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Nutrient chart · Fruiting crops

Fruiting Crop EC and pH Chart by Stage: tomato, pepper, cucumber

Fruiting crops are fed on a curve that rises through the season, and almost every home failure comes from applying the peak value too early or jumping to it in a single step. The stage markers here are tied to visible events on the plant, not to a calendar.

By The Grow DeskPublished 10 Sept 2026Crop Tomato, pepper, cucumber
Stage targetsTomato, pepper, cucumber
StageFruiting, weeks 3-16
EC1.8 - 2.6 mS/cm
pH5.8 - 6.2
N-P-K2-1-3
StageECpHN-P-KNotes
Transplant to first truss1.4 - 1.65.9 - 6.12-1-2A young plant cannot use fruiting strength; pushing now costs two weeks
First truss set1.7 - 1.95.9 - 6.12-1-3Step up only after fruit has visibly set, not when flowers open
Second truss, marble sized2.2 - 2.46.0 - 6.22-1-3Peak demand; potassium uptake roughly triples over the vegetative stage
Continuous harvest2.4 - 2.66.0 - 6.22-1-4Hold rather than climb; a sudden jump here causes blossom-end rot
Late season, final 10 days2.0 - 2.26.1 - 6.22-1-3Ease back so the last fruit ripens rather than the plant stalling

Step up when the fruit sets, not when the flower opens

A tomato flower opens, gets pollinated, and only then begins to draw heavily on the plant's resources. Raising the EC when flowers open feeds a demand that has not arrived yet, and the excess salts sit in the root zone burning root tips that are still forming. Waiting until the fruit is visibly set — the size of a pea on a tomato, a marble on a pepper — matches the feed to the draw.

Potassium demand triples at the second truss

Through the vegetative stage a tomato takes up potassium and nitrogen at roughly similar rates. Once the second truss is filling, potassium uptake roughly triples while nitrogen stays flat. That is the reason the ratio moves from 2-1-2 to 2-1-3 and then 2-1-4: not because nitrogen becomes less useful, but because potassium becomes far more so. Keeping the same ratio at peak fruiting is one of the most common causes of a plant that ripens unevenly.

Blossom-end rot is a swing, not a shortage

On tomatoes and peppers, blossom-end rot appears when the plant cannot move calcium into a rapidly expanding fruit fast enough. The calcium is usually present in the solution. What fails is the transport, and transport fails when the root zone dries between cycles or the EC jumps suddenly. Raising calcium in the reservoir does not fix it; smoothing the irrigation does.

The pH window matters more as EC rises

At 1.5 mS/cm a pH drift to 6.6 costs you almost nothing. At 2.5 mS/cm the same drift starts precipitating calcium phosphate out of solution, and the precipitant is invisible until the plant shows a deficiency that the meter says cannot exist. Above 2.0 mS/cm, check pH daily rather than weekly.

Tubing diagram: Fruiting Crop EC and pH Chart by Stage: tomato, pepper, cucumber
Tubing diagram: Fruiting Crop EC and pH Chart by Stage: tomato, pepper, cucumber

Key points

  • 1.4-1.6 mS/cm from transplant until the first fruit sets
  • Step up on visible fruit set, never on open flowers
  • 2.4-2.6 mS/cm at continuous harvest, with a 2-1-4 ratio
  • Blossom-end rot follows dry cycles and EC jumps, not low calcium
  • Above 2.0 mS/cm check pH daily; precipitation starts around 6.6

Sources

Please noteThese EC, pH and ratio values are general references for common fruiting cultivars in home systems. They vary with water supply, climate and nutrient brand. Mix to your product label; this is informational content, not professional horticultural advice.

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