In field tests conducted near Tifton, Georgia, soil fumigation with either a methyl bromide-chloropicrin mixture (67-33%, 480 kg/ha) or metham (748 liters/ha) decreased weed infestation and increased growth and marketable yields of pepper (Capsicum annuum L.) transplants, compared with pepper planted consecutively without fumigation. Alternate-year rotation of pepper with rye also reduced weed infestation and increased yield. Weed control accounted for 81% of marketable transplant yield. Xanthomonas vesicatoria (Doidge) Dows. overwintered in pepper debris incorporated fresh or dried. Bacterial spot occurred too erratically to permit any conclusions except that the methyl bromide-chloropicrin fumigation failed to provide any control.
immobilize a considerable amount of the N applied from fertilizers ( White, 2006 ). Some growers are using compost in addition to sawdust to provide additional nutrients and organic matter ( Gale et al., 2006 ; Larco et al., 2014 ). Municipal yard debris
The number of pollen grains in anthers of Phaseolus vulgaris L. was estimated using a Coulter Counter, an electrical particle-counting device. Nine green buds were collected randomly from 3 plants grown in a growth chamber. From each bud, one anther at a time was excised and placed in liquid Ν for 3 sec. Pollen grains were transferred from the anthers into a drop of 0.3 M NaCl on a glass slide. The saline-pollen grain mixture was cleaned of all debris, and pollen was washed into a beaker containing the same solution. This procedure was repeated for the remaining 9 anthers of each bud. The total number of pollen grains per bud was determined using a Coulter Counter.
Field conditions associated with commercial cranberry (Vaccinium macrocarpon Ait.) production were simulated in greenhouse studies to determine the effect of soil surface characteristics on dichlobenil activity. Sand was compared with organic matter, in the form of leaf litter, as the surface layer. A seedling bioassay using alfalfa (Medicago sativa L.), a dichlobenil-sensitive plant, was employed to determine root growth response on herbicide-treated soil. When the herbicide was applied to a sand surface, root growth was greater as time after application elapsed, indicating loss of herbicide activity. Conversely, the presence of organic matter on the surface prolonged the activity of the herbicide. Composition of the surface layer was more important than the depth of the layer in determining herbicide persistence. The influence of cultural practices, such as the application of sand or the removal of surface debris, on herbicide activity should be considered when planning weed management strategies for cranberry production. Chemical name used: 2,6-dichlorobenzonitrile (dichlobenil).
Industrial-scale cultivation of plant cells for valuable product recovery (e.g. natural pigments, pharmaceutical compounds) can only be considered commercially-feasible when a fully-automated, predictable bioprocess is achieved. Automation of cell selection, quantification, and sorting procedures, and pinpointing of optimal microenvironmental regimes can be approached via machine vision. Macroscopic staging of Ajuga reptans callus masses (ranging between 2-6 g FW) permitted simultaneous rapid capture of top and side views. Area data used in a linear regression model yielded a reliable, non-destructive estimate of fresh mass. Suspension culture images from the same cell line were microscopically imaged at 4x (with an inverted microscope). Using color machine vision, the HSI (hue-saturation-intensity) coordinates were used to successfully separate pigmented cells and aggregates from non-pigmented cells, aggregates, and background debris. Time-course sampling of a routine suspension culture consistently allowed pigmented cells to be detected, and intensity could be correlated with the degree of pigmentation as verified using spectrophotometer analysis of parallel samples.
A scale-up process of lettuce (Lactuca sativa L.) suspension culture in a 2-liter bioreactor was investigated. Factors that influenced cell growth and differentiation, including foaming, the wall effect (inoculum adhering onto the vessel wall above the medium level), aeration, and dissolved oxygen (DO), were tested. The wall effect resulted in severe inoculum loss (10%) in 24 hours. Inoculum loss significantly decreased shoot regeneration. The wall effect was caused by two factors: 1) foaming caused by the interaction between air bubbles and inoculum, and 2) the bubbles produced by aeration. Foaming could be prevented by sieving the inoculum through a 400-pm screen filter and then rinsing the inoculum thoroughly with distilled water to remove single cells, cell debris, and the contents of broken cells. The wall effect caused by air bubbles could be prevented by putting a 150-μm screen column in the center of the bioreactor to isolate the aeration area from the inoculum. After the wall effect was removed, shoot regeneration in the bioreactor increased significantly to a level similar to that in 125-ml flasks at an aeration rate of 1 to 2 vvm (liters air/liters medium per rein). DO for this shoot regeneration level was ≈ 70% to 80%of saturation at the end of bioreactor culture.
