Abstract
The objective of this study was to evaluate the effect of population density and row spacing on field yield and other morphological characteristics of two commercial F1 maize hybrids of different biological cycle (Costanza and LG3535) in a four-year period. Field experiments were conducted in a split-split plot design, in two population densities and three types of row spacing, involving single or twin rows. Ten plants from each plot were selected randomly and plant height, ear emergence height, ear length, ear diameter, number of grain rows per ear, grains number per ear, grain weight per ear, spindle weight per ear, and spindle diameter were measured. Grain yield of each plot was measured and field yield, thousand kernel weight and bulk density were calculated. Four years of experimentation clarified that environmental conditions may distort all other effects of the factors studied. This study points out the best combination of plant density and row configuration. High populations and twin or narrow rows (50 cm) were found to be important for maximizing yield of modern maize hybrids. Differences between hybrids were not significant, although Costanza exhibited greater mean field yield performance (14,364 kg/ha). Plant density was a significant factor and yield was increasing from low to high plant population (from 13,900 to 14,527 kg/ha). Plant density and genetic materials affected thousand kernel weights that showed the highest value at low plant density (364 g). Row spacing showed a significant interaction with year. Generally, twin or narrow rows favored many characteristics, especially height characteristics. Plant height reached 320 cm and ear height reached 149 cm. Ear diameter was favored by low plant density. Some ear characteristics were found to be depended on the genotype behavior in the certain environmental conditions. For spindle weight per ear, a total interaction between years, row spacing, hybrids, and plant density was found. For spindle diameter, various significant interactions were found, including years (maximum also in 2009), row spacing, and plant density and also row spacing, hybrids, and plant density. Many correlations were found significant especially between yield and thousand kernel weight, spindle weight per ear, and ear diameter that may prove to be useful for plant breeders.
Highlights
The introduction in cultivation of single maize (Zea mays L.) hybrids and improved techniques of cultivation led to a spectacular increase in yields over the last 40 years
Row spacing had an extremely significant interaction with year, and the same was clear for hybrid behavior across years and in relation to row spacing, indicating different behavior of genotypes in different environmental conditions
A significant interaction was found between row spacing and plant density, indicating that row spacing may favor yielding performance within a reasonable plant density limit [6]
Summary
The introduction in cultivation of single maize (Zea mays L.) hybrids and improved techniques of cultivation led to a spectacular increase in yields over the last 40 years. Duvick [1] stated that increased field grain yield of modern hybrids is a result of improved tolerance in abiotic and biotic stresses, Agriculture 2019, 9, 160; doi:10.3390/agriculture9070160 www.mdpi.com/journal/agriculture. It is clear that modern hybrids have embedded stress tolerance especially in plant density stress [4], as well as other biotic and abiotic factors [5]. Larson and Hanway [7] reported different plant densities in order to achieve maximum yields in maize, including field yield. They reported that increasing plant density up to 70,000 or even 100,000 plants per hectare may result in optimum performance. Factors significantly affecting maize field yield are population density of plants, as well as row spacing [8]. It is assumed that plants spaced will give the minimum competition and maximum performance for each provisionally assigned plant density [8,9]
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