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- Author or Editor: David R. Hershey x
Abstract
One of the most important aspects of the physics of growing media in containers is the limited bulk volume of the medium (2,4). Bulk volume (BV) includes the volume of the medium solids and pore spaces (1). Despite the importance of BV in determining the amounts of air, water, and nutrients in the pot, BV is rarely specified in research articles involving plant growth in container media. Without BV, volumetric properties, such as bulk density (g/ml), container capacity (percent by volume), air-filled porosity (percent by volume) and fertilization and liming rates (kg/m3), cannot be converted to absolute amounts per pot. The purpose of this study was to develop equations to calculate BV using pot dimensions and medium height in the pot.
Rose periwinkle (C. roseus `Little Linda'), a common bedding plant, grown in Hoagland solution #1 with Fe-EDTA at 5 mg/L Fe had normal shoot morphology, but abnormal root morphology. The primary root was twisted and lateral roots were extremely stunted with dichotomous branching. Over a dozen other bedding and foliage plant species had normal root morphology when grown in an identical solution, and cuttings from periwinkle with abnormal roots produced normal roots when rooted in 2 mM CaCl2. When these rooted cuttings were grown in Fe free Hoagland solution #1, root morphology was normal, indicating that the Fe-EDTA caused the problem. Seedlings were then grown in solution for 30 days with Fe supplied as Fe-EDTA (both 5 mg/L and 1 mg/L Fe), Fe-DPTA (5 mg/L and 1 mg/L Fe), Fe-EDDHA (2.75 mg/L and 0.55 mg/L Fe) or Fe2O3 (1 g/L). Solution pH for all were in a normal range of 4.8 - 5.6 Only the seedlings grown with Fe2O3, Fe-EDTA (5 mg/L Fe) and Fe-DTPA (5 mg/L Fe) developed abnormal root structure. All others had normal roots.
Abstract
Pot chrysanthemums (Chrysanthemum ☓ morifolium Ramat. ‘Bright Golden Anne’) were grown vegetatively for 5 weeks at 10 application rates of K. Two critical K levels were determined by correlating top fresh weights with K concentration in the most recently mature leaves. The critical foliar level associated with maximum yield was 2.3% K and that associated with 90% of maximum yield was 1.3% K. Potassium concentrations in leaves showing the earliest signs of K deficiency symptoms ranged from 0.6 to 0.7% K.
Abstract
Rooted cuttings of Euonymus japonica Thunb. were grown in solution culture for 3 months and rates of NO3 -, Ca2+, K+, and Mg2+ absorption were measured by their disappearance from solution. During shoot elongation, absorption rates for these ions declined and the pH of the nutrient solution decreased to about 4. As a flush of shoot elongation ended, the absorption rates for the ions rose to much higher levels and the pH of the nutrient solution increased to 6 or above. The changes in the nutrient solution pH appear to be caused by changes in the relative cation-anion absorption.
Fundamental research on mineral nutrition of azalea has been restricted due to the lack of a model experimental system for growing azaleas in solution culture. The need to maintain a clean root system dictates that azalea cuttings be rooted in solution. A propagation system (HortScience 24:706) was used to root 10-cm long terminal shoot cuttings of azalea `Delaware Valley White' under intermittent mist in a greenhouse. Cutting bases were dipped in 8,000 mg/liter K-IBA for 40 seconds before rooting. Rooting percentages after 7 weeks were 6, 10, and 50% for rooting solutions of tap water, modified 20% Hoagland solution, and 2mM CaCl2, respectively. After an additional 5 weeks the rooting percentage had increased to 83% in the 2 mM CaCl2 treatment. Three other azalea cultivars were found to root much slower than `Delaware Valley White'. Acclimatization of rooted cuttings to the normal greenhouse environment is essential to prevent leaf necrosis and is accomplished by gradually reducing the misting frequency prior to removal from under intermittent mist.
