Fertilizing Alfalfa in Kentucky Southern States Training Feb, 19, 2003 Greg Schwab, Extension Soil Specialist UK Department of Agronomy
True or False: A fertile soil is always a productive soil.
Soil Sampling Micro Nutrients pH Management Manure applications Macro Nutrients Soil Fertility and Alfalfa Production Key Components Goal: Stand Longevity
Soil Sampling • Field Uniformity • Slope • Drainage • Cropping history Sampling Depth 4” for no-till 6” for conv.-till A sample should not represent more then 20 acres
Field 2 Field 3 Field 4 Field 1 Grid Sampling Using GPS Disadvantages COST!!! Labor and Analysis Generally, results in higher fertilizer application rates Grid should not be smaller than application equipment Advantages Year to year consistency High samples don’t mask low testing areas Answers diagnostic questions
Corn Alfalfa The effect of soil pH on the activity of soil micro-organisms, availability of plant nutrients, and occurrence of toxic elements
Agricultural Lime Pelletized Lime
Relationship Between Fineness and Reactive Surface Area 1” 1” Surface area = 6 sq. inches 1” One cubic inch of limestone ground to pass a 100-mesh screen would have approximately 60,000 sq. inches of surface area.
A soil pH of 6.5 – 7.0 is optimum for nitrogen-fixing bacteria
Not Inoculated Inoculated
Fertilizer Recommendation Philosophies Each ton of alfalfa contains: 14 lbs/ac P2O5 50 lbs/ac K2O For a 5-6 ton/ac crop: 75-90 lbs P2O5 25-300 lbs K2O
Philosophy #1 Build soil test to high level and maintain with annual applications equivalent to P and K in hay removal.
Philosophy #2 “Sufficiency” Probability of response based on field research
Effect of Nitrogen Fertilization on Alfalfa Yield Applied at Establishment Yield (12% H2O) N Rate1982 1983 Average …..…..tons/ac………. lbs N/ac 0 9.5 7.3 8.4 30 9.1 7.4 8.3 60 9.0 6.4 7.7 Dr. Lloyd Murdock, UK Extension Soils Specialist
UK’s Phosphate and Potash Recommendations for Alfalfa New Seedings Established Stands …….lbs per acre……. Soil Test LevelP2O5 K2OP2O K2O High (60P, 300K) 0 0 0 0 Medium (28-60P, 191-300K) 30-110 30-100 30-70 70-210 Low (< 28P, 191K) 120-160 110-160 80-120 220-300 Higher Yields- fields should be sampled every year for yields above 5 T/A.
LSD=0.12 Indiana Research Indicates that there is a seasonal K response 1999 Harvest 4 Yield 2000 Harvest 1 Yield LSD=NS (Berg, et al., 2002) K use efficiency can be increased by applying ½ fertilizer after last harvest and ½ after first harvest
Micronutrients Fe, Cu, Mn and Zn – no measurable yield response in Kentucky Boron (B) – often a limiting nutrient of alfalfa Annual applications after the seeding yr. 1.5-2.0 lbs of B/ac Borated fertilizer or fertilizer borate Toxicity?? Biannual Molybdenum (Mo) – deficiencies often occur when soil pH < 6.2 Apply 1 lb sodium molybdate/ac
Alfalfa 10 lbs B/a Boron Toxicity
Boron Toxicity Fescue 10 lbs B/a
Orchard Grass 10 lbs B/a Boron Toxicity
Boron Toxicity Timothy 10 lbs B/a
Manure Application on Alfalfa Solid Manures N P2O5 K2O %H2O ……….lbs per ton………. 11 7 10 80 Beef 11 9 12 80 Dairy Example: 10 tons of dairy manure would supply 110lbs. N 90 lbs P2O5 120 lbs K2O
Timing of Manure Application to Alfalfa * During last years of the stand. * Prior to establishment. * Least desirable is on young established stands. * Significant losses of nitrogen can occur during warm weather. * Rates should be based on the need for P and/or K.
Summary *pH probably single most important factor. *New Seedings – P and K applied before seeding. *Established Stands – P and K improves stand longevity. *Inoculated seed should not be mixed with K fertilizer. *Small advantage for fall fertilizer application. * Spring applications should be made after the first cutting. * Manure applications prior to planting or during later years of the stand