Sep20WedField Notes September 20, 2017 Joe Osterhaus, Sales Agronomist
A few weeks ago NACHURS tweeted out a picture of 10-34-0 sludge at the bottom of a large Co-op holding tank. This photo has been retweeted quite a few times, so I thought I would talk about why this happens. Anybody who has used 10-34-0 knows that it isn’t exactly the nicest fertilizer to work with, and anybody who has stored 10-34-0 has no doubt dealt with the impurities and metals falling out of solution leaving a layer of sludge in the bottom of their tanks. Why does this happen? What can we do differently? Let’s take a look.
Ammonium Polyphosphate (APP), 10-34-0, and not as common 11-37-0, is super phosphoric acid reacted with ammonia at high temperatures then cooled and diluted with water (this is a simplified version but you get the idea). Polyphosphates are chemical chains of phosphate molecules that have the ability to sequester heavy metals not fully removed during beneficiation of the raw phosphate ore. Many impurities remain such as chlorine, fluorine, magnesium, aluminum and carbon. APP or 10-34-0 begins to breakdown or hydrolyze, which is a normal process, as 10-34-0 is stored and used. As the fertilizer breaks down it can no longer sequester the heavy metals and they begin to fall out. This results in precipitates and sludge that need to be cleaned out of tanks every year or two. We all know that the low man on the totem pole gets this job.
What can you do to avoid this? Well, that all depends on what you are willing to do. You can switch from 10-34-0 to a different fertilizer. Generally if the fertilizer is green, amber, or black in color it contains super phosphoric acid (SPA) which is the base for APP fertilizers. Clear fertilizers look like water and use purified phosphoric acid (PPA) which is processed more and contains far fewer impurities. If processed even more it can be considered food grade phosphoric acid which is used in many processed foods like soft drinks. Generally speaking the more processing the more expensive the product.
NACHURS 6-24-6 is a green product which is 20% polyphosphate and 80% orthophosphate which is readily available phosphate. This is very competitively priced and is by far easier handling and less corrosive than 10-34-0. Generally the cheaper the fertilizer the more APP it contains and the more impurities there are. Most NACHURS starters are clear using PPA which is 100% orthophosphate; it is a little higher priced but many say it is money well spent.