Search Results

You are looking at 1 - 10 of 17 items for

  • Author or Editor: P.A. Loretan x
  • All content x
Clear All Modify Search
Free access

A.A. Trotman, W.A. Hill, D.G. Mortley, P.P. David, and P.A. Loretan

The effect of inoculation with Azospirillum brasilense strain Cd on mineral concentration in sweetpotato, [Ipomeo batatas (L) Lam cv. TI-155] tissue and ionic composition of plant nutrient solution was investigated in a greenhouse study. In the field, inoculation of sweetpotato with Azospirillum spp. has been reported to enhance. sweetpotato yield. In this study, 48-h old broth cultures were used as inoculum at a population density of approx. 1 × 108 cfu/ml. The inoculum (0.20 L) was added to the reservoirs containing 30.4 L of a modified half Hoagland's plant nutrient solution at 28 days after the start of the experiment Results indicate that percent total nitrogen in sweetpotato foliage tended to be higher for the inoculated fibrous mat than in the fibrous mat for non-inoculated plants. The percent total nitrogen in storage roots for the non-inoculated treatment tended to be higher than in storage roots for inoculated plants. Inoculation resulted in a slight increase in foliar phosphorus concentration but had no effect on phosphorus concentration in sweetpotato storage and fibrous root samples. Inoculation tended to reduce foliar calcium concentration. Magnesium concentration in leaf tissue was not influenced by inoculation. Foliar potassium concentration tended to increase slightly. The effect of inoculation on potassium concentration in sweetpotato root tissue was not well-defined; potassium concentration tended to be higher in fibrous root tissue for the inoculated treatment. But in storage root tissue, potassium concentration was higher for the non-inoculated treatment than for the inoculated treatment. Inoculation did not affect foliar concentrations of any of the micronutrients measured. This study indicates no effect of inoculation on ionic strength of nutrients in solution reservoirs.

Free access

A.A. Trotman, C.E. Mortley, D.G. Mortley, P.P. David, and P.A. Loretan

Hydroponic growing systems have the potential to maximize phytomass production of peanut (Arachis hypogea) for Controlled Ecological Life Support Systems (CELSS). Two greenhouse experiments were conducted with plant nutrients supplied in a modified Evan's solutionusing a nutrient film technique. The objective of this research was to determine the effect of hydroponic growing systems on pod and foliage yield of `New Improved Spanish' and `Georgia Red' peanut. Sub-objectives were to evaluate (i) the impact of channel size and (ii) the impact of gradation in pore size on the separation of the rooting zone from the zone of gynophore development. The treatments consisted in the first experiment of a wide channel (122 by 15 by 46 cm) fitted with a perforated (3.0mm diam.) PVC grid; a narrow channel (122 by 15 by 15 cm) either fitted with a perforated grid or without a grid. For 'New Improved Spanish' peanut dry foliage yield tended to be higher in the wide channel treatment (0.33 kg/sq m). But the narrow channel yielded the highest mean pod dry weight (0.12 kg/sq m). Pore sizes of the screens ranged from infinity (no screen). perforated grid, square mesh. filtering screen (75u) and solid screen (no pores). For `Georgia Red' peanut, the impact of gradation in pore size of screens was variable: pod number was highest with the filtering (food) screen (216/sq m) but pod dry weight was highest for the square mesh treatment (0.09 kg/sq m). Foliage yield was significantly greater for the filtering (food) screen (1.12 kg/sq m) than in any of the other treatments. The findings of the research indicate that use of screens is feasible and will not retard pod development. The presence of a perforated grid tended to result in lower phytomass production for `New Improved Spanish' peanut.

Free access

S. Burrell, D. Mortley, P. Loretan, A.A Trotman, P. P David, and G. W. Carver

The effects of light intensity on three sweetpotato cultivars [Ipomoea batatas (L.) Lam] were evaluated in growth chambers, as part of NASA's Closed Ecological Life Support Systems (CELSS) program for long duration space missions. Vine cuttings of `TI-155', `GA Jet', and TUJ1 were grown using nutrient film technique (NFT) in a modified half Hoagland's solution with a 1:2.4 N:K ratio in channels (0.15×0.15×1.2 m). Plants were exposed to irradiance levels of 360 or 720 umols m-2s-1 with an 18/6 photoperiod in a randomized complete block design with two replications. Temperature was set at 28:22 lightdark and RH was 70%. Differences in plant response to were more related to cultivars than the effect of light intensity. Storage root number (8) fresh, (786 g/plant) and dry weights (139 g/plant) were highest for `TI-155' while foliage fresh and dry weights were highest for `TUJ1' when averaged across light levels. TI-155' (921 g/plant) and `GA Jet' (538 g/plant) produced greater yields at higher irradiance. `TUJ1' produced a higher yield (438 g/plant at the lower intensity compared to 219 (g/plant) at the higher intensity, suggesting this cultivar could produce storage roots in similar conditions in a CELSS.

