) 28-0-0 -49

Urea 46-0-0 -81

Urea (Sulfur-coated) 38-0-0-16 -118

Poultry Litter 3-3-2 ~10* Approximate CaCO3 (limestone) equivalent per 100 lb of product. For

example, it will take 61 lbs of pure lime to neutralize the acidifying effect that ammonium nitrate has on the soil.

** Must be injected into the sod. Not recommended for bermudagrass production.

The Effectiveness of Some Alternative N Sources at Low, Medium, and High Fertilization Rates on Hybrid Bermudagrasses (Relative to

Ammonium Nitrate).

The Effectiveness of Some Alternative N Sources at Low, Medium, and High Fertilization Rates on Hybrid Bermudagrasses (Relative to

Ammonium Nitrate).

Nitrogen Source Fertilization Rates

< 200 lbs* 250-350 lbs > 400 lbs

Ammonium Nitrate 100% 100% 100%

Amm. Sulfate 95-97% 95-105% 60-70%

Anhyd. Ammonia 92-94% 93-95% 94-95%

UAN Solution 70-75% 85-92% 92-95%

Urea 79-82% 82-92% 88-93%* Actual lbs of N per acre per year. Source: Burton and Jackson, 1962; Silveria et al., 2007.

Alternative N SourcesAlternative N Sources

Take-home message: If you have to use a urea-based product, be

careful about cutting your rate back too much.

- They are relatively less effective at low rates.

Poultry Litter for Hay FieldsPoultry Litter for Hay Fields

• Weed pressure does increase Not a source of weed seed Changes the fertility and makes

broadleaf weeds more competitive.

• Potassium fertilization may not be adequate Poultry Litter: 3-3-2 Ideal bermudagrass fertilizer: 4-1-3

• May result in excessive sulfur levels Some evidence for a link to copper

deficiency in cattle.

Too much of a good thing?Too much of a good thing?

ResourcesResources

www.georgiaforages.comwww.georgiaforages.com

QUESTIONS?QUESTIONS?

Recommended