N is burning the Carbon Pool

     Two recent events have triggered this post.  I recently gave a presentation on why our operation has gone to a ULDDS (ultra-low disturbance direct seed) system along with sharing our cover crop experience (as limited as it is) to a group of NRCS trainee's from across eastern Washington, and, an article that came out in the July issue of NO-TILL Farmer, titled "Excessive 'N' Application Burning the Carbon Pool (vol. 46, #7).
      The first event had fertility on their minds as part of the general discussion on soil health.  the article authored by Richard Mulvaney, a University of Illinois fertility specialist, had specifics.  His position is based on mining documents on fertility, and data sets, going back 100 years.  His comments helped me to link pieces of a foggy puzzle about crop fertility and how it will react on soil health.  His recommendations are going to be a challenge for us to address.  The following is what I found engaging:  (most will be paraphrased)

      ---soil is an important source of N.

      ---applying N does not build organic matter.

      ---you can not bank N by adding N.   Soil microbes use it to burn the carbon they find in residues and soil organic matter.  This results in less C and less SOM.   (my thought: --this may be why we struggle to move SOM above 3%)

      ---"You can never decouple carbon and N --not on this Earth....".  Microbes use N to make enzymes so they can burn the carbon that supplies their energy.  Every enzyme has N.

      ---crop rotation is best.  Corn yields are better in rotation than with continuous corn, and done with much lower fertilizer inputs.  The data tells me that fertilizer cannot replace rotation for highest yields. (my thoughts: Follows Beck's principal, rotation-rotation-rotation)

      ---Mulvaney's best short-term option for growers would be to increase efficiency by putting more of the fertilizer N, "into the crop" when it is needed. --by:

                           ---Use tests to determine what the soil can provide.

                           ---Don't apply NH3 in the fall.  There is no crop (corn in this case), and there is a lot of microbes that will use the N.  (my thinking: --our fall wheat does not need all the N that we customarily place with it.)

                           ---Sidedress N to synchronize fertilization with crops N demand.  Ideally, shift from ammonia to nitrate fertilizers despite the greater risk of N loss through leaching and denitrification.  Mulvaney & colleagues base this idea on scientific evidence that plants have an edge in taking up nitrates, whereas microbes are better competitors for ammonium.

      ---the 1947 book, The Soil and Health by Sir Albert Howard, claims that there will never be sustainable agriculture until animals are put back on the land.  It's a cycle.  Do we need to rethink the big picture.  (my thought: --several people heavy into covers are going this route)