Seed rate is the number of seeds planted per area to achieve an adequate plant population. Understanding seed rate is important to maximize crop yields by ensuring the correct plant density. To calculate seed rate, determine the target plant population, seed germination percentage from testing, expected field establishment percentage, seeds per kilogram, and use the formula: Planting Rate = Target population / (Seeds per kg x Establishment % x Germination %). For example, with a target of 800,000 plants/ha, 90% germination, 75% establishment, and 27,500 seeds/kg, the seed rate is 43 kg/ha.

1. Seed Rate Calculation
By: Sayed Mohammad Naim KHALID
Jan 2012
Kabul, Afghanistan
What is seed rate?
Seed rate is the number of seeds to be planted in a specified surface or area to achieve an
adequate stand. Seeding rates for cereals are still commonly given in figures of kilograms of seed
per hectare or Jirib. Such rates are both convenient and useful to indicate the approximate
quantity of seed that is required.
Why understanding seed is rate important?
The correct plant population is an important factor in maximizing yield of crops. It will help the
overall health of the plant and vigor of the plant. To obtain the targeted population it is necessary
not only to have quality sowing seed but also be able to accurately calculate seeding rates. It is
surprising the difference a slight variation in seed size or germination makes to the seeding rate
required to achieve a target plant density. Seed size, quality and germination vary between
varieties, from year to year, from field to field and should be checked for each seed line to be
used.
How to calculating seeding rate?
Tools
1. Balance
2. Calculator
3. Paper and pen
Procedure
1. Know your target population goal or plants per hectare
2. Know the results of a germination test which provides an indication of expected plant
establishment in the field,
3. Know the expected plant establishment
4. Know Thousand Kernel Weight (TKW) for the seed to be planted.
5. Finally, use the following formula to calculate seed rate
𝑃𝑙𝑎𝑛𝑡𝑖𝑛𝑔 𝑅𝑎𝑡𝑒 =
𝑇𝑎𝑟𝑔𝑒𝑡 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 (
𝑃𝑙𝑎𝑛𝑡𝑠
ℎ𝑎
)
𝑆𝑒𝑒𝑑 𝑝𝑒𝑟 𝑘𝑔 𝑋 𝐸𝑠𝑡𝑎𝑏𝑙𝑖𝑠ℎ𝑚𝑒𝑛𝑡 % 𝑋 𝐺𝑒𝑟𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 %
For example if the target plant population is 800,000 , the germination % is 0.9 and expected field
establishment % is 0.75. In addition we assume that if the size of wheat seed is average so in 1
kg there will be 27500 seeds. Thus the result will be calculated as follow:
𝑃𝑙𝑎𝑛𝑡𝑖𝑛𝑔 𝑅𝑎𝑡𝑒 =
800,000
27500 𝑋 0.75 𝑋 0.9
= 43 (
𝑘𝑔
ℎ𝑎
)
We can also calculate the seed rate through the following formulas:
Seeds/ha = Target plant population (plants/ha) ÷ Germination % ÷ Expected field
establishment %
Planting Rate (kg/ha)= Seeds/ha ÷ Seeds/kg
For example
Seeds/ha = 800,000 ÷ 0.9 ÷ 0.75 = 1185185
Planting rate = 1185185 ÷ 27 500 = 43 kg/ha