Fertilizing Alfalfa in Kentucky

Southern States Training Feb, 19, 2003

Greg Schwab, Extension Soil Specialist

UK Department of Agronomy

True or False: True or False: A fertile soil is always a productive soil.A fertile soil is always a productive soil.

Soil Compaction?

Soil Fertility and Alfalfa Production

Key Components

Soil Sampling

pH Management

Macro Nutrients

Micro Nutrients

Manure applications

Goal: Stand Longevity Goal: Stand Longevity

Soil SamplingSoil Sampling

Field UniformityField Uniformity•SlopeSlope

•DrainageDrainage•Cropping historyCropping history

A sample shouldA sample shouldnot representnot representmore then 20more then 20

acresacres

Sampling DepthSampling Depth4” for no-till4” for no-till

6” for conv.-till6” for conv.-till

Sample in Management Zones

Field 1

Field 2 Field 3

Field 4

Grid Sampling Using GPS

AdvantagesYear to year consistencyHigh samples don’t mask low testing areasAnswers diagnostic questions

Disadvantages COST!!! Labor and AnalysisGenerally, results in higher fertilizer application ratesGrid should not be smaller than application equipment

The effect of soil The effect of soil pH on the activity pH on the activity of soil micro-of soil micro-organisms, organisms, availability of plant availability of plant nutrients, and nutrients, and occurrence of toxic occurrence of toxic elementselements

CornCorn AlfalfaAlfalfa

Agricultural Lime

Pelletized Lime

Relationship Between Fineness and Reactive Surface Area

1”

1”

1”

Surface area = 6 sq. inches

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 A soil pH of 6.5 – 7.0 is optimum for nitrogen-fixing bacteriafor 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

maintain with annualapplications equivalent to P and K in hay removal.

and

Philosophy #2“Sufficiency”

Probability of response based on field research

Effect of Nitrogen Fertilization on Alfalfa Yield Applied at Establishment

Yield (12% H2O)

N Rate 1982 1983 Average

lbs N/ac …..…..tons/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 AlfalfaUK’s Phosphate and Potash Recommendations for Alfalfa

New Seedings Established StandsNew Seedings Established Stands

Soil Test Level P2O5 K2O P2O K2OSoil Test Level P2O5 K2O P2O K2O

…….lbs per acre…….…….lbs per acre…….

High (60P, 300K) 0 0 0 0High (60P, 300K) 0 0 0 0

Medium (28-60P, 191-300K) 30-110 30-100 30-70 70-210 Medium (28-60P, 191-300K) 30-110 30-100 30-70 70-210

Low (< 28P, 191K) 120-160 110-160 80-120 220-300 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.Higher Yields- fields should be sampled every year for yields above 5 T/A.

Potassium Deficiency

Indiana Research Indicates that there is a seasonal K response

2.05

2.10

2.15

2.20

2.25

2.30

2.35

2.40

0 100 200 300 400

Potassium, lbs k2O/acreY

ield

, ton

s/ac

re

0.75

0.80

0.85

0.90

0.95

1.00

0 100 200 300 400

Potassium, lbs K2O/acre

Yie

ld, t

ons/

acre

LSD=0.12 LSD=NS

1999 Harvest 4 Yield 2000 Harvest 1 Yield

(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 alfalfaAnnual applications after the seeding yr.

1.5-2.0 lbs of B/acBorated fertilizer or fertilizer borate

Molybdenum (Mo) – deficiencies often occur when soil pH < 6.2Apply 1 lb sodium molybdate/ac

Toxicity??

Biannual

Boron Deficiency

Alfalfa 10 lbs B/a

Boron Toxicity

Fescue 10 lbs B/a

Boron Toxicity

Orchard Grass10 lbs B/a

Boron Toxicity

Timothy10 lbs B/a

Boron Toxicity

Manure Application on Alfalfa

N P2O5 K2O %H2OSolid Manures

Beef

……….lbs per ton……….

11 7 10 80

Dairy 11 9 12 80

Example: 10 tons of dairy manure would supply 110lbs. N90 lbs P2O5

120 lbs K2O

Timing of Manure Application to AlfalfaTiming of Manure Application to Alfalfa

* Prior to establishment.

* During last years of the stand.

* 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

* New Seedings – P and K applied before seeding.

* 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

* pH probably single most important factor.

* Established Stands – P and K improves stand longevity.

Questions/Comments