Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: Donald J. Makus x
Clear All Modify Search

Four week-old pepper (Capsicum annuum) cultivars Sonora Anaheim and Capistrano were transplanted on 7 Oct. 2004 into a sandy loam soil near Weslaco, Texas (lat. 26°08'N). Plants were subject to eight treatments consisting of sweet sorghum mulch, mycorrhizal (Bio Organics) inoculation, kaolin (Surround) application and their factorial combinations. Mulch was applied at 2.4 kg·m-2 and kaolin weekly at 25 kg·ha-1. Mulch applications reduced soil temperatures at 5 cm typically 8 °C during the 1200–1800 HR period of the day during the first 14 days after planting, but decreased soil temperatures to less than 2 °C by 22 Dec. Volumetric soil moisture content at 0–20 cm was initially 4% (absolute) higher in the mulch treatments during the first week after planting but deceased with time as the mulch deteriorated. Mulching increased root dry weight 70 days after transplanting. Mycorrhizal association was evaluated in four treatments, where incidence of mycorrhizal infection was “mulch + mycorrhizae” > “mycorrhizae only” = `“mulch only” » “control.” Kaolin reduced plant height, plant top fresh weight, and improved yield in both cultivars by increasing earlier flowering and, in the case of `Sonora Anaheim', reducing fruit drop caused by pepper weevil (Anthonomus eugenii). In both cultivars, mulch reduced yields and mycorrhizal inoculation gave no agronomic benefit.

Free access

Field-grown mustard greens, Brassica juncea, were used to validate several observations of a greenhouse study which reported nutrient changes in mustard greens grown, in part, under ambient and reduced light. The cultivar Florida Broadleaf was transplanted into a Hildago sandy clay soil near Weslaco, Texas (26° 08' Lat.) on 6 Nov 2003. Greens were fertigated with 30 kg·ha-1 of N on 1 Dec. Plants 14 days before harvest were grown under the following four light regimes: (1) continuous ambient light; (2) 7 days of 50% shade then 7 days of ambient light; (3) 7 days of ambient light then 7 days of 50% shade; and (4) 14 days of 50% shade. Cumulative solar light was 28.9 and 19.4 kW/m2 during the first and second 7 days, respectively. Measured cumulative light, as PPFD, for treatments 1-4 were 108, 67, 78, and 44 mm·m-2·s-1, respectively. Plants were harvested at 0800, 1100, and 1400 h on 2 Jan. 2004. Shade during the last 7 days generally evoked the greatest responses. Increased shade duration did not significantly effect the agronomic performance, but did increase leaf total carotenoids, chlorophylls, water content, and reduced total ascorbate levels. As time of daylight progressed, sample plant weight and average leaf weight decreased in shaded plants only. Free ascorbic acid, chlorophyll a:b ratio, and the chlorophyll to carotenoid ratio decreased with time of day. Cumulative sunlight, as PPFD, was significantly correlated with total ascorbate (fresh weight basis), chlorophyll a:b ratio, and plant weight (P < 0.06) and negatively correlated with chlorophylls and total carotenoids (dry weight basis). Thus, cloudy weather prior to harvest can reduce leaf Vitamin C and alter leaf greenness

Free access


Anthocyanins (Acy) in ripening blueberry fruit of the cv. Wolcott were identified and their amounts estimated spectrophotometrically. Fifteen Acy, all combinations of Mv, Pt, Pn, Dp, and Cy with glu, gal, or arab4 in the 3-position were found in unripe, red fruit. Ripe and overripe fruit contained all these Acy except Pn-gal. Cy-glu and Cy-gal comprised about 40% of the total Acy in unripe fruit, while Mv-glu and Mv-gal constituted about 60% in the overripe fruit. The relative proportions of 3-glucosides, 3-galactosides, and 3-arabinosides remained fairly constant throughout fruit ripening.

Open Access

Frost damage to `Jersey Giant' asparagus (Asparagus officinalis L.) spears was evaluated in noncovered and black plastic-covered field plots following a spring frost episode. In the noncovered plots, 78% of spears were killed as compared to only 17% under the plastic rowcovers. Laboratory studies using natural frost simulations indicated that the spears of both treatments were frost hardy to -2.8C. Air temperature data in the field plots during the frost episode indicated that spears in noncovered plots were at lower temperatures (-4.0 to -4.8C vs. -2.8C) ≈4 to 5 hours longer than spears under rowcovers. The large difference in the spear-kill may be due to the difference in the combined effect of the degree and duration of freezing to which the spears had been exposed.

Free access