How to Add Nitrogen to Your Soil for Healthy, Prolific Plants

Nitrogen is a critical element for the plants growing in your garden. They need nitrogen to help them with photosynthesis, the process by which plants get energy from the sun. They also need nitrogen to help build amino acids, which form the proteins plants need to survive. While the air around us contains nitrogen, most plants can't utilize it in this form. Instead, they must obtain nitrogen from the soil. But not all soils are nitrogen-rich, and even if yours is, nitrogen can deplete over time. It's up to gardeners to properly manage the nitrogen in their soil so their plants can keep growing. Here are a few expert-approved ways to add nitrogen to your soil for healthy, prolific plants. 

Use Compost

Compost consists of the perfect ratio of carbon-rich brown material and nitrogen-rich green material, making it a great way to boost nitrogen levels in the soil. "Incorporating organic matter is one of the best ways to introduce many of the necessary nutrients needed by plants, including nitrogen," says horticulture extension specialist Aaron Steil. "Compost has the added benefit of improving the structure of the soil, allowing more availability of water and air, which promotes healthy root growth." Work a few inches of compost into your garden beds to increase nitrogen levels over time.

Rotate Crops with Legumes

Certain plants, like alfalfa, peas, and beans, are "nitrogen fixers," meaning they can put nitrogen back into the soil. According to Steil, microorganisms called rhizobia bacteria live in small nodules on the roots of these plants, converting the nitrogen in our atmosphere into nitrogen compounds. He notes that this process is mutually beneficial to both the microorganisms and the nitrogen fixer. The microorganisms can obtain food and energy from the root of the plant and the plant has a source of nitrogen it can use to grow and develop. 

Try Grass Clippings

An easy and accessible way to add nitrogen back into your soil is with grass clippings. "Using a mulching mower to return clippings to the lawn is a great way to reduce fertilizer needs, but they will not replace it," says Steil. "Mulching grass clippings can provide up to a fourth of the nitrogen needed to grow a healthy lawn, allowing you to use less fertilizer." Steil adds that you can add grass clippings to your compost pile as nitrogen-rich green material, but make sure the clippings don't contain weeds or you risk spreading these pesky plants to your garden. 

Apply Fertilizer

Typically, compost alone cannot provide all the nitrogen your garden needs for the plants to stay healthy and productive, which is especially true in the vegetable garden, says Steil. He recommends supplementing with traditional or natural fertilizers, like blood meal or fish emulsion. Conducting a soil test will tell you if your soil is nitrogen-deficient and which fertilizers will help improve it. 

Use Multiple Solutions

As with many gardening tasks, an assortment of solutions is usually more effective than a single option, so aim to supplement with more than one form of nitrogen for best results. "I keep my soil nitrogen-rich by adding plenty of compost, such as kitchen scraps or aged manure—it breaks down quickly and feeds the soil well," says Austin. "I also rely on legumes like peas and beans in my crop rotation. They naturally fix nitrogen into the soil, which sets up the next planting for success without needing store-bought fertilizers."