Thomas H. Yeager

EFFECT OF PETUNIA STOCK PLANT NUTRITIONAL STATUS ON FERTILIZER RESPONSE DURING PROPAGATION

Fertilization strategies during stock plant and cutting production are linked in terms of cutting nutrient levels and quality. Objectives were to evaluate (1) the effect of stock plant nutrition on tissue nutrient concentration and growth during vegetative propagation and (2) response to fertilizer during propagation for cuttings with 4 different initial tissue nutrient concentrations. ‘Supertunia Royal Velvet’ petunia stock plants were grown under constant fertigation of 0, 50, 100 or 200 mg nitrogen (N).L−1 for 21 days. The 200 mg N.L−1 solution contained 150 nitrate (NO3-N), 50 ammonium (NH4-N), 24 phosphorus (P), 166 potassium (K), 40 calcium (Ca), 20 magnesium (Mg), 0.7 sulfur (S), 1.0 iron (Fe), 0.5 manganese (Mn), 0.5 zinc (Zn), 0.24 copper (Cu), 0.24 boron (B), and 0.1 molybdenum (Mo). Providing a complete fertilizer during propagation of petunia, beginning immediately after sticking of cuttings, reduces the risk of nutrient deficiency. Particularly in situations where fertilizer is not applied early during propagation, stock plants should be managed to ensure unrooted cuttings have adequate nutrient reserves.

NEW IRRIGATION-PLANT PRODUCTION SYSTEM FOR WATER CONSERVATION IN ORNAMENTAL NURSERIES: QUANTIFICATION AND EVALUATION OF IRRIGATION, RUNOFF, PLANT BIOMASS, AND IRRIGATION EFFICIENCIES

A new irrigation/plant production system, Multi-Pot Box System (MPBS), was field-evaluated during the two growing seasons (summer and fall, 2001) for efficient use of irrigation and rainfall for container nursery plant production. The system was compared to the conventional system (CS) irrigated with overhead sprinklers. Viburnum odoratissimum (Ker-Gawl.) was grown as a test plant. The following treatments were imposed: (i) three white color MPBSs with side-mount water level switches installed at 0.01, 0.02, and 0.03 m from the bottom of the system reservoir, (ii) three black color MPBSs with level switches installed at the same depths as in the white MPBSs, and (iii) control (CS). The level switches controlled the water levels at pre-determined levels and triggered irrigations automatically at these threshold levels. The white and black MPBSs were very effective in increasing irrigation water use efficiencies (IWUE), rainfall harvesting, and plant biomass production as compared to the CS. For example, in the summer season, only about 30% of the plant water use in the MPBSs was supplied by irrigation water, thus, reducing irrigation requirements and resulting in high IWUE. The color of the MPBS had a significant effect on plant growth but no significant effect on irrigation demand or runoff. The water use efficiencies and plant biomass production of the white MPBS were significantly greater (p < 0.05) as compared to the black MPBS. The efficiencies and plant biomass production of the black MPBS were significantly greater than the CS. In the fall, the white and black MPBS with level switches installed at 0.01 m resulted in the lowest irrigation demands. In the summer, about half of the total rainfall (320 mm) was captured in the reservoir of the MPBSs. In the fall season, approximately 30% of the total rainfall (90 mm) was captured in both systems and later used by plants. At least 92% and 76% of water savings, relative to the CS, were achieved by using the white MPBS in the summer and fall, respectively. Results suggested that under these experimental and similar climatic conditions, the white MPBS is superior to the black MPBS and CS. The white MPBS presents a potential opportunity for an efficient irrigation and significant water savings for container-grown nurseries.

Evaluation of Soil Moisture Sensors, and Their Use to Control Irrigation Systems for Containers in the Nursery Industry

Water savings are important from an economical and environmental point of view. The nursery industry accounts for a large amount of the water used for agricultural purposes. The high porosity of substrates used to grow plants in containers affects the precision of moisture sensors, hence the need to evaluate their efficacy in this type of growing media. This paper describes studies that use time domain reflectometry (TDR) and tensiometers as soil moisture sensors in conjunction with a computer controlled irrigation system. Both sensors have their advantages and disadvantages, however, compared against a common timer-controlled system the TDR system accounted for water savings above 60%, and with the tensiometers the savings were around 50%.

Response of four woody ornamental species to superphosphate and controlled-release fertilizers

Abstract Shoot dry weights of Ilex vomitoria Ait. ‘Schellings Dwarf’, Pittosporum tobira Thunb., and Juniperus chinensis L. ‘Blue Vase’ fertilized with Sref 20N‐2P‐8K and Step (micronutrient formulation) or Osmocote 18N‐3P‐10K and Micromax (micronutrient formulation) were not different when grown in a 1 sedge peat: 1 cypress sawdust: 1 cypress shavings (v/v/v) medium with or without superphosphate. Photinia X fraseri Dress shoot and root dry weights decreased if supersphosphate was added to the growing medium and fertilized with Sref and Step, but were not different when fertilized with Osmocote and Micromax. Shoot tissue P levels of P. X fraseri and P. tobira increased with the addition of superphosphate regardless if Osmocote and Micromax or Sref and Step were used, but there was no corresponding increase in shoot dry weight. Water soluble P levels of the superphosphate amended medium with Sref and Step decreased about 70 ppm during the 6‐month experimental period.

Nitrogen Uptake and Allocation in Sweet Viburnum During a Root Growth Flush

ABSTRACT Most woody ornamentals exhibit episodic growth flushes and nitrogen (N) uptake has also been demonstrated to be seasonal. However, there is little information on N uptake in relationship to plant growth cycle. In this study, N uptake and allocation of sweet viburnum during periods of low and high root elongation rates were studied. Plants were fertilized with ammonium nitrate (15NH4 15NO3) and after 6 d N absorption was determined. Significantly more N was absorbed by plants with low root elongation rate compared with plants with high root elongation rate. About 70% of the N absorbed by plants with low root elongation rate was allocated to the mature leaves compared to 35% on plants with high root elongation rate. It was evident that root growth activity influenced N absorption and allocation. Although only a small amount of the N absorbed by plants with low root elongation rates was allocated to the immature leaves, significantly more N was allocated to the immature leaves by plants with high root elongation rates. It is possible that the N necessary to support immature leaf growth, when root elongation rate is low, is provided by mobilization from other parts, possibly mature leaves.

Influence of shoot pruning time on the removal of accumulated N, P, and K and subsequent growth of Ligustrum sinense lour. ‘Variegatum‘

Abstract Greenhouse‐grown Ligustrum sinense ‘Variegatum’ plants pruned after 4, 5, 6, or 7 weeks of growth had similar dry weights 4 weeks after each pruning time. The mg of N, P, and K removed in pruned shoot tips was minimized by pruning at the 4‐week pruning treatment. Delaying pruning each week resulted in an increase in the amount of N, P, and K removed and the ratio of mg of N, P, and K removed in shoot tips to N, P, and K accumulated by shoots for each pruning time.