Browsing by Author "Upadhyaya, M.K."

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Influence of preharvest water stress on postharvest moisture loss of carrots (Daucus carota L.)
(Taylor & Francis, 2015-11-07) Shibairo, Solomon I.; Upadhyaya, M.K.; Toivonen, Peter M A
To understand the relationship between preharvest water stress and postharvest moisture loss, carrot cvs Eagle and Paramount were grown in muck soil in 6 1 pots (eight carrots per pot) in a greenhouse at the University of British Columbia. The plants were watered to field capacity every second day for 5.5 months prior to receiving 100,75,50 and 25% field capacity water stress treatments (for 4.5 weeks), henceforth referred to as low, medium, high and severe water stress respectively. Postharvest moisture loss of carrots stored at 13μC and 32% relative humidity was monitored every second day for three weeks. The percent moisture loss was low in the low water stressed, and high in the severely water stressed carrots of both cultivars. Root crown diameter, weight, and water and osmotic potentials decreased, whereas specific surface area and relative solute leakage increased with increasing preharvest water stress. The results show that carrots adjust to water stress by lowering water and osmotic potentials. Root water potential, followed by relative solute leakage, were the variables which accounted for most of the variation in moisture loss. It is suggested that preharvest water stress lowers membrane integrity of carrot roots, and this may enhance moisture loss during storage.
Weed Control in Cole Crops and Onion (Allium cepa) Using Ammonium Nitrate
(Cambridge University Press, 1996-12) Bitterlich, Iris; Upadhyaya, M.K.; Shibairo, Solomon I.
Weed control in cole crops and onion by postemergence spraying with liquid ammonium nitrate was studied to determine its feasibility under Fraser Valley, British Columbia conditions. Ammonium nitrate solutions (7.5, 10, 15 and 20% N) were applied at 800 L ha−1 on warm, sunny days. Shepherd's-purse, low cudweed, redroot pigweed and ladysthumb were susceptible to this treatment; common lambsquarters, common purslane and annual bluegrass were tolerant. In order to determine the effect of weed density on weed control, several shepherd's-purse densities were established in broccoli and sprayed with ammonium nitrate solution (20% N; 800 L ha−1). Two days after treatment, weed control was 87.2% for an initial density of 500 shepherd's-purse plants m−2 (1987) and 76.1% for an initial density of 988 plants m−2 (1988). The seedlings that survived the treatment were sufficiently set back that they did not cause any adverse effect on crop yield. In a separate study, cabbage and onion were found to be tolerant to the ammonium nitrate treatment. Initially, cauliflower, broccoli and Brussels sprouts growth was slightly inhibited by the ammonium nitrate treatment but the plants recovered and crop yield was not affected.