Take steps to know your emergence percentage
By Jeremy Boychyn M.Sc, P.Ag, Agronomy Research Extension Specialist
Plenty of focus is placed on thousand kernel weight (TKW) when calculating seeding rates. Seeding based on per cent germination provides the number of viable seeds sown. However, when seeding based on TKW, emergence per cent (plant stand compared to the number of viable seeds sown) is unknown, therefore collecting plant stand counts 21 days after seeding provides the actual emergence percentage. Twenty-one days after seeding is the ideal time to be able to identify each plant during counting. Counting earlier or later than 21 days can lead to missing plants that have not emerged or challenges discerning between plants due to advanced growth.
Knowing your emergence percentage sets expectations for seeding rates and plant stand in the following years. The more accurate we can estimate field emergence, the better we can attain target plant stands to maximize yield potential.
There are many reasons why crop emergence can differ from your seed test’s germination value. Soil and seed-borne disease, soil moisture, predation, seed-to-soil contact, seed-to-seed competition, fertilizer injury, soil crusting, trash levels, seeding depth, and more can impact the seed’s germination and emergence. Many of these factors will vary from farm to farm, field to field, and year to year. However, by determining the emergence percentage on your representative fields every year, you will get more accurate seeding rate calculations.
Below is a step-by-step process you can follow to begin collecting emergence percentages on your farm.
Calculating emergence percentage:
1. Know the number of seeds you planted per meter (or foot) of row. To know this information, you must base your seeding rates on TKW.
2. For those fields where you plan to assess plant stand, set a reminder to take plant stand counts 21 days after seeding. I find this is the easiest to do on the day of sowing. Set the alert in your calendar or mark it on your kitchen calendar. Additionally, note seeding moisture conditions so you can determine what factors may have increased or decreased emergence.
3. At 21 days after seeding, scout your fields to get an overall idea of field emergence. Depending on environmental conditions, emergence can vary greatly across the field.
4. Select 6-10 locations within the field to collect plant stand counts. Here are some guidelines to follow when selecting locations:
a) Avoid areas of extreme such as very dry hilltops and wet slough bottoms
b) Select areas that are representative of the majority of the field
c) Increased field variability means you will want to collect plant stand counts from more locations (count 10 rather than 6 locations).
d) If your farm implements variable seeding rates, you can take plant stand counts within each seeding rate zone. The number of counts you should take per zone and in each field will vary depending on many factors. Speak to your agronomist regarding the best steps to take.
5. At each location selected in step 4, count the number of plants in a square meter or a square foot. Inquire with your crop input retailer to see if they have tools to assist with determining a square foot or square meter. Some will have pre-sized collapsible squares. If you don’t have a square, a measuring tape will do fine. Your row spacing will determine the length of the row you use for your plant counts.
a) For number of plants per square foot: A square foot is 12”x12” OR 144 in2. You want to know how many plants are growing in that 144 in2. So, divide 144” by your row spacing (inches) and that will provide the length of the row you need to count plants in. For 10” rows, 144÷10 =14.4. So for 10” rows, count the number of plants in 14.4” of row. This gives the number of plants per square foot. For 9” row, 144÷9 =16. So for 9” rows count the number of plants in 16” row. This gives the number of plants per square foot.
b) Calculate the average plant stand from all 6-10 locations you counted.
6. Take the average value you determined in step 5b and divide it into your target TKW seeding rate. If your target seeding was 35 viable seeds/ft2 and your plant stand is 26 plants/ft2, your emergence percentage is just over 74% (26÷35).
7. Take note of early-season moisture conditions to help explain why your emergence counts might be lower or higher than expected. It may also be beneficial to note other factors that you feel may have impacted emergence. These factors could include deep seeding, insect damage, etc.
8. Use the emergence percentage determined in step 6, seeding moisture conditions from step 2, and the environmental condition noted in step 7 to determine emergence percentage expectations for future years when field conditions are similar.