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  • Author or Editor: J.M. White x
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Abstract

Rolling organic soil after plowing and drag disking resulted in significantly lower marketable yields, more forks (branching) and less stubbed (premature blunting resulting in an unmarketable root) carrots (Daucus carota L.) than not rolling. Using a rotary tiller before bedding had no significant effect on yield or other characteristics measured. Bed making with a tilrovator or bed shaper did not significantly affect yield, root length, number of forked, crooked or split carrot roots. Compaction, as measured with a penetrometer, did not have a linear relationship between the eight tillage treatments used in preparing beds and any of the root characteristics measured such as yield, length or number of misshapen roots.

Open Access

Abstract

Effects of soil compaction on early root growth of carrot (Daucus carota L.) growing in organic soil contained in specially constructed pots were studied under controlled environmental conditions. Screened and steamed mucky peat soil was artificially compacted with an applied pressure of 0.45 — 2.23 bars to produce soil densities of 0.7 — 1.1 g/cm3. Soil strength, measured as penetrometer resistance was directly related to applied compacting pressure and highly dependent upon soil moisture. Highest soil strengths were produced when the soil contained 52-58% moisture. Taproot lengths 16 days after seeding were significantly shorter at each increase in soil strength produced by applied compacting pressures of 0.45, 1.12, 1.51, and 2.23 bars. Rates of early taproot growth measured at 2-day intervals for 18 days were similarly decreased with increasing soil strength. Young taproots grew normally through compaction zones produced by 0.45 bars but were severely impeded when compaction zones produced by 1.12, 1.51, and 2.23 bars were encountered. Roots impeded by high soil strength were frequently thickened and convoluted with increased branching but no significant differences between treatments could be detected. Effects of soil compaction on mature roots were evidenced by abnormally short, blunt, and abruptly tapered roots. Mature root weight, diameter, and length decreased with increasing soil compaction.

Open Access

Abstract

Effects of water saturation of the soil on early root growth of carrot (Daucus carota L.) were studied using specially designed pots containing organic soil. Water saturated soil conditions were created by raising the water table to envelop actively growing carrot root tips on the 6th day after planting pre-germinated seed. Water saturation was maintained for intervals of 12 hours to 7 days. Sixteen days after seeding (DAS), taproots subjected to as little as a 12 hour period of water saturated soil at 6 DAS were significantly shorter and exhibited more discolored root tips and forked roots than roots growing under normal moisture conditions. After 78 days of growth, the roots subjected to water saturated soil at 6 DAS were significantly shorter, weighed less, and were smaller in diameter than controls. The height of the carrot tops was not affected by treatments.

Open Access

Abstract

Tolerance of carrot seeds (Daucus carota L.) to heat treatments that could eradicate seedborne pathogens was investigated. Germination and emergence of seedlings from seeds treated in hot water at 35, 40, 45, 50, or 55C from 4 to 20 min were not affected, but seeds treated at 60C for 8 min or more were affected adversely. At 45 and 50C, treatment durations as long as 48 min did not affect emergence, but >20 min at 55C reduced emergence. Similar results were obtained when seeds were treated at the same temperatures in water containing 1.1% sodium hypochlorite (NaOCI). Emergence of seeds treated in hot water or 1.1% NaOCl and planted within 5 days generally was similar to that of treated seeds stored for 90 days at 20C in 60% RH before planting. Any existing differences were small and not clearly related to temperature–duration treatment combinations. Percent emergence from seeds of 19 out of 25 hybrid cultivars treated at 50C for 15 min was reduced by an average of 2.9%, but differences for untreated seeds ranged from −13.3% to +4.8%. Emergence from hot water-treated seeds was reduced after 6 weeks of storage at 70% and 80% RH, but not at 20% to 60% RH. Prolonged treatment and the higher temperatures were particularly effective in reducing populations of seedborne Alternaria dauci.

Open Access

Abstract

Early root growth of carrots (Daucus carota L.) was studied in specially constructed pots containing organic soil under controlled environments at 16°, 20°, 24°, and 28°C. Carrot tops produced greater amounts of bio-mass on a fresh or dry weight basis than did roots, whereas taproots demonstrated faster rates of linear growth than did the tops throughout the 24-day sampling period at all temperatures. The optimum range of temperatures for carrot root growth was 20-24°C. Taproots reached the potential length for market-acceptable storage roots (15.2 cm) between 12 and 16 days after planting at 20°, 24°, and 28°C and after 20 days at 16°C. Average taproot lengths after 24 days at 16°, 20°, 24°, and 28°C were 23.6, 38.5, 35.6, and 16.7 cm, respectively. Secondary roots had developed by the 8th day and tertiary roots by the 20th day. Tertiary roots were confined to the upper 5 cm of the root system at this early date.

