Source-Sink Balance in Two Current Argentinean Maize Hybrids.

Maize is considered to be sink limited during the grain filling period. Nevertheless, yield progress based on sink capacity could lead to a source limitation during this stage. The objective of this work was to determine source-sink components (i. e., reproductive growth and ear demand). Two current Argentinean high yield potential hybrids were sown at Balcarce in 2011-12 growing season under non-limiting conditions for growth. Five source levels during grain filling were evaluated: i) control (undisturbed crop), ii) and iii) 6-day 83% shading imposed at 457 GDD and 692 GDD after silking, and iv) and v) thinning each other plant at the same moments as shadings. A complete randomized block design with factorial arrangement of treatments was applied. Biomass production between R1 and R6, grain yield, kernel number, weight per kernel were measured and source and sink capacity were estimated. Yield variation among source levels was accounted for by weight per kernel. Yield in control plots was similar between hybrids; however hybrids differed in sink capacity. The hybrid that presented the highest sink capacity also showed the highest yield response to thinning and shading. These results emphasize the importance of the source-sink balance as a determinant of yield response to environmental conditions during the grain filling period.