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V. A. Khan, C. Stevens, J. Y. LU, M. K. Kabwe, and Z. Haung

Clear (CM), and black plastic (BM) mulches and bare (BS) soil plus VisPore (V) row cover (VCM, VBM, VBS), CM, BM, and BS in combination with drip irrigation and three planting dates January 3rd, February 16th, and March 16th, 1990, were used to evaluate the yield of `Georgia' collard greens. At the 1st planting date, both mulches and row cover treatments had significantly higher yield. At the 2nd and 3rd planting dates there were significant interactions between mulch and row cover. The interaction at the the 2nd planting date showed that yield was highest with VCM and VBS treatments and at the 3rd planting date CM, BM and VBS increased yield, respectively. The number of days to harvest decreased with each planting date and bolting was not observed for any planting date or treatment combination.

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V. A. Khan, C. Stevens, J. Y. Lu, M. Kabwe, and Z. Haung

Clear (CM) and black (BM) plastic mulch and bare soil (BS) plus VisPore (V) row cover (VCM, VBM, VBS), BM, CM and BS in combination with drip irrigation were used to evaluate the growth response of these treatment combinations on 5 and 9 wks old `Clemson Spineless' okra transplants grown in sandy loam soil. Mulched treatments significantly increased the survival rate of 5 wks old transplants while VCM and VBM treatments increased significantly the number of vegetative branches of 5 wks over 9 wks old transplants. Total and marketable yield, as well as total and marketable number of pods were significantly influenced by mulched treatments rather than by the age of transplants.

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C. Stevens, V. A. Khan, J. Y. Lu, M. A. Wilson, Z. Haung, and J. E. Brown

In 1988 and 1989 a muscadine vineyard at Tuskegeee, Alabama was treated by post plant soil solarization (PSS) (covering of moist soil around 'Carlos' muscadine plants (Vitis rotundifolia Michx.) with clear polyethylene plastic mulch to achieve high soil temperature for 30 and 75 days, respectively during PSS. Grape plants grown in solarized soils showed increases in growth response such as increased yield. Foliage of grape plants was evaluated for reaction to black rot incited by Guignardia bidwellii. A significant reduction of the foliage disease black rot was observed. The number of lesions per leaf, lesion size and percent leaves with lesions were significantly reduced by as much as 56% up to three years after solarization.

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C. Stevens, V. A. Khan, J. Y. Lu, M. K. Kabwe, Z. Haung, M. A. Wilson, and J. E. Brown

In 1988 and 1989 a muscadine vineyard at Tuskegee, Alabama was treated by post soil solarization (PSS) (covering of moist soil around muscadine plants with clear polyethylene plastic mulch to achieve high soil temperature) for 30 and 75 days, respectively. The average soil temperature in 1989 of 50 and 35 C at 5cm depth for solarized and bare soil, respectively during PSS. The results showed no visible detrimental effect on `Carlos' muscadine (Vitis rotundifolia) from the increased heating of the soil. And the grape plants grown in solarized soils showed increases in growth response e.g. increased yield, revitalization of new softwood vines, vine weight/plant, etc. Uneven ripening of muscadine grapes was reduced on plants grown in PSS over bare soil as indicated by the increases in the percent soluble solids content of grape berries.

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C. Stevens, V. A. Khan, J. L. Lu, C. L. Wilson, E. Chalutz, M. K. Kabwe, and Z. Haung

Jewel sweetpotato storage roots previously treated with ultraviolet (UV–C) light and then stored for 30 days before artificial inoculation with Fusarium solani showed increased resistance to Fusarium root rot; as indicated by reduced lesion size, the rate of decay development of rotted tissues. There was a hormetic relationship between the incidence of Fusarium root rot and UV–C doses. The optimum dose of UV which reduced Fusarium root rot was 3.6× 104 ergs/mm2. Exposure of sweetpotato to UV–C doses promoted phenylalanine ammonia–lyase (PAL)4 production with the maximum PAL activity occurring at 3.6×104 ergs/mm2. Crude extracts from UV–C treated sweetpotatoes reduced germination, germ tube elongation and growth of F. solani when compared to untreated extracts.

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C. Stevens, C. L. Wilson, J. Y. Lu, V. A. Khan, E. Chalutz, M. K. Kabwe, Z. Haung, S. Droby, and L. Pusey

Low doses of ultraviolet light (254nm UV–C) irradiation reduced postharvest rots of pome, stone and citrus fruits. Brown rot (Monilinia fructicola) of `Elberta' and `Loring' peaches was significantly reduced by UV–C. Alternaria rot (Alternaria spp.) and bitter rot (Colletotrichum spp.) the principal storage rots of `Golden Delicious apples showed significant reduction following UV–C treatment. Further application of UV–C was effective in controlling green mold rot (Penicillium digitatum) of `Dancy' Tangerines and `Marsh Seedless' grapefruits, stem end rot (Alternaria citri), as well as sour rot (Geotrichum candidum) of `Dancy' tangerines after irradiation.

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C. Stevens, P. L. Pusey, V. A. Khan, J. Y. Lu, C. L. Wilson, E. Chalutz, M. K. Kabwe, Z. Haung, O. Adeyeye, and J. Lin

Low hormetic doses of ultraviolet light (UV-C) stress on exposed peaches (Prunus persica). reduced brown rot resulting from field and artificial inoculation from Monilinia fructicola. To test the hypothesis that UV-C induced resistance through host responses the following tests involving biochemical changes (phenlyalanine ammonia-lyase activity (PAL) and ethylene production (EP)), bioassay of antifungal activity of tissue extracts to the fungus, and latent infection of rot free peaches previously treated with and without UV-C were determined. Exposure of peaches to UV-C dose of 7.5×104 ergs/mm2 promoted an increase in PAL and EP compared to the control. As the PAL activity increased, percent storage rots decreased. Antifungal activity to the fungal conidia in UV-C treated peach extract showed that the percent conidia germination was reduced 3 folds. Preharvest infection of brown rot which indicated latent infection was significantly reduced. To test for the germicidal effect of UV-C on M. fructicola on the surface of peaches, an artificial epiphytic population of the fungus was deposited on the peaches. A negative relationship between UV-C dose of 1.3 to 40×104 ergs /mm2, colony forming units and number of decaying brown rot lesions were found.

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V. A. Khan, C. Stevens, J. Y. Lu, J. E. Brown, E. G. Rhoden, M. A. Wilson, M. K. Kabwe, and Z. Haung

An early planting (January) of 8 wks. old collards (Brassica oleracea (L) var. acephala `Georgia Collards') and subsequently followed by `Crimson Sweet' watermelon transplants (April) on clear and black polyethylene mulches and bare soil plus VisPore row cover (VCM, VBM, VBS), clear and black polyethylene mulches and bare soil (CM, BM, BS) in combination with drip irrigation were transplanted on the same plots. Marketable yield of collards (March) was significantly greater for mulched and row cover treatments than bare soil. Watermelon (harvested June 7th, 1990) total and marketable numbers and yield were significantly greater when grown on mulched treatments than bare soil. Mono-cropping of watermelon were profitable under VCM, VBM, CM and BM treatments and collards when grown as a mono-crop was not profitable under any system. By sharing the costs of production under a double-cropping system the profitability of watermelons increased when grown under VCM, VBM, CM, BM VBS and for collards under VCM and VBM treatments.