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H.T. Kraus, S.L. Warren, G.J. Bjorkquist, A.W. Lowder, C.M. Tchir and K.N. Walton

only main effects of species and ratio are presented. Number of flower buds, leaf dry weight, and leaf area increased linearly with decreasing N:P:K ratio (increasing P and K concentrations) to a maximum at a ratio of 2:1:2 (data not presented). However

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Zhongchun Jiang

Information about micronutrient concentrations of plants in general can be found in botany and plant physiology textbooks, but micronutrient concentrations in field-grown lettuce is hard to find and so are concentrations of heavy metals. Lettuce consumers may be concerned with heavy metal concentrations and information about heavy metal concentrations may help consumers make a choice. This study examined the concentrations of eight micronutrients and five heavy metals in field-grown lettuce with different fertilization programs. Under the field conditions, different NPK fertilizers and fertilization rates did not differ in the leaf concentrations of micronutrients and heavy metals. The overall means of Fe, Na, Mo, and Ni concentrations in the lettuce were 663, 710, 0.9, and 1.9 μg·g–1 of dry leaves, respectively. These values were significantly higher (over 500% greater) than the values found in textbooks for plants in general. Mean Mn, Cu, B, and Zn concentrations were 55.5, 7.3, 23.7, and 28.4 μg·g–1 of dry leaves, respectively, which are in general agreement with textbook values. Mean concentrations of heavy metals Cd, Co, Cr, and Pb were 1.5, 1.0, 2.9, and 4.5 μg·g–1 of dry leaves, respectively, whereas mean Al concentration was 498.5 micrograms per gram of dry leaves. These results indicate that concentrations of some elements in lettuce leaves can be high under certain field conditions. It would be beneficial for lettuce growers and consumers to have this information.

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Xenia Wolff

Chayote (Sechium edule Swartz) is a minor vegetable crop gaining in popularity in the U.S., but with only scant cultural information on it available. The soil pH and water requirements-and the effects of various soil amendments on plant productivity were detemined in three separate greenhouse pot studies. Chayote plants were grown in either one of eight soil pH levels (5.0 to 6.5), were watered at one of three rates (1.3, 2.5, or 5.0 cm per week), or were planted in one of 16 soil amendment treatments (Oliver silt loam soil or a 1 soil: 1 peat moss (v/v) mix amended with inorganic N-P-K fertilizer, 25 or 50 kg cow or rabbit manure/ha, or 12.5 or 25 kg chicken manure/ha). Data on date of germination, plant height, single and total leaf areas, total plant and separate plant part fresh and dry weights, and presence of flowers were collected. Greatest plant productivity was achieved with a soil pH range of 5.6 to 6.5, a watering rate of 2.5 cm per week, and with several of the soil amendment treatments.

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T. Tamada

The fertilizer responsiveness to macronutrients of `Woodard' was investigated to obtain the data for the recommended rate of fertilizer application in a rabbiteye blueberry.

One-year-old rooted cuttings of 'Woodard was grown under water culture in 1991. The plot was consisted of 13, a control (application rate: N-28, P-30, K-40, Ca-40, Mg-24 ppm) and 12 high volume application plots of macronutrients (applicated 5 times that of the control).

The growth (dry mater per bush) was most superior in the N+Mg plot, most inferior in the N+Ca, the other plots was medium. As compared with the control, the growth of N+Mg, P+K, P+Ca, P+Mg, K+Ca, K+Ca+Mg and Ca+Mg plots was better than the control, and the growth of N+K, N+P+K and K+Mg plots was below. The concentration of macroelements in leaves of the control plot was low among all of. In each plots of high volume application of macronutrients, the concentration of the macroelements in leaves with some exceptions, became high, and the interaction between nutrient elements was confirmed. The difference of the growth of `Woodard' was considerd to be caused not only by the excess of some macroelements but also the imbalance of certain elements in the leaf and root.

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John Clemens and R. Hugh Morton

Containerized plants of Heliconia psittacorum L.f. × H. spathocircinata Aristeguieta `Golden Torch' were grown in a greenhouse for 8 months from early summer to winter under selected combinations of N, P, and K. Fertilizer rates ranged from zero to rates that exceeded those reported in the literature by 50% to 100%. Biomass variables (vegetative and inflorescence dry weight, and leaf area) were predicted to be maximized at high N and high N to P, and N to K ratios corresponding to N-P-K application rates of 1.2, 0.5, and 0.6 kg·m-3, respectively (≈2:1:1). However, the number of shoots and flowers produced per rhizome were maximal at lower N to K ratios (1:1). Flower yield could therefore be optimized with appropriate fertilization, provided attention was paid to the N to K ratio so that the size of plants and their flowers was not compromised by efforts to increase shoot and flower number. The heavier the rhizome planted, the shorter the time for shoot emergence and flowering to occur, and the greater the number of flowers harvested. However, rhizome weight had no effect on number of shoots to emerge. The probability of shoots flowering declined markedly with order of shoot emergence, although this could be increased with appropriate mineral nutrition. The maximum number of leaves subtending the inflorescence (seven) was obtained at high N and P rates. Flower production was probably limited by declining solar radiation in autumn, and by within-plant competition for rooting space.

