ENVIRONMENTAL EDUCATION SERIES
ENVIRONMENTAL QUALITY
Agriculture & Natural Resources
EXTENSION ENVIRONMENTAL EDUCATION, AUBURN UNIVERSITY, AL 36849-5647
Soil Testing Can Help The Rural Environment
ANR-720, 1992. By Charles Mitchell, Extension Agronomist, Agronomy, Auburn University 
The proper use of manures and fertilizers are essential to sustain agriculture in Alabama. Soil testing is one tool that has been emphasized for decades as essential to safe and economical fertilizer use. Today, it is still essential. In fact, where nutrient recommendations are followed within reasonable guidelines of soil testing and other best management practices are followed, there has been no indication of excessive nutrients entering surface or groundwaters. Fertilizers and manure can, in fact, help improve our environment by enhancing productivity and fertilizer efficiency on the land we farm.

 Soil Testing For The Farmer

 In past years, soil testing was emphasized solely as a means to encourage farmers to fertilize and lime their crops for maximum economic production. Soon, however, it may be required before any soil amendments are applied to land. Why? Because soil test interpretations and recommendations have been misused by some to mean a minimum amount of nutrients to apply rather than an optimum/economical amount.

 Excessive nutrient applications are not only wasteful, but could be damaging to surface and groundwater. Excessive phosphorus from surface runoff can potentially cause eutrophication (oxygen depletion) of lakes and streams. Unused nitrate (from animal manures and fertilizers) can leach into shallow, underground aquifers.

 Sure, farmers who applied more nitrogen, phosphorus, or micronutrients than research-based soil tests called for usually made good yields--maybe the best in the county. Yet, excessive nutrients resulted in excessive cost. In turn, this decreased their profits. Nationwide research on farms and experiment stations has proven over and over again that University-based soil test recommendations result in yields as good or better than excessive nutrient applications, and always result in a much higher return to the grower (Table 1). In every case where surface or groundwater contamination from nutrients (either from manures or fertilizers) has been identified, it has been traced back to widespread, excess application of manures or fertilizers. Following research-based soil test recommendations can make money for the farmer and help the environment.
 
 
Table 1. Net returns after fertilizer costs based on experiments in several states comparing University research-based fertilizer recommendations with those from other sources.
  Net Returns After Fertilization
State Year Crop* University soil
test recommendations		 Other
recommendations
  ----------$/acre----------
AL 1985 Soybeans 148 69
AL 1986 Soybeans 156 137
AL 1987 Corn silage 348 324
KY 1986 Corn grain 216 167-195
KY 1977-79 Corn grain 120 80
NE-1 1974-80 Corn grain 237 163-235
NE-2 1974-80 Corn grain 209 122
TN 1980-84 Soybeans 152 132-145
*Values for returns were for soybeans @$5.50/bu, corn silage @$22/ton, and corn grain @$1.50/bu.

For more information, call your county Extension office. Look in your telephone directory under your county's name to find the number.
Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability. 

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