They [farmers on Eastern Shore of Maryland] put in an order
for pellets because they hear it keeps deer away from the beans, but they make
a second order because they see a difference. I am not sure what it is, but it
might be micronutrients.” I was asking
Synagro’s Steve McMahon about the aspects of dried biosolids that “sell.” This
was not the first time I had heard these “pitches:” pellets are a deer
repellent; pellets are like a vitamin pill for the soil. Are either of these
aspects of biosolids true?
As we are experiencing with COVID-19 and with presidential
politics, the lies we tell ourselves and the truths we hold as “self-evident”
are hard to dig into. Can science help us avoid unexamined biases we hold and
the lies we tell ourselves? With respect to biosolids, can science tell us if biosolids
pellets repel deer and if biosolids are a vitamin for the soil?
Fascinatingly, even though billions of people are concerned
with nutrition and many hundred thousand scientists attend to human and
environmental health issues, clear irrefutable answers to basic questions are
in short supply. Can there be any surprise, then, that clear irrefutable
answers on biosolids are also in short supply?
Issue of human health remain controversial, and how science
works to clarify these issues is a metaphor for how we use science to
demonstrate the benefits of biosolids.
Isn’t it true that vitamins for the human body are good?
Science is mostly NO, not supporting multi-vitamins. “There is no indication that supplementation
is necessary for healthy, non-pregnant, non-lactating adults” according to a
2019 review article Minimal
Purposes of Multivitamins. Science supports Vitamin D for people without
sun exposure, iron for women of child-bearing age, and folic acid for pregnant
women, but almost nothing else. “Essential minerals,” like zinc, seem
unsupported as necessary supplements. So, can we be sure biosolids as vitamin
are necessarily good?
Is it true that foods labeled organic are more nutritious
than conventional foods? The science is mixed, YES and NO. One review article (A
literature‐based comparison of nutrient and contaminant contents between
organic and conventional vegetables and potatoes) says, sometimes yes,
sometimes no, but “it becomes difficult to justify general claims indicating a
surplus value of organic over conventional vegetables and potatoes.” So, can we
be sure the “organic” label would connote better nutrition.
Is it true that a wholly plant-based diet confers greater
health than a meat-eating diet? The science is not clear, and mostly NO. A
major study (Nutrition
and Health – The Association between Eating Behavior and Various Health
Parameters: A Matched Sample Study) out of Austria suggests that
vegetarians are less healthy overall than folks eating conventionally. So, can
we be sure biosolids users deploy biosolids for the right reasons?
Is it true that bacon is no good!? The scientific evidence
is YES (Aw, say it is not true!). The 2020 review article Red
and Processed Meats and Health Risks: How Strong Is the Evidence? says“…dietary guidelines should continue to
emphasize dietary patterns low in red and processed meats and high in minimally
processed plant foods such as fruits and vegetables, whole grains, nuts, and
legumes.” So, can we be sure biosolids is always good for soil, particularly considering
pH changes, high phosphorus and low potassium.
Is it true that vegetarianism is better for the planet? The
answer is YES, BUT. As the commentary “Why
the debate between vegans and meat-eaters is pointless” says “it is a
complex question exactly what kind of food system would be ideal… Keep an open
mind.” So, are biosolids nutrients, contributing to the circular economy, infallibly
preferred to fossilized sources?
Isn’t it true that avoiding GMOs makes a difference in a
person’s health? Again, the science is
not clear. As one large German study (Republished
study: long-term toxicity of a Roundup herbicide and a Roundup-tolerant
genetically modified maize) concluded: “Our findings imply that long-term
(2 year) feeding trials need to be conducted to thoroughly evaluate the safety
of GM foods and pesticides in their full commercial formulations.” So, are the
organic micropollutants added to soil with biosolids clearly without risks?
Science cannot give us firm answers to such huge questions
of human and environmental health. What can we expect of the answers about the
safety and effectiveness of biosolids as a fertilizer, as a vitamin for soils
that deters deer?
Are biosolids safe to use? The answer is a firm YES, at
least as firm a conclusion as scientists are apt to make. My original “go-to”
document is the iconic 2005 journal article Sustainable
land application: An overview. No less significant is the 2002 WERF report Evaluating
risks and benefits of soil amendments used in agriculture,” with its many
hundreds of journal citations. But nothing quite rises to the most current resource
than the collective response by soil scientists in the W4170 group, in its
technical answers to the EPA OIG Report. The OIG “Report:
EPA Unable to Assess the Impact of Hundreds of Unregulated Pollutants in
Land-Applied Biosolids on Human Health and the Environment” was regarded as
ill-informed and misleading by scientists familiar with the original regulatory
development. Their response was brought together in the release of W4170
Multistate Research Committee Response to USEPA OIG Report No. 19-P-0002. The
elements and compounds for which research into risks is warranted are countable
on two hands.
