This week's observation is related to yield response to two management practices, tile drainage and no-till.
We often hear these two practices being talked about together, for example, "If I install tile drainage, I can start using no-till on high clay, valley soils." I'm not sure I have the answer, but I like the thought process of stacking tools. Let's talk about what the data/research tell us to help guide decisions.
At the Soil Health and Agriculture Research Extension Farm in Mooreton, N.D., we have been evaluating yield response for a corn (2016), soybean (2017), wheat (2018) rotation on Fargo clay soils. Here's the setup: The northern half (80 acres) of the field is tiled and the southern 80 acres are un-tiled. There are no-till and conventional tillage (chisel plow, field cultivator) replicated strips (three of each) on both the tiled and un-tiled parts of the field. There are full size equipment strips, not small plots. The entire field is planted to one crop.
The no-till parts of the field (on both tiled and un-tiled) have cover crops in each part of the rotation. We interseeded corn with cereal rye/radish, planted green with soybean, flew on an oat/radish cover crop mix before leaf drop in soybean, and used a practice called bio-strip till with radish/faba bean/flax into wheat stubble.
We hand-collected grain from specific points and also used yield monitors and weigh wagons to determine crop yields. We collected soil samples in each of the strips for measuring soil health parameters. (The soil data will be in a follow-up Soil Health Minute).
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Here are the results. Let's first look at the three graphs on the left-hand side of the figure. These are for the no-tile and tile crop yield comparison. The black square is the average yield and the color squares on either side of that black square show the variability in yield (similar to the highs and lows you see on a yield monitor during harvest). Look at both the average yield and the variability because that tells you the whole story.
In 2016, the average corn yield was higher on the un-tiled part of the field than the tiled. Average soybean and wheat yields were not different between tiled and un-tiled treatments (or in other words, we consider the yields to be the same).
Let's now look at the graphs on the right-hand side of the figure. The average corn yield was higher on the no-till/cover crop treatments than the conventional tillage management approach. Average soybean and wheat yields were the same.
With both the tile/no-tile and conventional/no-till comparison, we need to keep in mind that these results represent sample locations from a single field. If we wanted to gain more confidence that these crops consistently responded to these practices in this way, we would need to repeat this study on multiple, similar fields.
We know that yield isn't everything when we are talking about a soil health system, but overall, what does this dataset tell us? We are not seeing a consistent difference in yields by management (tiled/un-tiled; conventional/no-till) of the three crops for the treatments. For example, we are not seeing that corn, soybean and wheat yields are ALL higher on the un-tiled part of the field versus the tiled. We are also not seeing consistently higher yields on no-till/cover crop versus conventional tillage. This is OK; it means we need to continue taking measurements and evaluating the system long-term.
I'm also OK with seeing "no difference" in yield because then we can look at the inputs and costs associated with inputs. Then you can decide what is most important: Income? Ability to reduce erosion? Peace of mind? Water management? It is likely a combination of goals, but now you have some data/research to consider as well.
Research credits: Caley Gasch (NDSU Soil Health) and Aaron Daigh (NDSU Soil Science)
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