Ethephon [(2‐chloroethyl)phosphonic acid] effectively reduces lodging in barley (Hordeum vulgare L.), but also may have positive or negative influences on grain yield and yield components even if lodging does not occur. The objective of this study was to investigate the effects of ethephon on yield and yield components of barley under western Canadian conditions. In 1987, 1988, and 1989 at Winnipeg MB, ‘Argyle’ conventional height and ‘Samson’ semidwarf barley were grown at 100 and 300 plants m−2 and treated with ethephon at Zadoks growth stage 35 or 45. At harvest, grain yield samples were taken by hand or by combine, and yield components were determined. When lodging occurred, Belgian lodging indices were determined. The two cultivars responded similarly to ethephon application. Hand‐harvested grain yields were either unaffected or reduced by ethephon, but combine‐harvested yield tended to be increased by ethephon in 1989 when lodging was severe in untreated plots. Reductions in hand‐harvested grain yield of ethephon‐treated plots were primarily due to reductions in kernels per spike, which occurred in all 3 yr for barley grown at both plant densities. Ethephon increased spikes per plant for barley grown at both 100 and 300 plants m−2 in 1987, which at the low plant density compensated for reductions in kernels per spike and kernel mass. Barley in ethephon‐treated plots tended to be delayed in maturity compared with untreated plots. This was particularly true in 1987 and 1989, when late tiller emergence was promoted to the greatest extent by ethephon when moisture conditions were favorable. The potential for ethephon to cause yield reductions restricts the use of ethephon in western Canada to situations where the risk of severe lodging is high.
Emergence of wheat (Triticum aestivum L.) seedlings usually occurs over a period of several days, resulting in nonuniformity among neighboring plants. The impact of nonuniformity in time of emergence on grain yield has not been determined. We determined effect of planting depth on relative date of seedling emergence, and of relative date of emergence on grain‐bearing tillers and grain yield per plant. Large seed (39.8 ± 4.59 mg kernel−1) in 1989, and large (41.7 ± 3.83 mg kernel−1) and small seeds (24.3 ± 4.56 mg kernel−1) in 1990 were obtained from ‘Roblin’ wheat. Seeds were hand.planted at 25‐, 50‐, and 75‐mm depths on Neuborst clay loam (fine‐loamy, frigid, Aquic Haploborolls) at Portage la Prairie, MB. Plants were tagged the day they emerged, and individual plant yield was determined at harvest. Planting depths did not differ for total percent emergence in 1989, but in 1990, increasing planting depth led to decreased total emergence. Gompertz growth model predictions of inflection time, maximum emergence rate, and cumulative percent emergence indicated that seedling emergence rate decreased as planting depth increased, and the decrease was greater with small seed than with large seed. The first date on which seedlings emerged each year was designated as Day 1. Averaged across 2 yr, plants that emerged on Day 1 to 3 produced 1.4 times the yield of those emerged on Day 4 to 6, and 3.2 times the yield of those emerged on Day 7 to 9. Reduced yield of late emerged plants was due primarily to fewer grain‐bearing tillers. This research demonstrates the benefit of shallow placement of large seeds in minimizing variation in time of seedling emergence among plants, and increasing grain yield.
