Soil Tests and Amendments
6 | Unit 1.11
Instructor’s Lecture 1 Outline
- Excess fertilizer use and fertilizer pollution (see Unit 3.3, Environmental Issues in Modern Agriculture)
a) Nitrogen and phosphorus deposition in surface and sub surface water, leading to
eutrophication
b) Nitrate leaching and groundwater contamination
c) Question: Is there greater efficiency or reduced nutrient runoff from “organic”
farms?
- Summary
D. Soil Testing as a Soil Fertility Management Tool
- A soil test provides current quantitative information on the nutrient content and the
nutrient supplying capacity of a soil - Soil analyses can provide an accurate determination of a soil’s textural classification
- A soil analysis provides quantitative data allowing for the comparison of a given soil’s
nutrient and chemical profile with established agronomic benchmarks of soil fertility - Soil analysis also helps to identify nutrients that exists at very low levels—“limiting
nutrients”—that may result in acute plant nutrient deficiencies - Soil testing provides essential information that may be used in developing nutrient
budgets - The use of soil tests for periodic monitoring of soil nutrient levels allows a grower to
gauge nutrient depletion or accumulation - Specialized testing: E.g., toxics, pesticides, heavy metals, nutrient profiles of compost
- Summary
E. Soil Testing and Recommendation Philosophies
- Sufficient Levels of Available Nutrients (SLAN) approach
- Cation Saturation Ratio (CSR) approach
- Nutrient Build-Up and Maintenance approach
- Most testing services have established optimal ratios for general soil fertility that are
a combination of SLAN, CSR, and Nutrient Build-Up and Maintenance approaches.
As different testing services use different extraction techniques, it is import to consult
with your local testing service on the system they use in developing recommendations.
Always request “best practices” benchmarks from the testing service in order to
maintain the highest yield and soil quality.