Effect of Late Nitrogen Applications on Grain Filling in Corn

Abstract

Rationale and Objectives • Yield improvement in corn over the past few decades has been accompanied by an increase in plant nitrogen (N) uptake, with modern hybrids absorbing more N during reproductive stages, while delaying N remobilization to the grain for later in the growing season. • To evaluate the effect of late-season N applications in distinct corn genotypes, grain yield and grain filling parameters were evaluated in field experiments under different N regimes using recent and historical Pioneer ® brand corn hybrids. • Experiments were conducted in two environments, one irrigated and one non-irrigated. Study Description • Year: 2017 • Location: Ashland Bottoms Research Farm, Manhattan, KS (Soil pH = 5.9, soil organic matter = 1.34%, 50 ppm of phosphorus (Mehlich), and 158 ppm of potassium) • Environments: Non-Irrigated, Irrigated • Planting Date: May 5 • Plot Size: 10 x 70 ft • Experimental Design: Split-plot • Hybrid/Brand 1 : • Nitrogen Application Timings (Sub-Plot Factor):-0 N (non-fertilized check)-Planting + V6 + R1-Planting + V6 + 2 weeks after R1 • Data Collected:-Yield (combine harvest)-Yield components (kernel number, kernel weight).-Grain filling was measured beginning at the R2 growth stage, collecting one ear per plot every 3-4 days. Ten kernels from the central portion of the ear were sampled to track changes in kernel dry weight and water volume during the entire period.-Total aboveground biomass-Leaf area index (LAI, Plant Canopy Analyzer LAI 2200) Results • Kernel number and kernel weight were both positively correlated with final grain yield (R 2 = 0.58 and R 2 =0.43, respectively) for all hybrid and treatment combinations. • Total aboveground biomass and leaf area index were measured at the R1 and R3 growth stages to determine correlation with final yield. No differences among nitrogen treatments were detected. • Table 3 summarizes average yields and yield components for fertilizer N rate levels (N) and corn hybrids (H). Corn Yield • Yield significantly differed among hybrids (P ≤ 0.05) with a positive trend between the year of release of the hybrid and yields, from 176.8 bu/acre for Pioneer ® hybrid 3394 (1991) to 205.5 bu/acre for Pioneer ® P1197AM™ brand corn (2014) average across N treatments (Figure 1). • As expected, fertilized treatments differed from the zero N treatment (with a more prominent effect under irrigated conditions). • There was no significant difference in average yield between the two N treatments (Figure 1). Yield Components • Significant differences among N treatments and hybrids were found for kernel number (P ≤ 0.001 and P ≤ 0.05, respectively), and among N treatments for kernel weight (P ≤ 0.001) (Table 3).