Corn hybrid response to in-furrow starter fertilizer as affected by planting date

Use of in-furrow starter fertilizer (IFSF) is common in the Upper Midwest to enhance early-season corn (Zea mays L.) growth because of cold soils in the early spring which limit P uptake by corn. The objective of this study was to evaluate the agronomic and economic responses of corn to IFSF and how this was affected by planting date (PD) for hybrids of contrasting relative maturity (RM). A 3-yr experiment was conducted in 2010 to 2012 at two locations in southern Minnesota which evaluated IFSF at 0 and 65 kg ha^–1 of 100–150–0 (g kg^–1 N–P–K) with three corn hybrids (94-, 99-, and 104-d RM) planted on three dates spaced on 10- to 16-d intervals. Delaying PD resulted in greater corn plant density, grain moisture at harvest, and kernel m^–2, and decreased early-season plant height, days to silking, kernel mass, and corn grain yield. Planting a laterRM hybrid resulted in greater early-season plant height, days to silking, grain moisture at harvest, kernel mass, and biomass and grain yield. In-furrow starter fertilizer increased early-season plant height and kernel mass and decreased days to silking, grain moisture at harvest, and kernel m^–2. Economic net return to grain production was not affected by IFSF. Results from this study confirm that planting mid- to late-RM hybrids during late April to mid-May produces greatest net return in the Upper Midwest, and that the response of grain yield to IFSF is not affected by PD for hybrids of differing RM.