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Nutrient Management of Irrigated Alfalfa and Timothy
Ross H. McKenzie
Old Agronomist
Lethbridge
Irrigated Crop Production Conf.
Lethbridge, AB
Jan 19, 2016
Introduction
• Alfalfa and Timothy are excellent crops to include in an irrigated crop rotation.
• Both have high nutrient requirements demands for soil nutrients.
• Both use up to 4 to 5 inches of water for each ton of dry matter produced.
1. Benefits of forage in crop rotation
2. Soil testing and analysis3. Nitrogen and N fixation
4. Phosphorus5. Potassium
6. Sulphur
7. Micro’s
Outline:
Benefits of Alfalfa & Timothyin the Crop Rotation
• Increased soil quality and soil health
• Increased soil organic matter and soil carbon levels
• Improved soil structure
– Increased water infiltration and internal drainage
• Increased soil fertility and increased nitrogen release benefits
– Reduced nitrogen fertilizer requirements for several years after Alfalfa
• Reduced weed and disease pressure
• Increase yields of following crops
Benefits of Forage in a Crop Rotation
Nitrogen Benefit After Alfalfa
• N fertilizer can be reduced by
–Up to 50% the first year after Alfalfa.
–30% the second year after Alfalfa
• Wheat protein increased by up to 2% after Alfalfa
Nutrient Requirements
Alfalfa Nutrient Removal
Nutrient 6 Tons (lbs/ac)MacronutrientsNitrogen (N) 300+Phosphate (P2O5) 60 - 75Potassium Potash (K2O) 250+
Sulphur (S) 30 Calcium (Ca) 150Magnesium (Mg) 30
MicronutrientsBoron (B) 0.4Copper (Cu) 0.06Iron (Fe) 1.5Manganese (Mn) 0.6Molybdenum (Mo) 0.012Zinc (Zn) 0.3
Timothy Nutrient Removal
Nutrient Amount Removed (lbs/ac)5 Tons
Macronutrients:Nitrogen (N) 200+Phosphate (P2O5) 50Potash (K2O) 200Sulphur (S) 25Calcium (Ca) 150Magnesium (Mg) 25
Micronutrients:Boron (B) 0.4Copper (Cu) 0.05Iron (Fe) 1.5Manganese (Mn) 0.5Molybdenum (Mo) 0.01Zinc (Zn) 0.25
Soil Sampling and Testing
Why Soil Test?
• Gives an excellent inventory
–plant available nutrients
–soil chemical factors important for crop production.
• Provides a basis for recommending additional nutrients.
Soil Sampling:
• Depths:
– 0-6”
– 6-12”
– 12-24”
0-6” - N, P, K, S, pH, EC + micro’s*
6-12” - N, P, K, S, pH, EC + micro’s*
12-24” - N, S, pH, EC
* Before establishment
Soil analysis:
• Modified Kelowna extractant is used for:
–NO3-N, P and K
• Don’t use Bray or Olsen methods!!
• CaCl2 is used to extract SO4-S
• DTPA – is used for metal micronutrients – Cu, Fe, Mn and Zn
• Hot water is used to extract Boron
Nitrogen (N) Nutrition of Alfalfa
Nitrogen and Alfalfa:
• N fertilizer is rarely required on established Alfalfa.
• Alfalfa can "fix" its own nitrogen (N) with Rhizobium meliloti, a bacteria that lives in association with roots.
• Bacteria form nodules on the plant roots and convert nitrogen gas (N2) from the air, into a form that plants can use. Alfalfa is effective at fixing N.
• A 6 ton/ac Alfalfa crop can fix up to 300+ lb/ac of N/yr.
Nodules contain bacteria which fix N for Alfalfa growth
N fixation:
• Alfalfa seed must be inoculated with R. meliloti.
• N-fixation by Alfalfa may decline after a stand is 4 or 5 years old.
• Poor yielding stands should be terminated and seeded to an annual crop for several years before being reseeding to Alfalfa.
0 N 180 lb N/ac Urea Spring Broadcast
Timothy – Lethbridge – June 13, 2006
Nitrogen for Timothy
90 Urea N 45 lb N/ac Urea Spring Broadcast
Timothy – Lethbridge – June 13, 2006
135 ESN N 135 lb N/ac AN Spring Broadcast
Timothy – Lethbridge – June 13, 2006
45 AN N 45 lb N/ac Urea Spring Broadcast
Timothy – Lethbridge – June 13, 2006
45 AN N 90 lb N/ac ESN Spring Broadcast
Timothy – Bow Island – June 19, 2006
N Rates for Timothy
• Spring for first cut:
–120 to 135 lb N/ac - very early spring
• Immediately after first cut is off:
–70 to 100 lb N/ac – irrigate immediately after
Timothy Nitrogen Choices• Spring broadcast urea (46-0-0)
– Best option – if broadcast very early in spring (when very when soil is cool !)
– Watch weather forecast and consider volatilization potential
• Spring broadcast ESN
– NO – release rate is TOO SLOW!
