I am planning to analyze manure samples for Total Kjeldahl NItrogen, Total Kjeldahl Phosphorus, and dissolved reactive phosphorus using and AQ2 analyzer. I would like to also look at plant-available secondary and micronutrients using ICP-OES but am running into some challenges.
First of all, I have seen that it might be tricky to use ICP-OES for organic samples: https://www.thermofisher.com/us/en/home/industrial/spectroscopy-elemental-isotope-analysis/spectroscopy-elemental-isotope-analysis-learning-center/trace-elemental-analysis-tea-information/icp-oes-information/icp-oes-sample-preparation.html
Second, I have seen that different nutrients would require different kinds of digestion/extraction, and I might have to prepare multiple samples according to the amount of time I have. The EPA has a method on digestion for soils but this does not include manure and digestion for the purpose of finding plant-available nutrients, though I may end up discarding the "plant-available" category: https://www.epa.gov/esam/epa-method-3050b-acid-digestion-sediments-sludges-and-soils
Page 2 under "Sample preparation methods" offers two extraction methods plus hot-water extraction that I have seen elsewhere: https://www.agilent.com/cs/library/applications/5991-5675EN_app_note_4200_mp-aes-nutrients_soils.pdf
I would like to know if these are legitimate thoughts on how to analyze manure nutrient contents. Thanks for any help.