US Investigational Allowances for Macronutrients
* For N guarantees above 32%, the investigational allowance shall be 0.88
# For P2O5 guarantees above 52% and K2O guarantees above 62%, contact the Association of American Plant Food Officials (AAPFCO) IA investigator.
For guarantees not listed, calculate the appropriate value by interpolation.
For TSP the investigational allowance shall be: 1.53.
US Investigational Allowances for Micronutrients
Secondary and Micro plant nutrients shall be deemed deficient if the analysis of any element is below the guarantee by an amount exceeding the values calculated according to the following schedule:
Investigational Allowances
A commercial fertilizer shall be deemed Deficient if the analysis of any nutrient is below the guarantee by an amount exceeding the values in the following schedule, or if the overall index value of the fertilizer is below 98%. Note: For these investigational allowances to be applicable, the recommended AOAC International procedures for obtaining samples, preparation and analysis must be used. These are described in Official Methods of Analysis of the Association of Official Analytical Chemists, 13th Edition, 1980, and in succeeding issues of the Journal of the Association of Official Analytical Chemists. In evaluating replicate data, Table 19, page 935, Journal of the Association of Official Analytical Chemists, Volume 49, No. 5, October, 1966, should be followed.
