III.Fertilizing Forages Dennis Hancock, PhD. Extension Forage Specialist UGA – Dept. of Crop and...
32
III. Fertilizing Forages Dennis Hancock, PhD. Extension Forage Specialist UGA – Dept. of Crop and Soil Sciences
-
Upload
ashley-jacobs -
Category
Documents
-
view
214 -
download
1
Transcript of III.Fertilizing Forages Dennis Hancock, PhD. Extension Forage Specialist UGA – Dept. of Crop and...
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?
