Improvement of Plant Quality with Alumina-Buffered Phosphorus Fertilizer Progress Reports - June 2001
Annual Progress Report
Improvement of Plant Quality with Alumina-Buffered Phosphorus Fertilizer
Kathleen M. Brown and Jonathan P. Lynch, Dept. Horticulture, Penn State
University
Terrill Nell, Dept. Environmental Horticulture, University of Florida
Industry needs addressed:
With financial support from AFE, we have developed a novel fertilizer
technology for container plants that provides continuous, optimal levels of
phosphorus to plant roots based on actual plant phosphorus requirements, while
eliminating leaching from the container. Plants grown using this alumina-buffered
phosphorus fertilizer are of equal or better quality than conventionally grown
plants and have improved tolerance to drought stress. Leaching of phosphorus is
drastically reduced, especially compared with use of soluble fertilizers, but
even compared with slow release fertilizers such as Osmocote. Thus, the two
major benefits are improved plant quality and reduced pollution.
Research conducted:
Commercial development of alumina-P product
We have made considerable progress in the last year on commercial-scale
manufacturing of an alumina product that could be used by the industry. A
European manufacturer, Martinswerk (part of Alusuisse) has developed their own
method of loading the alumina with phosphorus and is willing to supply us with
large amounts for commercial-scale trials in the U.S. We will be testing their
material in the field at the Penn State research farm this summer in a related
project on vegetable production. If this goes well, we will use the same
material in trials in Florida with Yoder Brothers, proposed as part of this
project.
A second manufacturer, Alcoa, has been working with us to develop a method
for loading their material. We now have tested several methods and found one
that works well. This is a scaled-up method that would allow production of
commercial quantities of Al-P. This material will also be tested in our field
trials on vegetable production this summer, and if successful at Yoder’s in
the fall.
Testing of Al-P on floriculture crops
We have just finished two experiments in our greenhouses testing the Al-P
products from Martinswerk and Alcoa on mum production. In the first experiment,
we tested Martinswerk Al-P desorbing at 25, 150, and 225 µM P in peat-based
medium and in sand from Yoder Brothers’ farm. The crop was ‘Pelee’ and ‘White
Diamond’ mums planted 3 cuttings per pot. The two higher desorbing
concentrations performed better, while plants grown at the lowest concentration
were substantially smaller than the other plants. With the higher desorbing
concentrations, the plants were still somewhat smaller than the control
(15-5-15) plants, but had a better, more compact appearance, and as many or more
shoots (branches). Flower and flower bud number was unaffected by P treatment
for ‘Pelee’ but was reduced by 25 or 225 µM Al-P, but not 150 µM Al-P, for
‘White Diamond’ plants grown in peat mix. The plants grown in sand were
smaller and had fewer buds and flowers for all Al-P treatments, and P levels in
leachate were lower than those in peat mix, indicating that higher P desorbing
concentrations are needed in sand than in peat. The bud vs. flower numbers
seemed to indicate a slight delay in reproductive development in Al-P plants.
The second experiment, testing Alcoa products, showed that these products
produced a slightly smaller plant than those fertilized with 15-5-15. There were
differences among the 3 products tested, which were manufactured in different
ways and had a range if P-buffering concentrations from 55 to 100 µM.
Trials with Yoder Brothers
In our previous trial at Yoder Brothers in Alva, FL, we incorporated Al-P
that we made into raised beds used for stock plant mum production, and the Al-P
provided adequate P nutrition for nearly two years. We then recharged the
alumina by adding fresh P to the beds, and additional crops have been grown on
those beds for a third year, without addition of more Al-P and without the need
for additional phosphorus fertilizer.
Postharvest quality of poinsettia
In a trial at the University of Florida, poinsettias ‘Freedom Red’ and
‘Peterstar Red’ were grown with conventional fertigation (15-15-15) or one
of four Al-P treatments: 1% or 2% w/v Al-P desorbing at 33 µM, or 1% or 2% w/v
Al-P desorbing at 97 µM P. As expected, the Al-P reduced P concentrations in
leachate dramatically, from 80-97% depending on Al-P application rate and
desorbing concentration. For ‘Freedom Red’, dry weight of the shoot at
maturity was slightly less when plants were grown with Al-P at 33 µM desorbing
concentration than conventionally fertilized controls, but it was not
significantly different at 97 µM desorbing concentration of Al-P. ‘Peterstar
Red’ poinsettias showed a more drastic reduction with the lower concentration
of Al-P and a slight reduction at 97 µM. We believe that most of the reduction
with even the lower Al-P concentration was due to an excessively low pH of the
Al-P nutrient solutions during the early part of the experiment, which only
affected the no-P nutrient solutions, and therefore not the control plants. Once
the pH was adjusted, the plants recovered and grew up to adequate size. All
plants were of acceptable quality by the end of the experiment. There were no
significant differences in postproduction life or quality among treatments.
