Effects of plant population on leaf area index, cob characteristics and grain yield of early maturing maize cultivars (FAO 100-400)

Maize (Zea mays L.) growth in non-typical maize growing regions has several limitations with respect to agronomic characteristics of cultivars, and their reactions on changes of production system in specific climate. Two long term field experiments were carried out to investigate the effect of plant populations (PP) on the leaf area index (LAI), grain yield and cob characteristics of maize cultivars in Maribor, Slovenia. In the first experiment, an increase of PP from 4.5 to 13.5 plants per m(2) did not affect the LAI of four older maize cultivars at the 7-9-leaf stage, but significant differences between cultivars, years and PP appeared at brooming (from 1.58 to 7.07). In this stage, a strong correlation existed between LAI and grain yield (r = 0.87**). Reduction of LAI from brooming to waxy maturity averaged 9.7%. PP explained 93-99% of the variation in grain yield depending on cultivars. Some cultivars lodged at the highest PP in some years. Increased PP significantly changed the following cob characteristics, weight of 1000 kernels, cob length, number of kernel rows, and number of kernels per row. In the second experiment, 11 recent cultivars expressed a relatively small trend of grain yield increases when PP was increased from 7 to 13 plants per m(2). At high PP, the percent of plants decaying after emergence increased up to 27% during the vegetation period. Therefore, we conclude that the information on suitable PP for each maize cultivar is one of the key factors for planning maize production. (C) 2002 Elsevier Science B.V. All rights reserved.