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  • Author or Editor: Nanik Setyowati x
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Plant growth and yield of broccoli (`Green Comet'), and cauliflower (`Majestic', `Snow Crown') cultivars were evaluated by no-tillage (NT) and conventional tillage (CT) in the fall 1987 with NH4NO3 applied dry or through the trickle line. Total plant dry weight, plant stand, average head weight and number of heads harvested were not affected by tillage system. `Snow Crown' plants had less of the following leaf area, dry weight, plant stand, number of heads harvested, and total head weight, than `Majestic', especially in NT where NH4NO3 applied dry. In the greenhouse, cauliflower cultivars had similar leaf area, leaf dry weight, and mot dry weight at 30, 45, and 60 days after growing in sand culture while broccoli cultivars had similar leaf area, leaf dry weight, and mot dry weight after 35, 50, and 65 days. Generally, nutrient uptake was similar at each sampling date for cultivars within crops. Cultivars had similar leaf water and osmotic potentials when grown for 2 weeks in modified growth chambers at either 23.9 or 29.4 C day, and 18.3 C night. These plants were then root-pruned and grown in sand culture for 3 weeks. Leaf area, mot dry weight, and plant dry weight was greeter for `Majestic' than for `Snow Crown' and `Olympus'.

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Dithiopyr (Dimension, Monsanto) is a turfgrass herbicide currently under evaluation for use in ornamentals. Granular herbicide depth and seed placement were evaluated in greenhouse studies with tolerant or susceptible weeds. Dithiopyr was applied preemergence to weeds at the rate of 2.24 kg/ha to Maury silt loam soil. Weed seeds were planted routinely at 0.64 cm depth. Dithiopyr placed at the soil surface or 0.64 cm in depth caused the greatest injury to seedlings, followed by dithiopyr at 1.28 cm depth. Dithiopyr at 2.54 and 3.81 cm below the surface had no effect upon seedling growth. When seeding depth was investigated, seed placed at 0.64, 1.28 or 1.91 cm below the surface showed greatest seedling injury when dithiopyr was routinely applied at 0.64 cm depth. Seed placement on the soil surface resulted in the least injury to weeds.

Peat moss was added to Maury silt loam soil and to sand to investigate the influence of organic matter upon activity. Soil with 2% peat resulted in the least injury to selected weed seedlings while sand, and sand plus up to 3% peat showed greatest injury. Sand amended with 5 and 6% peat also resulted in less injury to weed seedlings. Ivy leaf morningglory and KY 31 fescue were most tolerant of dithiopyr while barnyardgrass and large crabgrass were most sensitive. Dithiopyr uptake, translocation and metabolism studies will be conducted with susceptible and tolerant weed and woody ornamental species.

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Field studies have shown that dithiopyr has potential as a herbicide in ornamental nursery crops. Previous work has shown that certain weeds differed considerably in their tolerance to dithiopyr, both in the field and in the greenhouse. Four weeds were selected on the basis of these studies; large crabgrass and velvetleaf, both susceptible, and barnyardgrass and ivyleaf morningglory, tolerant species.

Root uptake was assessed in these four species by treating seedlings with 0.5 μCi of 14C-labelled dithiopyr dissolved in half strength Hoaglands solution. Whole plants were sampled at 12, 24, 48 and 96 hour after treatment (HAT) and plants were separated into roots and shoots. Dithiopyr levels and polar metabolites were measured after methanolic extraction of plant parts. Insoluble 14C levels were measured after biological oxidation. At 12 HAT, TLC and HPLC separation of extracts showed no detectable metabolites of dithiopyr. By 24 HAT, two polar metabolites were detected in both root and shoot extracts of all species. Total 14C and polar metabolites increased in roots and shoots over time. Species differences in total 14C uptake and metabolism were noted, potentially contributing to dithiopyr selectivity differences.

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