Although sweet corn must be harvested during optimal maturity to obtain best eating quality, a finite capacity of vegetable processing facilities and steady demand for fresh produce necessitate an elongated harvest period. Producers extend harvest by staggering planting dates and planting hybrids with different maturity dates. In the north central United States, sweet corn is planted from 1 or 2 weeks before the frost-free date until the first week of July (Anonymous, 2003). A range of planting dates results in crop exposure to different stress factors with later plantings generally being subjected to more diseases and insects. In addition, cold soils at early plantings and cooler late-season growing conditions at later plantings broaden abiotic stresses to the crop.
Knowledge of sweet corn response to environmental conditions has led to improvements in crop production. Work by Arnold and others (Arnold, 1960, 1974; Hortik and Arnold, 1965) identified relationships between air temperature and sweet corn development. Lass et al. (1993) reported several regression models that improved prediction of harvest date from environmental conditions after planting. More recently, several authors have demonstrated that negative impacts of adverse environmental conditions can be dampened by transplanting (Welbaum et al., 2001), adjusting plant population density (Rangarajan et al., 2002) or seeding depth (Barr et al., 2000), and mulching (Kwabiah, 2004). Management of pests is affected by the environmental conditions associated with different planting dates (Malvar et al., 2002; Williams, 2006). Advances in crop management coupled with improved stress tolerance and efficiency in plant growth accounts for the nearly sixfold increase in hybrid maize yield over the last 75 years (Duvick, 2005).
Although sweet corn is planted across a range of dates, most research on planting date effects on maize growth and yield response have been conducted in dent corn. In comparison of dent corn hybrids differing in relative maturity, phenological development of late-maturing hybrids was affected most by delayed planting (Nielsen et al., 2002) and photoperiod (Hunter et al., 1974). Maximum yield was achieved by planting dent corn ≈10 May near Lincoln, NE, whereas planting earlier or later reduced leaf area index, leaf area duration, total biomass, and grain yield (Swanson and Willhelm, 1996). Dent corn germplasm and agronomic practices differ starkly from sweet corn production. This includes a much narrower planting window, a longer time to maturity, and later physiological growth stage at the time of harvest for dent corn compared with sweet corn.
The few published reports on sweet corn suggest crop growth may not be uniform across planting dates. Planting dates separated by 3 weeks in Wisconsin had no effect on plant height, but did influence days to silking and yield components of crosses of several open-pollinated sweet corn cultivars (Revilla and Tracy, 1997). From research in Newfoundland, where conditions permit only short-season (62- to 67-d) hybrids to be grown, days from planting to emergence decreased some 50% through May because of cold soils early in the month (Kwabiah, 2004). In addition, sweet corn yield increased as planting was delayed through May, presumably as stand establishment improved. An 82-d hybrid in Illinois grew on average 22 cm taller with 18% more total shoot biomass and 43% less leaf area index (LAI) when planted in late June compared with early May (Williams and Lindquist, 2007). Few, if any, studies have characterized sweet corn growth and yield in response to the changing environmental conditions resulting from a complete range of planting dates used by growers. If indeed sweet corn growth responses vary systematically with planting date, thorough knowledge of the phenomenon may yield new opportunities for advancing crop management.
The goal of this work was to identify the significance of the planting date effects on sweet corn. A popular sweet corn hybrid grown over a complete range of planting dates of the north central United States was used to quantify the effect of planting date on sweet corn establishment, growth, and yield components.
Anonymous. 2003. Sweet corn pest management strategic plan, north central states. 1 Oct. 2003. <http://pestdata.ncsu.edu/pmsp/pdf/NCSweetcorn.pdf>.
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