Sowing Date and Maize Productivity: II. Kernel Number Determination

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Abstract
Kernel number in maize (Zea mays L.) depends on the physiological conditions of the crop at flowering. Our objective was to study the effect of sowing date on the relationship between crop growth rates in the 4‐wk‐period bracketing silking and the components of final kernel number. A commercial hybrid (DK636) was grown in the field at four sowing dates (mid‐September, mid‐October, mid‐November, and mid‐December) for 3 yr at INTA Balcarce Experimental Station, Argentina, at a density of 8.6 plants m−2, without water and nutrients limitations. Significant reductions in final kernel number per unit area of crop were observed when sowing date was delayed. Final number of kernels per unit area was associated with the number of kernels per ear and with the number of ears at harvest. No significant differences were found among sowing dates for maximal number of spikelets per ear at flowering, indicating that kernel abortion was the main factor determining the differences in final kernel number per ear. Reductions in crop growth rate after silking determined decreases in the number of kernels set per ear, whereas reductions in number of ears were not associated with crop growth rate in the presilking period, in which an important allocation of assimilates to structural vegetative growth and maintenance respiration in late sowings would be associated with high ear barrenness.

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