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P. J. Ndolo and E. G. Rhoden

Root growth of sweet potato [Ipomoea batatas (L) Lam.] cvs `TI-82-155', `Centennial' and `Rojo Blanco' in coarse fritted clay soil, was investigated under greenhouse conditions. The sweet potato cultivars were harvested at 41 and 82 days after planting. Dry weight of fibrous roots of all cultivars were similar at day 41. Fibrous root weight of `Rojo Blanco' increased by 5% while those of the other cultivars increased by 168%. Mean fibrous root length per centimeter depth was not significantly different among cultivars. Although fresh weight of storage roots of `Rojo Blanco' was significantly lower than those of the other cultivars, their dry weights were similar. `TI-82-155' and `Rojo Blanco' had fewer storage roots compared to the other cultivars, however, storage root length of `TI-82-155' or `Rojo Blanco' was greater than that of `Georgia Jet' or `Centennial'. Length to diameter ratio of the storage root of `Rojo Blanco' was significantly greater than that of `TI-82-155' and `Georgia Jet'.

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P.J. Ndolo, E.G. Rhoden, and G. W. Carver

A greenhouse study was conducted to investigate the uptake, accumulation and percent recovery of N, P, K, Ca and Mg by sweet potato (Ipomoea batatas) cv `TI-155', `Centennial', `Georgia Jet' and `Rojo Blanco'. These cultivars were grown in a fritted clay medium and harvested after 42 and 32 days. There were no significant difference in total elements uptake among the cultivars at 42 days. However, Georgia Jet accumulated more P and K than TI-155 and had higher levels of K than Rojo Blanco at day 82. Total accumulation of elements increased significantly from 42 to 82 days. Leaves accounted for most of the plant N at both harvest periods. Storage roots contained significantly more K than leaves, vines or fibrous roots. Percent N, P and K uptake was significantly lower at 42 than at 82 days. Cultivars also had no significant difference in percent uptake at day 42. However, at day 82, Georgia Jet showed a significantly higher P and K percent recovery than Rojo Blanco.

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P. J. Ndolo and E. G. Rhoden

Root growth of sweet potato [Ipomoea batatas (L) Lam.] cvs `TI-82-155', `Centennial' and `Rojo Blanco' in coarse fritted clay soil, was investigated under greenhouse conditions. The sweet potato cultivars were harvested at 41 and 82 days after planting. Dry weight of fibrous roots of all cultivars were similar at day 41. Fibrous root weight of `Rojo Blanco' increased by 5% while those of the other cultivars increased by 168%. Mean fibrous root length per centimeter depth was not significantly different among cultivars. Although fresh weight of storage roots of `Rojo Blanco' was significantly lower than those of the other cultivars, their dry weights were similar. `TI-82-155' and `Rojo Blanco' had fewer storage roots compared to the other cultivars, however, storage root length of `TI-82-155' or `Rojo Blanco' was greater than that of `Georgia Jet' or `Centennial'. Length to diameter ratio of the storage root of `Rojo Blanco' was significantly greater than that of `TI-82-155' and `Georgia Jet'.

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E. G. Rhoden, P. J. Ndolo, and G. W. Carver

A greenhouse study was conducted to investigate the ability of sweetpotato (Ipomoea batatas), cv. `Centennial', `Rojo Blanco', `Georgia Jet' and `TI-82-155', fibrous roots to accumulate N, P, K, Ca and Mg. Sweetpotato plants were grown in a fritted clay medium and harvested 42 and 82 days after planting. Fibrous roots comprised 22 to 28.1% and 3.9 to 11.1% of the plant dry weight at 42 and 82 days after planting, respectively. There was no difference in the average root length/cm depth of soil among the four sweetpotato cultivars at day 42. While there was no difference in average root length among `Centennial', `Rojo Blanco' and `TI-82-155', these cultivars were significantly different from `Georgia Jet' at day 82. For the four cultivars, there were no significant differences in N, P, K, Mg and Ca Uptake at day 42, but each cultivar absorbed significantly more of each element 82 days after planting. `Georgia Jet' absorbed significantly more of the nutrients measured than the other cultivars, resulting in the highest dry matter yield. The data show that the efficient uptake and utilization of nutrients by sweetpotato are related to the amount of fibrous roots present.

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Susan L. Steinberg, Gerard J. Kluitenberg, Scott B. Jones, Nihad E. Daidzic, Lakshmi N. Reddi, Ming Xiao, Markus Tuller, Rebecca M. Newman, Dani Or, and J. Iwan D. Alexander

Baked ceramic aggregates (fritted clay, arcillite) have been used for plant research both on the ground and in microgravity. Optimal control of water and air within the root zone in any gravity environment depends on physical and hydraulic properties of the aggregate, which were evaluated for 0.25-1-mm and 1-2-mm particle size distributions. The maximum bulk densities obtained by any packing technique were 0.68 and 0.64 g·cm-3 for 0.25-1-mm and 1-2-mm particles, respectively. Wettable porosity obtained by infiltration with water was ≈65%, substantially lower than total porosity of ≈74%. Aggregate of both particle sizes exhibited a bimodal pore size distribution consisting of inter-aggregate macropores and intra-aggregate micropores, with the transition from macro- to microporosity beginning at volumetric water content of ≈36% to 39%. For inter-aggregate water contents that support optimal plant growth there is 45% change in water content that occurs over a relatively small matric suction range of 0-20 cm H2O for 0.25-1-mm and 0 to -10 cm H2O for 1-2-mm aggregate. Hysteresis is substantial between draining and wetting aggregate, which results in as much as a ≈10% to 20% difference in volumetric water content for a given matric potential. Hydraulic conductivity was approximately an order of magnitude higher for 1-2-mm than for 0.25-1-mm aggregate until significant drainage of the inter-aggregate pore space occurred. The large change in water content for a relatively small change in matric potential suggests that significant differences in water retention may be observed in microgravity as compared to earth.

