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C.L. Mackowiak, R.M. Wheeler, G.W. Stutte, N.C. Yorio, and L.M. Ruffe

Peanut (Arachis hypogaea L.) plants were grown hydroponically, using continuously recirculating nutrient solution. Two culture tray designs were tested; one tray design used only nutrient solution, while the other used a sphagnum-filled pod development compartment just beneath the cover and above the nutrient solution. Both trays were fitted with slotted covers to allow developing gynophores to reach the root zone. Peanut seed yields averaged 350 g·m-2 dry mass, regardless of tray design, suggesting that substrate is not required for hydroponic peanut production.

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D.G. Mortley, C.K. Bonsi, P.A. Loretan, W.A. Hill, and C.E. Morris

Growth chamber experiments were conducted to study the physiological and growth response of peanut (Arachis hypogaea L.) to 50% and 85% relative humidity (RH). The objective was to determine the effects of RH on pod and seed yield, harvest index, and flowering of peanut grown by the nutrient film technique (NFT). `Georgia Red' peanut plants (14 days old) were planted into growth channels (0.15 × 0.15 × 1.2 m). Plants were spaced 25 cm apart with 15 cm between channels. A modified half-Hoagland solution with an additional 2 mm Ca was used. Solution pH was maintained between 6.4 and 6.7, and electrical conductivity (EC) ranged between 1100 and 1200 μS·cm–1. Temperature regimes of 28/22 °C were maintained during the light/dark periods (12 hours each) with photosynthetic photon flux (PPF) at canopy level of 500 μmol·m–2·s–1. Foliage and pod fresh and dry weights, total seed yield, harvest index (HI), and seed maturity were greater at high than at low RH. Plants grown at 85% RH had greater total and individual leaflet area and stomatal conductance, flowered 3 days earlier and had a greater number of flowers reaching anthesis. Gynophores grew more rapidly at 85% than at 50% RH.

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K. Stanciel, D.G. Mortley, D.R. Hileman, P.A. Loretan, C.K. Bonsi, and W.A. Hill

The effects of elevated CO2 on growth, pod, and seed yield, and gas exchange of `Georgia Red' peanut (Arachis hypogaea L.) were evaluated under controlled environmental conditions. Plants were exposed to concentrations of 400 (ambient), 800, and 1200 μmol·mol–1 CO2 in reach-in growth chambers. Foliage fresh and dry weights increased with increased CO2 up to 800 μmol·mol–1, but declined at 1200 μmol·mol–1. The number and the fresh and dry weights of pods also increased with increasing CO2 concentration. However, the yield of immature pods was not significantly influenced by increased CO2. Total seed yield increased 33% from ambient to 800 μmol·mol–1 CO2, and 4% from 800 to 1200 μmol·mol–1 CO2. Harvest index increased with increasing CO2. Branch length increased while specific leaf area decreased linearly as CO2 increased from ambient to 1200 μmol·mol–1. Net photosynthetic rate was highest among plants grown at 800 μmol·mol–1. Stomatal conductance decreased with increased CO2. Carboxylation efficiency was similar among plants grown at 400 and 800 μmol·mol–1 and decreased at 1200 μmol·mol–1CO2. These results suggest that CO2 enrichment from 400 to 800 μmol·mol–1 had positive effects on peanut growth and yield, but above 800 μmol·mol–1 enrichment seed yield increased only marginally.

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D.G. Mortley, C.K. Bonsi, W.A. Hill, and C.E. Morris

