Improvement of Plant Quality With Alumina-Buffered Posporus Fertilizer Progress Report –June 1999
Project Progress Report Cover Page & Requirements
11 Glen-Ed Professional Park, Glen Carbon, Illinois 62034 Telephone: 618.692.0045 Fax: 618.692.4045 Email:
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outlining results and specific benefits to the industry especially new information identified, (3) outline next steps and future for
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Progress reports enable the board and industry to keep abreast of the work accomplished in each project receiving AFE
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Date: May 15, 1999
Title of Project: Improvement of Plant Quality with Alumina-Buffered Phosphorus Fertilizer
Institution(s): Penn State University
AFE Grant Amount: $14,339 Grant Period: July 1, 1998 to June 30, 1999
Project Completion Date (as indicated on proposal application) June 30, 1999
Project Leader: Jonathan P. Lynch
Title: Associate Professor of Plant Nutrition
Address: 102 Tyson Building, Penn State University, University Park, PA 16802
Telephone: (814) 863-2260 Fax: (814) 863-6139 Email: JPL4@psu.edu
Additional Researchers (Names): Kathleen M. Brown and Gary Moorman
Progress Report: Improvement of Plant Quality with Alumina-Buffered Phosphorus Fertilizer
The specific objectives of this project were:
1) To conduct postproduction evaluation of poinsettia, florist azalea, and chrysanthemums grown with Al-P.
2) To determine whether Al-P fertilizer affects resistance to Botrytis infection of foliage or Pythium root rot.
This was a one-year project to do preliminary work on objective 1 and complete the study described in objective 2, which
began during the previous year.
Postproduction Evaluations
These investigations were carried out in cooperation with Dr. Terrill Nell at the University of Florida and Yoder Brothers in
Alva, Florida. We were interested in the effects of alumina-buffered phosphorus (Al-P) fertilizer on quality of flowering plants
and cuttings (mums), as well as on leaching of P into the runoff water from the nursery.
Florist Azalea: Four cultivars, Prize, Cherish, Party Favor, and Gloria, were planted in coir in 6-inch pots during February
1998. The fertilizer treatments were: control (P from phosphoric acid), 1% Al-P or 2% Al-P. The Al-P desorbed P at a
concentration of 113 µM. There were 4 blocks and each block contained 10 plants per treatment, for a total of 576 plants.
Plants were grown outdoors under shadecloth at Yoder Brothers’ Alva facility. Leachate was collected at weekly intervals
through most of the growing period and analyzed for P content at Penn State. Data were collected on dry weight of pinched
shoots. Mature, unflowered plants were shipped to Penn State in December, 1998 for evaluation and leaf nutrient analysis.
Another set of plants were forced and shipped in January, 1999, half to Penn State and half to the University of Florida for
postproduction evaluation. Postproduction evaluation at Penn State occurred in a greenhouse and included a drought treatment,
while evaluations at University of Florida were done in a simulated consumer environment especially designed for
postproduction studies.
Phosphorus concentrations in leachate were reduced by 64% (in 2% Al-P) to 70% (in 1% Al-P) by using Al-P instead of the
usual soluble form of phosphorus. Dry weight of pinches was not significantly affected by Al-P except that ‘Party Favor’ control
pinch weights were higher at the second pinch, and ‘Prize’ 1% Al-P pinch weights were higher at the 3rd pinch. Quality of
unforced plants was not significantly affected, except that at 2% Al-P, Prize plants showed more chlorosis than for the other
two treatments. Prize plants grown in 1% Al-P had the same amount of chlorosis as controls, and showed slightly greater dry
weight accumulation. There were no other significant differences in plant growth among fertilizer treatments, though there was a
trend toward greater weight and volume with Al-P in all cultivars.
In forced plants evaluated at Penn State, postharvest life in the greenhouse was about 6 weeks before substantial flower
spotting and wilting commenced. ‘Gloria’ plants were delayed about a week in their flowering by Al-P, while the other cultivars
were not significantly affected. Drought did not substantially affect postharvest life of any cultivars or treatments. Later in the
experiment, tan colored spots were observed before flower wilting on some cultivars, especially ‘Prize’. These spots were most
plentiful in control plants. At 6 weeks, 60% of flowers on control plants were spotted, while only 32% were spotted on 1%
Al-P plants. The flowers on the other cultivars showed less spotting than ‘Prize’ and were not significantly affected by Al-P.
