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 Copyright
 Introduction
 Functional design
 Discussion
 Conclusion






Group Title: Research report - Bradenton Agricultural Research & Education Center - GC1976-6
Title: Functional design of the gradient-mulch concept
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00067699/00001
 Material Information
Title: Functional design of the gradient-mulch concept
Series Title: Bradenton AREC research report
Physical Description: 3 leaves : ; 28 cm.
Language: English
Creator: Geraldson, C. M ( Carroll Morton ), 1918-
Agricultural Research & Education Center (Bradenton, Fla.)
Publisher: Agricultural Research & Education Center, IFAS, University of Florida
Place of Publication: Bradenton Fla
Publication Date: 1976
 Subjects
Subject: Mulching -- Florida   ( lcsh )
Soil amendments -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: C.M. Geraldson.
General Note: Caption title.
General Note: "July 1976."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067699
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 72472481

Table of Contents
    Copyright
        Copyright
    Introduction
        Page 1
    Functional design
        Page 2
    Discussion
        Page 2
    Conclusion
        Page 3
Full Text





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Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
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Copyright 2005, Board of Trustees, University
of Florida






AGRICULTURAL RESEARCH & EDUCATION CENTER
c IFAS, University of Florida
Bradenton, Florida T- \ 'i

FUNCTIONAL DESIGN OF THE GRADIENT-MULCH CONCEPT

C. M. Geraldson

Bradenton AREC Research Report GC1976-6 July 1976


For the past 15 years the various components that have been integrated into the
gradient-mulch system have been under selection and evaluation in a continuing ap-
proach toward obtaining maximum production efficiency. From results of experiments
at the Bradenton Research Center and evaluations in the field, a description of the
basic components is as follows:

1. Soil: Myakka fine sand limed to a pH of 6.5+. Myakka has a spodic horizon
(hard pan) ranging in depth from 15 to 30 inches; organic matter of 1.5 to 2.0%;
and a pH of 4.0 to 4.5 before liming.

2. Soil bed: constructed and pressed to a height of 10 to 12 inches above
the row middle with a constant water table maintained 16 to 18 inches belcw the sur-
face of the flat topped soil bed.

3. Fertilizers: (a) Materials that contribute minimal soluble salts (phospho-
rus, lime and micronutrients) incorporated in the soil or soil bed, (b) the major
portions of the soluble nutrients (primarily nitrogen and potash) required by the
crop, banded preferably 6-12 inches from the plant row on the soil bed surface;
rilnor portions (2 to 5%) of the soluble nutrients (starter fertilizer) broadcast
over the bed surface.

NOTE: Quantities and ratios which may be altered with regard to crop require-
ment are not considered as basic for gradient function and will be discussed later.

4. Fumigation: Optional, but often required to minimize problems associated
with the continued use of old land.

5. Mulch: Application of a full bed mulch: The soil bed delimited by satu-
rated soil above the water table and the mulch anchored below the row middle level,
a situation which confines root development in that portion of the soil bed where
the functional gradient has been established.

A production system provides physical support, water, air and nutrients for the
crop. Most such systems provide these components with some degree of variability
which, in turn, affects the production and production-efficiency-. Deficiencies or
excesses can occur as a result of extremes in variabilities. Variations in irriga-
tion (systems, frequency, quantities) and rainfall can alter the moisture and air
in the root environment. The soil and fertilizer (rate, ratio, source and placement)
alter the concentration and balance of nutrients in the root environment. Further-
more, salts can and do move with moisture providing interdependent variables. In
terms of production, these components become exceedingly difficult to define because
of the associated variability. The gradient-mulch concept is designed to establish
a stable integration of all components in the system in orc-r to minimize variability
and maximize production as well as production efficiency.




-2-


FUNCTIONAL DESIGN

A reciprocal moisture-air gradient is provided by maintaining the constant
water table a given distance below the flat topped soil bed. Thus, a 2-dimensional
range of decreasing moisture-increasing air is provided from a level of saturation
to the bed surface. A 3-dimensional concentration gradient decreasing outward from
the banded surface application of fertilizer is superimposed on the moisture-air
gradient. Thus the root from a seed or seedling can develop in that portion of the
bed where the most favorable levels of nutrients, moisture and air coincide. Once
the root system becomes established in a favorable portion of the soil bed, then
nutrients and moisture must continue to be supplied to the root in a way that nutri-
ent and moisture movement will not alter the root environment. This is accomplished
by the functional design of the applied gradient; nutrients are replaced by diffusion
from the band to the root as removed by the root. Moisture is similarly supplied
from the water table as required. The less soluble nutrients mixed in the bed con-
tinue to become available by equilibrium action also as removed by the root.
Thus a minimal-stress root environment is established, maintaining the favorable
and essentially non-variable root environment regardless of an increasing crop
requirement. This is most important when considering the magnitude of requirement
per unit of time of the more intensively grown crops.

