Research has shown that starter fertilizer gives no-till corn an early growth kick and usually boosts yield.
Can starter also stoke corn planted in tilled soils?
According to 1996-97 University of Illinois tests, starter boosts the early growth of reduced-till corn, but does not consistently bring higher yields.
The two-year trials were held at six locations scattered around the state, for a total of 12 comparisons. The six sites varied in existing fertility, soil type and crop rotation.
Cooperating farmers typically did primary tillage, such as chisel plowing, in fall, and secondary tillage, such as field cultivating, in spring. About 15% of soybean residue or 35% of corn residue remained after planting.
Spring weather was wet in 1996, followed by cool, high-yield summer conditions. In 1997, a cool, dry spring was followed by a hot, dry pollination period.
The starter was applied as zero, 12.5 or 25 lbs/acre N, zero or 30 lbs/acre P2O5, and zero or 20 lbs/acre K2O. Most was put on in a band 2" below and 2" to the side of the seed. But in some cases, N was dribbled on the surface.
"Early season growth was increased by N in 11 of the 12 comparisons, while P increased growth in five cases," reports Illinois soil scientist Bob Hoeft.
"Treatments supplying 25 lbs of N per acre increased plant growth more consistently than did 12.5 lbs N per acre. And placing the N fertilizer in a 2 x 2 band increased plant weight more than did dribbling N on the soil surface."
Grain yields were increased in three of 10 comparisons by banded treatments that contained N or N and P. (Yields were not taken at two 1997 locations due to poor pollination.)
The increases came at three locations in 1996. There were a few apparent increases at other locations, but the lack of consistency led researchers to believe the responses may not have been reproducible.
"The lack of yield response to starter fertilizer in 1997, even though early growth was increased by an average of 50%, may have been due largely to unfavorable weather conditions at pollination time," Hoeft explains. "That un favorable environment likely neutralized any positive effects the starter fertilizer may have contributed to early plant growth."
In a second experiment, Hoeft and his colleagues determined whether 10 lbs/acre of sulfur, 0.25 lb/acre of zinc or 0.50 pint/acre of ACA, an additive containing N and zinc, improved the performance of a 25-30-0 starter.
When starter N and P increased grain yields, adding sulfur, zinc or ACA did not further increase yields, nor did they consistently increase plant weight.