Using Cover Crops as Undercover Diagnostic Tools for Farmers and Scientists

Using Cover Crops as Undercover Diagnostic Tools for Farmers and Scientists


When I started working with farmers
about 30 years ago one of the main things I was interested in was how plants, other than cash crops, can help farmers to improve yields and solve a whole bunch of other problems like soil erosion. Now this interest has continued in my research at the USDA where I’ve focused a lot of my time on cover crops, and how they can affect a whole bunch of
different things in a farming system. But, what if we change our perspective and go deep into the soil and rather than ask how does the cover crop affect the soil, how about if we ask: How does the soil down here affect the cover crop up there? And can these amazing plants with their deep root systems help us to look for problems or patterns in fields? In other words, can we use cover crops as
diagnostic tools? Kind of like when you go to the doctor, and the doctor takes out a good old-fashioned stethoscope and and is able to hear things deep inside of
your body. I’m gonna give you two very visual examples of how cover crops can be very effective and efficient diagnostic tools for underground issues
in a field. We’ll start with a simple example, and then look at a more complicated one. So here’s a cereal cover crop in one of my organic research fields and you can see a very clear stripy pattern. What’s causing this? Well, I’ve seen this stripy pattern many times when a winter cereal cover crop is grown
right after disking down strawberry beds. [TRACTOR ENGINE SOUND] So these dark green areas are where the
strawberry furrows used to be and the yellow areas are where the bed tops were. This pattern often lasts for the whole cover crop, but then it goes away pretty soon after that as the nutrient levels in the field even out. Okay now let’s look at a more complicated situation in one of my other research fields. So often when we’ve grown a cereal or a mustard cover crop here I’ve noticed this strange diagonal pattern that’s always occurred in the same place and it really puzzled me because the pattern wasn’t related to anything that we’d done in the field. And I wondered if there might be something deep down in the soil that
might help us to understand this pattern. So to figure it out we set up a grid and took a soil core in the center of each of these squares to a depth of about a hundred and twenty centimeters. And then we did a texture analysis to look for the percentages of sand silt and clay in the top and the bottom of each core. Now what we found amazed me. While the soil surface was pretty similar across the field with about 75 percent sand, things were very different deep down and here’s a figure that shows that. So the shade of yellow color indicates the amount of sand where darker yellow means more sand. And as you can clearly see there’s a
diagonal pattern of more sand in the area which is where the cover crop
didn’t grow as well. Now this is probably because there was more drainage there and less nutrients for the cover crop to take up in that area. So the next time
you go to the doctor, and they take out a stethoscope to listen for patterns deep inside of your body, think of cover crops and how they can help farmers and scientists to look for patterns deep inside the soil. Some of these patterns are related to management while other patterns are just characteristics of the field that we really can’t change very easily, but at least we now understand
them. Take care. [MUSIC]

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