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Re: [SANET-MG] citation for greenhouse study comparing impact organic/conventional soil on plant health?

Hello Laura and Steve,

Abstracts for 3 more recent articles authored/coauthored by Larry Phelan
related to the impact of "mineral balance" on herbivory are appended below:



Micronutrient interactions on soybean growth and the developmental
performance of three insect herbivores
Author(s): Beanland L, Phelan PL, Salminen S
Source: ENVIRONMENTAL ENTOMOLOGY 32 (3): 641-651 JUN 2003
Document Type: Article
Language: English
Cited References: 34      Times Cited: 3
Abstract: Although the importance of plant mineral nutrition on insect
herbivory has long been recognized, studies have focused almost solely on
the effects of varying levels of a single nutrient. One aspect of the
relationship between plant nutrition and herbivory largely ignored is the
proportions among minerals. The mineral balance hypothesis Postulates a
plant nutritional state with optimal levels and proportions among minerals
that enhances plant growth and suppresses herbivore performance. As part of
a systematic series of studies to determine the optimal proportions of
minerals for soybeans (Glycine max), plants were grown in hydroponic
solution with different proportions of boron (B), zinc (Zn), and iron (Fe),
using a D-optimal experimental design for constrained mixtures. In this
design, B and Fe varied from 0 to 0.05 mM in the nutrient solutions, whereas
Zn ranged from 0 to 0.01 mM. Three soybean feeders, the polyphagous soybean
looper (Pseudoplusia includens [Walker]), the oligophagous Mexican bean
beetle (Epilachna varivestis Mulsant), and the velvetbean caterpillar
(Ancarsia gemmatalis Hubner), were fed leaves front the plants and their
developmental performance was evaluated using polynomial models. For all
three species, developmental performance was highest on plants grown in
solutions without B. Weight gain by velvetbean caterpillar larvae, whose
feeding was terminated at 6 d, showed a linear response to mineral
proportion (adjusted r(2) = 0.49), peaking at B:Zn:Fe = 0:20:80. Soybean
looper pupal weight and larval developmental time showed predominantly
quadratic responses determined primarily by B:Fe ratio (adjusted r(2) = 0.33
and 0.67, respectively). Mexican bean beetle showed the most complex
response to mineral proportion, with cubic models of adult weight (adjusted
r(2) = 0.66) and developmental time (adjusted r(2) = 0.45) that indicated
significant interactions among all three minerals. Soybean shoot growth was
described by a reduced cubic model (adjusted r(2) = 0.83), but unlike the
insects, plants grew poorly in nutrient solutions lacking B. Rather,
soybeans grew best at intermediate mineral proportions, and consistent with
the mineral balance hypothesis, herbivores did relatively poorly on these
plants. Also consistent with the hypothesis, the effect of Zn on plant
growth and herbivore development was dependent on the ratio of the other two

Soil-management history and the role of plant mineral balance as a
determinant of maize susceptibility to the European corn borer
Author(s): Phelan PL
Document Type: Article
Language: English
Cited References: 20      Times Cited: 5
Abstract: Proponents of organic farming have long suggested that their
methods produce "healthy" crops that are less susceptible to insects and
diseases. Experimental comparisons of European corn borer (ECB) egg-laying
response to maize plants grown in a greenhouse in soil collected from either
organically or conventionally managed farms provided evidence consistent
with these assertions. in each of three paired comparisons, higher
egg-laying occurred on plants in conventional soil. Subsequent studies
suggested that differences in ECB ovipositional preference were related to
plant-mineral balance; a three-mineral quadratic model showed strong
predictive power for ECB oviposition. A role for plant minerals was also
suggested in a study of paired maize fields with high and low ECB
populations compared at three different geographic locations. Significant
differences in leaf-mineral profiles between fields were measured that were
consistent across locations. Based on these cumulative findings, it is
hypothesized that: (1) maize plants with an optimal mineral balance show
lower susceptibility to insect pests, (2) determining the effects of
minerals on susceptibility must include consideration of both ratios and
absolute levels, and (3) a more resistant physiological state is more likely
in organically managed soils because of the inherent greater capacity of
these soils to buffer availability of minerals to plants.

Soil-management history and host preference by Ostrinia nubilalis: Evidence
for plant mineral balance mediating insect-plant interactions
Author(s): Phelan PL, Norris KH, Mason JF
Source: ENVIRONMENTAL ENTOMOLOGY 25 (6): 1329-1336 DEC 1996
Document Type: Article
Language: English
Cited References: 26      Times Cited: 13
Abstract: Organic-farming practitioners have long suggested that maximizing
soil biotic activity results in crops of reduced susceptibility to pests. In
the current study, we examined the ovipositional preference of Ostrinia
nubilalis (Hubner), the European corn borer, on sweet corn grown in the
greenhouse using soils from neighboring organic and conventional farms and
fertilized with NH4NO3, cow-manure compost, or left unamended. In addition
to ovipositional preference, we compared photosynthetic potential,
leaf-mineral profiles, and biochemical profiles measured by near-infrared
(NIR) spectroscopy. Significant variation in O. nubilalis oviposition among
fertilizer treatments was measured for plants in conventional soil, but not
for those in organic soil. Photosynthetic parameters, notably net
photosynthesis and stomatal conductance, correlated strongly with plant
biomass accumulation, but no correlations with O. nubilalis preference were
detected. In contrast, a quadratic model of 3 leaf-mineral levels (Zn, Al,
and N) showed a strong relationship with O. nubilalis oviposition (adjusted
r(2) = 0.71); plant growth was best described by a quadratic model of N
alone (adjusted r(2) = 0.69). The greatest differences in NIR spectra were
caused by protein, and soil-fertilizer combinations producing the lowest
protein levels were those whose plants received the greatest number of 0.
nubilalis eggs. We suggest that differences in corn acceptibility to 0.
nubilalis is at least in part mediated by plant mineral balance, which
incorporates both absolute levels and ratios of minerals, and that an
optimal balance of these minerals is more likely to occur in organically
managed soil because of an inherent property of reducing variation in
mineral availability in those soils.

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