Free access

M.A. Sherif, P.A. Loretan, A.A. Trotman, J.Y. Lu, and L.C. Garner

Nutrient technique (NFT) and deep water culture (DWC) hydroponic systems were used to grow sweetpotao to study the effect of four nutrient solution treatments on: translocation of nutrients and plant and microbial population growth in split-root channels. 'TU-155'cuttings (15 cm) were prerooted for 30 days in sand in 4 cm CPVC pipes 46 cm in length. A modified half Hoagland (MHH) solution was supplied ad libidum. After 30 days, plants were removed and the roots of each plant were cleaned and split evenly between two channels (15 cm deep by 15 cm wide by 1.2 m long). four plants per channel. Nutrient solution treatments (replicated) were: MHH-MHH: MHH-Air, MHH-deionized water (DIW); and monovalent (Mono) - divalent (Dival) anions and cations. Solution samples were continuously collected at 7-day intervals for microbial population profiling. Plants were harvested after growing for 120 days in a greenhouse. Storage roots, when produced, were similar in nutritive components. However, no storage roots were produced in Air or Mono channels and only a few in DIW. Fresh and dry weights for storage roots and foliage were highest in MHH-MHH in both NFT and DWC in repeated experiments. Population counts indicated that nutrient solution composition influenced the size of the microbial population in NFT. Population counts were highest in Dival channels. The microbial population counts (4.20-7.49 cfu/mL) were. relatively high in both NFT and DWC systems.

Free access

P.P. David, A.A. Trotman, D.G. Mortley, C.K. Bonsi, P.A. Loretan, and W.A. Hill

Greenhouse studies were conducted to determine the effect of harvesting sweetpotato [Ipomoea batatas L. (Lam.)] foliage tips (terminal 15 cm) on storage root yield, edible biomass index (EBI), and linear growth rate. Plants were grown hydroponically from 15-cm vine cuttings planted in 0.15 × 0.15 × 1.2-m growth channels using a recirculating nutrient film technique system. Nutrients were supplied from a modified half-strength Hoagland solution with a 1 N: 2.4 K ratio. Foliage tips were removed at 14-day intervals beginning 42 days after transplanting. Final harvest was at 120 days after planting. At the end of the growing season, harvested foliage tips totaled 225 g/plant (fresh mass). Foliage removal significantly reduced storage root yield, shoot biomass, and linear growth rate expressed on a canopy cover basis. The EBI was higher for plants with foliage removed than for the control.

Free access

D.G. Mortley, P A. Loretan, A.A Trotman, P. P David, L.C Garner, and G. W. Carver

The effects of altering, nutrient solution N:K ratio on growth of `TI-155' sweetpotato [Ipomoea batatas (L.) Lam] was evaluated in a greenhouse, as part of NASA's Closed Ecological Life Support Systems (CELSS) program for long duration space missions. Vine cuttings of `TI-155', were grown using nutrient film technique (NFT) in a modified half Hoagland's solution in channels (0.15×0.15×1.2 m). Plants were grown for 42 days in a culture solution in which N was doubled (6 mM) in order to accelerate foliage growth after which treatment N:K ratios of 1:2.4, (control) 1:4.8, and 1:7.2 were initiated. A randomized complete block design with 4 replications was used. The number of storage roots/plant increased linearly as K was increased in the solution. Storage root fresh and dry weights, growth rate (g m-2 d-1), fibrous root dry weight, foliage fresh and dry weights, and edible biomass index (root mass/total plant mass), though not significant all increased as K was increased in the nutrient solution. Nutrient solution analyses showed that K uptake was greatest in plants at the highest K level, while nitrate uptake was steady over the duration of crop growth regardless of treatments.

Free access

S. Burrell, D. Mortley, P. Loretan, L. Garner, A. Trotman, P. David, and G. W. Carver

The effects of photoperiod and light intensity on two sweetpotato cultivars [Ipomoea batatas (L.) Lam] were evaluated in growth chambers. Vine cuttings of `TI-155' and `GA Jet' were grown using nutrient film technique (NFT) in a modified half Hoaglands solution with a 1:2.4 N:K ratio in channels (0.15×0.15×1.2 m). Plants were exposed to 9:600 or 18:300 umols m-2 s-1 photoperiod:light intensity treatments in a randomized complete block design with two replications. Temperature was set at 28:22 light:dark and RH was 70%. Storage root fresh and dry weights and fibrous root dry weight for both cultivars were significantly higher for plants exposed to longer photoperiod and lower light intensity than for those at a shorter photoperiod and higher light intensity. Foliage fresh weight for TI-155' was higher at 18:300 photoperiod:light intensity but dry weights were similar. Foliage fresh and dry weights for `GA Jet' and number of storagage roots/plant for both cultivars were similar regardless of treatments.

Free access

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

The effects of within-channel spacings (WCS; 13, 18, 25 cm) and between-channel spacings (BCS; 13, 25,38 cm) on yield and linear growth rate of sweetpotatoes [Ipomoea batalas (L.) Lam.] grown by use of the nutrient film technique (NFT) were evaluated. Storage root count, fresh and dry weights, and linear growth rate, expressed as root area, declined linearly in response to decreased BCS, while fresh and dry foliage weight decreased linearly and quadratically as spacing was reduced within the growth channels. Neither linear growth rate on a canopy area basis nor the edible biomass index was significantly affected by WCS or BCS.

Free access

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 sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.

Free access

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.