NAVY BEAN YIELD NITROGEN AND ZINC

Dry bean (Phaseolus vulgaris L.) generally responds to nitrogen (N) fertilizer with increased yields, but N can delay maturity and cause yield and quality losses from early fall frost. Maintaining adequate zinc (Zn) nutrition in bean promotes earlier maturity. This study was conducted to determine if Zn application can overcome maturity delays possible with the N recommended for high bean yields. Three zinc sulfate (ZnSO4) treatments (O Zn, 5.6 kg Zn/ha banded adjacent to the row, and 11.2 kg Zn/ha broadcast and incorporated) were applied in combination with five N rates (0, 45, 90, 134, and 179 kg/ha). Whole plants were sampled at the R1 growth stage (onset of flowering) and analyzed for N and Zn content. Maturity was estimated by determining the percentage of mature pods at the R8-R9 growth stage. Yields were estimated by harvesting 12.2 m of row at maturity. Zinc fertilization generally increased mature-pod percentages with banded Zn producing the most consistent response. Zinc did not consistently affect bean yield. Yield and mature-pod percentage generally increased and decreased, respectively, with increasing N rate. Whole-plant N concentrations increased linearly with increasing N rate but did not differ among Zn treatments. Mean plant Zn concentrations were increased by Zn fertilizer and related well with mature-pod percentage means. In situations of high available N, short growing seasons, or with late planting, Zn applications can reduce the risk of crop losses from early fall frost.