Residue Raises Complicated Questions

Conservation tillage offers trade-offs when controlling pests in crops.

Image by Pamela Smith

To quote comedian John Mulaney, “It is so much easier not to do things than to do them, that you would do anything is remarkable.” Now, I’m not lazy, but if I can be more effective by not doing something, why not? This is why conservation tillage--any practice that reduces or eliminates tillage--appeals to my sensibilities. And, more than half of growers in the U.S. seem to agree. Conservation tillage takes some effort, yet when there are benefits to not doing something, why wouldn’t you? But when it comes to pest management, how does conservation tillage affect the pests?

Folks can have strong opinions about tillage practices. In short, conservation tillage provides several benefits. By reducing or eliminating the need to till the soil on a regular basis, growers can increase a field’s organic matter and reduce soil compaction. That leads to more water percolating through the soil and greater root growth. These fields retain higher moisture levels and have lower erosion rates. And, growers switching to reduced tillage save on the costs of equipment maintenance, fuel and labor.

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CON-TILL TRADE-OFFS. But, what benefits growers also benefits pests. Insects use the soil or crop residue as a place to nap during the winter. By eliminating or reducing tillage, these tiny menaces get plenty of beauty sleep before popping out in the spring. And, because the soil holds more moisture, no-till soil is cooler for later in the season, making some crops vulnerable longer to pests targeting seedlings.

Some of the increased risks are more of an issue during the transition from conventional tillage to reduced-tillage practices (four to five years), but others will continue beyond the transition period. Regardless, conservation tillage requires a greater focus on management. Practices that can control weeds, cover crops and properly timed herbicide applications can also limit the presence of some pests that rely on early-season weed foliage (i.e., armyworms, cutworms). Planting cultivars that are quicker to mature may avoid the threat of early- and late-season pests. Growers can also rotate crops each season to prevent pests from becoming established in a field or plant-mixed crops, which can increase natural enemy habitats and lower field attractiveness to pests.

BENEFICIAL INSECTS. But, past the transition period, fields can experience net-positive effects from conservation tillage. The reduced soil and residue upheaval provide habitats for beneficial insects. Pests that live part or all of their lives in contact with the soil are likely prey for ants, beetles and spiders. Other insects, such as aphids, are less likely to land in fields with residue, delaying their establishment until crop plants have grown beyond their most vulnerable stages. Over time, these benefits can supplement or reduce active management compared to the benefits provided by tillage.

Conservation tillage is no silver bullet for farm management, but it does provide a new approach to manage better. If you can soldier through the transition years, you may reap the benefits of healthier soil, greater water retention and lower costs. Pest management under this system requires greater attention to the situation on the ground (pun intended) and will keep you busy. But, you may find your pest control to be equally, if not more, effective, as you’ll have assistance from thousands of tiny helpers.

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