We have run several trials now on fertilization with Al-P and crop quality
and postproduction life. Although there have been problems with several of the
experiments, we have conducted enough experiments to be confident that Al-P
provides adequate phosphorus for good growth and quality with no detrimental
effects on postproduction longevity. We feel confident enough of this that we
have decided to drop the postproduction quality evaluations from our renewal
application.
Professional and published information
Nell, T, R Leonard, B. Snyder, K. Brown, J. Lynch. Testing Alumina-Buffered
P Fertilizer. Poster for AFE visit during January 2001 Board meeting, University
of Florida.
Brown, KB and JP Lynch. 2000. “Intelligent Media” Improves Crop
Quality and Reduces Phosphorus Leaching. Joint board meeting of the Pennsylvania
Landscape and Nursery Association and the Pennsylvania Floriculture Industry
Association 9/21/00, University Park, PA.
Application for Continued Funding
We are requesting a third and final year of support for this project. The
final year will be devoted to developing Al-P for use by the floriculture
industry, as described below. We are dropping the section on postharvest
evaluation (with the support of Dr. Nell), with a concomitant reduction in the
budget, since we feel confident that there are no detrimental effects of Al-P on
postproduction life, and that beneficial effects seem to be confined to plants
exposed to drought (as demonstrated by our previous work).
Goals & objectives for the coming year:
During the coming year, our objectives will be:
To complete one additional greenhouse experiment testing the best products
from Martinswerk and Alcoa, incorporated at 2 rates, on mum production.
We have tested the Martinswerk product manufactured to desorb at 3
different rates on mum production in one experiment, and three different
Alcoa products in a second experiment. This final experiment will be a
side-by-side comparison of two of the Martinswerk products, buffering at 150
and 225 µm, and another Alcoa product manufactured in a better way and
buffering at 125 µM P. These products will be incorporated into the medium
at two rates (0.5% and 1.0%).
To put in a large-scale trial in raised ground beds at Yoder Brothers,
Alva, Florida, to test the ability of the commercially produced Al-P products
to supply P in commercial production of mums.
Provided that the greenhouse trial proposed above does not suggest any
problems with the commercial Al-P products, a new trial will be installed at
Yoder Brothers facility in Alva, FL. The test materials will be incorporated
into the top 8 inches of soil in raised beds used for mum production. The
soil there is mostly sand, and the raised beds are topped with plastic mulch
and drip irrigation. This trial will be the same as our previous experiment,
except that we will use commercially produced Al-P instead of our “homemade”
material. We will monitor P leaching, plant performance, and our ability to
recharge the Al-P in situ. Recharging experiments will also be
performed in our labs using various soils and media (including sand from
Yoder Brothers’ farm). The ability to recharge the Al-P is an important
aspect of commercialization for some parts of the industry, since this would
reduce or eliminate the need for repeat Al-P applications to permanent (or
those with repeat use) beds or plots, and therefore would reduce the
long-term cost.
To continue working with Alcoa to optimize conditions for Al-P loading to
produce a consistent, high-quality product.
We will continue to work with technicians at Alcoa to help them develop a
loading method that produces a high-quality product suitable for the
horticulture industries. We will be checking for quality aspects such as P-desorption
rates, longevity of the product, pH effects, etc.
Anticipated impacts of research
Our preliminary data indicates satisfactory performance of both the Alcoa
and Martinswerk products in container culture. Provided that these products
continue to perform well in the proposed greenhouse and outdoor (Yoder) trials,
these companies will be willing to (1) support our further research needed for
assuring product quality; and (2) consider marketing a commercial product that
could be used by the horticulture industry. Martinswerk has already provided
funding for testing their product, and we believe that Alcoa can be convinced to
do so in the near future. Therefore, AFE funding has served, and will serve for
one additional year, to provide “seed money” for adequate development of
this technology that support for its further development can be moved to the
manufacturers.
Dissemination plan for the results
We will continue to publish our reports in scientific and technical
(industry oriented) publications as appropriate, and to present information to
industry groups. Our research will also serve as the basis for product claims
made by manufacturers and distributors of the commercial product, once released.
