If you want to add fertilizer at this stage, mix it in with the soil at the bottom of the hole and then place a layer of unfertilized soil on top. If the tomato plant roots touch raw fertilizer, they can get burned. [3] X Research source Adding horticultural grit can also help improve drainage. [4] X Expert Source Olivia ChoongPlant & Gardening Specialist Expert Interview. 3 September 2021.

There’s some disagreement about whether indoor seedlings really need fertilizer. Wait until they have 2-3 sets of leaves before fertilizing, unless you see signs of malnourishment like yellowing leaves. Look for crystallized salt on the soil surface. This is a sign you’re over-feeding or over-fertilizing the plant.

If you added lots of nutrient-rich materials like banana peels and bones to your compost, you probably don’t need any fertilizer yet.

Follow the instructions on the fertilizer bag since the amount and application can vary by product. Generally, you want to scratch your fertilizer into the soil about 6 inches (15 cm) away from the plant to avoid damage. If you’re adding more compost in place of fertilizer, spread 3 to 4 inches (7. 6 to 10. 2 cm) of compost on top of your soil around the base of the plant and let it sit. If the bottom leaves of your tomato plant are turning yellow, it probably means the plant needs more nitrogen.

Tomato plants might need more potassium during this phase. Switch fertilizers or add organic potassium sources, like chopped up banana peels, to your soil.

If you’re growing determinate tomatoes, you can stop fertilizing after the fruits start ripening and change their color. [11] X Research source

Tomato plants generally need 1 inch (2. 5 cm) to 2 inches (5. 1 cm) of water per week. Early in the season, watering once a day is enough. As it gets hotter, you might need to water twice a day. Always water the plant before fertilizing, never after.

A pH level of 5. 5 to 7 is ideal for tomato plants. Each U. S. state’s cooperative extension service assists farmers and gardeners with multiple services including soil testing. Tests are typically between $15-20. [14] X Research source If you can’t get a test done and you haven’t had issues with tomato plants before, assume you have balanced soil.

Nitrogen encourages leaf growth and lusciousness. Potassium helps the plant grow quickly. Phosphorus assists with root growth and development as well as flowering. Tomatoes also need micronutrients in smaller quantities like calcium, magnesium, zinc, and boron.

If your soil is balanced or high in nitrogen, choose a fertilizer that has more phosphorus than nitrogen, like a 5-10-10. If you’re lacking nitrogen, go with something balanced like a 10-10-10 or an 8-8-8. Too much nitrogen makes leafy plants with few tomatoes. If your soil is already rich in natural fertilizers, you may not need a synthetic blend. If you want to add some, choose a fertilizer with balanced NPK levels, like a 10-10-10.