Managing N when going to no-till

Farmers have all heard the horror stories about switching to no-till. The stories usually center around corn that experienced a nitrogen deficiency, resulting in symptoms such as stunted growth or yellowing/firing, and sometimes even reduced yields. Unfortunately, these few stories can lead growers to dismiss no-till altogether without considering how it might show up differently on their farm—especially when practiced properly—and the efficiency, profitability, and soil health benefits no-till practices provide.

That’s not to say the no-till transition doesn’t sometimes come with a dose of agronomic challenges. But, these challenges don’t have to be roadblockers, as long as growers understand the changes occurring in the soil and have appropriate management strategies. In particular, a grower should understand the effects of tillage, and no-till, on soil biology and nitrogen availability.

When soil gets tilled, a lot of things happen physically and biologically. Soil organisms get exposed to oxygen, causing a short-term feeding frenzy. They digest readily available soil organic matter and, in the process, provide a temporary spike in plant-available nitrogen. Often that spike provides a nice boost to corn planted about a week after that last tillage event. However, disrupting the soil also causes a long-term decline in soil biology by reducing the physical conditions for soil biology to live, resulting in a decline in the capacity of that soil microbiome to process residue into nutrients.

So when soil that has been tilled long-term goes to no-till, and a high nitrogen-demand crop like corn is planted, not only does the tillage “feeding frenzy” not occur, but that microbiome also has a much smaller capacity to process soil organic matter—at least, at first. 

This means that when growers adopt no-till practices, they need to alter their nitrogen management strategy for high nitrogen-demand crops. Here are a few ways to do that:

1. Shift nitrogen from pre-plant to closer to planting
2. Spoon-feed nitrogen right before peak N demand (V-8 to tassel) 
3. Plant a legume-heavy cover crop ahead of your cash crop
4. If possible, start the switch to no-till on low nitrogen-demand crops, such as soybeans

The longer that soil stays in no-till, the more the soil biology will return to its natural high levels, improving the soil’s natural capacity to create plant-available nitrogen while cutting fertilizer and application costs. Implementing strategies that boost natural soil biology—such as diverse cover crop mixes—will speed up the return of your soil’s natural health and, along with it, increase the capacity of your soil to not only store more nitrogen, but provide more of it to your cash crop. 

By Ryan Stockwell, Indigo Ag Senior Manager of Grower Engagement and Wisconsin Farmer