Corn (Zea mays L.) kernels are subject to breakage during postharvest handling. Manipulation of crop management factors has influenced kernel breakage susceptibility, but the effects of hybrid, plant density, harvest moisture content, and drying temperature on breakage susceptibility have not been studied under long growing season conditions. Field experiments were conducted in 1985 and 1986 at Ridgetown, Ontario. Five commercial hybrids were grown at different plant densities (5.5 and 7.0 plants m−2 in both years, and 6.3 plants m−2 in 1985), harvested at 300 and 240 g kg−1 moisture content (wet basis), and dried at different air temperatures (20, 40, and 80°C in 1985; 20 and 100°C in 1986) to approximately 150 g kg−1 moisture content. A Wisconsin breakage tester was used to measure breakage susceptibility. Small increases in breakage were consistently associated with increased plant densities. Reductions in breakage were sometimes associated with lower grain moisture content at harvest. The largest and most consistent changes in breakage susceptibility were due to changes in drying temperatures. Increased drying temperatures resulted in increased breakage, but there was variation among the hybrids in the size of the response. The results indicate that breakage susceptibility is an inherited trait that is also influenced by crop management. Kernel breakage can be reduced by proper choice of hybrids, drying at low air temperature, and harvesting at low grain moisture content. In both years, increased breakage susceptibility was related to higher levels of endosperm stress cracks, tendency towards roundness in shape, and increased levels of harvest damage in the form of visible chips or cracks.
Ethephon [(2‐chloroethyl)phosphonic acid] used for lodging protection in barley (Hordeum vulgare L.) often increases spikes m−2. The degree to which such additional spikes contribute to yield has not been reported, and neither has the source of such spikes been determined. This study was undertaken to determine the effects of ethephon on tiller emergence and survival, as well as the contribution to yield of additional spikes appearing on ethephon treated barley plants. Ethephon was applied at Zadoks growth stage (GS) 35 and/or 45 at 240 g ha−1 to ‘Argyle’ conventional height and ‘Samson’ semidwarf barley grown at 100 and 300 plants m−2 at Winnipeg, MB. Ten plants per plot were observed at intervals through the growing seasons; tillers were tagged as they emerged and their contributions to spikes per plant and grain yield were determined at harvest. The two cultivars responded similarly to ethephon application. In all 3 yr and at both plant densities, ethephon application increased shoots per plant. Application at GS 45 increased shoots per plant more than at GS 35 in 1987 when moisture was adequate, but less in 1988 when some moisture stress may have affected barley at GS 45. Late appearing shoots contributed up to 32 and 15% of spikes per plant and grain yield per plant, respectively, for both plant densities in 1987 and for the low plant density in 1989. Increased spikes per plant due to ethephon application were attributable to late tiller production and survival rather than to prevention of senescence of early formed tillers. The increase of spikes per plant by ethephon should be a positive influence on grain yield, but total yield per plant was often decreased and was never increased by ethephon because ethephon also caused reductions in kernels per spike.
The tendency of corn (Zea mays L.) kernels to break during postharvest handling causes problems for several user groups. Crop management factors have been reported to influence breakage susceptibility, but the effects of hybrid, plant density, harvest moisture content, and drying temperature on grain corn breakage susceptibility have not yet been investigated in a single study. To this end, a field experiment was established in May 1985, at the Arkell Research Station, Arkell, Ontario. Five commercial hybrids, Hyland HL2280, DeKalb XLll, Co-op 2645, First Line 1636, and Pioneer 3949, were grown at 5.6 and 7.1 plants m-2 , harvested at 310 and 240 g kg-• moisture content (wet basis) and dried at 30 and 80°C to approximately ISO g kg-• moisture content. A Wisconsin Breakage Tester was used to measure breakage susceptibility. In the breakage tests, the main effects were statistically significant, as well as the interactions of hybrid with plant density, harvest moisture, and drying temperature, and of harvest moisture with drying temperature. Of these, only the interaction of hybrid with drying temperature resulted in differences large enough to be commercially significant. Four hybrids were relatively resistant to breakage when dried at 30°C; when dried at 80°C, increases in breakage susceptibility were much larger for two hybrids than for the other three. Of the other parameters measured, the degree of multiple stress cracking and kernel length were most strongly related to breakage susceptibility, but levels of severe kernel damage and fine broken corn ( <4.76 mm), and kernel thickness were also related to breakage susceptibility. Test weight was not related to breakage susceptibility.Additional Index Words: Zea mays L., Hybrid, Plant density, Harvest moisture content, Drying temperature, Wisconsin Breakage Tester.
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