EFFECTS OF POPULATION-DENSITY ON THE YIELD AND YIELD COMPONENTS OF LEAFY REDUCED-STATURE MAIZE IN SHORT-SEASON AREAS

Maize hybrids which yield well, mature earlier and tolerate higher pop ulation densities better than the currently available hybrids would be more suitable for production in short-season areas. Leafy reduced-sta ture maize hybrids, which have only recently become available, have tr aits which address these criteria. The objective of this study was to evaluate the effects of different population densities (50 000, 100 00 0, 150 000, and 200 000 plants ha(-1)) on the yield and yield componen ts of one leafy reduced-stature (LRS), one non-leafy reduced-stature ( NLRS), and two conventional control hybrids (Pioneer 3979, <2500 CHU; and Pioneer 3902, 2600-2700 CHU) at two locations. All hybrids had the highest kernel number per row and single plant grain yields at the lo west population densities, however, as plant density increased these v ariables decreased more in the conventional hybrids than the LRS and N LRS hybrids, which demonstrates the greater tolerance of the latter to the stresses associated with higher plant densities. Grain yield was highest for all hybrids, except for NLRS, at 100 000 plants ha(-1) wit h the LRS hybrid and Pioneer 3902 having the highest yields (11.4 vs. 9.8; 12.0 vs. 10.4) at locations 1 and 2 respectively. The LRS hybrid matured before either of the conventional hybrids and out yielded Pion eer 3979 at both sites. Harvest index was not affected by population d ensity and this value was not different among the NLRS and conventiona l hybrids. However, the harvest index of the LRS hybrid was greater th an the others. LRS and NLRS hybrids had lower moisture contents and ea rlier maturities than conventional hybrids. Rapid growth of the first ear, a higher yield per unit leaf area, and a higher harvest index are indications that LRS hybrids should be more tolerant of higher popula tion densities than the conventional hybrids.