No Till Notes - cover crops, part 4


I’ve been writing about my limited experience with cover crops grazed for forage and planted back to a cash crop. It may be in today’s modern production agriculture we need to adopt the same concepts used a few generations ago to manage their fertility concerns prior to the adoption of commercial fertilization. We may have overlooked or forgotten the concepts our fathers and grandfathers used to improve their soils, the same soils we are working with today.

I came across a picture of my grandfather, John Daniel Watson, standing in a field of oats and vetch planted for grazing, hay, or maybe he plowed it under for fertility. In any event, he knew the concept of planting a diverse cover crop to improve the soil, and then planting the field back to a cash crop at a later date. It’s the same concept we are introducing back into our farming operations today. This concept is nothing new, but one we have possibly underutilized since commercial fertilizers became available.

Obviously, my grandfather didn’t have the science or technology we have today to examine why this concept is effective, he just knew from experience that it worked. Here is a summary of what we’ve learned to date with our own introduction of this concept.

Through a biomass sampling we learned we had 174 pounds of nitrogen in the plant material on the soil surface. We also decided that with a Carbon to Nitrogen ratio of 39:1 approximately 50 pounds of this nitrogen would be available for this year’s corn crop. We also learned from a soil sample test that 220 pounds of nitrogen were recommended to produce a 200 bushel per acre corn crop.

Using an established plant population analysis we determined we have 34,000 established plants per acre in this field. This is determined by measuring 17 feet of row in 30” row spacing, counting the plants within 17 feet, and multiplying the plants per 17 feet by 1,000. In our region you can estimate a potential yield by multiplying 6.5 bushels of corn times the 34 plants within the 17 foot average, which gives us a yield potential of approximately 220 bushels per acre.

Through microbial testing we learned we have a diverse and good population of soil microbes in our soil. With the use of the Haney test we know this test showed we needed only 92 pounds of nitrogen to produce a 200 bushel corn crop. The soil microbes will supply the remaining nitrogen for the corn crop through mineralization of the soil organic matter.

We have applied 160 pounds of commercial fertilizer to this field of corn. We have now conducted 2 plant tissue analysis of the corn crop, one at the crop stage growth of V10 and another at tasseling. Both plant tissue tests have shown the crop to be in the high sufficient range at 3.24 percent nitrogen. The plants have adequate nitrogen available for high yielding corn.

We have applied approximately 60 pounds less nitrogen than the soil sample called for, yet we have adequate nitrogen to produce high yielding corn. I feel the additional nitrogen is being supplied by the cover crop residues, previous crop residues, and the soil microbes. What we don’t know is if we could have reduced our commercial fertilizer rates even more?

We have a dry land trial with differing nitrogen fertilizing rates that I would like to visit with you about in another article. This experiment has raised even more questions about what our soils can do if we give a healthy soil a chance to work for us.


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