Relying solely on an above-ground evaluation is only offering strip-tillers a partial report card of crop health.

Holding plants accountable for their yield promise requires an understanding of how fertilizer timing, placement and performance intersect with root structure and development, according to veteran agronomist Mike Petersen.

Having dug more than 1,500 soil pits during his 35 year career, Petersen says strip-till and accurate nutrient applications can achieve 300-bushel corn more efficiently and affordably than conventional tillage.

Speaking at the 2015 National Strip-Tillage Conference, he recommended applying 30-50% of the needed fertilizer with the strip-till during his general session on smart fertility programs. Petersen says that product type and placement can have a heavy impact if it’s not well thought out.

“Many times, you’ll have to do a fall application, because we know how our soil conditions can be in the central and eastern part of the Corn Belt,” he says. “Be smart about it. If you are going to use dry fertilizer, use products like ESN — a coated product that is going to last.

“When you are looking at liquid products, don’t place it too deep, because then you are going to lose it.” 

Part of developing a solid strip-till system is understanding how roots grow at a few pivotal stages. In his research, Petersen has examined soil profiles once per week from late April to early September — monitoring things like temperature, nutrient absorption and water uptake. These tests have guided his understanding of fertilizer placement and timing.

“With early root systems, around V1, you’ll see that a seedling root without any starter fertilizer is probably going to get about 4-6 inches long,” says Petersen. “But with starter fertilizer placed directly in the seed trench, you’ll see it jump up to 6-12 inches. Having top quality nutrients, micronutrients and even biologicals in your starter package make a tremendous impact.”

Petersen also earmarks 15 days after emergence as an important time in the life of the corn crop. It’s at this point that the root structure starts feeding itself on the nutrients that have been made available in the strip — which is why depth is important.     

“You won’t have a very big system of roots yet, but if you’ve placed nutrition along with the seed at a certain depth, usually between 4 and 6 inches with phosphorus and potassium, you have a chance for that seedling root to get into that and feed itself,” says Petersen. “Roots actually don’t seek nutrients; they thrive in the presence of them.”

Petersen is among the rank of strip-till advocates that feel strongly about placing fertilizer in the strip with the strip-till rig, saying that farmers running a rig naked are doing themselves a disservice.

“With strip-till, we can place nutrients in the zone, and there’s no reason not to, unless you have very sandy soils that will lose them out of the bottom,” he says. “Roots don’t grow upward, unless they’re from a mango tree. We’re also headed for the Environmental Protection Agency (EPA) regulating nitrogen (N) application, and placing it in the strip is more efficient.”

Read more on Mike Petersen’s approach for digging deeper into strip-till fertility with “Looking at Strip-Tilled Corn from the Roots Up," and listen below to an exclusive Strip-Till Farmer podcast with Petersen, Getting to the Root of Strip-Till Fertility: