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

TU-155 and Georgia-Jet early, TU-1892 and Carver late maturing sweet-potato cultivars. were evaluated in the field to determine the effect of flower removal (FR) would have on marketable storage, root numbers and yield. Other parameters measured were leaf area and numbers, plant fresh and dry weight. Plants were sampled at 57 and 71 days after transplanting (DAT). All flowers were hand removed and the 1st harvest began 45 days DAT for the early and at 60 DAT for the late maturing cultivars. All flower harvests concluded 22 days after 1st harvest began and roots were harvested 120 DAT. There was significant differences among cultivars for total flower production with N-1892 and Georgia-Jet having the highest flower production. FR treatments for N-155 and Georgia-Jet showed significant increases for plant dry weight, leaf area and numbers 71 DAT while Carver and TU-1892 showed no significant differences for the same sample period. Marketable root numbers were not significantly affected by FR but marketable yields for all cultivars were. Overall, the cultivars showed variation both within and among maturity groups in their response to FR treatments, for example N-155 had a 39% compared to 3% increase for Georgia-let while Carver had a 15% increase in marketable yield compared to 5% for TU-1891.

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V.A. Khan, C. Stevens, J. Y. Lu, D. I. Collins, M. A. Wilson, J. E. Brown, M.K. Kabwe, and O. Adeyeye

A study was conducted in 1991 to determine the effect high soil temperatures would have on `Clemson Spineless' okra plants transplanted into field plots during 60 days of active soil solarization (solar heating of the soil using clear plastic during the summer period). Solarized plots were planted to a winter cover crop which served as an organic amendment, which was rototilled into the top 15 cm of the soil before solarizing. Okra transplants were planted on the outer edges of the plots one month after the solarization process commenced and drip irrigated. Three weeks (wk) after transplanting, a complete fertilizer at the rate of 200 parts per million was applied to the plots giving the following treatment combinations: solarized non-fertilized control (SNF), non-solarized non-fertilized control (NSNF), solar fertilized (SF). and non-solarized fertilized (NSF). Results showed that the increased soil temperature did not have any deleterious effect on the okra plants grown in SNF or SF plots. However, plants grown in SF plots suffered severe fertilizer bums which affected plant density and yield. This indicated a rapid breakdown of soil organic matter provided sufficient nutrients to sustain a late-season crop of okra. Plant height, marketable yield vegetative branching and income generated were greater in SNF compared to SF, NSF and NSNF plots, respectively.

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C. Stevens, L. P. Pusey, V.A. Khan, J.Y. Lu, C.L. Wilson, M.A. Wilson, M.K. Kabwe, J. Liu, E. Chaultz, and S. Droby

Flavorcrest, Camden. C. L. Wilson, Loring, Elberta, Summergold and Harken peach varieties were inoculated and naturally infected with Monilinia fructicolo after ultraviolet light irradiation (W-C 254nm) showed increased resistance to brown rot disease. Although dosages ranged from 0 to 20 KJ/m2. 7.5 KJ/m2 was considered the most effective for the peach varieties tested. Pretreatment of peaches by field spraying or dipping into a benomyl fungicide showed no significant differences between non-treated and UV-C treated peaches. However. a combination of a low dose of benomyl (.15g/L) 3 days following UV-C treatment showed a synergistic effect on brown rot reduction when compared to Peaches treated with UV-C alone and a greater reduction of brow rot than benomyl control.

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Victor A. Kahn, C. Stevens, T. Mafolo, C. Bonsi, J.Y. Lu, E.G. Rhoden, M.A. Wilson, M.J.E. Brown, K. Kabwe, and Y. Adeyeye

TU-82-155 and `Georgia-Jet' early maturing. `Carver II', TU-1892 and `Rojo-Blanco' late maturing sweetpotato, cultivars were evaluated in the field for 0.20 and 40% vine removal (VR) at 8 wk after transplanting. Parameters measured were: leaf area index (LAI) recovery, net assimilation rate, foliage crop growth rate (FCGR), storage roots crop growth rate (RCGR). alpha a (the mean relative growth rate in dry wt to the mean relative growth rate in leaf area over a time interval) or the partitioning of assimilates, total and marketable yield. A split. splitplot design was used and plants were sampled at 3 and 8 wk following VR. Except for TU-82-155 all cultivars showed significant LAI recovery above the control at 3 and 8 wk after vine removal when 20% of the vines were removed while at the 40% VR, only 'Georgia-Jet'. TU-1892 and 'Carver II' showed significant increases in LAI for the same periods. Net assimilation rate showed significant interactions while FCGR was not significantly affected by either 20 or 40 VR compared to the control at 3 or 8 wk after VR. RCGR was significantly affected by both levels of VR at 3 and 8 wk after VR and surplus assimilates (alpha a) showed significant interactions between cultivars and % VR. Told yield declined for all cultivars irrespective to maturity groups with the sharpest decrease being at the 20% VR. All cultivars except TU-82-155 showed a decrease in marketable yield, the increase in marketable yield of TU-82-155 was due to a lower non-marketable yield.

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Victor A Khan, C. Stevens, T. Mafolo, C. Bonsi, J.Y. Lu, E.G. Rhoden, M. A. Wilson, M. K. Kabwe, and Y. Adeyeye

TU-82-155 and `Georgia-Jet' early maturing. `Carver II'. TU-1892 and `Rojo-Blanco' late maturing sweepotato cultivars were evaluated in the field for: leaf area index (LAI), net assimilation rate, foliage crop growth rate (FCGR), storage roots crop growth rate (RCGR) and alpha a (the mean relative growth rate in dry wt to the mean relative growth rate in leaf area over a time interval) or the partitioning of assimilates. A split plot design was used and plants were sampled at 6, 8, 11 and 16 wk after transplanting. The results from study showed that LAI reached maximum development 8 and 12 wk after transplanting for early and late maturing cultivars, respectively. All cultivars irrespective to maturity groups showed a reduction in net assimilation rate 6 wk after transplanting while FCGR for early maturing cultivars gradually declined 6 wk after transplanting and varied among late maturing cultivars. `Carver II' showed increases in FCGR up to 11 wk after transplanting then rapidly declined while `Rojo-Blanco' and TU-1892 began to decline 8 and 6 wk after transplanting, respectively. RCGR showed rapid increases (100 g.m /area/week) and (150 g/m /area/week) for early and late maturing cultivars beginning 6 wk after transplanting and this increase continued until the 12th and 8 th wk after transplanting for early and late maturing cultivars, respectively. Cultivars from both maturity groups began to produce surplus assimilates (Alpha a) 6 wk after transplanting. which coincided with the rapid increases in RCGR at the same time. Thus indicating that storage root enlargement begins after the plant had accumulated a surplus of assimilates.

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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.

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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.