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Hassan Salehi and Morteza Khosh-Khui

Turfgrass seeds can be sown individually, in mixes, or overseeded to provide green color and uniform surfaces in all the seasons. This investigation was conducted to compare different turfgrass species and their seed mixtures. In this research, the turfgrasses—perennial ryegrass (Lolium perenne L. `Barball'), kentucky bluegrass (Poa pratensis L. `Merion'), common bermudagrass (Cynodon dactylon [L.] Pers.), and strong creeping red fescue (Festuca rubra L. var. rubra `Shadow')—in monoculture or in mixtures of 1:1 (by weight) and a 1:1:1:1 (by weight) and two sport turfgrasses—BAR 11 (Barenbrug Co.) and MM (Mommersteeg Co.)—were used. The seeds were sown in March and October (spring and fall sowing) in 1998 and 1999. The experiments were conducted in a split-split block design with year as main plot, sowing season as subplot, and turfgrass types as subsubplot. The turfgrasses were compared by measuring visual quality, chlorophyll index after winter and summer, rooting depth, verdure and/or root fresh and dry weight, tiller density, and clippings fresh and dry weight. Fall sowing was superior to spring sowing and resulted in greater root growth, clipping yield, and chlorophyll content. Poa+Cynodon seed mixture was the best treatment and had high tiller density, root growth, and chlorophyll content. Lolium and Festuca monocultures, and Poa+Festuca and Cynodon+Festuca seed mixtures were not suitable with regard to low tiller density, sensitivity to high temperatures, low root growth, and low tiller density, respectively. The cool-warm-season seed mixture (Poa+Cynodon) can be used alternatively in overseeding programs in the areas with soil and environmental conditions similar to this research site.

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Sharon Edney, Jeffrey Richards, Matthew Sisko, Neil Yorio, Gary Stutte, and Raymond Wheeler

Development of a crop production system that can be used on the International Space Station, long duration transit missions, and a lunar/Mars habitat, is a part of NASA's Advanced Life Support (ALS) research efforts. Selected crops require the capability to be grown under environmental conditions that might be encountered in the open cabin of a space vehicle. It is also likely that the crops will be grown in a mixed-cropping system to increase the production efficiency and variety for the crew's dietary supplementation. Three candidate ALS salad crops, radish (Raphanus sativus L. cv. Cherry Bomb II), lettuce (Lactuca sativa L. cv. Flandria) and bunching onion (Allium fistulosum L. cv. Kinka) were grown hydroponically as either monoculture (control) or mixed-crop within a walk-in growth chamber with baseline environments maintained at 50% relative humidity, 300 μmol·m-2·s-1 PPF and a 16-hour light/8-hour dark photoperiod under cool-white fluorescent lamps. Environmental treatments in separate tests were performed with either 400, 1200, or 4000 μmol·mol-1 CO2 combined with temperature treatments of 25 °C or 28 °C. Weekly time-course harvests were taken over 28 days of growth. Results showed that none of the species experienced negative effects when grown together under mixed-crop conditions compared to monoculture growth conditions.

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Sharon L. Edney, Jeffrey T. Richards, Matthew D. Sisko, Neil C. Yorio, Gary W. Stutte, and Raymond M. Wheeler

The development of a crop production system that can be used on the International Space Station, long-duration transit missions, and lunar or Mars habitats, has been a part of NASA's Advanced Life Support (ALS) research efforts. Crops that can be grown under environmental conditions that might be encountered in the open cabin of a space vehicle would be an advantageous choice. The production efficiency of the system would be enhanced by growing these crops in a mixed-crop arrangement. This would also increase the variety of fresh foods available for the crew's dietary supplementation. Three candidate ALS salad crops, radish (Raphanus sativus L. cv. Cherry Bomb II), lettuce (Lactuca sativa L. cv. Flandria), and bunching onion (Allium fistulosum L. cv. Kinka) were grown hydroponically as either monoculture (control) or mixed-crop within a walk-in growth chamber with baseline environments maintained at 22 °C, 50% RH, 17.2 mol·m-2·d-1 light intensity and a 16-h light/8-h dark photoperiod under cool-white fluorescent lamps. Tests were carried out at three different CO2 concentrations: 400, 1200, and 4000 μmol·mol-1. Weekly time-course harvests were taken over 28 days of growth, and fresh mass, dry mass, and harvest index were determined. Results showed that none of the species experienced negative effects when grown together under mixed-crop conditions compared to monoculture growth conditions under the range of environmental conditions tested.

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James J.K. Leary and Joe DeFrank*

Two long-term field experiments were conducted from 1998 to 2000 to compare the yields of marketable eggplant in a buffelgrass living mulch system to a conventional monoculture bare ground system. The initial experiment compared the yields in the conventional treatment to living mulch treatments, that were chemically suppressed at three levels of sethoxydim applied at 0.1, 0.2, and 0.3 kg·ha-1 a.i. Regression analysis did not reveal a significant linear response of eggplant yield to increasing levels of sethoxydim. The average cumulative yield of the three living mulch treatments, 130 days after transplant (DAT), was 4,296 kg·ha-1 compared to 2,079 kg·ha-1 for the conventional treatment. The higher yield in the living mulch treatments was due to a mite infestation that was much more pronounced in conventional plots. In the follow-up experiment, three different living mulch management (mechanical suppression, chemical suppression, and untreated) treatments were compared to a conventional monoculture bare ground treatment. There was no mite infestation affecting this experiment and cumulative yields of marketable fruit at 159 DAT were 5,362, 4,521, 4,155, and 2,535 kg·ha-1 for conventional bare ground, mechanical suppression, chemical suppression and untreated living mulch treatments, respectively. Orthogonal comparisons showed that the yields from the conventional treatments were not significantly different from the suppressed living mulch treatments. However, the eggplant yields from the unmanaged living mulch treatments were significantly reduced in comparison to the conventional and also the suppressed living mulch treatments.

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Virginia I. Lohr

There is a long history of problems associated with the overuse of specific plants in agricultural monocultures. The Irish potato famine of 1845 to 1850, which was caused partly by dependence on a single variety of potato ( Solanum tuberosum

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John R. Teasdale and Aref A. Abdul-Baki

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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Matthew A. Cutulle, Jeffrey F. Derr, David McCall, Brandon Horvath, and Adam D. Nichols

increase the quality of the turf stand when compared with individual monocultures of these species. Seeding mixtures of different species increase the genetic variability of a turfgrass stand ( Donald, 1963 ). Environmental stresses such as drought

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Jose G. Franco, Stephen R. King, Joseph G. Masabni, and Astrid Volder

with monocultures; i.e., less complex systems. We also hypothesized that this reduction in weed biomass would be the result of increased leaf area and aboveground plant biomass intercepting solar radiation. The species used in this study were peanut

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Tatiana Pagan Loeiro da Cunha-Chiamolera, Miguel Urrestarazu, Arthur Bernardes Cecílio Filho, and Isidro Morales

each monoculture crop. Materials and Methods Growing conditions. The experiment was conducted in a plastic no heated greenhouse at the University of Almería (Universidad de Almería), Spain, located at 36°50′25″N and 2°28′05″W and at an elevation of 23 m

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Gilbert Miller and Jeremy Greene

when LER is lower than 1.0, intercropping negatively effects the growth and yield of the plants grown in mixtures ( Willey and Rao, 1980 ). However, according to Garnier et al. (1997) , evaluating an intercropped vs. a monoculture system based on LER