Seeding By Plant Population

Seeding rates are usually given in bu/acre; however, a preferred method to determine optimum seeding rates is to consider final plant stands. Using this method, producers need to take into account the desired plant population, the variety seed size (thousand kernel weight) and the percentage seed survival.

 Seeding Rate (lb/acre) = Desired Plant Population/ft 2 x (1,000 kernel weight)  *% Expected Seed Survival x 10

The desired plant population (plants/ft2) varies depending on the crop. For specific populations, refer to the seeding section of each crop.

The 1,000-kernel weight is measured simply by counting out 1,000 seeds of grain and obtaining the weight in grams. Seed weights vary between varieties, fields, crop types and from year to year. This difference can be used to determine optimum seeding rates and seed drill calibration.

Expected seed survival is the expected germination less a small amount for seedling mortality. For example, under normal conditions expect approximately 95 per cent germination. However, if planting in unfavourable conditions, i.e., cold, wet soil, expect approximately 90-93 per cent germination as 3-5 per cent of the viable seed will not produce a plant.

* Expected seedling survival is used in its decimal form (90 per cent = 0.9).

Seeding Drill Calibration

Once the desired seeding rate is calculated, the next step is to calibrate the seed drill so that it drops the right amount of seed. The following steps tell you how many grams of seed should be collected from one drill run after driving a specified distance.

1. Calculate expected output per run of your seed drill over a measured distance.
2. Tie collecting bag over the outlet from one drill run.
3. Drive a measured distance (i.e., 100 ft).
1. Measure and stake required distance.
1. Count number of turns of front tractor tire to go required distance.
2. Weigh or count output from measured drill run.
3. Adjust seeding rate.
4. Repeat if necessary.
 Seed gm/100 ft of row (6" row spacing) = Seeding Rate (lb/acre) 2

 Number of seeds/100 ft of row = Seed gm/100 ft of row x 1,000 Weight of 1,000 seeds (grams)

OR

 Number of seeds/ft of row = Desired plant density x Row spacing *per cent Expected seed survival x 12

For further information, contact your GO representative.