The Farm Journal Test Plots set out to understand the differences in nitrogen and phosphorus starter rates applied at planting.  

Starter test plots dial in early season nutrient needs

In the quest for higher yields, identifying the limiting factors helps to guide your steps along the path. Starter fertilizer is a tool that provides young corn with key nutrients, particularly phosphorus and nitrogen.

Farm Journal Field Agronomist Ken Ferrie reminds farmers that the keys to nutrient management are the three R’s: right place, right time and right rate. Supplying the necessary amount of phosphorus and nitrogen at planting can boost your corn yields to a higher plateau. (See "Strategic Placement," February 2012, for more on applying starter in the right place.)

"Never let corn have a bad day, and that starts at the beginning," Ferrie says. "Let corn talk to you and tell you what it needs."

To investigate starter blends, Ferrie led a crew to conduct test plots in central Illinois and Farm Journal Associate Field Agronomist Missy Bauer did the same in southern Michigan.

"We’ve looked at starter fertilizer in test plots for two decades," Ferrie says. "On average, applying starter fertilizer with the planter can boost yields 7 bu. to 10 bu. However, this past year in a number of our starter plots we saw higher than typical responses to starter because we

advanced the plants’ maturity into a safer reproductive stage during the extreme heat."

What does your corn crave? Farmers have different goals for applying fertilizer with the planter. Some focus on early-season nitrogen needs, others target early phosphorus needs and some try to tackle both.

"When I think about how corn responds, I separate nitrogen responses from traditional starter responses caused by phosphorus," Ferrie explains. "If a farmer is getting as big of a response from straight 28 as starter, the corn is telling him he isn’t supplying enough early nitrogen."

Ferrie conducted his test plots in two fields: one corn after soybeans, the other corn on corn. The test plots were planted with an eight-row Kinze EdgeVac planter, and mixes of 7-22-5 plus zinc, 28% nitrogen, 50/50 mixes of the two, and 60/40 mixes of the two, all applied on a per-acre basis.

The starter attachments included the Huckstep shoe and the Yetter 2959 coulter injector. Starter was also dribbled above the row.

In the corn/soybean field, the dry fertilizer program included 30 lb. of nitrogen broadcast in the fall and 90 lb. broadcast preplant; the rest was sidedressed. The field showed the greatest response to the 7-22-5 starter blend applied with a Huckstep shoe, which mounts between the disk openers.

"Farmers should consider how they apply nitrogen, how much nitrogen is in the starter and if they are meeting early nitrogen needs," Ferrie says. "This farmer managed his nitrogen upfront and in-season with sidedress. The corn plants responded most to the highest level of phosphorus because it was the limiting factor, not nitrogen."

In the corn-on-corn field, there was more residue and a higher carbon penalty. The farmer applied 30 lb. of nitrogen in the fall and 150 lb. of nitrogen preplant (he originally planned to apply 90 lb. but increased the rate to help pay the carbon penalty and compensate for a wet spring).

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