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  • Author or Editor: Harry A. Mills x
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Abstract

Multiple applications of nitrapyrin (5 ppm/pot/week) increased NO3-N retention significantly over the control, and medium NO3-N was consistantly higher with multiple applications than with a single preplant application of nitrapyrin (50 ppm) when NO3-N was the fertilizer source. Multiple applications of nitrapyrin were less effective in increasing plant growth than a single application with an NH4-N fertilizer source.

Open Access

Crop-specific tailoring of fertilizer composition and timing of application reduces expense and runoff pollution. We examined the effects N forms and ratios have on growth, development, and utilization of nutrients in poinsettia (Euphorbia pulcherrima Willd. Ex Klotz.). Rooted cuttings of poinsettia `Freedom' were grown to flowering (10 weeks) in aerated solution culture under greenhouse conditions. Treatments consisted of five N ratios (percent ammonium: percent nitrate) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg·L–1. Dry mass for all plant parts and height increased as the ratio of NO 3 increased. Leaf and bract areas were greatest with ratios of 25:75 and 50:50, respectively. Plants receiving 100% NH 4 + exhibited severe ammonium toxicity symptoms and uptake of all macronutrients was suppressed. Average weekly uptake of NH 4 + , NO 3 , P, and K was significantly affected by the treatments. Maximum uptake of NO 3 and K occurred with 100% NO 3 , P with 25:75, and NH 4 + with 100% NH 4 + . Uptake averaged across all treatments was divided into physiological growth stages (GS) to identify peak demand periods. The greatest uptake of NH 4 + and NO 3 was from the beginning of treatments to floral induction (GSI). Uptake of P, K, and Mg peaked at GSII, floral induction to visible bud. Visible bud to anthesis (GSIII) had the lowest uptake for all nutrients. These results demonstrate how NH 4 + : NO 3 ratios and stage of development can influence growth and nutrient absorption.

Free access

Mature zucchini squash plants (Cucurbita pepo L.) were grown under four NO3:NH4 ratios (1:0, 3:1, 1:1, and 1:3) to determine effects on macronutrient nutrition. Plants were grown in solution culture under greenhouse conditions. Treatments were applied at first bloom. Highest uptake of Ca and Mg occurred in the 1:0 NO3:NH4 treatment while higher K uptake was found in the 3:1 NO3:NH4 treatment. Total nitrogen uptake was greatest in the 1:1 and 3:1 NO3:NH4 treatments. A 3:1 NO3:NH4 ratio applied at first bloom gave best overall uptake of N, K, Ca, and Mg.

Free access

Mature zucchini squash plants (Cucurbita pepo L.) were grown under four NO3:NH4 ratios (1:0, 3:1, 1:1, and 1:3) to determine effects on macronutrient nutrition. Plants were grown in solution culture under greenhouse conditions. Treatments were applied at first bloom. Highest uptake of Ca and Mg occurred in the 1:0 NO3:NH4 treatment while higher K uptake was found in the 3:1 NO3:NH4 treatment. Total nitrogen uptake was greatest in the 1:1 and 3:1 NO3:NH4 treatments. A 3:1 NO3:NH4 ratio applied at first bloom gave best overall uptake of N, K, Ca, and Mg.

Free access

Nutritional levels of mature vs. young leaves of Anthurium (Anthurium andraeanum Linden.) cultivars were determined over a seven year period. Nutritional levels for essential nutrients tested (B, Ca++, Cu++, Fe++, K+, Mg++, Mn++, Mo-, P, and Zn++) were determined with inductively coupled plasma emission spectrometry. Kjeldahl N was determined with a flow injection analyzer. The young leaf, 90% mature, was determined to be the most accurate predictor of the nutritional status of anthuriums. These values were established for the cultivars `Kozohara', `Nitta Orange', `Kaumana', and `Ozaki'.

Free access

Abstract

The establishment of an average elemental composition for snap bean to satisfy nutritional labelling requirements is probably not possible. Analysis for the elemental content of 40 frozen snap bean samples collected at 8 locations in the United States revealed a wide range in concentration for the 18 elements determined. Several causes for this wide variation are suggested.

Open Access

Abstract

In a laboratory incubation study with soil inoculum, terrazole [5-ethoxy-3(trichloromethyl)1,2,4 thiadiazole] at 0.02 to 200 ppm in liquid culture suppressed N2 and N2O evolution and increased NO3-N retention. A Cecil clay soil, treated with terrazole at concentrations of 0.5 and 2.0 ppm, retained more NO3-N than the control in a greenhouse study.

Open Access

Abstract

Inhibition of N2 and N2O evolution from a liquid medium inoculated with soil was obtained with low levels (0.2, 2, and 20 ppm) of 2-chloro-6-(trichloromethyl)pyridine. Concurrent with the reductions in N2 and N2O evolution was increased NO3 retention in the medium. Results from this study confirm that nitrapyrin effectively inhibits denitrification in vitro at rates comparable to that applied in the field.

Open Access

Abstract

N-demand periods and the form and quantity of N absorbed during the growth cycle of sweet corn (Zea Mays L.) was determined for ‘Silver Queen’ grown in solution culture with a N ratio of 50% NO3–50% NH4. Absorption of NO3 and NH4 were similar up to the tasseling stage. During the tasseling stage, NO3 was absorbed at rates greater than NH4, while during the ear development stage NH4 was absorbed at rates higher than NO3. Evaluation of N demand during the growth cycle shows that 60% of the total N absorbed occurred during the tasseling-ear development stage. These results indicate that with ‘Silver Queen’, greater efficiency of applied N fertilizer can be obtained by correlating rate of N and form of N to a specific growth stage.

Open Access

Brassica species are important economic vegetable crop, and it is possible to enrich them with selenium (Se) to supplement human diets. The health benefits associated with increased Se consumption include cancer suppression, reduced heart disease, and immune system enhancement. Vegetables enriched with Se can serve as excellent delivery systems of organic Se forms, which are more beneficial than traditional Se supplements. The vegetable Brassicas are consumed not only for their flavor, but also for their nutritional content. A heterogeneous population of rapid-cycling B. oleracea was used as a model system to study the effects of added selenate-Se on other plant micro- and macronutrients. Plants were grown in nutrient solutions amended with sodium selenate at 0.0, 3.0, 6.0, and 9.0 mg·L–1. Leaf tissues were then analyzed for nutrient content. Boron (P = 0.001) and iron (P = 0.01) content decreased, while selenium (P = 0.001), sulfur (P = 0.001), and potassium (P = 0.001) increased with increasing selenate-Se. Significant quadratic responses were found for calcium (P = 0.02), copper (P = 0.05), magnesium (P = 0.01), and molybdenum (P = 0.01). No differences in leaf fresh or dry weight were detected. Changes in plant nutrient content can be expected when Brassicas are enhanced for delivery of beneficial organic Se.

Free access