The effect of high-pressure washing (HPW) on the surface morphology and physiology of citrus fruit was examined. Mature white (Citrus paradisi Macf. `Marsh') and red (Citrus paradisi Macf. `Ruby Red') grapefruit, oranges (Citrus sinensis L. `Hamlin'), and tangelos (Citrus reticulata Blanco × Citrus paradisi Macf. `Orlando') were washed on a roller brush bed and under a water spraying system for which water pressure was varied. Washing white grapefruit and oranges for 10 seconds under conventional low water pressure (345 kPa at cone nozzle) had little effect on peel wax fine structure. Washing fruit for 10 seconds under high water pressure (1380 or 2760 kPa at veejet nozzle) removed most epicuticular wax platelets from the surface as well as other surface debris such as sand grains. Despite the removal of epicuticular wax, HPW did not affect whole fruit mass loss or exchange of water, O2, or CO2 at the midsection of the fruit. Analysis of the effect of nozzle pressure (345, 1380, or 2760 kPa), period of exposure (10 or 60 seconds), and wax application on internal gas concentrations 18 hours after washing showed that increasing nozzle pressure increased internal CO2 concentrations while waxing increased internal ethylene and CO2 concentrations and decreased O2 concentrations. An apparent wound ethylene response was often elicited from fruit washed under high pressures (≥2070 kPa) or for long exposure times (≥30 seconds).
This study evaluated the total and marketable yield of three peach cultivars [Prunus persica (L.) Batsch. `Autumnglo', `Harvester', and `Redhaven'] when mechanical pruning and harvesting systems were used and trees were grown under three irrigation regimes. All cultivars were trunk-shaken using an experimental inertial shaker on an over-the-row (OTR) shake–catch harvester. `Autumnglo' also was hand-harvested at all irrigation regimes. Fruit damage was not significantly affected by irrigation. A significant source of fruit damage was pruning debris that remained in the canopy after hedging and became lodged in the fruit-conveying system, resulting in cultivar effects on fruit damage. Total yield of firm-ripe fruit was similar among cultivars in 1987 and 1988. However, `Autumnglo' trees had a higher percentage of marketable fruit than `Redhaven' or `Harvester' in 1987 and 1991. Mechanical harvesting appeared to accelerate the decline of `Autumnglo' as shown by tree deaths and greater symptom expression of Prunus necrotic ringspot virus. The potential for a single mechanical harvest of peaches is limited because of the difficulty in managing the ripening window, the high potential for fruit damage, and the possibility of accelerated tree decline for disease-susceptible cultivars.
The Atlantic hurricane season stretches from June to November, and the vegetable growing season in South Florida begins in August. This means that pre-plant, planting, and early harvesting operations are performed during hurricane season. Three major hurricanes striking our area during two consecutive growing seasons have helped to teach us how to give vegetable crops the best chance of survival. On a 4-ha farm growing diversified vegetable crops, there have been clear differences in crop survival. Tiny seedlings of most crops were generally killed by driving rains and strong winds. However, 7- to 10-cm-tall transplants in plastic cell trays survived surprisingly well when placed on the ground in an area that did not flood and was protected from flying debris. During the hurricane with the highest winds, large plants, such as tomatoes and squash, were defoliated. Even plants that survived defoliation and regrew were injured, so they were vulnerable to diseases later in the season. It actually appears to be best not to stake crops in extremely high winds. Staked and tied tomatoes often broke off at the top string. In winds of over 90 knots, unstaked eggplants fared best of any mature crops. They fell over immediately and, lying on the ground, were protected from the high winds. After the storm passed, they were pulled upright, staked and tied, and produced excellent yields. Sweet corn also fell over, but, over a period of a week, gradually returned to about a 45° angle where it produced about 30% of the normal yield. Of course, each hurricane has different characteristics; what works in one may not be the best during others. We are, however, hoping not to have a chance to learn more about how crops survive hurricanes.
An understanding of nitrogen (N) uptake and the partitioning of N during the season by the carrot crop (Daucus carota subsp. sativus [Hoffm.] Arkang.) is required to develop more efficient N fertilization practices. Experiments were conducted on both organic and mineral soils to track the accumulation of dry matter (DM) and N over the growing season and to develop an N budget of the crop. Treatments included two carrot cultivars (`Idaho' and `Fontana') and 5 N rates ranging from 0% to 200% of the provincial recommendations in Ontario. Foliage and root samples were collected biweekly from selected treatments during the growing season and assessed for total N concentration. Harvest samples were used to calculate N uptake, N in debris, and net N removal values. Accumulation of DM and N in the roots was low until 50 to 60 days after seeding (DAS) and then increased linearly until harvest for all 3 years regardless of the soil type, cultivar, and N rate. Foliage dry weight and N accumulation were more significant by 50 to 60 DAS, increased linearly between 50 and 100 DAS, and reached a maximum or declined slightly beyond 100 DAS in most cases. The N application rates required to maximize yield on mineral soil resulted in a net loss of N from the system, except when sufficient N was available from the soil to produce optimal yield. On organic soil, a net removal of N occurred at all N application rates in all years. Carrots could be used as an N catch crop to reduce N losses in a vegetable rotation in conditions of high soil residual N, thereby improving the N use efficiency (NUE) of the crop rotation.