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  • Author or Editor: A. Abdul-Baki x
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Hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) and mixtures of rye with hairy vetch and/or crimson clover were compared for no-tillage production of staked, fresh-market tomatoes (Lycopersicon esculentum Mill.) on raised beds. All cover crops were evaluated both with or without a postemergence application of metribuzin for weed control. Biomass of cover crop mixtures were higher than that of the hairy vetch monocrop. Cover crop nitrogen content varied little among legume monocrops and all mixtures but was lower in the rye monocrop. The C:N ratio of legume monocrops and all mixtures was <30 but that of the rye monocrop was >50, suggesting that nitrogen immobilization probably occurred only in the rye monocrop. Marketable fruit yield was similar in the legume monocrops and all mixtures but was lower in the rye monocrop when weeds were controlled by metribuzin. When no herbicide was applied, cover crop mixtures reduced weed emergence and biomass compared to the legume monocrops. Despite weed suppression by cover crop mixtures, tomatoes grown in the mixtures without herbicide yielded lower than the corresponding treatments with herbicide in 2 of 3 years. Chemical name used: [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one](metribuzin).

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Heat-tolerant and -sensitive Lycopersicon esculentum Mill. and L. pimpinellifolium (Jusl.) Mill. genotypes were grown in the greenhouse under optimum- (27/23C, day/night) and high-temperature (35/23C) stress regimes. Heat tolerance levels in the genotypes were established by determining percent fruit set at high and optimum temperatures. Under optimum temperature, fruit set ranged from 41% to 84% and from 45% to 91% in the heat-sensitive and heat-tolerant genotypes, respectively. Under high temperature, no fruit set in the most heat-sensitive genotypes. Fruit set in the heat-tolerant genotypes ranged from 45% to 65%. In vitro germination and tube growth of pollen taken from genotypes grown under optimum temperature conditions were determined before and after subjecting the pollen to 45C for 1, 2, and 4 hours. The response of pollen to heat treatments was genotype dependent and not a general predictor of fruit set under high-temperature stress.

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Nitrogen requirements by fresh-market field tomatoes (Lycopersicon esculentum Mill.) were determined on plants grown in a hairy vetch mulch (HVM) or in black polyethylene mulch (BPM). Nitrogen treatments were 0, 56, 112, and 168 kg/ha delivered weekly through the trickle system. Yields in BPM increased significantly with higher applications of nitrogen from 54 to 91 tons/ha and chlorophyll content of fully expanded leaves increased from 7.8 to 11.3 OD664 per 100 mg fresh weight. In contrast, neither yield nor chlorophyll content of leaves increased significantly by adding nitrogen. The 0 nitrogen treatment in HVM yielded 89 ton/ha and chlorophyll content was 13.5 OD664 making it equivalent to those in BPM that had received 168 kg nitrogen/ha. The results suggest that hairy vetch can provide all the nitrogen required by the subsequent tomato crop and produces high yields and vigorous plants.

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Hairy vetch, subterranean clover, polyethylene black mulch (PBM), and Horto paper were evaluated in field-grown fresh market production of tomatoes (Lycopersicon esculentum Mill), cv `Sunny'. Plant mulches were grown in beds in the fall, mowed immediately before planting, and the tomato seedlings were planted without tillage in a low input system. Yields (t.ha-1) for hairy vetch, subterranean clover, PBM, Horto paper, and no mulch were 72.1, 46.6, 59.9, 54.0, and 29.8, respectively. Although the tomato plants grown under plant mulches received 50% of the recommended fertilizer application, they produced more vigorous plants than those in other treatments. Plant mulches were effective in controlling growth of weeds and infestation by Colorado potato beetle.

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Abstract

The leachate from seed of tomato (Lycopersicon esculentum Mill., PI 341984), an accession whose seeds germinate well at low temperatures, promoted the germination of seeds of the same and other tomato cultivars. The leachate from ‘Red Rock’ seed, a cultivar whose seeds germinate poorly at low temperatures, inhibited the germination of seeds of the same and other tomato cultivars. The promotive and inhibitory effects of these leachates on seed germination is apparently highly specific and restricted to tomato seeds. The activity was highest in fresh seeds and the responses were best exhibited at low germination temperatures.

