Tomato · Fertility notes

Best fertilizer for tomatoes

There is no single best fertilizer for tomatoes. Cited university sheets start with a soil test, then list rates and timing that apply to that geography. This page does not prescribe a product, blend a BioArva NPK, or rank brands. Use a lab report, local Extension guidance, and applicable labels before changing a fertility program.

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Fertilizer notes on this page are source-specific ranges, not a BioArva prescription. Use a lab report, local Extension guidance, and applicable labels before changing a fertility program.

This Field Book does not recommend homemade remedies or Epsom-salt programs; use a lab report, local Extension guidance, and applicable labels before changing a fertility program.

Hands holding a soil sample

A soil sample ready for a lab report.

What the sources say — at a glance

One source per card. Facts are not averaged.

Clemson HGIC 1323 (South Carolina)

A soil test is the method they name for fertilization needs. Lime and pre-plant fertilizer per that report. Side-dress calcium nitrate on their sheet three to four weeks after planting.

Details and limits (6)
  • Lab

    A soil test is the method they name for determining fertilization needs of the crop. Lab-first note — not a BioArva prescription and not a kit sale.

  • Pre-plant

    Apply lime and pre-plant fertilizer according to soil-test recommendations; broadcast evenly and incorporate to around 6 inches. Process on their sheet — not a BioArva rate.

  • Side-dress

    They describe side-dressing 1 pound of calcium nitrate — analysis they name as 15.5-0-0 — per 100 square feet (30 feet of row) three to four weeks after planting. Source rate/timing only — not a BioArva prescription.

  • Side-dress

    On sandier soil, they say this side-dress may need to be split into two applications three to four weeks apart. Condition on their sheet — not a BioArva schedule.

  • Placement

    Their sheet lists side-dressing fertilizer 4 to 6 inches away from the plants. Placement note only — not a BioArva prescription.

  • Limit

    South Carolina sheet. Named analyses are theirs — not a BioArva product or ranking.

Utah State Extension (Utah)

Determine fertilizer needs with a soil test, then follow that report. Compost cap: no more than 1 inch of well-composted organic matter per 100 square feet.

Details and limits (4)
  • Lab

    Before planting, determine fertilizer needs with a soil test and then follow the recommendations given with the test report. Local-report note — not a BioArva rate and not an amendment list.

  • Compost

    If you fertilize with compost, they describe no more than 1 inch of well-composted organic matter per 100 square feet. Source cap — not a BioArva compost program.

  • Side-dress

    Their sheet lists side-dressing each plant with 1/2 tablespoon of a fertilizer whose analysis they name as 21-0-0, sprinkled around the plants at 4 and 8 weeks after transplanting, then watering it in. Source rate/timing — not a BioArva prescription.

  • Limit

    Utah garden tomato page. Named analysis is theirs — not a BioArva product.

Penn State Extension (Pennsylvania)

Absent a soil test, they describe 2–3 pounds per 100 square feet of a complete fertilizer they name as 10-10-10. High nitrogen: luxuriant foliage with delayed flowering.

Details and limits (3)
  • Fallback

    Absent soil-test recommendations, they describe working in 2–3 pounds per 100 square feet of a complete fertilizer they name as 10-10-10. Source fallback — not a BioArva prescription, not a product, and not a substitute for a lab report.

  • Pattern

    Their sheet describes luxuriant foliage with delayed flowering and fruiting in the context of more fertilizer or a high-nitrogen fertilizer. Source-observed pattern only — not a diagnosis, not feed advice, and not a BioArva prescription.

  • Limit

    Pennsylvania tomato sheet. 10-10-10 is their named analysis, not a BioArva SKU.

UNH Extension (New Hampshire)

Better to use a soil test; lacking data they describe 2½ pounds of 10-10-10 (or equivalent) per 100 square feet about 2 weeks before planting.

Details and limits (3)
  • Fallback

    They say it is better to use a soil test; lacking test data they describe 2½ pounds of a complete fertilizer they name as 10-10-10 (or the equivalent) per 100 square feet, worked in about 2 weeks before planting. Source fallback — not a BioArva prescription.

  • Pattern

    Their sheet describes lush, vigorous foliage with little fruit production in the context of excess nitrogen. Source-observed pattern only — not a diagnosis, not feed advice, and not a BioArva prescription.

  • Limit

    New Hampshire tomato sheet only.

Iowa State Extension (Iowa)

If no soil test, 1–2 pounds of 10-10-10 per 100 square feet before planting. Three to four weeks after transplanting, a dilute solution on their sheet.

Details and limits (4)
  • Fallback

    If a soil test has not been conducted, they describe incorporating 1–2 pounds of all-purpose garden fertilizer they name as 10-10-10 per 100 square feet before planting. Source fallback — not a BioArva prescription.

  • Side-dress

    Their sheet lists, three to four weeks after transplanting, a dilute fertilizer solution: 1–2 tablespoons of a fertilizer whose analysis they name as 10-10-10 (or a similar analysis) dissolved in a gallon of water, or a water-soluble fertilizer. Source method — not a BioArva prescription.

  • Pattern

    Their sheet describes excessive vegetative (leafy) growth and possible inhibited fruit development in the context of over-fertilization. Source-observed pattern only — not a diagnosis, not feed advice, and not a BioArva prescription.

  • Limit

    Iowa tomato sheet only.

Cornell (New York)

Sidedress about 1/2 cup of 5-10-5 per plant when fruits are about 1 inch, and again when harvest begins. High-nitrogen: three or more times N than P or K.

Details and limits (3)
  • Side-dress

    Their sheet lists sidedressing about 1/2 cup of a fertilizer whose analysis they name as 5-10-5 per plant, worked shallowly into the top inch, when fruits are about 1 inch in diameter and again when harvest begins. Source rate/timing — not a BioArva prescription.

  • Pattern

    Their sheet lists high-nitrogen fertilizers as those with three or more times nitrogen than phosphorus or potassium. Ratio context only — not a BioArva prescription and not a product choice.

  • Limit

    New York tomato guide. Named analysis is theirs — not a BioArva product.

UGA C1089 (Georgia)

First fertilization at planting; not again until pollination has taken place and dime-sized fruit has appeared.

Details and limits (2)
  • Timing

    They describe a first fertilization at planting time, and not again until pollination has taken place and dime-sized fruit has appeared. Timing on their sheet — not a BioArva calendar and not an outcome promise.

  • Limit

    Georgia C1089 only.

Arizona Extension (Arizona)

Generally, a plant fertilized early in its life is described as not fertilized after the first fruit is set. Conditional source timing — not a BioArva stop rule.

Details and limits (2)
  • Timing

    Their sheet lists a conditional timing note: generally, a plant fertilized early in its life is described as not fertilized after the first fruit is set. Conditional source timing note — not a BioArva stop rule and not a BioArva prescription.

  • Limit

    Arizona sheet only.

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Verified suppliers only

No supplier on this page

When a partner is listed, it will be outbound and disclosed. Nothing to buy here. Fertilizer, soils, and pesticides stay off this slot.

How we verify suppliers

Sampling notes live on garden soil test. In-season water and support stay on tomato plant care.

How we know — methodology. Ranges and assertions are cited per source, not blended.