Fundamental research on mineral nutrition of azalea has been restricted due to the lack of a model experimental system for growing azaleas in solution culture. The need to maintain a clean root system dictates that azalea cuttings be rooted in solution. A propagation system (HortScience 24:706) was used to root 10-cm long terminal shoot cuttings of azalea `Delaware Valley White' under intermittent mist in a greenhouse. Cutting bases were dipped in 8,000 mg/liter K-IBA for 40 seconds before rooting. Rooting percentages after 7 weeks were 6, 10, and 50% for rooting solutions of tap water, modified 20% Hoagland solution, and 2mM CaCl2, respectively. After an additional 5 weeks the rooting percentage had increased to 83% in the 2 mM CaCl2 treatment. Three other azalea cultivars were found to root much slower than `Delaware Valley White'. Acclimatization of rooted cuttings to the normal greenhouse environment is essential to prevent leaf necrosis and is accomplished by gradually reducing the misting frequency prior to removal from under intermittent mist.
A Venturi-type proportioner (VP), trade name Hozon, can be used for an inexpensive, hands-on laboratory exercise that demonstrates the effect of water pressure on dilution ratio and water flow. Using electrical conductivity (EC) meters to determine solution concentration allows students to discover that the dilution ratio increases with water pressure, from 1:10 at 15 psi to 1:15 at 55 psi. The greater dilution at higher pressure can be explained by measuring the water flow, which is 2.3 gal/min (8.7 litersžmin-1) at 15 psi but 3.5 gal/min (13.2 litersžmin-1) at 55 psi. Experiments relating water pressure to dilution ratio provide experience in use and calibration of VPs and EC meters, as well as graph preparation and interpretation.
Single-pinched poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch `V-14 Glory') received 210 mg·L-1 constant N fertigation from Hoagland solution with N sources of 100% NO3-N or 60% NO3-N : 40% NH4-N, P concentrations of 7.8 or 23 mg·L-1, and leaching fractions (LFs) of 0, 0.2, or 0.4. The P fertigation rates did not significantly affect plant growth measurements and N leaching. Shoot dry masses and leaf and bract areas of plants fertigated with 60% NO3-N were 11% to 26% greater than those fertigated with 100% NO3-N. Shoot dry mass at the 0 LF was 27% smaller than those at the 0.4 LF. The total amount of N applied via fertigation was 1.7 g at the 0 LF and 3.3 g at the 0.4 LF. Leachate N concentration ranged from 170 to 850 mg·L-1. Nitrogen recovery was 74% to 91%, and the percentage of fertigation N recovered in leachate ranged from 51% at the 0.2 LF to 74% at the 0.4 LF. With a 0.4 LF and 210 mg·L-1 N fertigation, 15% to 22% of the recovered N was found in the shoots, and 68% to 75% was found in the leachate. Even with a 0.2 LF, >50% of the N recovered was found in the leachate. Premium marketable quality poinsettia were produced with N at 210 mg·L-1 from 60% NO3-N : 40% NH4-N fertigation solution at the 0.4 LF. To reduce N leaching to the environment, good marketable quality poinsettias could be grown at a LF of ≤0.2 with 210 mg·L-1 N fertigation if quality irrigation water is available and if a small reduction in growth is acceptable.
Poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch `V-14 Glory') grown as single-pinched plants and received constant fertigation of Hoagland solution with N at 210 mg·L-1 of 100% NO3-N or 60% NO3-N : 40% NH4-N; P at 7.8 and 23 mg·L-1; and leaching fractions (LFs) of 0, 0.2, or 0.4. The P at 23 mg·L-1 used in this study was about half the P concentration typically provided from a 20N-4.4P-16.6K fertilizer at 200 mg·L-1 N fertigation. The total P applied via fertigation ranged from 51 mg at the 0 LF to 360 mg at the 0.4 LF. The leachate P concentration ranged from 0.2 to 46 mg·L-1. With P at 7.8 mg·L-1, the percentage of total P recovered in the leachate was 6% to 7%. At 23 mg·L-1 P fertigation, however, the total P recovered in the leachate with 60% NO3-N treatment was 2-times greater than with 100% NO3-N treatment. This result is attributed to a lower substrate pH, which resulted from NH4-N uptake and nitrification processes with 60% NO3-N fertigation. The P concentration in the recently matured leaves with 7.8 mg·L-1 P fertigation was in the normal range of 0.3% to 0.6%. Fertigation P can be reduced by up to 80% and still be sufficient for producing quality poinsettias. Reducing the fertigation P concentration is beneficial because it reduces P leaching, reduces fertilizer costs, and reduces luxury consumption.