Regulating nitrogen is a tricky task
I’m not superstitious, but I am a little stitious: cutting hay will trigger rain fall, knock on wood or get bad luck, don’t ever start a new project on a Friday, and never assume you don’t have enough nitrogen. If you would ask anyone at the research level in agriculture, “what is the most difficult thing to study?” they will undoubtably say nitrogen. For all of it’s wide use, do we fully understand how to determine when, what, and where nitrogen is best used? (Full disclaimer, this is going to be a very relaxed, basic discussion about nitrogen and we will avoid getting lostin- the-weeds with topics like ammonium vs ammonia, mineralization, nitrification, so on and so forth).
Nitrogen is king when it comes to plant development because it is the major proponent in the chlorophyl production, which captures sunlight to turn into energy in the plant, and to synthesize amino acids and eventually create proteins. All in all, N influences rapid growth and is the most influential for the development of plants leaves, roots, stalks and flowers. When we do not have enough or do not make it accessible, the crop/plant will show it through yellowing tissue and general slower growth.
Nitrogen isn’t just important for crops in the field, but plays an important for field management as well. For efficient nutrient use and soil productivity their exists a balance between carbon and nitrogen, or C:N. Fungi, bacteria, protozoa, want to have a balance diet of carbon and nitrogen, and the minute there is an excessive amount of one, or the other, they make an attempt to balance it out. To break down residue with higher carbon content, like corn stalks, small grain stubble/straw, soybean stems take quite a bit of energy for the biology in the soil to consume it/break it down, and so they seek nitrogen to keep themselves balanced. If a crop is planted into a field that has an imbalance of carbon and nitrogen, it will run the risk of not getting enough nitrogen. But not enough nitrogen isn’t the only problem. You could also have too much nitrogen. When we look at nitrogen use efficiency studies from UW Discovery Farms, UW Ag Research we can find that it is possible to overapply N fertilizer on crops. The plant can only take up so much, efficiently. It’s like Thanksgiving dinner; you have all the food you could possibly eat, but after multiple helpings you eventually have to stop and loosen your belt buckle because you can’t eat any more. One more example is an alfalfa field that has excessive nitrogen, causing blocky soil. A lot of people misdiagnose the compaction caused in alfalfa fields from harvest equipment, but it is because the alfalfa produces so much nitrogen for itself than it would ever need, releasing excessive amounts into the soil. The biology, desperate to balance it’s C:N diet, starts to eat carbon out of the soil aggregates. This turns the field from loose, pilly soil (optimal) into hard, blocky dirt (poor).
To remedy these nitrogen woes, farmers arms themselves with various approaches and assessments. More growers are adding forage grasses to their alfalfa fields to take up the extra nitrogen, adding extra nitrogen fertilizer at planting for corn/soybeans to help fuel germination while biology is working hard to break down residue, and using cover crops to sequester nutrients and release extra fertility. Soil and tissue testing is also a viable option. Pre-side dress testing is where you take a 12-inch soil sample, between the rows of corn. Take a sample per 10-20 acres to find out how much nitrogen is available in the ground. For a tissue test you would either take the whole plant for the leaves to find out how much is in the plant. This helps farmers determine if the crop is getting enough fertility. Tests like these are very helpful determining more targeted applications but do take about 5-7 days to get the results back. AgSource, located in Stratford, has been a helpful lab for me and I would encourage you to check them out (on the web or visit their office). Another lab to take samples to would be Rock River labs, that have an office in Colby. With corn up at v3-v5 in our area you might not have enough time to take tests, so reach out to your agronomist to determine best rate of nitrogen on your crop.
The Soil
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