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Message: <blockquote data-quote="Allen" data-source="post: 493215" data-attributes="member: 389">I'm sorry that I didn't see this earlier, because the highlighted part is incorrect.   Nitrogen in the fertilizer is generally in the NO3 (nitrate) form once dissolved in water and available to plants.  I studied this fairly extensively for my Master's thesis and once it gets down to the water table as NO3, it doesn't last very long before our relatively young geologic materials react with organic carbon and pyrite in biologically mediated chemical reactions to remove the NO3 by converting it to N2 (nitrogen gas).  By intercepting this fertilizer contaminated water prematurely through tile drains, it places that water back in a surface drain, which preserves the NO3 because it is thermodynamically more stable in an oxygenated environment. In general, everywhere I looked at the water chemistry at the top of the water table, it was highly contaminated with NO3.  It didn't/doesn't last long though in the water column as once the oxygen disappeared, the NO3 takes over as the most available and energetic oxidant while anaerobic bacteria become more and more prevalent with depth. Basically, tile drains reduce the resident times for NO3 contaminated groundwater and prevent its full removal by our geologically young sediments in our aquifers.  The primary components soils that contain enough organic carbon and pyrite to help remove the NO3.  There are drawbacks to this though.  One of the biggest heavy metal contaminants associated with the organic carbon and pyrite is arsenic.  Hence, the chemical reactions also tend to increase heavy metal content of the groundwater.  There are huge swaths of ND where arsenic is a major concern in drinking water wells.At one time, ND investigated the potential for an arsenic based superfund site down in the Hankinson area.  It was thought that poor storage and spills of grasshopper baits during the Dirty 30s were the source of the problem.  As it turns out a mass balance of how much arsenic is contained in the groundwater vastly exceeds what was reasonably used as grasshopper poisons.I too am not necessarily a big fan of tile drain use as we have developed over the past 30+ years, but am also of the opinion that it has a place in agriculture. The bottom line is that through groundwater sampling, it's very easy to demonstrate ND farmers over apply nitrogen and phosphorus based fertilizers.  Their saving's grace is that our soils are far more reactive being the sands are based off of sedimentary rocks, versus the primarily igneous rock derived sands and gravels of our communist neighbor to the east.  That's why MN has much tighter controls on fertilizer application than ND.  Farmers are shown by fertilizer salespeople their yield potential versus application rates of fertilizer.  They are not shown how much escapes the root zone and makes it into the groundwater, because doing so would reduce the sales of fertilizer.  Basically, if no fertilizer escaped the root zone, the plants would be nitrogen limited...and that means they would be leaving some production on the table.  Balancing yield with lost nitrogen is something very few farmers do.  While good business, they just don't have the skillset to really sharpen their pencils on this one.  They would need to know exactly how much NO3 is getting to the water table, and that's a labor intensive and financially expensive thing to measure.</blockquote>

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