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RESEARCH: COLUMN STUDIES |
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THE ABSTRACTS BELOW:
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GOLD’n GRO®
9-0-1 + 7% Zn improves corn growth
in Zn-deficient soil: A preliminary study
Julie Chard and Bruce Bugbee
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ABSTRACT
Zinc deficiency can limit growth, especially on soils with low
organic matter and high pH. Chelated Zn fertilizers maximize Zn
bioavailability. We sought to determine the effectiveness of
soil-applied GOLD’n GRO 9-0-1 + 7% Zn, a chelated Zn source, to
reverse or prevent Zn deficiency. GOLD’n GRO was applied at 0 to 30
quarts per acre in a high pH soil. Controls included columns treated
with ammonium-nitrogen at the same level as the highest GOLD’n GRO
treatment. Plants treated with GOLD’n GRO had twice the dry mass,
were greener, and had increased zinc levels in the plant tissue
compared to the untreated control plants. A follow-up study will
evaluate lower concentrations of GOLD’n GRO and will determine the
effectiveness of unchelated, inorganic zinc sulfate.
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Beyond
Hydroponics: Improved procedures for
studying rhizosphere effects on plant nutrition
Julie Chard and Bruce Bugbee
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ABSTRACT
Hydroponic culture has been a cornerstone of plant nutrition since
the first studies by Hoagland and Arnon in the 1930’s. Liquid
hydroponic culture, however, almost completely eliminates
rhizosphere effects, which can have an enormous effect on nutrient
availability. There are a wide variety of porous substrates,
watering methods, and nutrient control methods that might be used to
study rhizosphere effects. We refined media and procedures to
optimize five root-zone factors: 1) water/oxygen balance, 2)
mechanical impedance similar to field soils, 3) buffered pH, 4)
precise control of nutrient concentrations, and 5) ease of removal
from roots. We tested several growth media and found that the method
used to pack the columns is as important as the growth medium. An
optimal air/water balance is achieved by using coarse media and
watering with small volumes, several times per day, using an
automated watering system. Specialized nutrient solutions and pH
control can be used to induce specific nutrient deficiencies, and
the rhizosphere pH can be manipulated by changing the ratio of NO3
to NH4.
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Simulating
the Field: How to Grow Plants
in Soil Columns in the Greenhouse
Julie Chard and Bruce Bugbee
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INTRODUCTION Why Soil Columns? In the field
of plant research it is often desirable to grow plants under
controlled conditions to minimize environmental variability from one
treatment to the next. The desired control can be achieved by growing
plants in containers in a greenhouse or growth chamber.
Plant growth in soil is straightforward in the field where soils are
deep, but soil moisture dynamics are altered significantly in small
containers. Drainage in the field results from the depth (thickness)
of the soil layer. Gravity alone is not adequate to remove water
from agricultural soils in pots.
Soil columns are an improvement over pots because they are deeper and
can therefore hold more soil and more plant-available water; the
longer the column, the better the water dynamics. A small surface area
to depth ratio enables the use of many columns and the application of
several randomized treatments within a small area.
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In plant research it is often
desirable to grow plants under controlled conditions to minimize
environmental variability from one treatment to the next. The desired
control can be achieved by growing plants in containers in a
greenhouse or growth chamber. Columnar containers are preferable
to pots because they can support deep root growth while taking up less
bench space. Many columns can be arranged within a small area, such as
a gas-exchange chamber, thereby maximizing the number of treatments
and replications in a given space. For studies of root growth
and morphology, an ideal containerized plant culture system should
provide: 1) adequate nutrients, water and oxygen; 2) appropriate
mechanical impedance to root elongation; 3) adequate depth to prevent
root binding; and 4) easy separation of roots from the root-zone
substrate. Standard potting substrates typically contain
sphagnum peat mixed with perlite or vermiculite. These well-drained,
organic-rich mixtures support an appropriate balance of water and
oxygen while also providing exchange surfaces for plant nutrients.
Separation of plant roots from the potting substrate, however, is
impossible.
We have developed a columnar plant culture system that supports
healthy plant growth while also enabling complete separation of the
roots from the growth substrate. Our substrate of choice is Turface®,
a porous ceramic produced by baking clay at high temperatures (Figure
1). Turface® drains well, resists compaction, and retains nutrients
well with a cation exchange capacity(CEC) of 33 meq/100 g.
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