How do plants obtain nitrogen without eating protein-rich food?

Plants obtain the nitrogen they need for growth through several specialized processes, as they do not rely on consuming protein-rich food like animals do. Instead, they primarily absorb inorganic nitrogen compounds from their environment.12

Soil Absorption

Most plants obtain nitrogen by absorbing nitrate ($N{O}_3^{-}$) or ammonium ($N{H}_4^{+}$) ions directly from the soil through their roots. These nutrients are often made available through the decomposition of organic matter by soil microorganisms.134

Nitrogen Fixation

Because atmospheric nitrogen is largely unusable by plants, they rely on nitrogen-fixing bacteria to convert it into usable forms.54
* Symbiotic Relationships: Certain plants, such as legumes, host bacteria like Rhizobium in their root nodules. These bacteria convert nitrogen gas into ammonia, which the plant then utilizes.53
* Free-living Organisms: Other nitrogen-fixing organisms, such as cyanobacteria and Azotobacter, live freely in the soil or water to fix nitrogen.513

Carnivorous Adaptations

In nutrient-poor environments like bogs, some carnivorous plants have evolved to trap and digest insects or other small animals. These plants remain photosynthetic and do not "eat" prey for energy; rather, they use the prey specifically as a supplemental source of nitrogen and other essential minerals.6