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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% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} exhibited severe ammonium toxicity symptoms and uptake of all macronutrients was suppressed. Average weekly uptake of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} , \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} , P, and K was significantly affected by the treatments. Maximum uptake of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and K occurred with 100% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} , P with 25:75, and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} with 100% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} . Uptake averaged across all treatments was divided into physiological growth stages (GS) to identify peak demand periods. The greatest uptake of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} 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 \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}:\mathrm{NO}_{3}^{-}\) \end{document} ratios and stage of development can influence growth and nutrient absorption.

Free access

Abstract

Nitrate and NH 4 + absorption by southernpeas (Vigna unguiculata (L.) Walp.) during the growth cycle was determined in solution culture at 7-day intervals. Dry weight and total mg of N for each plant part were determined at bloom initiation, pod initiation, and seed maturity. When the N concentration was deficient virtually all of the N 3 was absorbed by southernpea plants from the 3rd week until harvest. At sufficient N concentrations a single peak N 3 uptake period occurred in the growth cycle prior to bloom initiation. Nitrate absorption predominated when NH 4 + constituted 50% or more of the N form at both N concentrations. Ammonium had either 1, 2 or 3 absorption peaks depending upon its relative concentration with NO 3 . The first NH 4 + absorption peak was the largest and coincided with the growth cycle just prior to bloom initiation. Dry weight and N accumulation were greatest prior to bloom initiation. Subsequent accumulation occurred primarily in the seed. A reduction in N content and dry weight in the vegetative portions, particularly the leaves, coincided with the accumulation of N and dry weight in the seeds. Use of total mg of N in the vegetative tissue as a means of indicating the N status of the plant and subsequent yield was not accurate.

Open Access

Abstract

A commercial formulation of 2-chloro-6-(trichloromethyl)-pyridine (nitrapyrin) was incorporated within the N-fertilizer band in 2 consecutive years under widely different environmental conditions to evaluate the effect of nitrapyrin on denitrification occurring with field-grown sweet corn (Zea mays L.). Nitrapyrin significantly increased soil NO 3–N levels, total plant N, and yield; decreased rates of N2O evolved from the soil with both NH+ 4 and NO 3 forms of N-fertilizer. Denitrification appears to be a significant factor influencing the growth of sweet corn under field conditions, and nitrapyrin effectively inhibits the denitrification process.

Open Access

Abstract

Use of electrostatic spray deposition for the control of insect infestation in broccoli (Brassica oleracea L., Italica group) resulted in equal or greater control in comparison to conventional methods, and utilized ½ to 1/3 the quantity of insecticide with an 8-fold reduction in application volume. Laboratory tests documented a 1.86-fold improvement in the quantity of spray tracer deposited electrostatically onto broccoli plants as compared with conventional application.

Open Access

`Freedom' poinsettias (Euphorbia pulcherrima Willd. ex Kl.) were grown to flowering in solution culture for 11 weeks. Treatments consisted of five ammonium: nitrate nitrogen ratios: 1:0, 3:1, 1:1, 1:3, and 0:1 with a total N concentration of 150 mg N/liter. The balance of essential nutrients was supplied with a modified Hoagland's solution. Fresh weight, dry weight, and macro- and micronutrient content of bracts, leaves, petioles, stems, and roots were determined at the end of the study. Leaf and bract area also was measured. Maximum bract size was achieved with 100% nitrate (0:1) treatment. Leaves were largest with the 1:3 ratio. Plants receiving ammonium as the sole N source exhibited severe ammonium toxicity symptoms: stunted growth, foliar chlorosis and necrosis, premature leaf abscission, stunted and clubby roots, and delayed or nonexistent bract coloring. Dry weights for bracts, leaves, stems, and roots increased as the ratio of nitrate increased. Elemental uptake was monitored weekly. Nitrogen-form effect on the uptake, concentration, and partitioning of other nutrients also was evaluated.

Free 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

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

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