Brinkman's Nutrient Management Notes
December 15, 2006
The topic for this edition of the "Nutrient Notes" is making sure we understand what the information we provide is to be used for.
Many times we are asked to run RUSLE2 and the P-Index for producers. Remember to respect producer's or landowner's information. Information may be requested by many individuals: Technical Service Providers (TSP), coop or agronomy people, county board of supervisors, Iowa Department of Natural Resources (IDNR), etc... To protect the producer's information, the producer or landowner should have a signed statement for the release of this information and to whom it may be released to in the producer's file.
Okay, now back to understanding what the information is to be used for. We should understand that some of the tools we use have different interpretations on how they should be used. An example of this is determining "Dominant Critical Soil" for the conservation management unit (CMU). When determining dominant critical soil for use in the P-Index we have the NRCS method and the IDNR method. Chapter 65 page 50 - 65.17(17) b of the Iowa Code says that when sheet and rill erosion is calculated for the phosphorus index, the soil type used for the calculation shall be the most erosive soil map unit that is at least 10% of the total field area.
When completing a Comprehensive Nutrient Management Plan (CNMP), use the NRCS method only when determining the soil map unit. Another example is when we are doing a CNMP for a producer. A question that needs to be asked is this producer applying for a National Pollution Discharge Elimination Permit (NPDES)? If they are, we need to make sure that the requirements of the NPDES nutrient management plan (NMP) are being met. The rules for the NPDES permit are for the most part complete. If you are interested in what these requirements are let me know and I can provide assistance in this area. Also, if the producer is using our CNMP to meet any IDNR requirement make sure that the risk assessment category requirements of the P-Index of the IDNR are being meet. The risk category of medium 2 to <5 states that if the risk assessment falls into this category; the producer is limited to a phosphorus application that is no more than two times the crop removal for the rotation up to four years. If the risk assessment is five or greater, no application of manure can be made.
I hope this has cleared up some questions. Please remember that we need a producer's written permission before we can talk to anyone about their operation or release information pertaining to their operation. If you have any questions on anything mentioned above, let me know.