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Temperature and root length at selected locations within a raised bed under black polyethylene, hairy vetch (Vicia villosa Roth) residue, or bare soil were measured and correlated with tomato (Lycopersicon esculentum Mill.) growth. Early in the season, before the tomato leaf canopy closed, soil temperature was influenced more by vertical depth in the bed than by horizontal position across the bed. Maximum soil temperatures under black polyethylene averaged 5.7 and 3.4C greater than those under hairy vetch at 5 and 15 cm deep, respectively. More hours at optimum temperatures for root growth (20 to 30C) during the first 4 weeks of the season probably accounted for greater early root and shoot growth and greater early yield of tomatoes grown with black polyethylene than hairy vetch residue or bare soil. After canopy closure, soil temperatures under tomato foliage within the row were reduced by an average of 5.2 and 2.2C at 5 and 15 cm deep, respectively, compared to those on the outer edge of the beds. Most tomato roots were in areas of the bed covered by the tomato canopy where temperatures in all treatments remained in the optimum 20 to 30C range almost continuously. Soil temperature, therefore, did not explain why tomato plants in the hairy vetch treatment had equal or higher total yields than the black polyethylene or unmulched treatments.

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Abstract

The transport of arginine and α-aminoisobutyric acid from the cotyledon to the axis of Phaseolus lunatus L. was followed during a 4-day germination. Transport of both amino acids to the axis was slow during the first 2 days and increased rapidly during the third and fourth days of germination. Both amino acids accumulated in the axis of viable seeds. Alpha-aminoisobutyric acid was not metabolized by the cotyledon or axis, whereas arginine was rapidly fixed by both tissues into protein. Percent incorporation of arginine into protein was lower in the cotyledon than in the axis. Rapid synthesis of proteins in the cotyledon appears to limit transport and availability of amino acids to the axis. No transport or accumulation of α-aminoisobutyric acid was observed in seeds that lost germinability through accelerated aging.

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Hairy vetch, crimson clover, and rye, separately or in combination, were grown in the fall as cover crops and mowed in the spring to form an organic mulch in a no-tillage sustainable agricultural system for production of fresh-market tomatoes (Lycopersicon esculentum Mill, cv `Sunny'). Fruiting earliness, yield, and size were compared between the organic mulch treatments and those under bare soil, paper and black polyethylene mulches. Fruiting was about 9-10 days earlier under black polyethylene mulch than all other treatments. Total marketable yields (t·ha-1) under the mulch treatments were: hairy vetch, 85; hairy vetch plus rye, 69; crimson clover, 66; black polyethylene, 44; bare soil, 36; and Horto paper, 30. Average fruit size was significantly larger in all organic mulch treatments than in bare soil, Horto paper, and black polyethylene mulches. Early growth of tomato plants was highest with plastic but subsequent growth was highest with hairy vetch. Superior vigor with hairy vetch was probably the result of higher nitrogen concentration of vetch residue relative to the other cover crops.

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Tomato (Lycopersicon esculentum Mill., cv. Sunny) plants were grown in a sustainable agricultural system of mulches: black plastic, paper, hairy vetch, crimson clover, and hairy vetch + rye. Total yields were highest with hairy vetch (85.8 t ha-1) and lowest with paper mulch (30.0 t ha-1). The low fertilizer input hairy vetch, crimson clover and hairy vetch + rye treatments received one-half the N-P-K fertigation that was applied to other treatments. Immediately before mowing the cover crops, samples were analyzed. Five weeks after transplanting the tomatoes and at the end of 12 weeks, leaf samples were analyzed for macro- and micro-nutrients. Results of the cover crop analyses indicated minimal differences in N, P, K, Ca, Mg, Mn, B, and Fe concentrations. Tomato leaf analyses at 5 weeks after field planting showed that, among the macro-nutrients, only K was significantly higher in the hairy vetch, hairy vetch + rye, crimson clover, and black plastic treatments than in bare soil and paper mulch. End-of-season leaf analyses showed that significantly higher K was found in the vetch + rye treatment compared to all other treatments.

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Susceptibility of tomato (Lycopersicon esculentum Mill) genotpyes to the root-knot nematode Meloydogyne incognita and to heat stress can be evaluated in a single labor- and time-saving operation using a nondestructive in vitro excised root technique. Seeds are sterilized and germinated for 2 days on 1% water agar. Five-mm root sections are grown at 28 and 35 C for 30 days on Gamborg-B medium with and without nematode inoculum. Evaluation criteria include fresh and dry weight and the appearance of juveniles, adults, gulls, and egg masses. Evidence will be presented on the breakdown of resistance to M. incognita under high temperature stress.

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