Plug Tray Count and Seeding Quantity
Counts trays from finished plants required, germination, and cull.
Example
You enter
- Finished plants required 12000
- Cells per tray 288
- Germination rate (%) 92
- Cull rate at transplant (%) 5
- Seeds per cell 1
- Tray footprint (sq ft) 1.6
You get
- Usable plants per tray 251.7 of 288 cells survive to finish
- Trays to sow 48 trays, 13,824 cells
- Cells sown 13824
- Finished plants the sowing yields 12,082 -- a cushion of 82 (0.7%)
- Surplus 82.176
- Surplus (%) 0.6848
- Propagation bench 77 sq ft before aisles
- What order divided by cells would give 42
- Naive yield 10571.9
- Naive shortfall 1428.1
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeAgainst what dividing the order by the cell count would have given. The worked order needs 48 trays, not 42, and the naive count is short 1,428 plants, found at transplant when a re-sow is too late.
Formula or tableusable per tray = cells x germination rate x (1 - cull rate); trays = plants required / usable per tray, rounded up.
Source and editionThe seed lot's own tested germination rate and the grower's observed cull at transplant govern; a published germination figure is a laboratory result under ideal conditions.
Free accessPublic arithmetic; germination is on the seed lot's own tag.
What governsEstimate. AHJ and licensed professional govern.
API field namesplants_required, cells_per_tray, germination_pct, cull_pct, seeds_per_cell, tray_footprint_sqft, usable_per_tray, trays_to_sow, cells_sown, finished_yield, surplus, surplus_pct, bench_area_sqft, naive_trays, naive_yield, naive_shortfall
- Germination the lot's tested rate, not the species average; field conditions are worse than the laboratoryseed lot tag
- Bench area before aisles; the transplanted crop needs several times that on a different benchproduction schedule