Dear Science,

My tomato plants are struggling this summer. They are yellow and weak despite good amounts of sun and water. Is there anything wrong with using some Miracle-Gro? Would an organic fertilizer be better?

Waiting For A Bloom

Sunlight, water, and carbon dioxide aren't enough for your plant to grow. Generating new DNA bases requires nitrogen; your yellowing tomatoes need some. The atmosphere is about 70 percent nitrogen, but the nitrogen in the air is quite chemically inert. Capturing and connecting the otherwise content pairs of nitrogen to carbon or oxygen—fixing the nitrogen—takes a bit of chemical wrangling. Plants can't do this for themselves. Some bacteria, diazotrophs, can capture nitrogen, and the delightful legume family of plants hosts these bacteria as symbionts.

Chemical fertilizers are generated with modern chemical engineering, fixing nitrogen to carbon and oxygen with high temperatures and pressures through the Haber process. From the perspective of most plants, this fixed nitrogen is as usable and palatable as that made by bean plants. Organic fertilizers, typically from sewage sludge or animal manure, recycle some of the already-fixed nitrogen in the other parts of the biosphere. Crop rotation—planting a round of beans in your tired soil—also would do the trick.

Organic or chemical nitrogen fertilizers cause problems when they are overused. The runoff of the extra nitrogen causes a bloom of wild plants, disrupting the delicate balances of ecosystems. It isn't the source of the nitrogen—chemical engineering or industrially processed manure—that matters, it's how it's used.

You shouldn't fear the chemical fertilizer over the organic. Provided you use careful amounts of Miracle-Gro, your tomato plants will be fine. The same is true of an organic fertilizer. The fact that the chemical fertilizer comes from the other kind of plant isn't, in and of itself, a risk. Almost everything we eat or drink is genetically modified and processed. From pigs to corn to wheat to berries to broccoli—just about anything you'd find at an organic farmers market is the product of millennia of selective breeding, manipulation of the environment, and bending of the natural world. Fearing science, and the application of scientific knowledge to the problem of feeding humanity, is criminally irrational—particularly in a world with nearly seven billion people, many of whom are malnourished.

Overidealizing a romanticized notion of 19th-century agriculture—dating back to a time before we even had the most basic grasp of biology—goes beyond naive and into the absurd. Feeding all of us properly is going to require us to apply science to our food.

Next summer, plant some beans instead. The same advice applies to industrial farms.

Reasonably Yours,

Science

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