Soil Testing

Why test soils?to determine fertilizer needs

increased yieldsfaster growth

= money to grower

How much fertilizer is enough?Underfertilized

growth, yield reducedincreased susceptibility to

disease, insects

How much fertilizer is enough?Overfertilized

ties up micronutrientsleaches into groundwater –

nitrate pollution

expensive

How much fertilizer is enough?Best approach:

Frequent soil tests followed by low level applications of fertilizer at regular intervals

Plant Nutrient LevelsLevel 1: Deficient

growth, productivity slowed

Plant Nutrient LevelsLevel 2: Sufficient

plant needs satisfiedadding more fertilizer only increases

growth slightly - not worth cost

Plant Nutrient LevelsLevel 3: High

high nutrient levelsmaximum growthcan easily become too much - toxicity,

pollution, nutrient tie-ups.

Plant Nutrient LevelsLevel 4: Toxic

yields declineplant damage

Three methods for finding nutrient deficiencies in plants:

1 Visual inspectiondeficiency signsyield reductionsslow growthureliable

damage already done

2 Soil test measure nutrient levels of soil

most common method

determine lime, fertilizer needs

soil conditions not identified

3 Tissue testingmeasures nutrient levels in plant itself

bypasses soil to determine if nutrient was taken up by plant

measures nutrient levels in the plant itself

most complete and accurate

Testing basischemical reactions that

produce color changes depending on amount of minerals in soil

not always reliable - human error, results vary

Home test kitsMore common among

greenhouse and nursery growers

Results may vary and not compare w/ lab tests

Professional testing

Projessional LabLaboratory testing with

instruments

Extraction - filter water through soil sample

spectrophotometer - passes light through solution, measures amount of light absorbed

Professional Labuse charts to interpret measurements

based on validated tests on similar soils

results may vary from lab to lab

Professional labStandard laboratory series soil test

includes:

textureorganic matter contentpHnutrients – NPK

high, medium and low rating

ResultsBased on needs of area

Standard/Optional depending on labSoluble saltsCECCaSMgTrace elements

ResultsNitrogen difficult to test because

soluble

Test for organic matter storage - what crop took out

Soil TestingUniversity of

Wisconsin Extension and private labs perform soil tests

http://soiltest.cfans.umn.edu/http://www.soilperfect.com/

How to use test kit