What fertilizer provides the best calcium for tomatoes?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.Selecting an appropriate calcium fertilizer is critical for the health of your tomatoes. Calcium nitrate is superior compared to other fertilizers because of its quick absorption during the fruiting stage. Many organic growers use other calcium-based fertilizers, such as gypsum or bone meal. Avoid using fertilizers that have high nitrogen content. Nitrogen will suppress the uptake of calcium. In this section, we compare all the options.
Calcium Nitrate
- Fastest absorption during fruit development
- Apply as side-dressing monthly during fruiting
- ¼ pound per 100 square feet application rate
- Water immediately after application
Agricultural Gypsum
- Best for heavy clay soils without altering pH
- Apply 2 pounds per 100 square feet
- Works through calcium exchange not dissolution
- Reapply annually before planting season
Liquid Bone Meal
- Organic option with immediate availability
- Mix ¼ cup per gallon of water
- Apply as soil drench around root zone
- Use every 14 days during critical growth
Use fertilizer correctly for optimal efficacy, and side-dress with calcium nitrate six inches from the plant stems, watering thoroughly to dissolve the granules. Gypsum must always be incorporated into the soil before rainfall. Liquid bone meal works most optimally as a root drench. My plants responded the fastest when treated with side-dress or drench nitrate applications.
Calcium sources and ammonium fertilizers should never be used together because excess nitrogen creates a chemical competition between the two nutrients, which can lead to reduced effectiveness. Excessive potassium intake can also impede absorption. A soil test is appropriate before adding any supplements. I wasted an entire crop by overdosing on fertilizer before learning this lesson.
Organic alternatives to synthetic fertilizer have different application timings. Gypsum is typically applied in the fall for preparation of the spring planting season. Bone meal should be used early for the same reason, as it releases nutrients slowly over time. Both gypsum and bone meal should be used when the soil is consistently moist. Synthetic options can intervene more rapidly when immediate attention is needed.
Be aware of application errors. Excessive use of fertilizer can lead to salt accumulation. Using too little makes the plants vulnerable. Always use the amount recommended on the label or matched to soil test results. Ideally, your tomatoes will reward you with perfect, unblemished tomatoes if you nourish them properly.
Read the full article: Calcium Deficiency Tomatoes: Prevention and Solutions