Open Access
Authors: and

Abstract

Nine bedding plant vegetable and flower cultivars were grown in each of 10 night air and root media temperature regimes. Generally, fresh and dry weights were greater at 16°C than at 7° night air temperature when root-zone (RZ) heating was not used. Soil warming increased fresh and dry weights of all cultivars grown at 16° night air temperatures. When air temperatures were below 16°, soil warming maintained fresh and dry weights equivalent to or better than plants grown at 16° without soil warming. Two split-night (SN) air temperature regimes were as effective as a constant 16° night temperature, ranking first and 3rd in fresh and dry weight per unit of energy consumption. All soil warming treatments had higher energy productivity than the 16° air temperature treatment with no RZ heating.

Open Access
Authors: and

Abstract

Geranium (Pelargonium × hortorum Bailey ‘Red Elite’) seedlings were grown with five daily mean temperature (DMT) and daily light integral (DLI) treatment combinations: DMT of 23°C/day at DLI of 8.64 mol·day−1·m−2 (TI), DMT of 25° at 8.64 mol (T2), DMT of 23° at DLI of 17.28 mol, (T3) DMT of 25° at DLI 17.28 mol (T4), and DMT of 21° at 17.28 mol (C1). Using infrared thermometry to control leaf temperature, DMT had a greater influence on flower initiation at the transition stage and on flower bud development to macrobud stage than DLI. Seedlings in T4 reached transition stage 24 days after sowing with a cumulative irradiance of 415 mol. Transition occurred in T1 at 27 days from sowing, with a cumulative irradiance of only 233 mol. Some time after 27 days from sowing, transition occurred in T2, T3, and C1. With a DLI of 17.28 mol, a DMT reduction from 25° to 23° to 21° effected macrobuds in 42, 56, or 62 days after sowing, respectively; whereas with a DLI of 8.64 mol, a decrease from 25° to 23° effected macrobuds in 54 or 51 days.

Open Access
Authors: and

Abstract

Raw and coated seed of carrot (Daucus carota L. cv Danvers 126) were planted with Stanhay, Earthway and Planet Jr. seeders on October 1, 1976 at Sanford and Zellwood, Florida, and on October 8 and November 16 at Gainesville, Florida. Carrot roots were harvested and graded in February, April, and May, 1977. Differences in weight of marketable carrot roots occurred between planters at 3 of the 4 locations, whereas response to seed coating was independent of locations. The effect of planters on numbers of marketable carrots varied significantly at 2 of the locations, with no effect of seed coating related to location. No difference was found in response to raw or coated seed in number or weight of marketable carrots, whereas carrots from coated seed were slightly larger than from uncoated seed.

Open Access

Abstract

Seed treatments and soil covers were used to assess stand establishment and uniformity of direct-seeded cabbage (Brassica oleracea L. var capitata) under high and low soil temperatures. Generally, primed seeds did not result in increased or more uniform seedling emergence compared to untreated seeds. Germinated seeds sown with a magnesium silicate gel (Laponite) or a starch-acrylamide-acrylate polymer gel (Liquagel) resulted in incomplete stands under heat stress, and stands for all plantings were generally lower when cabbage seeds were sown in a gel than when sown without a gel. Peat-vermiculite (Plug-mix) and calcined clay (GrowSorb) seed covers improved stands regardless of seed treatment when average soil temperatures were ≥30°C. Under normal (25°) to cooler soil conditions stands were not improved by seed treatment or seed cover.

Open Access

Abstract

Experiments were conducted to evaluate the response of carrots (Daucus carota L.) to target plant densities of 39, 59, and 79 plants per meter of band with various row arrangements (2 band/bed with 2, 3, or 4 seeded rows/band with 3.8 to 11.4 cm between rows) on a Landerhill muck soil. Marketable and total carrot yields increased linearly with increased plant density from 24 to 85 plants per square meter. In 2 of 3 experiments, row arrangement significantly influenced yield; greatest yields were obtained when spacing between rows in a band was greater than 3.8 cm, indicating some advantage to increasing the distance between rows. Mean length and diameter of marketable roots decreased linearly with increased plant density. Length and diameter of marketable carrots were influenced by row arrangement in one of the 3 experiments. Carrots grown in rows spaced more than 3.8 cm apart were longer and had a greater diameter than did carrots grown with 3.8 cm between rows.

Open Access