This article originally appeared in the Winter 2004 edition of the Haney Farms Quarterly
Traditionally farmers have always thought of planting their crop in terms of bushels per acre. Bushels have been a unit of measure that we have felt comfortable with in the past because it was a function of pounds. For example, one bushel of barley is 48 pounds and if you seed two bushels per acre, you are seeding at 96 pounds. This was the simple convenient way because it usually was the same number every year. When you seed at the same rate every year you are not taking into consideration many of the important variables that can have dramatic affects on your yield and your bottom line.
According to Phil Thomas, Senior Agri-Coach with Agri-trend, “The optimum seeding rate will vary depending on several factors such as: length of growing season, location and potential for summer drought, seedbed firmness, moisture and temperature, variety seed size, germination and vigor, soil type, texture, pH, surface residue and tillage, depth of seeding, fertilizer placement, crop intended end us, weeds, insects and diseases.”
There are some drawbacks to this traditional system, which has spawned more agronomical based calculations for planting rates.
The problems are as follows:
- Does not consider the germination or mortality levels of the seed
- Does not consider the actual weight of the seed (1000 kernel weight). This is important because for example, not all barley weighs the same. Therefore you may think that you are planting 150 pounds per acre but are truly planting 125.
- There was no realization of the desired plant population
The calculation that is recommended by researchers is to obtain a desired plant population based on plants per square foot. This calculation takes into account the germination of the seed as well as the 1000 kernel weight and the row spacing of the drill. The following example will outline this concept more clearly.
Seeding rate (lb/ac) = desired plant population/ft² x 1,000 kernel wt (grams) Ã· (germination €“ mortality) Ã· 10.
In a Prairie Post article, Ross McKenzie of the Research station in Lethbridge states that, the plumper and more ideal the seed, the higher the seeding rate. Because plumper seeds weigh more, a larger sample will be required to attain the desired number of plants per square foot.€
Ross continued, once the seeding rate is determined the farmer must calibrate his drill to dispense the correct number of pounds of seed per acre.
At http://www.ropintheweb.ca/, click on the calculator tab and find the seeding rates section. In here you can enter your seed information to calculate the seeding rate that is best for you according to the variables discussed in this article. Farming in the 21st century requires accurate scientific based decisions because of lack of room for error due to decreasing margins.