Junk Food Is Bad for Plants, Too

plant fertilizer

Story at-a-glance -

  • Plants’ natural symbiotic relationship with soil microorganisms is disrupted by the use of synthetic fertilizer
  • The use of synthetic fertilizers results in higher yields and bigger produce that is less nutrient-dense
  • The mineral content of fruits and vegetables has declined by 5 percent to 40 percent over the last five to seven decades

By Dr. Mercola

Nitrogen, phosphorus and potassium, or NPK, are known as the “Big 3” nutrients that plants need to grow. Nitrogen, considered to be the most important of the Big 3, is essential for plants to form protein, which, as in humans, makes up much of a plant’s tissues.

Phosphorus is necessary for plants to use and store energy and carry out the process of photosynthesis. Without phosphorus, plants cannot grow and develop normally.

Potassium rounds out the Big 3. It helps plants to resist disease and helps increase crop yields. When combined into NPK fertilizer, the Big 3 nutrients help plants grow bigger, faster and, seemingly, healthier.

However, as noted in a recent Nautilus article authored by biologist Anne Biklé and David R. Montgomery, Dean’s professor of geomorphology at the University of Washington:1

“ … there is a trade-off. High-yielding crops raised on a steady diet of fertilizers appear to have lower levels of certain minerals and nutrients. The diet our crops eat influences what gets into our food, and what we get — or don’t get — out of these foods when we eat them.”

Plants Raised on Synthetic Fertilizer Look Good on the Outside, Lack Nutrients on the Inside

If you slurp down a large soda or eat a candy bar, you’ll feel an initial rush of energy. You may conclude that your sweet treat made you feel good and maybe even was good for you body, but then you’ll experience an inevitable crash.

The candy gives you an initial boost but is missing key elements your body needs to be healthy. Similarly, livestock raised on concentrated animal feeding operations (CAFOs) can be fattened up on grains, but they suffer increased diseases, and their meat is less nutritious, compared to livestock fed their natural diet.

Also similarly, plants given NPK will grow, but they’re missing out on key elements they need to thrive. Biklé and Montgomery continued:2

“ … the things that fuel plant growth on today’s farms, chiefly NPK fertilizers, are not the same things that plants need to stave off disease, heal from injuries, and fend off pests and pathogens.

In other words, our big human brains have long, and erroneously, conflated plant growth with plant health.

And herein lies a pickle for modern agriculture. The recipe for plant health is complex. It goes considerably beyond the simple mix of N, P, and K that plants need to grow.”

True Plant Health Depends on a Reciprocal Relationship With the Soil

To understand why raising plants on a “junk-food diet” of NPK is so detrimental to their ultimate health you first need to understand the importance of the rhizosphere. This term, coined in 1904 by German agronomist and plant physiologist Lorenz Hiltner, describes the plant root-soil interface.3

The rhizosphere is the area immediately around a plant’s root. It contains microorganisms that thrive on chemicals released from the plant’s roots. These chemicals, known as exudates, include carbohydrates, phytochemicals and other compounds.

In exchange for the exudates, the root microbiome supplies the plant with important metabolites for health, which, along with exposure to pests and pathogens, helps plants produce phytochemicals. A well-fed root microbiome will also supply plants with ample nitrogen, phosphorus and potassium.

Producing exudates is energy-intensive for plants, but well worth it to feed and establish a healthy root microbiome. This important symbiotic relationship is lost, however, when plants are raised on NPK. As Biklé and Montgomery explained:4

“ … when crops gorge on free NPK fertilizers it monkey-wrenches the symbiotic way of life for plant and root microbiome alike. Nothing, not even a brainless plant, is going to expend a third of its energy on something that can be had for free. And so their green bodies crank down exudate production.

The consequence? A root microbiome that produces fewer metabolites beneficial to plants. A fertilizer-fed plant may not need N, P, and K deliveries from its root microbiome, but in forgoing these things it loses out on the other things that the root microbiome delivers that foster plant health.

So we end up with big fat high-yielding crops that look good on the outside but are poor in minerals and phytochemicals on the inside …

A shuttered, starving root microbiome is the great undoing of the botanical worlds’ strategy for coupling a just-right rate of growth with a formidable built-in arsenal and pharmacy.”

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Plant Foods Aren’t as Healthy as They Used to Be

The mineral content of fruits and vegetables has declined by 5 percent to 40 percent over the last five to seven decades.5,6 Even wheat has declined in nutrients like iron and zinc over the last 100 years.

Today's vegetables may be larger but they typically do not contain more nutrients. Jumbo-sized produce often contains more dry matter than anything else, which dilutes mineral concentrations.

An additional problem is the "genetic dilution effect," in which selective breeding to increase crop yield has led to declines in protein, amino acids, and minerals. Breeders select for high yield, effectively selecting mostly for high carbohydrate content rather than nutrition.

According to a study published in the journal HortScience, “ … side-by-side plantings of low- and high-yield cultivars of broccoli and grains found consistently negative correlations between yield and concentrations of minerals and protein.”7

Beyond minerals and protein, phytochemical levels in plants are also changing. Ancient wild plants provided an astounding level of phytonutrients that are largely absent from our modern cultivated fruits and veggies.

For instance, wild dandelions contain seven times more phytonutrients than spinach, and purple potatoes native to Peru contain 28 times more anthocyanins than commonly consumed russet potatoes.8

The richly colored “Indian corn” now mostly used for holiday decorating was once widely consumed, and contained far more disease-fighting antioxidants and less sugar than today’s popular pale yellow sweet corn.