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Stephanie Rademan and Dyremple Marsh

A wide range of methodologies, ranging from Leonard jar to growth pouch have been used to investigate the nitrogen fixation process in leguminous crops. The effectiveness of most of these research methods have been questioned. Problems encountered vary from difficulty in root separation to water log conditions. This study was undertaken to determine the effect of different growing media on nodule development and harvestability. Black and Red seed coat kidney bean were surface sterilized and inoculated with the Rhizobium phaseoli strain UMR 1899. Seeds were planted in 8.5 cm diameter sterile clay pots containing the respective growing medium. These growing media were sand, Promix GM, Promix BX, and fritted clay. The black seed coat kidney bean had higher germination rate under all media for all dates recorded. Black kidney bean grown in sand and fritted clay had plant heights significantly greater than ones grown in the other media on the third harvest date. Nodule activities as measured by shoot dry weight and nodule number were significantly higher in both beans grown in fritted clay than in other media. Promix GM plants with dry weight of .45g for the black bean and .32g for the red beans were the lowest. Nodule separation from the growing media was easiest when plants were grown in sand, however, this was not significantly different from that of plants grown in fritted clay.

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Jinmin Fu, Bingru Huang, and Jack Fry

’ tall fescue were collected from the field on 4 Nov. 2001 and planted on a mixture of sand and fritted clay [9:1 (v:v); Profile Products, Deerfield, IL] contained in PVC tubes (10 cm diameter × 40 cm long). The grasses were grown for ≈90 d in growth

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Jonathan N. Egilla

Four-week-old seedlings of Scarlet eggplant (Solanum integrifolium Poir.), a short-day fruiting vegetable, were grown for 20 weeks in a greenhouse (G/H) from 14 Mar. to 2 Aug. 2005. Mean daily photosynthetic photon flux in the G/H was about 480, 349 and 71 μmol·m–2·s–1 above-, within canopy; and at pot level, respectively in July. Seedlings were grown either in Turface® (fritted clay) or fine sand. Fertilizer treatment consisted of 5 g Osmocote® (18% N-6% P2O5-12% K2O) per pot, plus 100 mL of Peat-lite® (15% N-16% P2O5-17% K2O) solution at 200 mg·L-1 of N twice weekly, or Peat-lite only. Seedling growth (plant height, leaf number) during the first 12 weeks in both growing media was similar regardless of fertilizer treatment. The number of lateral shoots (not fruit number, FRN) increased from early fruit set (week 14) until termination (week 20), but there were no significant (P = 0.05) growing media or fertilizer treatment effects. While root dry mass was similar in both growing media, shoot dry mass was significantly (P < 0.0001) increased in fritted clay. Conversely, FRN and fruit dry mass (FDM) were, respectively, 8- and 11-fold greater in sand compared with fritted clay. Fertilizer treatment had no significant (P = 0.05) effect on both FRN and FDM either in fritted clay or sand. These trends indicate that S. integrifolium can produce limited amounts of fruit under the long daylength conditions of the summer at reduced irradiance, but factors determining shoot growth may have significant influence on fruit yield under this condition.

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J.B. Beard, R.L. Green, and S.I. Sifers

Cultivar selection is one method used for the conservation of irrigation water. The primary objective of this research was to evaluate the evapotranspiration (ET) rates of 24 well-watered, turf-type bermudagrass (Cynodon spp.) genotypes under field conditions and established on a fritted clay root zone contained in plastic minilysimeter pots. A secondary objective was to correlate ET rate to leaf extension rate, a potential rapidly assessed predictor of the amount of leaf surface area present for ET. ET rates were determined by the water-balance method. Both the overall ET and leaf extension rate differed significantly among genotypes. ET rates were not correlated with leaf extension rates in individual years. Our data indicated a potential for water savings based on bermudagrass cultivar selection that was similar to the reported potential water savings based on warm-season turfgrass species selection.

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Patricia R. Knight, James R. Harris, and Jody Fanelli

Bareroot Corylus colurna were grown in 7.5-liter containers from 11 Apr. until 27 June 1994. The growing medium was fritted clay. Fertility levels included no fertilization, 100 ppm N, or 200 ppm N. Plants were root pruned to remove none or one-quarter to one-half of the primary roots. Root pruning at any level resulted in decreased height, shoot, and root dry weights and number and length of new shoots. One-quarter primary root removal resulted in lower root: shoot ratios compared to plants that were unpruned. One-half primary root removal further reduced root: shoot ratios. One-half primary root removal also reduced total leaf area compared to unpruned controls. Fertilization at 200 ppm N increased leaf numbers and total leaf areas compared to plants receiving no fertilization.