`Georgia Red' peanut (Arachis hypogaea L.) was grown hydroponically at 20/16 °C, 24/20 °C, 28/24 °C, and 32/28 °C, day/night air temperatures to evaluate effects on pod and seed yield, flowering, harvest index, and oil content. Ten-day-old peanut seedlings were transplanted into rectangular nutrient film technique troughs (0.15 × 0.15 × 1.2 m) and grown for 110 days. Growth chamber conditions were as follows: photosynthetic photon flux (PPF) mean of 436 μmol·m-2·s-1, 12 h light/12 h dark cycle, and 70% ± 5% relative humidity. The nutrient solution used was a modified half-Hoagland with pH and electrical conductivity maintained between 6.5 to 6.7, and 1000 to 1300 μS·cm-1, respectively, and was replenished weekly. Vegetative growth (foliage, stem growth, total leaf area, and leaf number) was substantially greater at increasingly warmer temperatures. Reproductive growth was significantly influenced by temperature. Flowering was extremely sensitive to temperature as the process was delayed or severely restricted at 20/16 °C. The number of gynophores decreased with temperature and was virtually nonexistent at the lowest temperature. Pod yield increased with temperatures up to 28/24 °C but declined by 15% at the highest temperature (32/28 °C). Seed yield, maturity, and harvest index were highest at 28/24 °C. Oil content (percent crude fat) increased an average of 23% and was highest at the warmest temperature (32/28 °C). These results clearly suggest that vegetative and reproductive growth, as well as oil content of peanut in controlled environments, are best at warmer temperatures of 28/24 °C to 32/28 °C than at cooler temperatures of 20/16 °C to 24/20 °C.

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D.G. Mortley, P.A. Loretan, W.A. Hill, C.K. Bonsi, C.E. Morris, R. Hall, and D. Sullen

`Georgia Red' peanut (Arachis hypogaea L.) and TU-82-155 sweetpotato [Ipomoea batatas (L.) Lam] were grown in monocultured or intercropped recirculating hydroponic systems in a greenhouse using the nutrient film technique (NFT). The objective was to determine whether growth and subsequent yield would be affected by intercropping. Treatments were sweetpotato monoculture (SP), peanut monoculture (PN), and sweetpotato and peanut grown in separate NFT channels but sharing a common nutrient solution (SP-PN). Greenhouse conditions ranged from 24 to 33 °C, 60% to 90% relative humidity (RH), and photosynthetic photon flux (PPF) of 200 to 1700 μmol·m-2·s-1. Sweetpotato cuttings (15 cm long) and 14-day-old seedlings of peanuts were planted into growth channels (0.15 × 0.15 × 1.2 m). Plants were spaced 25 cm apart within and 25 cm apart between growing channels. A modified half-Hoagland solution with a 1 N : 2.4 K ratio was used. Solution pH was maintained between 5.5 and 6.0 for treatments involving SP and 6.4 and 6.7 for PN. Electrical conductivity (EC) ranged between 1100 and 1200 μS·cm-1. The number of storage roots per sweetpotato plant was similar for both SP and SP-PN. Storage root fresh and dry mass were 29% and 36% greater, respectively, for plants in the SP-PN treatment than for plants in the SP treatment. The percent dry mass of the storage roots, dry mass of fibrous and pencil roots, and the length-to-diameter ratio of storage roots were similar for SP and SP-PN sweetpotato plants. Likewise, foliage fresh and dry mass and harvest index were not significantly influenced by treatment. Total dry mass was 37% greater for PN than for SP-PN peanut plants, and pod dry mass was 82% higher. Mature and total seed dry mass and fibrous root dry mass were significantly greater for PN than for SP-PN plants. Harvest index (HI) was similar for both treatments. Root length tended to be lower for seedlings grown in the nutrient solution from the SP-PN treatment.

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M. Lenny Wells and Eric P. Prostko

.L. Prostko, E.P. Bednarz, C.W. Davis, J.W. 2005 Cotton response to simulated imazapic residues Weed Technol. 19 1045 1049 Grichar, W.J. Nester, P.R. 1997 Nutsedge ( Cyperus spp.) control in peanut ( Arachis hypogaea ) with AC 263,222 and imazethapyr Weed

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Brian A. Kahn, John P. Damicone, Kenneth E. Jackson, James E. Motes, and Mark E. Payton

Nematodes (Meloidogyne sp.) are a potential problem when paprika peppers (Capsicum annuum L.) are grown in fields historically planted to peanuts (Arachis hypogaea L.). Nine nematicide treatments were evaluated over 3 years in field experiments on paprika pepper. Materials tested included the chitin nematicide ClandoSan and six chemicals: fosthiazate, carbofuran, aldicarb, oxamyl, fenamiphos, and dichloropropene. Stands at harvest were increased relative to the control by ClandoSan in 2 of 3 years. Other horticultural effects (plant dry mass and fruit yield) were minimal for all nine nematicide treatments. No one nematicide treatment consistently reduced nematode counts at harvest relative to the control. Nematode counts at harvest were greater in plots treated with ClandoSan than in plots treated with any other material in 2 of 3 years. Nematicide treatments were not cost effective under the conditions of these studies.

