Dwarf sunflower response to row spacing, stand reduction, and defoliation at different growth stages

Abstract

Johnson, B. L. 2003. Dwarf sunflower response to row spacing, stand reduction, and defoliation at different growth stages.Can. J. Plant Sci. 83: 319-326. Growth compensation of dwarf sunflower (Helianthus annuus L.) hybrids to low initial stands, later stand losses, or plant defoliation has not been reported regarding replanting decisions and crop insurance yield loss assessment. Three experiments were conducted to study the affect of stand reduction, defoliation, and row spacing on dwarf sunflower yield and quality when grown in eastern North Dakota. Experiment 1 evaluated stand reduction (0, 25, 50 and 75%) applied at growth stages (V4, R1 and R6) in 15, 45 and 76 cm spaced rows. Row spacing interactions with stand reduction and growth stage were not significant for yield indicating growth stage and stand reduction effects on yield response were independent of row spacing. In exp. 2, significant growth stage (V4, V8, R1, R2, R3, R5 and R6) by stand reduction (0, 12, 25, 37, 50, 62 and 75%) interaction showed stand reduction at vegetative growth stages not influencing yield, but as maturity progressed yield reductions became greater with increased stand reduction. Achene weight increased with increasing stand reduction at vegetative and early reproductive stages. A reciprocal relationship was noted between achene weight and achene oil content where oil content decreased as achene weight increased. Interaction of growth stage (R1 and R6) and defoliation (0, 25, 50, 75 and 100%) in exp. 3 indicated greater reduction in yield, test weight, 1000-achene weight, and achene oil content as defoliatin increased at growth stage R6. Yield compensating ability of dwarf sunflower is dependent on type and level of damage and growth stage of occurrence, with total yield reduction considering all effects.Key words: Sunflower, Helianthus annuus L., row spacing, stand reduction, defoliation Johnson, B. L. 2003. Réaction du tournesol nain à l'écartement des rangs, à la réduction du peuplement et à la défoliation à différents stades de croissance. Can. J. Plant Sci. 83: 319-326.Quand on décide de replanter ou quand on évalue les pertes de rendement pour l'assurance-récolte, on tient rarement compte de la manière dont les hybrides du tournesol nain (Helianthus annuus L.) peuvent compenser un faible peuplement initial, la réduction ultérieure du peuplement ou la défoliation par leur croissance. L'auteur a entrepris trois expériences en vue de déterminer les conséquences d'une diminution du peuplement, de la défoliation et de l'écartement des rangs sur le rendement et la qualité du tournesol nain cultivé dans le Dakota Nord. La première expérience a servi à évaluer les effets d'une réduction du peuplement (de 0, 25, 50 et 75 %) à divers stades de croissance (V4, R1 et R6) dans une culture aux rangs espacés de 15, de 45 ou de 76 cm. L'écartement des rangs n'a pas d'interaction sensible avec la réduction du peuplement ni le stade de croissance, signe que ces deux paramètres agissent indépendamment du premier. Dans la deuxième expérien...

Effect of Agronomic Amendments on Growth and Yield of Sunflower

“…Probably, aeration due to proper line sowing, easy interception of light and adequate reception of soil moisture and nutrients was the major advantage to the plants sown through drilling method over other seedling techniques. These results are in agreement with those of Johnson et al (2010) who concluded that drilling sown sunflowers resulted in greater head size and under this sowing technique the plants get optimally greater share of nutrients from the soil and utilize natural resources from the environment. The increasing planting density caused increased plant population, more competition among plants to grow vigorously, while under 30 cm plant spacing due to lowest plant population, the plants experienced better utilization of applied inputs and natural resources.…”

“…Shariti and Amin (2003) found that with increasing planting density, the allocated share of the average plant for nutrients, other inputs and natural resources. Johnson et al (2010) and Pereira, & Hall (2019) reported that the thicker stems in sunflower ensure the plants to establish bigger seed head to produce more seed rows. Similarly, FeSO4 application resulted in encouraging results in regards to stem thickness, because there is interrelationship of stem thickness with the yield contributing traits.…”

Simulated beetle defoliation on willow genotypes in mixture and monotype plantations

“…A number of studies have been undertaken using mechanical defoliation as a substitute for insect or animal herbivory, disease, environmental extremes or other mechanical damage on plants as diverse as sunflowers (Johnson, 2003) and butternut squash (Rangarajan et al , 2003). The technique has been widely applied to experiments with trees, such as aspen (Hogg et al , 2002), oak (Li & Ma, 2003) and mountain birch (Anttonen et al , 2002) as well as in species with needles such as Scots pine (Honkanen & Haukioja, 1994) and white spruce (Piene, 2003).…”

Effects of nitrogen and plant density on dwarf sunflower hybrids

“…The performances of tall, semi-dwarf and dwarf sunflower hybrids are different at various plant populations. The reduced-height sunflower hybrids responded better to high plant populations than the standard and tall hybrids did (Stanojević, 1989;Vannozi and Baldini, 1990;Feoli, 1993;Fick et al, 1985;Johnson, 2002).…”