Response to Plant Densities and Nitrogen Levels for Four Maize Cultivars from Different Eras of Breeding¹

Abstract

We evaluated the performance of maize (Zea mays L.) cultivars representing 10‐yr eras in 12 treatment combinations of plant densities and N levels. There were four open‐pollinated (OP) varieties and six 10‐yr (1930 to 1980) eras, four cultivars per era, of singlecross hybrids. A primary purpose was to compare the hybrids and eras for interaction with plant densities and N levels. The cultivars were grown for 2 yr near Ames, IA at densities of 34 445, 51 661, and 68 889 plants ha−1 and N levels of 0, 80, 160, and 240 kg N ha−1. Grain yields among densities averaged over N levels and cultivars were not different; yields among N levels averaged over densities and cultivars were highly significantly different (P < 0.01). The yield increase from 0 to 80 kg N ha−1 was 78.1%; from 80 to 160 kg N ha−1, 15.8%, but there was no further increase at 240 kg N ha−1. Cultivars ✕ densities and cultivars ✕ N‐levels interactions were highly significant. Cultivars from OP to 1960 eras had either nonsignificant (positive or negative), or significantly negative linear responses to plant densities. Conversely, all cultivars in the 1970 and 1980 eras had positive linear responses; for five of the eight, the responses were significant. All cultivars had highly significant, positive linear responses to N levels. There was no directional trend over successive eras of hybrids for relative values of linear responses to N levels. The second‐order interaction of densities ✕ N levels ✕ cultivars was significant for yield. Eighteen of 28 cultivars had significant linear ✕ linear components; consequently, densities and N levels were not independent factors, and a cultivar seemed to have a specific density ✕ N‐level combination for maximum grain yield. Ear length was the yield component that had highest correlations with yield, among treatments combinations.

Yield, Quality Components, and Nitrogen Levels of Silage Corn Fertilized with Urea and Zeolite

“…Nitrogen improves biomass production because it promotes a higher photosynthetic rate by an increase in crop radiation interception and in conversion efficiency into biomass (Novoa and Loamis, 1981). Results are consistent with those observed by Carlone and Russell (1987), O'Leary and Rehm (1990), Muchow and Sinclair (1994) and Cox et al (1993). These results confirms those repots from Ming and Mumpton (1989), McGilloway et al (2003), Gruener et al (2003) and Rehakova et al (2004) and also indicate that zeolite minerals are able to contribute to increasing N uptake through the control of retention of ammonium ion−formed by urea hydrolysis in the soil, due to zeolite high cation exchange capacity and ammonium withdrawal from soil solution (Bartz and Jones, 1983;Ferguson and Pepper, 1987).…”

Nitrogen fertilization impact on agronomic traits of maize hybrids released at different decades

“…In absolute values, modern hybrid Ag 9012 presented an yield edge over the older materials that ranged from 1,350 to 1,500 kg ha -1 , depending on the amount of N applied to the soil. The impact of N on grain yield depicted in Figure 1 showed that hybrids cultivated in Southern Brazil during the last 40 years presented the same kind of behavior described by Castleberry et al (1984), Carlone & Russel (1987), Russel (1991) and Duvick (1994) for hybrids cultivated in the West US Corn Belt. Modern-day hybrid Ag 9012 had greater grain yield than did hybrids of earlier eras at all N rates evaluated in the trial.…”

“…This yield enhancement can be largely attributed to the release of genetic superior hybrids, higher plant densities, increased use of chemical fertilizers, reduction of row spacing, improved cultural practices, better weed and pest control (Carlone & Russel, 1987;Dwyer et al, 1991;.…”

“…Moreover, it may contribute to the release of hybrids which have greater yield potential but also require a stronger N input to express their agronomic superiority. The use of high N levels during hybrid development may also lead to the selection of genotypes that have luxury consumption of N (Carlone & Russel, 1987).…”

Efeitos de épocas de aplicação de nitrogênio no rendimento de grãos do milho

“…A adubação do milho com N é importante, porque ele é um dos principais nutrientes que favorecem a elevação dos rendimentos de grãos desta cultura (Cardwell, 1982), apesar de seus efeitos dependerem de fatores genotípicos (Carlone & Russell, 1987) e ambientais (Bondavalli et al, 1970). Novais et al (1974), Fox et al (1986) e Melgar et al (1991) demonstraram que o parcelamento da adubação nitrogenada proporciona rendimentos de grãos de milho superiores aos obtidos com a aplicação do N de uma só vez, especialmente quando esta aplicação total é feita em determinadas épocas.…”