| Abstrakt: |
Field experiments were conducted in 2001 and 2002 at the University of Thessaly Research Farm in Velestino, using three planting dates, namely: ultra-early (U-E, March 1 or 2), early (E), and normal (N) that were at least 2 weeks apart. Three maize hybrids were used: Eleonora, Pregia, and Constanza of 130, 123, and 125 day maturities, respectively. Maize emergence in the U-E planting was delayed by 8 days (19 DAP) compared with the N planting. Ear formation, fertilization and the black-layer appearance were always approximately 2 weeks ahead for the U-E compared with the other plantings. Although percentage emergence in the U-E was initially (at 4 WAP) the lowest, the final stands were similar (>94%) in either planting. Plant height and plant dry matter were lower at the U-E compared with the N planting. Only the hybrid Pregia showed the highest ratio below ground (BG) to above ground (AG) at all plantings. Leaf area index (LAI) at V6-V8 stage was highest in the N planting (differences were mainly due to hybrid Eleonora). In 2001, grain yield in the U-E was 22% lower than that of N planting. The yield component primarily responsible for this yield penalty in the U-E planting was the number of grains and not the number of rows or test weight. In 2002, however, the situation was reverse; the U-E planting gave 10% higher yields than the N planting. Irrigation in 2002 was 33% lower than that in 2001. It appears that the increased yield of the U-E planting was manifested when maize irrigation was the least favorable. The positive effect of the U-E planting is documented for the least favorable conditions. Grain moisture content at harvest was steadily lower in the U-E compared with the other plantings. Regarding weed control, it appears that a POST-application of herbicides would offer a higher weed control and grain yields than a PRE-application of herbicides. [ABSTRACT FROM AUTHOR] |
