Nitrogen rate and timing considerations on yield and physiological parameters of corn canopy

One year corn field experiment was conducted at a research farm of Agriculture and Agri-Food Canada, located in L'Acadie, Quebec, Canada. The experiment was a completely randomized block design with five N treatments and four replications. The five N treatments received N 0, 20, 45, 113 and 225 kg/ha(N 45 kg/ha was applied at sowing, and N 180 kg/ha at 10 days after sowing), respectively, at sowing, and N 0, 93, 68, 0 and 0 kg/ha, respectively, at side-dressing, i.e. N0, N20+93, N45+68, N113, and SAT225. Corn density is 79000 plants/ha, and the cultivar is Pioneer 38B84. The results show that SPAD reading, PN, LAI, aboveground dry biomass, canopy chlorophyll density (SPAD×LAI) and canopy photosynthetic capacity (PN×LAI) are increased with basal N rates increasing before side-dressing, while Dualex reading is decreased. Compared to N113, SPAD readings in the N20+93 and N45+68 treatments are significantly increased. The split N applications have no significant influences on Dualex reading and PN. The LAI, aboveground dry biomass, SPAD×LAI and PN×LAI of N20+93 and N45+68 are significantly lower, but the grain yields are significantly higher than those of N113. There are no significant differences in corn grain yield between N20+93 and N45+68, however, the N deficiency is appeared earlier in N20+93 than in N45+68. No significant differences between N113, N20+93 or N45+68, on one hand, and SAT225, on the other hand, are observed in SPAD reading, Dualex reading, PN, LAI, aboveground dry biomass, SPAD×LAI and PN×LAI at 25-60 days after emergence, while corn grain yields of N113, N20+93 and N45+68 are significantly lower than that of SAT225. Split N application can significantly increase corn grain yield compared to only one application at sowing, and N45+68 is better than N20+93. Under our experimental condition, a total N application with N 113 kg/ha do not produce the same corn grain yield as SAT225. Both SPAD and Dualex readings show significant correlation with corn plant N concentration, and then can be used as an instant and non-destructive diagnostic tool for corn N status evaluation.