Effects of simulated hail damage manifested by stem cutoff on seed yield and agronomic traits in Brassica napus L.

摘要

A simulated hail-damage study was conducted in North Dakotaacross 2 years. The experiment was conducted in a randomizedcomplete block design with two factors, viz., five levels of stemcutoff and four growth stages; each combination was replicatedthreetimes. Data on seed yield plot-1 and other yield-contributingtraits were taken. A statistically significant seed yield reductioncompared with the control was observed at 75% and 90% levelof stem cutoff. Stem cutoff at 90% flowering stage caused higherseed yield reduction compared with 4th to 5th leaf rosette, bolting,and 50% flowering stages. A regression equation was developedto estimate the seed yield losses attributable to treatments at 90% flowering stage and different levels of stem cutoff. The estimatede-conomic losses were $52, $104, $156, and $188 hectare-1 for 25%, 50%, 75%, and 90% stem cutoff, respectively. The 1,000-seed weight was significantly increased as level of stem cutoffincreased and growth stage advanced. Seed oil content wasalsoincreased as growth stage advanced. Primary branches,pods plant-1, seeds pod-1, and harvest index plant-1 weresignificantly reduced by both growth stage and level of stem cutoff.The secondary branches and biomass piant-1 were significantlyreduced by growth stage and level of stem cutoff, respectively.Our findings of differential yield losses by stem cutoff with differentgrowth stages should assist (1) growers in taking a critical decisionon whether they will keep or replant the crop, and (2) crop adjustersin deciding on compensation.