DISCUSSION

The soil-bed provides the physical base on which the system is established.
Water table depth is critical in relation to soil type and the precision in leveling
and engineering to maintain the water table as prescribed. Some soils are not suit-
able for seepage irrigation, some less suitable than Myakka fine sand, but many
sandy soils in peninsular Florida can be used similarly to those in the Manatee-Ruskin
area. As an example of component integration, it might be necessary to alter bed
dimensions or the water table level to compensate for certain soil variations. In
any event, a properly related gradient system should be established and delimited
to function as designed.

Once a root system has been established in a suitably favorable portion of the
soil bed, water table fluctuations can alter the air-moisture gradient to one that
is less favorable. Salts can also be moved in or out of an existing root environ-
ment, thus unfavorably altering the nutrient concentration and balance. Residual
salts, irrigation water salts and fertilizers incorporated into the bed move upward
with seepage irrigation resulting in accumulations in the upper portions of the bed.
Germinating seed or young transplants are especially vulnerable to this accumulation
which can further concentrate in the soil solution at the plant holes in the mulch
due to evaporation at that location. Therefore, good quality irrigation water and
soil with minimal residual salts are highly recommended as prerequisites for a
desired cropping site. Furthermore, fertilizers incorporated in the bed depending
on quantity and placement, add to that which comes with the water and the soil.
Fertilizers applied on the bed surface broadcast or banded do not contribute to
the salt which moves upward through the root zone in the bed; thus do not alter the
functioning of the gradient.

It is also evident that nutrients incorporated in the bed as well as deeper water,
tables favor deeper root systems which in turn are more vulnerable to excess water
resulting from heavy rains and/or inadequate drainage. Roots cease to elongate after
2 to 3 minutes without oxygen and may be killed within a few hours*. Varying degrees
of crop damage occurred in the Manatee-Ruskin area when 2 to 6 inches of rain fell



*Huck, M. G. 1970. Variation in tap root elongation rate as influenced by composi-
tion of the soil air. Agron. J. 62:815-18.




-2-


FUNCTIONAL DESIGN

A reciprocal moisture-air gradient is provided by maintaining the constant
water table a given distance below the flat topped soil bed. Thus, a 2-dimensional
range of decreasing moisture-increasing air is provided from a level of saturation
to the bed surface. A 3-dimensional concentration gradient decreasing outward from
the banded surface application of fertilizer is superimposed on the moisture-air
gradient. Thus the root from a seed or seedling can develop in that portion of the
bed where the most favorable levels of nutrients, moisture and air coincide. Once
the root system becomes established in a favorable portion of the soil bed, then
nutrients and moisture must continue to be supplied to the root in a way that nutri-
ent and moisture movement will not alter the root environment. This is accomplished
by the functional design of the applied gradient; nutrients are replaced by diffusion
from the band to the root as removed by the root. Moisture is similarly supplied
from the water table as required. The less soluble nutrients mixed in the bed con-
tinue to become available by equilibrium action also as removed by the root.
Thus a minimal-stress root environment is established, maintaining the favorable
and essentially non-variable root environment regardless of an increasing crop
requirement. This is most important when considering the magnitude of requirement
per unit of time of the more intensively grown crops.

DISCUSSION

The soil-bed provides the physical base on which the system is established.
Water table depth is critical in relation to soil type and the precision in leveling
and engineering to maintain the water table as prescribed. Some soils are not suit-
able for seepage irrigation, some less suitable than Myakka fine sand, but many
sandy soils in peninsular Florida can be used similarly to those in the Manatee-Ruskin
area. As an example of component integration, it might be necessary to alter bed
dimensions or the water table level to compensate for certain soil variations. In
any event, a properly related gradient system should be established and delimited
to function as designed.

