Re: Nitrogen Soil Test...interesting
marv ,
what you say is very true! most growers watch the tip of their plants for a
reading of nitrogen.......MB
>The Scoop on Soil Testing for Nitrogen
>Nitrogen can be added to soil in many forms. It can be applied as nitrates,
>ammonium, urea, etc. Soon after the nitrogen is added and if there is some
>moisture present, the indiginous bacteria called nitrosomonas and nitrobacter
>convert all forms of nitrogen to the nitrate form. The nitrate form of
>nitrogen is an ion with a negative charge (NO3-). The clays in South Carolina
>soils also have a negative charge and since similar charges repel, the
>nitrates are not attracted to the clays like the posit ively charged calcium,
>magnesium and potassium ions. Nitrates are also very soluble in water. As a
>result, the nitrate ions are very mobile in the soil and move through quite
>readily as water percolates down into the soil. If a soil is sandy, nitrates
>move through the soil even faster due to the large pore space and faster
>percolation of water. These factors are the reason for environmental and
>health concerns regarding nitrate movement into groundwater.
>
>Because of nitrogen's rapid conversion to the nitrate form and its subsequent
>movement through the soil, it makes the soil test for nitrogen quite
>difficult to interpret. By the time you receive soil test results for nitrate
>nitrogen, it may have alre ady moved through the soil if some rain had fallen
>between sample collection and reporting of lab results. Some soil tests for
>nitrogen are done for certain crops but it is still in an experimental stage
>and not widely used or accepted in our region. Re searchers will collect soil
>samples at several depth intervals to monitor the nitrate movement during a
>crop's growing season.
>
>Because of the mobility of nitrogen in the soil, most states in the Eastern
>region of the U.S. just make a blanket recommendation for each crop with the
>assumption that most of the residual nitrogen from the previous crop has
>moved past the root zone f or the new crop. You will notice that for many
>crops, nitrogen is recommended as a split application. If all of the nitrogen
>was added at the beginning of a growing season, much of it would move past
>the root zone before the crop matures. Splitting app lications allows the
>nitrogen to be applied more in accordance to the crop's needs at different
>stages of growth and thus reduce leaching.
>
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