Slow-growing tomato plants absorb a lot of nutrients from the soil. It’s especially important to replenish the nutrients in potted tomato plants regularly because their roots have limited access to garden soil. Nitrogen is necessary to support photosynthesis and leaf growth as well as strong roots. Using homemade or store bought organic nitrogen fertilizers has the extra advantage of keeping the soil healthy by filling it with beneficial microorganisms that break down nutrients into elements the tomato plants can easily digest.
Check your garden store for organic nitrogen fertilizers like powdered fish meal, liquid fish emulsion, guano, or worm castings. All of these are natural, slow-release nitrogen fertilizers that tomatoes love. The fertilizers that come from animals can have a strong smell, but it will fade within a day or two. Worm castings can be used on indoor tomato plants with no bad smell at all.
Add bone meal to guano or other manure-based fertilizers, which are heavy in nitrogen but low in potassium. If a tomato plant gets too much nitrogen, it will produce large, lush leaves but little or no fruit.Tomatoes need the potassium in bone meal for good flowering and fruits.
Dilute fish emulsion according to the instructions on the bottle, and only use as much powdered fertilizers as directed. Don’t be tempted to give tomato plants more animal-based organic fertilizers than recommended on the package because they can burn the roots and kill the plant. Compost and worm castings are safe to apply regularly and often.
Transplant tomato starts or plant tomato seeds into soil mixed with compost. The compost will provide a slow-release nitrogen fertilizer that has a good balance of other elements. Sprinkle a layer of worm castings on the soil’s surface after planting or transplanting.
Fertilize tomatoes immediately after transplanting with fish, bone, or manure-based fertilizers. Water in the fertilizers and cover the soil with mulch or compost.
Spray foliage with diluted fish emulsion. Mix a teaspoon of liquid fish emulsion into a quart of water to spray on a few plants. For larger tomato plantings, mix two ounces into a gallon of water. Spray the leaves and stems every two weeks, preferably in the morning.
Use diluted worm castings to feed tomato plants by mixing a handful of worm castings into a gallon of water. Add a teaspoon of molasses and aerate the bucket overnight with an aquarium pump. Use the mixture as a foliar spray or to water plants.
Give tomato plants a boost two weeks after transplanting or germination, and continue to fertilize them every two weeks until the first fruits appear. Give potted plants a handful of compost or worm castings, or apply a small amount of fish or bone meal according to the instructions and the size of the pot. For garden tomatoes, dig the fertilizer a couple inches into the soil around the plant, several inches away from the stalk. Water fertilizer in well, and make sure soil around the plants is always moist.
Avoid getting powdered organic fertilizers on leaves and stems because these substances get hot as they decompose and will burn the plant.