Guide

How to calculate the seed rate per acre

Plants per acre from the spacing, seeds from the germination, pounds from the grain weight.

The calculation

Plants per acre = 43,560 sq ft ÷ (row spacing × spacing in the row, in feet) × seeds per hill.
Seeds per acre = plants ÷ germination rate.
Weight = seeds × 1000-grain weight ÷ 1,000.

Example

Corn in 30 in rows, one seed every 6.5 in: about 32,170 plants per acre. With 90 % germination, sow about 35,740 seeds per acre.

Why germination matters

A lot at 85 % needs 18 % more seed than one at 100 % for the same stand. The rate is on the seed tag; a simple rag-doll test at home gives it too.

With Seed Calc

Each crop starts from a common seed rate; set your spacing, germination and grain weight to get the seed for the whole field, in bags. See Seed rate calculator.

Other guides

NPK to urea, DAP, MOP

A soil test gives pounds of N, P and K. The dealer sells bags of products. Here is the bridge.

Spray tanks

The total of liquid, the full tanks, and the last tank, where most mistakes happen.

Calibrate a sprayer

A jug, a stopwatch and a measured pass give the gallons per acre your sprayer really applies.

Measure field area

Every quantity follows from the area. Here are the ways to get it, and how far to trust each.

Know what to buy before the season

Measure the field, enter your doses, send the list. No subscription.