Once a root system has been established in a suitably favorable portion of the
soil bed, water table fluctuations can alter the air-moisture gradient to one that
is less favorable. Salts can also be moved in or out of an existing root environ-
ment, thus unfavorably altering the nutrient concentration and balance. Residual
salts, irrigation water salts and fertilizers incorporated into the bed move upward
with seepage irrigation resulting in accumulations in the upper portions of the bed.
Germinating seed or young transplants are especially vulnerable to this accumulation
which can further concentrate in the soil solution at the plant holes in the mulch
due to evaporation at that location. Therefore, good quality irrigation water and
soil with minimal residual salts are highly recommended as prerequisites for a
desired cropping site. Furthermore, fertilizers incorporated in the bed depending
on quantity and placement, add to that which comes with the water and the soil.
Fertilizers applied on the bed surface broadcast or banded do not contribute to
the salt which moves upward through the root zone in the bed; thus do not alter the
functioning of the gradient.

It is also evident that nutrients incorporated in the bed as well as deeper water,
tables favor deeper root systems which in turn are more vulnerable to excess water
resulting from heavy rains and/or inadequate drainage. Roots cease to elongate after
2 to 3 minutes without oxygen and may be killed within a few hours*. Varying degrees
of crop damage occurred in the Manatee-Ruskin area when 2 to 6 inches of rain fell



*Huck, M. G. 1970. Variation in tap root elongation rate as influenced by composi-
tion of the soil air. Agron. J. 62:815-18.







during a short time span during mid-harvest season May 15, 1976. The degree of
damage was relevant to the depth of the root system as well as the quantity of
rain. Damage was indicated by water wilt as well as eventual deterioration. A
measure of ionic concentration at various depths in the soil profile also indicated
the depth of the root environment. At the research center with 4.8 inches of rain
rid all soluble fertilizers applied on the bed surface, wilt did not occur and damage
ws minimal. Plants were severely damaged in experiments using trickle irrigation
which promotes deeper root systems. Trickle irrigation in the Homestead area has
been successfully used as a component in a full bed mulch system. It is possible
that drainage potential for the Rockland soil would permit the maintenance of a
functional deep root system.

The ionic content of the root environment can be defined by choice of fertili-
zer ratio and source materials. With increasing quantities of fertilizer, the root
environment may shift further away from the surface applied source without altering
the ionic content. The quantity of a given soluble fertilizer applied on the soil
bed surface should vary with the crop. With trellised tomatoes 2000 lbs of 18-0-25-2
derived from KN03, MgS04, NHN03, or perhaps some Ca(N03)2 would supply sufficient
nutrients for 3000+ marketable units. In contrast, 1000 Ibs would be sufficient for
a ground crop harvested only 2 to 3 times. The choice of ratios and source materials
might also vary with the crop; a 1-1 (N-K20) ratio is recommended for sweet corn.
Some tomato growers prefer a 1:2 ratio for example, a 10-3-20. However, experimen-
tally and supported by limited commercial evaluation, yields, quality, and fruit size
have generally been superior with the 18-0-25-2 used in conjunction with the pre-
scribed gradient mulch system. Phosphorus at a rate of 100: bs P205/acre has been
sufficient to supply P for any crop growing in previously cropped soil (contains
residual P). Virgin soil should receive about twice the P205 indicated above. In
order for the gradient to function as defined, the surface applied fertilizers must
be soluble; therefore, organic or slow release materials are not recommended.

When water supplied by the seep method is inadequate, it is possible that nutri-
ents incorporated in the bed may be more available than nutrients placed on the bed
surface, but the system may then be more vulnerable to excess salt or water. The
incidence and degree of variability proportionately alters the gradient. It should
be emphasized that a production system with minimal variables provides the potential
for maximum predictability, consistency and efficiency of that system.

CONCLUSION

The gradient-mulch system utilizes a combination of components integrated to
establish a root environment that functionally provides an optimal combination of
nutrients, moisture and air which can be functionally sustained with minimal stress
during the entire growing season. Such a system favors a consistent and maximum
production efficiency. The prescribed procedure has-been-presented so that the
components, as well as alternatives, can be placed in a proper perspective with
regard to potential production and production efficiency. It should be emphasized
that mulch is a protective component for a combination of contributing components
that are functionally integrated to provide the maximum potential of the concept.




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