Are agricultural soils in need of micronutrient
supplementation? Science suggests the answer generally is NO. But this is a
complicated question, and scientific answers require more resources of time and
money than usually available. One
article that underscores this is Effects
of Nutrient Antagonism and Synergism on Yield and Fertilizer Use Efficiency.
This study starts out “great potential to increase the nutrient use efficiency,
and consequently, yield levels by considering all essential plant nutrients
(macronutrients N, P, K, Ca, Mg, and S and micronutrients Cl, Fe, B, Mn, Zn,
Cu, Mo, and Ni) in fertilizer products and fertilization strategies.” The
authors point out that “Studies about the effects of an annual fertilization
with micronutrients to compensate for the removal by crop are rare.” Yet they
hold the point of view that “balancing the composition, amount, timing, and
mode of delivery of fertilizers to plants and soil, thereby aiming to overcome
antagonism and stimulate synergism.” Does biosolids accomplish this balancing?
Can the balance of nutrients in soil affect the nutrient
quality of the crops growing on them?
The answer seems to be YES. This area of scientific inquiry stands as
its own discipline. A publication on this topic is Fertilizing
Crops to Improve Human Health: a Scientific Review. The conclusion of this report is “Fertilizer
contributes to both the quantity and quality of the food produced. Used in the
right way-applying the right source at the right rate, time and place-and on
the right crops, it contributes immensely to the health and well-being of
humanity.”
Do the micronutrients in biosolids impart a natural balance
of micronutrients to the soil? The answer is “LIKELY YES.” The abundance and
order of nutrient concentrations in biosolids mirrors that of the
concentrations in plant tissues. This can be seen by lining up in rank order
the essential nutrients for plant growth (K>N>Ca>S>Cl>P>Mg>Mn>Fe>Zn>Cu>B
>Ni [Source: Plant
nutrient functions and deficiency and toxicity symptom]) against the
abundance and order of micronutrients in biosolids (Ca>N>P>Fe>Mg>Mn>K>Zn>Cu>B>Mo>Ni
[derived from Targeted National
Sewage Sludge Surveys). The primary outlier is
potassium (K). Because K is a very soluble cation, it passes out in wastewater
effluent rather than attach well to biosolids organic matter. Biosolids concentrations better mirror plant
tissue concentrations than soil concentrations.
Soil micronutrients loadings do not reflect micronutrient availability
to crop roots Vegetable crop scientist
George Antonious demonstrates this fact in Elevated concentrations of
trace elements in soil do not necessarily reflect metals available to plants.
Can the micronutrients in biosolids boost the yield and
nutrient content of crops? The answer is LIKELY NO. I checked in with several
of the scientists who worked on the W4170 report. First, most crops are not
subject to deficiencies in micronutrients, so additions through biosolids will
not register an effect. Second, the vast
majority of farmers we would be working with are among the top producers by
design of our programs, with implemented nutrient management and conservation
plans, with soils adjusted for proper soil pH, and with established soil metals
test results. One of our science friends said a farmer once provided anecdotal
testimonial to a zinc deficiency corrected by biosolids. Another researcher had
worked on a coarse-textured, iron-deficient soil, and biosolids had demonstrated
yield benefits. Another scientist cautioned about the opposite concern; deficiencies
of Zn, Mn and Cu could be induced by lime-stabilized biosolids. But, in
general, crop yield increases from the micronutrients contained in biosolids are
not a “thing.”
Can biosolids be the basis for repairing soils with a demonstrably
damaged balance of nutrients? The answer is YES. Iconic work by Rufus Chaney
and Sally Brown showed how biosolids products repaired mine sites and damaged
urban soils ( In
situ soil treatments to reduce the phyto- and bioavailability of lead, zinc,
and cadmium, Greening
a Steel Mill Slag Brownfield with Biosolids and Sediments: A Case Study,
and Biosolids
Products for Urban Agriculture). What is more, biosolids enable poor soils
to sustain economically valuable production, as in biofuel crops (Sylvis
to support green coal mine reclamation project in Alberta).
The question of real importance: can biosolids repel deer? Most likely
YES! The evidence is not just anecdotal.
First, Milorganite stands behind this benefit of its dried biosolids product.
It posts several “science” articles in its support (e.g., Using Milorganite® to temporarily repel
white-tailed deer from food plots).
Various professional columnists (e.g., Gardens All) and technical bodies (e.g., University of Georgia Extension) recommend use of Milorganite as deer
repellant.
That is good enough
for me. Certain lifestyle choices and biases are best held as faith, clear and
true, rather than subjected to scientific scrutiny, incomplete and messy. My
breakfast will continue to embrace blueberries and granola, full of
antioxidants and fiber, and I will continue to have faith in biosolids as a
“multivitamin for soil.”
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