Starter Fertilizer in Continuous Corn Production in the Midwest.

Previous research has shown that starter fertilizer, a small amount of fertilizer placed with or near the seed at planting, often accelerates early season growth and increases biomass production, but does not always increase grain yield in corn (Zea mays L.). Our objective was to evaluate the effects of starter fertilizer on crop growth and development, as well as grain yield and moisture in continuous corn cropping systems. Treatments consisted of no fertilizer applied at planting (Control), a "Popup" application of 4 kg ha-1 N and 6 kg P ha-1 placed in-furrow with the seed (PU), an application of 28 kg ha-1 N and 11 kg P ha-1 placed 5 cm to one side and 5 cm below (5x5) the seed (S), a combination of 3.8 kg ha-1 N and 11 kg P ha-1 applied in-furrow and 24 kg ha-1 N and 9 kg P ha-1 applied 5x5 (P+S), and an application of 56 kg ha-1 N and 22 kg P ha-1 placed 5x5 (SH). The total N rate applied, but not P rate, was equalized across all treatments with variable sidedress N rates. The study was conducted in 2015 at 4 locations with varying weather conditions, soil types, and management practices. Final plant population was unaffected by starter treatments. Crop growth and development responses to starter fertilizer treatments were similar across all locations. Dry matter and plant height increased 140% and 49%, respectively, with the SH treatment relative to the Control. Other treatments had intermediate effects. For almost all locations and starter fertilizers, compared to the Control, total nutrient content for N and P increased as the rate of starter N increased, while tissue concentrations for N and P decreased. Starter fertilizer accelerated the rate of leaf collar appearance throughout the vegetative growth period, beginning as early as the 2-leaf collar stage (V2). As the season progressed, phenological differences among the treatments increased even after total applied N was equalized with the sidedress N applications. Flowering occurred sooner in the P+S and SH treatments than in the Control or PU treatments and the timing of the S treatment flowering was intermediate. On average, grain moisture of the PU, S, P+S, and SH treatments were 0.5, 1.1, 1.6, and 1.7 percentage points lower than the Control treatment. However, grain yield was affected by starter treatments at only one location, increasing by 3.7, 6.2, 7.4, and 9.2 percent relative to the Control for the PU, S, P+S, and SH treatments, respectively. Yield of the SH treatment at that location was significantly higher than that of the PU treatment, but no different than the S or P+S treatment.