Article 4169.03 of the Standard Specifications specifies the requirements for all fertilizers.


All fertilizer furnished shall be labeled in accordance with the rules and regulations of the Iowa Department of Agriculture. Their rules and regulations provide for regular monitoring and require that each unit of fertilizer furnished shall provide on the label or on the invoice the net weight, the name and address of the manufacturer and/or distributor and the name and guaranteed analysis of the product.



Acceptance of fertilizer for Iowa Department of Transportation projects will be based on a current valid license from the Iowa Department of Agriculture.  The list of licensed fertilizer suppliers is at  



Prior to fertilizing, the entire lot of fertilizer to be used should be inspected for damage due to exposure to moisture. Evidence of contamination or other reasons which would indicate the quality of the fertilizer is questionable, would be considered cause for holding until the lots or bags in question have been approved and/or tested before use. The Iowa Department of Agriculture maintains a monitoring program for fertilizers; therefore routine samples for testing will not be required.



If sampling is required, the following procedure should be used. From lots of ten bags or more take one core from each of ten bags. When necessary to sample lots of less than ten bags, take 10 cores, but at least one core from each bag present. Take cores as follows:  Lay bag horizontally and insert long probe diagonally from end to end. Remove approximately 1 lb. from each bag and combine with other nine samples to make up test sample.


Each bag must be checked for brand and grade before probing for the sample.


Bulk truckloads can be sampled by taking ten vertical cores at uniformly distributed locations throughout the load.


A minimum of 3 lbs. of fertilizer is needed for a complete analysis. Samples should be placed in a plastic sack similar to those used for cement samples.


Liquid fertilizer samples may be taken directly from the mixing vat or from the delivery line. The entire vat must be thoroughly agitated before the sample is taken.


In sampling liquid fertilizer from a point in the delivery line, a sufficient quantity must be pumped out to insure that no unmixed material is in the line before the sample is taken.


Place the sample in a clear 1-quart glass jar or a polyethylene container.


All samples shall be submitted to the Office of Materials with Sample Identification Form #193. The form shall contain the pertinent data, which appears on the label or invoice.