Al-P grown plants seemed to show slightly delayed flower wilting as the postproduction life neared its end.
At the University of Florida, plants at the marketable stage (at least 8 flowers open) were sleeved, boxed, and subjected to
simulated transport at 43 F for 4 days before being placed in the simulated consumer environment at 70 F and low light. There
were no significant differences in quality among fertilizer treatments in this evaluation.
Mums: Chrysanthemum stock plants were planted in raised sand beds outdoors under shade cloth at Yoder Brothers facility in
Alva, FL in October, 1998. There were 7 cultivars and 3 fertilizer treatments, control, 1% Al-P, and 2% Al-P, arranged in a
single long bed divided into sections, some with the Al-P mixed into the bed and some not. There were 4 blocks (sections) per
treatment. Plants were supplied with soluble fertilizer during irrigation according to Yoder’s normal production practice, except
P was omitted from Al-P plots. Drainage tile was placed below each section to permit collection of leachate. Leachate samples
were taken weekly. Data were also collected on cutting production, quality of cuttings, nutrient content of foliage, rooting of
cuttings, and growth and quality of forced plants from these cuttings.
As with the azalea, Al-P substantially reduced leaching of P from the beds. Total P leaching over the entire production period
(October through February) was reduced by 70% in 1% Al-P and 60% in 2% Al-P compared with controls.
There was no significant difference in dry weight of cuttings from plants grown with Al-P vs. control fertilization. Rooting of
cuttings was not significantly affected by Al-P supplied either during stock plant production or during rooting.
Plants are currently being grown to maturity at the University of Florida for evaluation of plant quality and postproduction
longevity. These plants are being grown with the same P treatment as the stock plants from which the cuttings came.
Poinsettia: Poinsettia plants were grown at the University of Florida using conventional fertilizer or Al-P. Unfortunately, there
was an error in the loading or testing of the Al-P used in this experiment and all the Al-P plants were P deficient, so we did not
obtain any useful information from this experiment. This experiment will be repeated during fall, 1999.
Effects of Al-P on Disease Resistance
In cooperation with Dr. Gary Moorman at Penn State (Plant Pathology) we tested whether Al-P affected resistance of
geraniums to gray mold (Botrytis) or Pythium root rot. There were no significant differences among fertilizer treatments in any of
these tests.
Conclusions from these tests
The most important result from these trials is that floriculture crops grown with Al-P rather than conventional fertilizer are of
equal or better quality than controls and are produced with greatly reduced release of P into leachate water. This is very
important for the ability of growers to produce high quality crops in an “environmentally friendly” manner. Excess P release from
nurseries, greenhouses, and farms is a major concern of the US EPA and state environmental agencies. For example, Florida
has high leaching rates through their sandy soil and runoff waters enter sensitive wetlands such as the Everglades. In the
northeast, we are concerned about nutrient runoff polluting the Chesapeake Bay. Improved production practices will help
growers to stay in business while complying with federal and state regulations, which are likely to become more stringent with
time.
The trial with florist azalea was particularly valuable because the production time is so long (more than a year if forcing and
postharvest evaluations are included). During this time the Al-P that was added at the onset of the experiment continued to
provide optimal P for plant growth without the need for recharging (i.e. adding soluble P to replace P lost from the alumina).
Therefore, the Al-P can be used in commercial production systems for at least a year before recharging is necessary.
Future Directions
Yoder Brothers and the University of Florida are willing to continue cooperative work on application of Al-P in commercial
production systems. As proposed in our currently pending application, we would like to continue testing floriculture crops with
Al-P. In the bed we previously used for mum production at Yoder’s, we will produce another crop without adding more Al-P
or charging the Al-P that is already present. This will tell us more about the ability of this material to continue releasing P over
the long term and its resistance to mechanical disturbances such as tilling.
We are investigating the possibility of using different forms of buffering alumina, different methods of supplying P to the buffering
material, and working with manufacturers on scaling up the technology. Yoder Brothers would like to put in a larger scale trial
in the sandy soil at Alva, for which we would need much greater quantities of material. Therefore, Al-P production and
commercialization issues are becoming critical for further development of this technology.