As written by Biklé and Montgomery, “ … NPK fertilizers translate into lower phytochemical levels. When plants grow explosively they tend to cut back on making phytochemicals.”

Pesticides Further Tinker With the Natural Order of Plant Life

Many phytochemicals produced by plants act as a natural defense system to protect plants from predators. When a bug such as a caterpillar chews on a plant's leaf, the plant "hears" the vibrations of the chewing and produces a phytochemical to defend itself from further harm.9

When crops are sprayed with pesticides, herbicides, and fungicides, however, the plant has less of a need to produce these in-house phytochemical weapons. Biklé and Montgomery wrote:10

Why produce an energetically expensive mustard oil bomb if there are no herbivores around? This situation spurs plants to make fewer defensive phytochemicals, as well as those that serve as nutrients bound for the bustling rhizosphere.

These events translate into less food for the root microbiome … A plant’s roots go from being a vital, two-way trade zone to one-way straws sucking up fertilizers.

… Faced with an all-you-can-eat buffet, that’s exactly what a plant’s green body sets out to do. They shunt a good deal of the energy they make through photosynthesis to building biomass, shortchanging themselves on the energy they need to make phytochemicals.

Ramping down phytochemical production depletes a plant’s homemade arsenal and pharmacy, making them as vulnerable as a sick animal within sight of a predator.

And so we swoop in — dousing couch-potato crops and soils with poisons to do what plant phytochemicals and root microbiomes have done for millions of years.”

Synthetic Nitrogen Fertilizer Leads to the Destruction of Organic Matter in Soil

Carbon is the main component of organic matter in soil, which is why organic matter is often referred to as a “carbon sink” (as opposed to a carbon source).

It's estimated that one-third of the surplus carbon dioxide in the atmosphere stems from poor land-management processes that contribute to the loss of carbon, as carbon dioxide, from farmlands.11 Altering our agricultural practices in such a way as to return and confine organic matter and carbon in the soil, on the other hand, would help:

Regenerate the soil

Limit agricultural water usage with no till and crop covers

Increase crop yields

Reduce the need for agricultural chemicals and additives, if not eliminate such need entirely in time

Reduce atmospheric carbon dioxide levels

Reduce air and water pollution by lessening the need for herbicides, pesticides, and synthetic fertilizers

Unfortunately, in order to achieve these benefits, the use of synthetic nitrogen fertilizers would need to be drastically reduced, as they’re one of the greatest threats to organic matter in the soil. The non-profit organization GRAIN reported:12

“Despite industry propaganda to the contrary, recent studies demonstrate that chemical fertilizers are responsible for much of the massive loss of organic matter that has occurred in the world's soils since the pre-industrial era.

"In numerous publications spanning more than 100 years and a wide variety of cropping and tillage practices, we found consistent evidence of an organic carbon decline for fertilized soils throughout the world," says University of Illinois soils scientist Charlie Boast.

Soils around the world have lost, on average, at least 1–2 percentage points of organic matter in the top 30 cm since chemical fertilizers began to be used. This amounts to some 150,000–205,000 million tons of organic matter, which has resulted in 220,000–330,000 million tons of CO2 emitted into the air or 30 percent of the current excess CO2 in the atmosphere!”

Fertilizers are Destroying Fisheries, Contaminating Drinking Water

The environmental toll of synthetic fertilizer is steep, even beyond its role in crop health, soil health and nutrient levels in produce. As fertilizer runs off of farms in agricultural states like Minnesota, Iowa, Illinois, Wisconsin, Missouri and others, it enters the Mississippi River, leading to an overabundance of nutrients, including nitrogen and phosphorus, in the water.

This, in turn, leads to the development of algal blooms, which alter the food chain and deplete oxygen, leading to dead zones. One of the largest dead zones worldwide can be found in the Gulf of Mexico, beginning at the Mississippi River delta.13 Fisheries in the Gulf of Mexico have been destroyed as a result.

Further, researchers from the University of Waterloo in Canada analyzed more than 2,000 soil samples from the Mississippi River Basin. Evidence of significant buildup of nitrogen was found far below the soil surface at depths of 10 inches to 3.2 feet.14

The finding brings up grave concerns for the environment, even if nitrogen fertilizers stop being used, because it shows nitrogen is being stored in the soil. Excess nitrogen accumulated deep in the soil could continue to leach into groundwater for 35 years after the fertilizer use is ceased.

Eliminating Chemical Fertilizers Is Key for Sustainable Agriculture

Fertilizer companies claim their products are necessary to feed the world, but research suggests working with nature instead of against it — via agroecology or “ecological farming” — can produce as much food without the need for chemical fertilizers. According to GRAIN:15

“The elimination of chemical fertilizers is one of the easiest and most effective places to start. Cutting out chemical fertilizers could reduce annual global greenhouse emissions by as much as 10% …

Additionally, the shift from chemical fertilizers to agroecological practices would allow farmers to rebuild organic matter in the world's soils, and thus capture a possible two- thirds of the current excess CO2 in the atmosphere within 50 years.”

On an individual level you can help by buying organic food as well as food from farmers who are using natural methods and soil-regenerative techniques, such as no till, cover crops, composting and livestock integration, in lieu of synthetic fertilizer. This will naturally help you to eat better too, since typically only real whole foods are grown this way (while most processed foods are the product of destructive industrial nitrogen-fertilizer-laden agriculture).