Container-grown plants of sweet gum (Liquidambar styraciflua L.) were transplanted to the Held and soil moisture tension of the transplanted rootball was recorded following transplantation and irrigation. Tension in the transplanted rootball increased more rapidly than in the control or in the soil adjacent to the rootball. Greater moisture loss from the transplant is attributed to loss of available water from the rootball as a result of drainage by the field soil profile following irrigation. To avoid moisture stress irrigation frequency of a new transplant may need to be even greater than required had it remained in the container.
Chrysanthemum cuttings were rooted in peat having different levels of exchangeable Mg and Ca. When exchangeable Mg was greater than 80% rooting was severely impaired. Mist waters containing increasing proportions of Mg caused rooting failure in both sand and peat when the percentage of total cations was 70% Mg. Ca deficiency symptoms developed in the highest Mg mist treatment. Leaching of Ca from the leaf is indicated.
An aspect of mist propagation which may be important in rooting cuttings is the quality of water used in misting. This may be particularly important in arid regions where many waters contain significant concentrations of salts. Although waters have been classified (1) for general irrigation purposes on the basis of total salts, sodium rating, boron concentration, etc., the propagator sometimes overlooks these properties of his mist water.
The construction and evaluation of a small, inexpensive tensiometer fitted with a pressure transducer (PT) and suitable for container media measurements is presented. The PT must be calibrated against known tensions before use, because the millivolt output from the PT varies with input voltage. The air volume above the liquid in the tensiometer that is sampled by the PT should be about 0.25 ml for an accurate (within 4%) and quick (10-20 sec) response. Tension measured with a PT was nearly identical to that measured with a mercury manometer in the range from 6.8 to 196 kPa (7-200 cm of water) during dry-down of a container with a plant (Paulownia tomentosa).
Chrysanthemum morifolium cv. Brilliant Anne was grown in 13 different media under frequent irrigation such that all media were nominally at container capacity. Media were selected to represent a range in airfilled porosity (0–20%) at container capacity with a depth of 12 cm. Substantial addition of organic amendment (40–90% v/v) improved aeration in a poorly aggregated loam and in two sands. Peat plus vermiculite had the best aeration of all media. Thirty day top yields were related to aeration properties of the media measured at container capacity. A value of 10–15% air-filled porosity was generally related to best growth. Oxygen diffusion rate (ODR) for the medium profile provided a better correlation with plant growth than air-filled porosity. A profile ODR of 45g O2 × 10‒8 cm-2 min-1 and above gave best growth.
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.
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.
Nitrogen leaching losses of 21, 40 and 49% were measured from container-grown `Royalty' roses irrigated for one year with nutrient solutions containing 77, 154 and 231 mg N/l. There were no significant differences in number of flowers per plant or dry matter per plant. The N present in the harvested flowers accounted for 43, 27 and 17% of the N applied for the 77, 154 and 231 mg N/l treatments, respectively.
Plants receiving 154 mg N/l at leaching fractions of 0.1, 0.25 and 0.5 had corresponding N leaching losses of 22, 38 and 56%. In this experiment, however, the 0.5 leaching fraction produced yields significantly higher than those of the 0.1 and 0.25 treatments. The N recovered in the harvested flowers accounted for 28, 25 and 19% of that applied to the 0.1, 0.25 and 0.5 treatments, respectively.
The results of these studies suggest that modifications in current irrigation and fertilization practices of greenhouse roses would result in a considerable reduction of N leaching losses and enhance N fertilizer use efficiency, without loss of cut flower yield and quality.
N deprivation is known to increase the rate of N uptake by graminaceous plants, but such response has not been reported for mature woody plants. A recirculating nutrient solution system was utilized to study the effect of intermittent N-deprivation on N uptake by mature `Royalty' rose plants. Plants received a nutrient solution lacking N for 4, 8 or 16 days, after which one containing N was supplied for 4 days. N-deprivation resulted in a 2-3 fold increase in N uptake rate compared to control plants supplied continuously with N (e.g., 143 vs 62 mg N plant-1 day-t). The magnitude of this deprivation-enhanced N uptake was not affected by either the duration of N-deprivation or the plant developmental stage.
A characteristic diurnal pattern of N uptake was observed in both N-starved and control plants. Uptake oscillated between minimum rates in the morning and maximum rates in the evening, the latter occurring 4-6 hr after the maximum transpiration rates.
The ability to increase the rate of N uptake in roses by depriving them of N for several days may be of practical importance for increasing N fertilizer use efficiency and decreasing N losses to leaching.
N uptake by greenhouse roses is out of phase with flower shoot elongation, such that N uptake is highest when shoots are not growing and lowest when shoots are elongating rapidly. Isotopically labelled 15N fertilizer was supplied at different stages of one flowering cycle to `Royalty' rose plants growing in a static nutrient solution system to study the partitioning of recently-absorbed N and the dynamics of N partitioning. After a two-day exposure, whole plants were harvested, separated into old and new leaves, stems, and roots, and analyzed for total N and 15N enrichment. During rapid shoot elongation, N uptake by roots supplied 16 to 36% of shoot N demand. The remaining N came from other organs, particularly old stems and leaves. The increased N uptake later in the flowering cycle was sufficient to meet shoot N demand and replenish the N supply in old foliage and woody tissues. These organs continued to accumulate N until the subsequent bud break, when this N became available for the next cycle of flowering shoot growth.