Ultra-early planting effects on maize crop development, yield, and weed control
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 Nplanting. 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. Copyright © by The Haworth Press, Inc. All rights reserved.