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C.L. Mackowiak, R.M. Wheeler, G.W. Stutte, and N.C. Yorio

As part of NASA's effort with bioregenerative life support systems, the growth of candidate crops is being investigated in controlled environments. Peanut (Arachis hypogaea L.) was selected for the high oil and protein content of its seed. Peanut cvs. Pronto and Early Bunch were grown from seed, using recirculating nutrient film technique (NFT) in 6-cm-deep, trapazoidal culture trays. The trays were fitted with slotted covers, which allowed developing pegs to reach the root zone. Use of a separate moss-filled pegging compartment above the root zone (tray within a tray) had little effect on seed yield, but resulted in a 60% increase in the nitric acid requirements for pH control. Yields from both cultivars were equivalent to field values on an area basis; however, harvest indices were lower than field values due to the luxuriant canopy growth under controlled environment conditions. Proximate analysis of seeds was similar to field values, with the exception of fat, which was ≈15% lower, and ash, which was ≈30% greater under controlled environment conditions, regardless of cultivar.

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S. Bekal and J.O. Becker

Recently, sting nematodes were discovered associated with dying turfgrass in several golf courses in Coachella Valley, Calif. Based on their morphology and internal transcribed spacer (ITS) rDNA restriction pattern, the pests were identified as Belonolaimus longicaudatus Rau. This study was undertaken to determine the host status of 60 different plant species and cultivars for a California population of B. longicaudatus. The host range tests were conducted under greenhouse conditions at 25 ± 2 °C and ambient light. At the second-leaf stage, each pot was infested with 55 ± 12 adults or fourth-stage juveniles per 150 g of blow sand. The population densities determined after 7 weeks of incubation qualified >80% of the plants tested as good hosts with a reproduction factor (Rf = Pf/Pi) > 4. The majority of those were grasses, although reproduction was best on Gossypium hirsutum L. with Rf = 58.6. While Capsicum annuum L., Medicago sativa L., Arachis hypogaea L., Euphorbia glyptosperma Engelm., Cucumis sativus L., and Daucus carota L. were less suitable host plants with Rf < 4, only Abelmoschus esculentus (L.) Moench, Citrullus lanatus Thunb., and Nicotiana tabacum L. were nonhosts among the tested species. This sting nematode population had a high reproductive fitness on a majority of species tested and must be considered a major threat for most agricultural and horticultural crops grown in sandy soils.

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V.M. Russo

Crop rotations can reduce problems that occur in monoculture planting systems. In 1990, at Lane, Okla., 0.5 ha of Bernow fine-loamy soil was planted to peanut (Arachis hypogaea L.). In the following 5 years, bell pepper (Capsicum annuum var. annuum L.), cucumber (Cucumis sativas L.), navy bean (Phaseolus vulgaris L.), and cabbage (Brassica oleracea L. Capitata group) were planted in one of four rotations after 1, 2, or 3 years of peanut. The first vegetable planting in each annual rotation was followed by either vegetables or peanut in following years. In 3 of the 6 years, peanut or vegetables were planted in each rotation. Peanut yields in the first year averaged 6.6 Mg·ha-1, but were <1.9 Mg·ha-1 thereafter. Yields of the first vegetable planting, which followed 1 or 2 years of peanut, were normal for this location, but were significantly lower after 3 years of peanut. For second or third plantings of vegetables in rotations, yields were reduced up to 50% compared to the first vegetable planting. For most crops, the rotation that had 3 years of peanut followed by 3 years of vegetables generally produced the least cumulative yield. Numbers of sclerotia produced by soilborne plant pathogenic fungi fluctuated over the years, but were the same in the spring of the second and sixth years. Rotating these crops appears to have limited applicability for maintaining high vegetable or peanut yields.