All plants need nutrients, which are found naturally in the soil. But over time, they deplete and need to be replenished for the plants to thrive.

Most fertilizers contain three primary nutrients: nitrogen, phosphorus and potassium, represented by the NPK ratio on the package. Nitrogen directs the plant to channel its energy into green, leafy growth; phosphorus promotes the development of roots, fruits and flowers; and potassium is beneficial to the overall health of the plant.

Many fertilizers also contain secondary nutrients, like calcium and magnesium, and micronutrients like iron, copper, boron, manganese, zinc, and molybdenum. All are necessary for optimal plant growth.

The good news is that they don’t have to come from a bag or a bottle.

There are many ways for home gardeners to save money while providing their plants with high quality nutrients.

Take grass clippings into account: if you leave them on the lawn after mowing, you will no longer need fertilizer. As they decompose, fresh clippings release a natural source of nitrogen into the soil that will support lawn grasses (don’t use fresh clippings in flower beds, they will burn your plants).

Compost is the best soil amendment available. It increases the moisture retention of sand, improves clay drainage and adds beneficial nutrients to the soil. Incorporate generous amounts into flowerbeds or planting holes, or use in place of mulch.

If composting isn’t your bag, there’s no need to buy any: Simply collect fruit and vegetable peelings and other kitchen scraps (but not meat, dairy or fat) in a bowl on your work surface. Each time it fills up, dig its contents into the garden. As the waste decomposes, it adds nutrients to the soil. Just be sure to bury them at least 10 to 12 inches deep to avoid attracting hungry wildlife, and dig several inches away from plant rows to avoid root damage.

Many gardeners treat their plants with fish emulsion, a quick-release organic liquid fertilizer made from whole fish and by-products of the fishing industry. It contains nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and sodium, among other nutrients. It’s about as expensive as it sounds, but there are ways to avoid buying it.

Plants enjoy a wide range of fish applications, including a whole fish placed at the bottom of each planting hole, buried fish scraps (again, at least 10-12 inches deep), or an emulsion homemade fish fillet by soaking scales, bones and entrails. in a tightly closed 5 gallon bucket of water for at least a month, then strain the liquid and use it to water the plants. (Avoid using the drained water from canned tuna, though, as its high sodium content can harm the soil and your plants.)

If you are an angler, you already have access to these modifications. If you’re not, your local fishmonger may be willing to donate – or sell off – leftovers and heads that would otherwise be thrown away.

Plants also benefit from the water used by aquariums, which is rich in nitrogen and other nutrients.

When you boil vegetables and pour the water down the drain, you throw a seam of vitamins and minerals that could enrich your garden. And the water from boiled eggs is full of calcium, which is especially useful for tomatoes and peppers. Allow each to come to room temperature before application.

You can even use eggshells in place of garden lime, as both are made from calcium carbonate. Microwave for 2 minutes to dehydrate them, then grind them in a high power blender, coffee grinder or food processor. Incorporate the resulting mineral-rich powder into the soil. The same can be done with banana peels, which are packed with plant-boosting potassium.

I recently learned about the benefits of watering plants with homemade yeast infusion. I tried mixing a sachet of bread yeast and a tablespoon of sugar in a liter of warm water, then placing it in a dark place for 2 hours. Then I diluted the frothy mix with 3 gallons of water and applied about a cup to each plant. Three annual applications (no more) are recommended – one each time the plants begin to root, flower and fruit.

It’s too early to determine the benefits for my garden, but the science seems solid: when yeast digests sugar, it releases nitrogen, plant hormones, amino acids, enzymes and other root stimulators that promote plant growth and productivity. It also feeds beneficial soil bacteria and improves plant resistance to disease.

And the best part is that it costs around 79 cents to make.

Jessica Damiano writes regularly about gardening for The Associated Press. A master gardener and educator, she writes The Weekly Dirt newsletter and creates an annual wall calendar of daily gardening tips. Send her a note at [email protected] and find her at jessicadamiano.com and on Instagram @JesDamiano.