Growing lush, productive tomato plants requires providing them with the right nutrients at the proper times. While synthetic fertilizers offer an instant nutrient boost, organic options provide longer-lasting nourishment. When used correctly, organic tomato fertilizers enhance plant health, improve fruit yields, and contribute to superior flavor.
Tomatoes thrive when their soil contains a balanced supply of essential nutrients like nitrogen, phosphorus, and potassium. Organic fertilizers derived from natural sources can deliver these key elements without harsh chemicals.
Organic fertilizers also feed the microbial life in soil which is vital for releasing nutrients to plant roots. Here are some of the top organic fertilizer options for achieving thriving tomato plants and bountiful harvests.
Compost
Compost made from garden waste, livestock manure, and other organic materials is a foundational fertilizer for soil health. As it breaks down, compost releases a steady supply of major and minor nutrients. Compost also improves soil structure and moisture retention.
For tomatoes, add 1-2 inches of finished compost and mix thoroughly into planting beds before transplanting seedlings Compost can also be side-dressed around established plants as a nutrient booster during the growing season
Worm Castings
Worm castings, or vermicompost, consist of earthworm excrement filled with nutrients and beneficial microbes. Castings contain nitrogen, phosphorus, potassium, calcium, and magnesium. Their rich microbiology enhances tomato roots’ ability to uptake nutrients.
Mix 1-2 cups of worm castings into each planting hole before transplanting tomatoes. You can also brew worm casting tea to use as a foliar fertilizer spray
Fish Emulsion
Fish emulsion fertilizer provides an immediate nitrogen boost, with some phosphorus and potassium too. It comes from processing fish waste and has a strong odor. Fish emulsion stimulates leafy growth and can be applied every 2-4 weeks by mixing with water and pouring onto soil.
Manure
Aged manure from cows, horses, chickens, rabbits, and other livestock makes an excellent slow-release fertilizer. Manure provides a complete spectrum of major and minor nutrients. Well-rotted manure worked into beds before planting tomatoes gives them long-lasting nourishment.
Seaweed and Kelp Extracts
Seaweed and kelp are two types of marine vegetation harvested to produce organic fertilizers. Dried kelp meal or liquid kelp extract provides potassium, magnesium, iron, calcium and over 60 trace minerals. Seaweed fertilizer contains growth-promoting hormones along with a broad nutrient profile.
Liquid seaweed extracts can be used to fertilize tomatoes every 2-4 weeks. Kelp meal is best mixed into beds before planting.
Wood Ashes
The potassium and calcium in wood ashes make them valuable for fertilizing tomatoes. Sprinkling a small amount of wood ash around each transplant provides potassium. Excess potassium can inhibit the uptake of magnesium, so use wood ash sparingly and avoid over-applying it.
Bone Meal
Bone meal consists of finely ground animal bones that provide a steady phosphorus release. Phosphorus is vital for root development and flower/fruit production. Lightly mix bone meal into soil at planting time and again halfway through the season when tomatoes start setting fruit.
Banana Peels
Chopped, decomposed banana peels offer a readily available potassium boost. Peels should be dried or aged for at least 2 weeks before placing them in soil. Mix some chopped peels into planting holes or bury them next to established tomato plants. Leaving them on top of soil can attract pests.
Epsom Salt
Magnesium is an important mineral for photosynthesis and fruit production. Epsom salt contains magnesium that tomatoes can readily absorb. It also provides sulfur. Mix 1 tablespoon per foot of plant height around each tomato plant. Epsom salts dissolve quickly so re-apply monthly.
Liquid Fertilizers
Some gardeners brew their own liquid tomato fertilizer using ingredients like fish emulsion, molasses, compost tea, or manure tea. This provides an organic nutrient boost that you control. Commercial organic liquid fertilizers like fish emulsion or kelp extracts are also useful.
The microbe-rich nature of organic fertilizers leads to healthier tomato plants. While not an instant fix like chemical fertilizers, organic options improve soil nutrients over time for sustained results. Pay close attention to your plants’ needs and apply the right organic fertilizers at strategic times to grow robust tomatoes.
How to Apply Fertilizer to Tomato Plants
There are two main types of fertilizers: liquid and granular. I like liquid because its easy for the plants to take in. I compare it to drinking liquid cough syrup instead of trying to swallow a pill if youre sick. Liquid fertilizers typically need to be diluted before theyre applied so that you dont burn your plants. Whatever youre using, make sure to read the directions and avoid over-applying.
Lets look at two different ways to feed your tomato plants.
Spray a diluted liquid fertilizer onto the front and back of the leaves of your fruiting plant. The leaves will absorb the nutrients.
Avoid fertilizing with a foliar feed on days that are super sunny or right before rain. It’s best to wait for a cloudy day and spread the fertilizer early in the morning or late at night. When it rains, you might not be able to foliar feed, but you could do a side dressing instead. The rain will help the feed move through the plant’s system.
To the soil around the base of your tomato plants, you can add compost, liquid fertilizers like fish emulsion, or granular fertilizers. This replenishes nutrient levels and sustains plant growth. When you use granular fertilizer, you’ll rake it into the soil around the plants’ bases, being careful not to damage the roots. Make sure to water granular fertilizers in well.
By adding fertilizer on the side, it can be spread out in the soil and feed the plant’s roots before being taken up by the plant itself.
Phosphorus-Rich Organic Fertilizers for Flowering Tomato Plants
Again, our focus is on natural sources that will release nutrients over time.
- Meal made from fish bones: Fish bones naturally contain phosphorous and can be used in the garden as a leaf feed or a side dressing.
- Bone Meal: Bone meal is a slow-release fertilizer that you can mix into the hole where you plant or use as a side dressing during the growing season. You can also use it as a foliar feed.
- Chicken and rabbit manure: Animal manures add nitrogen and phosphorous to the soil, and you can use extra manure to give your plants more phosphorous.
- Kelp Meal—Made from seaweed, kelp meal is a natural fertilizer that has a balanced mix of nutrients and trace elements. For better plant health, sprinkle kelp meal around the plants’ bases.
- This is ground-up rock that adds potassium, phosphorus, and many micronutrients to your soil when mixed into the soil as a side dressing. It is also known as soft rock phosphate.
Of your different options, mineral sources are typically cheaper and will last longer.
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