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Using thousand kernel weight and seed bed utilization can help producers determine proper plant stands prior to seeding the crop.  The 1000 kernel weight calculation is as follows.

 (Desired Plant Population/ft² * 1,000 kernel weight) / (% Expected Seed Survival * 10) = Seeding Rate (lbs/acre)

Wheat Example:

General Assumptions:

A proper plant stand in wheat is 30 plants/ft²

Know product germination – poor seed can be under 90%

Seedling loss will increase from seeding early in cold wet conditions

Increase seeding rate if not using seed treatment

Increase seeding rate if poor fertility

Wheat 1000 kernel weight usually ranges from 29 to 41 grams

Example 1

Assume 97% germination and 3% seedling loss with seed treatment and planted mid-May in 10 Celsius soil temperature

30 plants/ft² * 38 grams/1000 kernel / 94% Survival * 10 = 121 lbs/acre

30 plants/ft²* 29 grams/1000 Kernel / 94% Survival * 10 = 95 lbs/acre

Example 2

                Assume 90% germination and 8% seedling loss from no seed treatment and planted late April in 2 Celsius soil temperature

30 plants/ft² * 38 grams/1000 kernel / 82% Survival * 10 = 139 lbs/acre

30 plants/ft²* 29 grams/1000 Kernel / 82% Survival * 10 = 106 lbs/acre

 

A lot of producers use a standard 120 lbs/acre seeding rate. In example 1 at 38 grams and good treated seed, results are right on. But, small seed at 120 lbs would result in 39 plants/ft². Unless the producer substantially raises fertility levels this will probably result in lower yields due to competition and low protein levels.

Purchase seed by the lb or know the bushel weight. 120 lbs / 60 lbs/bushel = 2 bushels/acre, at 65 lbs/bushel = 1.85 bushels/acre – 2 Bushels would equate to 3 plants/ft² less.

 

Canola example:

General Assumptions:

Canola can vary from 3.5 to 6.5 grams.

Recommended plant stand is 7 to 11 plants/ft².

Survival can be from only 50 to 80%, depending on environmental and mechanical factors.

Most producers plant canola at 5 lbs/acre

Example 1          

Assume 95% germination and 15% seedling loss with seed treatment and planted mid-May in 10 Celsius soil temperature                                                                                                                                     

11 plants/ft² * 6.5 grams/1000 kernel / 80% Survival * 10 = 8.5 lbs/acre   vs.    5 lbs seed = 6.1 plants/ft²

11 plants/ft² * 3.5 grams/1000 Kernel / 80% Survival * 10 = 4.5 lbs/acre   vs.   5 lbs seed = 11.4 plants/ft²

Example 2

                Assume 95% germination and 30% seedling loss from with seed treatment and planted late April in 2° Celsius soil temperature.

11 plants/ ft² * 6.5 grams/1000 kernel / 65% Survival * 10 = 9.5 lbs/acre vs.  5 lbs seed = 5.4 plants/ft²

11 plants/ft² * 3.5 grams/1000 Kernel / 65% Survival * 10 = 5.1 lbs/acre vs.   5 lbs seed = 10 plants/ft²

In example 1 the 6.5 gram sample at 5 lbs would result in only 6 plants/ft². Below lowest recommended stand and no safety net for stress losses from insects or adverse weather challenges. The 3.5 gram seed would in a 9.3 plants/ft² stand. Right in the middle of recommended stand.

In example 2 the 6.5 gram sample at 5 lbs would result in only 5.4 plants/ft². Well below lowest recommended stand and no safety net for stress losses as in insect or adverse weather challenges. The 3.5 gram seed would in a 10 plants/ft² stand, right on for a recommended stand.

Having a good plant stand will help to ensure an adequate yield.  Knowing the 1000 kernel weight of the seed and adjusting planting rate is crucial and will provide you with a more economic return on your seed costs. Adjusting for seeding rate, avoiding fertilizer damage, and ensuring proper and consistent seeding depth are all needed to increase the possibility of a good plant stand.

Canola 1000 k seed counts that I have seen to date range from 4.1 g (5 lbs gives 10 plants/ft² at 80 % survival) to 4.9 g (5 lbs seed rate gives 8 plants/ ft² at 80 % survival) which is quite low and could result in a very low plant stand and yield if crop is pressured by stresses such a moisture, insects or inconsistent seed depth.

For more information on this topic and how you can help your crop get off to the best start possible, please follow the link below to an article from Grain News which weighs in on other hazards to seed survival, and how to deal with these hazards.    Many hazards to seed survival