Soil Sampling Topic # 2036 Mr. Christensen
Dec 21, 2015
A little Review
O Horizon (Organic)A Horizon (Topsoil)
E Horizon (Subsurface)
B (Subsoil)C (Substratum)R (Bedrock)
Soil Map Montcalm County
Montcalm County, Michigan Fairplains Sheet 51 Scale 1:20,000
Mm McBride Sandy LoamCa Carlisle
Why Sample Soils?
• Determine plant nutrient availability• Diagnostic tool for problem soils• Soils in Michigan vary greatly and change
overtime due to crop removal• Tests include: pH, electrical conductivity
(EC), organic matter, nitrate-nitrogen, phosphorus, potassium and other micronutrients
What is pH?
• pH is a measure of the acidity or alkalinity in the soil.
• pH is measured by the number of hydrogen ions present in the soil solution
• The pH scale goes from 0 (acid) to 14 (alkaline) with 7 as neutral
What is pH?• pH uses a logarithmic scale for the hydrogen ion
concentration
pH 6.0 is 10-times more acidic than pH 7.0
pH 5.0 is 100-times more acidic than pH 7.0
MostAcid
Blueberries
4.0-5.1
Oats
5.0-7.0
Corn
5.5-7.5
Alfalfa
6.3-7.8
Cranberries
4.2-5.0
Potatoes
5.2-6.5
Grasses
5.5-7.5
Beans
6.0-7.5
Azalea
Magnolia >5.5
Trefoil
5.5-7.0
Sugar Beets
6.0-7.5
Strawberries
5.0-6.5
Wheat
5.5-7.0
Soybeans
6.0-7.0
Least Acid
pH Tolerance
Why is pH Important?
• Soil pH influences the availability of nutrients-a pH of 6-7 is generally favorable for plants, however some plants prefer more acid (blueberries, azaleas (4.5-5.2))or alkaline soils (monkshood, Lady fingers)
• Impacts the type and population of microorganisms (pH 6.6-7.3 is favorable for microbial activity that promotes nitrogen, sulfur and phosphorus availability.)
Ohio State University http://hcs.osu.edu/hcs412/sos6.htm
Alfalfa at Low pHPoor growthLack of Symbiotic bacteriaFor nitrogen fixation
Why is pH Important?
• Mobility of heavy metals increases with acidity and can leach into streams or aquifers
• Corrosive to steel under high alkalinity or highly acid soils, concrete is corroded at pH 5.5 or lower
• Impacts soil applied herbicide effectiveness
Why Does pH and Fertility Change?
• Climate
• Weather
• Soil Mineralogy (sulfur in the soils)
• Breakdown of organic matter
• Plants remove nutrients
• Anhydrous ammonia breakdown
Crop Nutrient Removal
Crop Yield Nutrients removed in harvest
bu/ton/acre N P2O5 K2OAlfalfa hay 6 ton 270 60 270Corn, grain 150 bu 135 64 42Corn, stover 4.5 ton 101 36 144Soybeans 50 bu 188 44 66Cucumbers 10 ton 20 12 36Celery 30 ton 150 60 480Wheat, grain 60 bu 75 38 23Wheat, straw 2.5 ton 30 8 53
How Do We Control pH?
• Soil acidity pH can be raised by adding lime materials (calcium oxide CaO)which neutralize the H+ ions and replacing them with calcium (Ca++)/magnesium (Mg++)
• Types of Limestone—burnt/hydrated (fast reacting), Calcic/Dolomitic (slower but less expensive), by-products (slag, paper mills,wood ash), Shell meal and Marl
• Lower pH using Aluminum Sulfate or Sulfur
Soil Sampling Equipment
Colorado State University http://www.colostate.edu/Depts/SoilCrop/extension/Newsletters/2002/Beans/planning.html
Soil ProbeSoil BorerBucketShovel/spadeSoil mapSpecimen Bag/Box
Soil Sampling
• Select/group Areas based on:
Soil type
Past management/cropping history
Topography
Field Size
10-15 acres per sample
Soil Sampling
• 20 cores per sample (1lb sample is 1 part in 2 million “acre furrow slice”)
• Consistent depth (plow depth 8 inches, minimum tillage include sample from the top 2 inches)
• timing pH, P and K every three years Nitrogen varies greatly, what are your nitrogen
credits? A pre-side dress test may be required to determine needs.
Soil Sampling Patterns
University of Montana http://www.montana.edu/wwwpb/pubs/mt8602.html
Zig-Zag Pattern
A. Aerial Photo of 67 acre fieldB. Management zonesC. 2 acre field grids
Lime Application MapBased on soil test results in each zone
Cooperative Extension Service The University of Georgia http://www.ces.ugs.edu/pubcd/B1208.htm
Grid Sampling
Linco Equipment Company-http://www.linco.com/atrssu.htm
Agro Company http://www.gpsagro.dk/index_uk.htm
12 Satellite accuracy 2 meters24 Satellite accuracy 10 cmUp to 7,250 samples a acreOn the go sampling is being tested
Successful Farming http://www.agriculture.com/sfonline/sf/1997/january/precisn/1.html
Apply up to 6 tons of lime per year, retest and reapply if necessary the next year
Average pH of 6.0 for field Average pH of 6.5 for field
Potassium application mapPhosphorus application map
Kansas State University http://www.oznet.ksu.edu/pr_prcag/sandpivot.shtml