No abstract

For dryland maize (Zea mays L.) production, it is believed that optimal hybrid choice pertains to time required to reach maturity. In our study, the main hypothesis was that density independence (ability of the hybrid to yield highly under both low and high density) is another key factor that deserves special consideration. To address the issue, fi eld experimentation was conducted under rainfed conditions at Martonvásár, Hungary for 11 yr. Treatments consisted of four N fertilizer rates (0, 100, 200, and 300 kg ha -1 ), four plant population densities (3, 5, 7, and 9 plants m -2 ), and four hybrids (Mara, Norma, Gazda, and Maraton). Variation in precipitation contributed to considerable variability in grain yield, which ranged from 1.46 to 7.67 T ha -1 . A positive relationship between optimum density and mean experimental yield indicated suitability of low and high plant populations for unfavorable and favorable seasons, respectively. Among hybrids, the mid-season Norma and full-season Maraton and Gazda hybrids were superior over the short-season Mara. However, Maraton hybrid exhibited a wide range of optimum densities, and performed as a density-independent hybrid. Th is characteristic enables hybrid planting at low density to meet requirements of the dry season and good utilization of occasional high rainfalls with less yield potential loss. Th is research indicated that breeding density-independent hybrids help in maize production under dryland conditions.

The responses of Hungarian-bred maize hybrids with different vegetation periods to sowing date, N fertiliser and plant density were studied in small-plot field experiments between 2002 and 2004. The maize grain yield was highest in the early and optimum sowing date treatments (8.563 and 8.325 t ha-1) and significantly less in the late and very late treatments (7.908 and 7.279 t ha-1). The year had a substantial effect on both the yield and the grain moisture content. In a long-term maize monoculture experiment set up in 1961, the N fertiliser responses of 6 maize hybrids with different vegetation periods were investigated. Averaged over the years 2002 and 2004 the maize grain yields in the N treatments were as follows (t ha-1): N0: 4.780, N80: 7.479, N160: 8.577, N240: 8.226. The grain yield and yield stability of maize were greatest at a N rate of 160 kg ha-1. The yield response was similar in both years, but the year had a considerable effect on the yield level. The N supplies to maize plants during the vegetation period could be well characterised using a SPAD 502 chlorophyll meter in the R3 phenological stage (18-22 days after silking). The plant density responses of maize hybrids were described by fitting a quadratic function to the data of 19-22 hybrids in the years 2002-2004. The optimum plant density averaged over the hybrids was between 67,483 and 70,161 plants ha-1. The maximum yield associated with optimum plant density was 7.978 t ha-1 in 2002, 6.60 t ha-1 in 2003 and 9.37 t ha-1 in 2004. The annual patterns of plant density responses for the maize hybrids exhibited considerable differences.