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Response of a Leafy and Non-Leafy Maize Hybrid to Population Densities and Fertilizer Nitrogen Levels

^a Agriculture and Agri-Food Canada, Central Experimental Farm, 960-Carling Avenue, Ottawa, ON, Canada, K1A 0C6
^b MacDonald Campus of McGill Univ., 21111 Lakeshore Road, Ste Anne de Bellevue, QC, Canada, H9X 3V9

View larger version (25K): [in a new window]   Fig. 1. Monthly mean temperatures (°C) and total monthly rain (mm) during the growing seasons (May to September) of 2003 and 2004 as compared to the long-term (1961–2004) average values in the ex-perimental site at Ottawa.

View larger version (32K): [in a new window]   Fig. 2. The number of barren plants as affected by (A) hybrids in each N treatment, (B) N x plant population density (PPD), (C) PPD alone, (D) PPD x hybrids, (E) N x PPD for Pioneer 3893, and (F) N x PPD for Maizex LF850 RR in 2003 growing season. The vertical bar is the LSD0.05 value.

View larger version (28K): [in a new window]   Fig. 3. Leaf area per plant measured destructively using LI-COR Plant Canopy Analyser at the silking stage as affected by (A) N treatment (N), (B) plant population density (PPD), and (C) leaf area index (LAI) as affected by N, and (D) interaction between hybrids and PPD for the LAI in 2003. The points on the line associated with different letters are significantly different at P 0.05, and the error bars (D) is LSD0.05.

View larger version (22K): [in a new window]   Fig. 4. Total photosynthetically active radiation (PAR) intercepted (%) by the canopy during the period from 0900 to 1700 h each day from V12 to 4 wk after silking in the two maize hybrids grown with 0 kg N ha–1 at a plant population density of 75 000 plants ha–1 (A) in 2003, (B) in 2004, and (C) effect of plant population at V12 and silking (R1) stages measured by Decagon AccuPAR in 2004. The bars associated with different letters in (C) are significantly different at P 0.05 for each stage of measurement.

View larger version (13K): [in a new window]   Fig. 5. Effect of N treatment on the leaf greenness (SPAD) measured at silking stage in two hybrids averaged over two growing seasons.

View larger version (19K): [in a new window]   Fig. 6. Effect of (A) N treatment and (B) plant population density on the grain dry weight per plant (g) in two growing seasons averaged over two maize hybrids.

View larger version (17K): [in a new window]   Fig. 7. Response of grain and silage yields (Mg ha–1) of maize to different N treatments averaged over two hybrids and 2 yr.

View larger version (17K): [in a new window]   Fig. 8. Response of grain yield (Mg ha–1) of maize to N treatments in 2 yr averaged over two maize hybrids.

View larger version (16K): [in a new window]   Fig. 9. Effect of plant population density on the harvest index (HI) of two maize hybrids in (A) 2003 and (B) 2004, averaged over four N treatments.