fertilizers provide nitrogen in one or both of these forms. The optimal NH 4 :NO 3 ratio depends on many factors, such as plant species, age of the plant, application timing, climate, and location ( Marschner, 2012 ). The responses of plant growth to N forms
Plant height, flower diameter, days to flower, and longevity of `Iridon' chrysanthemums [Dendranthemum × grandiflorum (Ramat.) Kitamura] were not affected by various N and K concentrations (112, 225, 337, and 450 mg·liter-1) supplied during the last 5 weeks of production. However, increasing N concentration increased medium conductance, while varying K concentration had no effect on conductance. Visual grade of `Iridon' after 3 weeks in a simulated interior environment showed an interaction between concentrations of N and K. In a second study, growth and longevity of `Iridon' were affected by NH4: NO3 ratios. Plants receiving a 0:1.0 ratio flowered 4 days later than plants receiving a 0.5:0.5 ratio and were taller than plants fertilized with a 1.0:0 ratio. Longevity was greater in plants receiving a 0:1.0 ratio than in those receiving 0.5:0.5 or 0.75:0.25 ratios. Also, longevity was similar in plants receiving NH4: NO3 ratios of 0:1.0, 0.1:0.9, 0.2:0.8, and 0.3:0.7. Plants receiving 0:1.0 lasted 6 days longer than those receiving a 0.4:0.6 ratio.
Abstract
Productivity of carnation (Dianthus caryophyllus L.), was increased to levels attained by C4 plants, such as corn, by adjusting the ratio of ammonium to nitrate N supplied to seasonal solar radiation levels. During periods of low solar radiation, the optimum ratio was one third ammonium and two thirds nitrate N. During periods of highest solar radiation, 100% nitrate was best. At high radiant intensity, reduction of nitrate N in carnation, a C3 plant, apparently increased net CO2 assimilation (growth) by decreasing photorespiration. Nitrate reduction served as an alternate sink for excess photosynthetic energy.
Abstract
The effect of N source (
study were 1) to quantify the effects on root zone pH for eight vegetable and herb species grown in peat-based substrate and hydroponic nutrient solution, and 2) to determine specific NH 4 + :NO 3 – ratios for each species estimated to have a neutral pH
, petunia, and pelargonium, along with six other bedding plant species, were grown with WSF that had NH 4 + :NO 3 – ratios of 40:60, 20:80, or 3:97 at 100 mg·L −1 N. A second experiment focused on the effect of N concentration and water alkalinity with
Abstract
Muskmelon (Cucumis melo L.) ‘Harvest Queen’ was grown in sand culture to investigate the effects of NH4:NO3 ratios on melon growth and elemental composition. Plants grown at NH4:NO3 ratios of 98:14, 84:28, and 56:56 developed NH4 toxicity symptoms, whereas plants grown with 20 ppm Mn and NH4:NO3 ratios of 0:112, 14:98, 28:84, and 56:56 developed Mn toxicity symptoms. Increasing the proportion of NH4 in nutrient solution up to 1:1 with NO3 decreased Mn concentrations in plant tissues and alleviated Mn toxicity symptoms, whereas at NH4:NO3 ratios of 84:28 and 98:14 uptake of Mn was inhibited and never reached a concentration in the tissue that developed toxicity symptoms. Shoot and root growth was greatest when grown at the 14:98 NH4:NO3 ratio. Increasing NH4 in the solution beyond 14 ppm in the 112-ppm N mixture resulted in increasing limitation of growth. Increasing Mn concentration in the nutrient solution to 20 ppm restricted growth at NH4:NO3 ratios ≤1. However, Mn treatment did not influence the growth of plants grown at NH4:NO3 ratios >1 at 84:28 and 98:14.
that all N was taken up in the anionic NO 3 − form. Species and solution NH 4 + :NO 3 − ratio were evaluated for effects on substrate-pH and meq of acid or base produced per L of substrate. Species were separated into clusters that corresponded to
The objectives of the present research were to study the effects of pH, NH4:NO3 ratio, and P concentration in the nutrient solution on development of Leucadendron R. Br. `Safari Sunset' [L. salignum Bergius × L. laureolum (Lam.) Fourc.]. The experiment was conducted in aero-hydroponic systems and involved six treatments in a nonfactorial design: two pH levels (5.5 and 7.5), two P levels (7 and 20 mg·L–1), and two NH4:NO3 ratios (60:40 and 25:75). The pH of the root environment was the most important factor controlling growth. Root cells were longer in plants grown at pH 5.5 than at pH 7.5, but width was not affected. Altering the NH4:NO3 ratio did not affect development regardless of pH. Increasing the P concentration from 7 to 20 mg·L–1 significantly decreased root fresh weight at the low pH and slightly reduced shoot growth. Nitrogen, P, K, Zn, and Mn concentrations were higher, while that of Fe was lower in plants grown at low pH. Reducing the NH4:NO3 ratio did not affect N concentration but increased P and K concentrations in the shoots. Increasing the P concentration significantly raised the P content of shoot and root tissues but reduced the content of Fe, Zn, and Mn.
Abstract
Stem caliper and sum of lateral branch lengths of container-grown Quercus shumardii seedlings increased more in 13 months when fertilized with 75:25, 50:50, 25:75 and 100:0 (NH4:NO3) ratios than with 100% NO3-N, regardless of fertilization rate. Stem caliper increased as fertilization rate increased from 5.7 to 11.4 g N/container yr. Height was unaffected by NH4:NO3 ratio or fertilization rate. Chlorosis was evident on plants that received 50% or more NO3-N. Media pH decreased with increasing NH4- N, and leaf N concentration increased from 1.16% with 100% NO3-N to 1.57% with 100% NH4-N.