• Spring broadcast Agrotain coated urea (46-0-0)
– Higher fertilizer cost for 10-12 days of protection – from volatilization!
– Good option if weather conditions are warm and windy
• Spring dribble banded UAN liquid (28-0-0)
– Good option – but consider volatilization potential – apply in early spring!
– Consider the higher cost of liquid N
– Can add Agrotain to liquid for 10 to 12 days of protection from volatiliztion!
• Spring broadcast Ammonium sulphate (21-0-0-24)
– Short term option – No N loss but will apply S at high rate
– Not preformed well in our winter wheat work
• Ammonium nitrate (34-0-0)
– Best product – BUT must import from USA – Good Luck!!
Phosphorus (P) Nutrition
Phosphorus
• Alfalfa and Timothy have a high requirement for phosphorus (P)
• Most irrigated soils in Alberta are naturally low in plant available P
• Residual P levels vary in irrigated soils
– Many fields have received phosphate fertilizer
– Manured fields usually have adequate P and K
• Soil testing is strongly recommended before establishing Alfalfa to determine P requirements
P Fertilizer Application Before Forage Establishment• A large single application of P fertilizer or the
application of manure or compost before establishing Alfalfa or Timothy is very effective to add P to soil.
• An application of 150 lb/ac of P2O5 before establishment.
• Phosphate fertilizer can be either banded or broadcast-incorporated prior to seeding Alfalfa or Timothy.
Phosphorus Fertilizer – Established Forage
• If soil P is < 90 lb/ac or if P was not applied before establishment
– Apply 50-60 lb/ac of P2O5 (Granular 11-52-0; 12-51-0) broadcast in early spring –every year
– Under moist conditions, Alfalfa and Timothy have feeder roots near the soil surface that can take up broadcast P with reasonable efficiency.
• Can use dribble applied or can fertigate with liquid P fertilizer (10-34-0)
• Manure or Compost is an excellent source of P.
0 P2O5 54 lb P2O5 /ac Spring Band
Timothy – Lethbridge – June 13, 2006
Phosphate Fertilizer – P2O5
2006 Lethbridge – First Cut
0
1000
2000
3000
4000
5000
6000
Yie
ld (
kg
/h
a)
Phosphate Response - Method & Rate
0
30 Br
60 Br
30 Bd
60 Bd
0 + 200
30 Br + 200
60 Br + 200
30 Bd + 200
60 Bd + 200
kg P2O5/ha
Potassium (K) Nutrition of Alfalfa
Potassium
• Alfalfa and Timothy have a high requirement for potassium (K).
• If soil K levels are less that 200 lb/ac of K (Kelowna or ammonium acetate extractable K), in the 0 to 6 inch depth
– K fertilizer is recommended and may need to be coupled with annual applications.
• Most irrigated loam and clay loam soils have adequate soil K!
• K is most commonly deficient on very sandy soils that are more intensively cropped.
• Use a soil test to determine if soil K levels are low or deficient.
Soil Test K Potassium (K2O ) Recommendations(0-6 inches) (lb/ac)
0 – 50 150 – 170 50 – 100 100 - 120 100 – 150 90 – 100 150 – 175 50 – 60
175 – 200 40 – 50
200 – 250 25 – 50
>250 0
Note: Based on the Kelowna or ammonium acetate soil K test method.
Annual Potassium Fertilizer Recommendations for Alfalfa and Timothy.
Placement and Application Options
• Establishment
–Broadcast K to build up soil test K before seeding
• Maintenance
–Apply following harvest to replace removal
–When soil K levels are high
•K fertilizer application can lead to high K levels in forage – which is not desirable!
Sulphur (S) Nutrition
Sulphur – on Irrigated Land
• S fertilizer is rarely required for perennial crops:
–Subsoil is usually relatively high in sulphate-S – roots have access to this S
–Approximately 30 lb S/ac is applied in 12” of irrigation water – in the Sulphate form!
Calcium and Magnesium- Not Needed - in southern Alberta
- Base Saturation method used to predict Ca and Mg is flawed practice.
- Should not be used to make recommendations!
Micronutrient Needs of Alfalfa
Low Soil Levels
Nutrient Low Soil Level
Boron < 0.2 ppm in 0-6” – Soil test is not reliable
Copper < 0.2 ppm in 0-6
Iron < 2.5 ppm in 0-6”
Manganese < 0.5 ppm in 0-6”
Zinc < 0.5 ppm in 0-6”
-Micronutrients are not normally deficient
-Deficiencies may occur on very sandy, low organic matter soils that are intensively cropped!
-If soils test low – try strips first!
Summary
• Nitrogen
– Inoculate alfalfa seed – before seeding
– Timothy – 120-135 lb N/ac in early spring and 70-100 lb N/ac for second cut
• Phosphorus - If soil P is low –
–Apply P2O5 before establishment – 150 lb/ac
–Annual application ~50-60 lb P2O5/ac
• Potassium (Potash fertilizer)
–Only needed if Soil Test K is <200 lb/ac
• Sulphur and Micronutrients – rarely needed!