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Muhammad S. Hadi, William S. Conway and Carl E. Sams

An experiment was conducted to investigate the effect of Ca nutrition on yield and incidence of blossom-end rot (BER) in tomato. Three levels of Ca (low = 20 ppm, medium = 200 ppm, and high = 1,000 ppm; selected to represent very deficient, normal, and very high levels of calcium) were applied to three cultivars of tomatoes (`Mountain Supreme', `Celebrity', and `Sunrise'; selected to represent genetic differences in susceptibility to BER) grown in modified Hoagland solutions using a greenhouse hydroponic system. The experiment was constructed in a randomized complete-block design with three blocks, two replications, three cultivars, and three calcium treatments. The source of basic nutrients was a 5–11–26 soluble fertilizer containing micronutrients. The ratio of N–P–K was adjusted to 1.0–1.3–3.0 by adding NH4NO3 (34% N). Calcium was added as CaCl2. Nitrogen concentrations were maintained at 30 (first month), 60 (second month), and 90 ppm (during fruit growth), while the concentration of other nutrients followed proportionally. Cultivars differed significantly in yield and average fruit weight but not in incidence of BER or leaf Ca concentration. There was no cultiva × calcium treatment interaction. Leaf Ca content across cultivars was increased by 34% and 44%, respectively, by the medium and high Ca treatments. Average fruit weight and total yield per plant were not significantly different between the low and medium Ca treatments, however, both were reduced by the high Ca treatment. Incidence of BER was 95% higher in the low rather than in the medium Ca treatment. There was no significant difference in BER between the medium and high Ca treatments.

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Brian E. Whipker and P. Allen Hammer

`Supjibi' poinsettias (Euphorbia pulcherrima Willd.) were grown hydroponically for 15 weeks in nutrient solutions with 100-15-100, 200-30-200, or 300-46-300 (in mg·L-1 of N-P-K) to determine nutrient uptake patterns and accumulation rates. Results indicate that increasing fertilization rates from 100 to 300 mg·L-1 of N and K did not significantly influence the plant dry mass or the nutrient concentration of P, K, Ca, Mg, Na, B, Cu, Fe, Mn, Mo, and Zn in poinsettias. NH4-N concentration in the leaves, stems, and roots were lowest with the 100-mg·L-1 N fertilization rate and increased as the N application rate increased to 200 and 300 mg·L-1. Leaf P concentration levels from 1 week after potting through anthesis were above 1.3%, which exceeds the recommended level of 0.9%. When the plant tissue dry mass for each fertilizer rate was transformed by the natural log and multiplied by the mean tissue nutrient concentration of each fertilizer rate, there were no significant differences among the three fertilization rates when the total plant nutrient content was modeled for N, P, or K. Increasing the fertilizer application rate above 100 mg·L-1 N and K and 15 mg·L-1 P decreased total plant content of Ca, Mg, Mn, and Zn and increased the total plant Fe content. The results of the weekly nutrient uptake based on the total plant nutrient content in this study suggests that weekly fertilization rates should increase over time from potting until anthesis. Rates (in mg) that increase from 23 to 57 for N (with 33% of the total N supplied in the NH4-N form), 9 to 18.5 for P, 19 to 57 for K, 6 to 15 for Ca, and 3 to 8 for Mg can be applied without leaching to poinsettias and produce adequate growth in the northern United States.

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Michael P. Harvey and Mark H. Brand

Studies conducted in 1998 and 1999 analyzed the influence of division size, nutrition, and potting medium pH on the growth rate of Hakonechloa macra `Aureola' in nursery-container production. For each study, divisions were made from container-grown nursery stock in late March, then established in 325-mL pots in a greenhouse prior to being transplanted to 3.7-L nursery containers in late May. Grass plants were grown outdoors, under 30% shade density cloth, with drip irrigation from June through September, and, excluding plants in the nutrition study, received top-dressed 17-6-10 slow-release fertilizer containing micronutrients. To determine the optimum division size for production, divisions of four sizes were made (based on one to two, four to six, eight to 10, or 12 to 15 buds per plant). There was a significant division size effect on bud count, leaf area, plant weight, width, and shoot count only when comparing the two lowest division sizes with the two highest. Treatment effects were insignificant among divisions containing one to two and four to six buds, or between eight to 10 and 12-15 buds. Both the larger two sizes produced marketable plants; therefore, divisions with eight to 10 buds are recommended for a schedule aimed at producing salable Hakonechloa over one growing season. The smallest division class is believed to be the more efficient size when one merely wishes to increase plant stock. In a separate study, a factorial trial testing ppm fertilizer (28, 56, 112, 224, and 448 ppm N) and N-P-K formulation (1-1-1, 2-1-2 and 4-1-4) did not generate significant differences between formulations. Plants were fertigated once a week, and EC levels were monitored bi-weekly from leachate collected in drainage saucers. Plant responses to N rates suggest that electrical conductivity levels be kept around 2.5 mS·cm-1 from a 112 ppm N fertilizer (EC can go as high as 4.0 mS·cm-1 with 224 ppm N). It was evident H. macra `Aureola' prefers acidic soil in production. When lime was not included in the potting mixture (a control treatment equating to a pH of about 4.5), leaf area, bud count, and shoot number doubled relative to the three lime treatments (2, 6, and 16 g lime/L of media, or 3.4, 10.1, and 26.9 lb/yard3).

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Michelle S. McGinnis, Stuart L. Warren and Ted E. Bilderback

treatments, and stem and leaf dry weights of all 20VC treatments were greater than PBS + NPK ( Table 2 ). Flower bud dry weight and number were similar for all four treatments at 35 DAP. At 56 DAP, flower bud dry weight and number were similar for all three

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Richard J. Henny, J. Chen and D.J. Norman

Dieffenbachia ‘Tropic Marianne’ (U.S. Plant Patent No. 8832). ‘Tropic Honey’ was selected because of its showy yellow–green leaf color, similar to ‘Tropic Marianne’. It is highlighted by a bright white midrib and dark green margins. In addition, ‘Tropic Honey