This time of year many farmers are out scouting. Spotty soybean fields are raising eyebrows and leaving farmers questioning whether there are enough plants to grow a crop. Here’s how you can calculate soybean populations in an unconventional, cost-effective way.
Raising the Replant Question
Spotty fields and not so perfect crops have farmers raising the replant question. Things usually go well and provide good stands, but every year replant decisions need to be made. WallacesFarmer writes,
Evaluating planter performance, seedling emergence scores and vigor, and getting an idea of how well seed treatments performed are some other potentially useful pieces of information that can be gathered while doing early-season stand counts.
Many factors have growers wondering if their stand is good enough. Things like soil crusting, seedling diseases, frost, hail, herbicide injury and other unfortunate events have them questioning if they need to take action.
First and foremost, look at the big picture. Taking a big picture view of your stand after emergence can tell a lot. It could also be beneficial to take a picture after a frost, hail, or damaging event. If plants did not emerge, or if they were killed, your replant decision could be made quickly.
With damaged plants, it is important to wait a little while to determine recovery. Flagging a few potential problem areas can help you when it comes time to decide.
Fields typically either look noticeably better or worse after a few days to a week, giving you more insight when making tough replant decisions.
Another way to gauge replant decisions is by taking stand counts.
There are several ways to do this. For instance, counting the number of bean plants per foot of row and comparing it to a chart. Some like the 1,000th-of-an-acre method. For example, counting the number of plants in a 30-inch row width that’s 17 feet, 5 inches long.
Another good option is the hula hoop method.
Soybean Fields Have Farmers Hula Hooping
Replant is a tough decision and depends on each farmer’s end goals. If a stand looks spotty, measure to see what population is left. Then, determine what the end yield will be. Check several areas of the field to determine an average. Checking at least five locations in a field is the recommendation for finding an average.
Upon entry into the field, toss the hula hoop to ensure random spot selection. After doing this five times, it should give an accurate representation as to what is in the field.
Count how many plants are in the hoop then multiply that by the hula hoop “factor” to determine average plants per acre. The factor represents how many hoops fit in one acre.
For example, a 24″ hula hoop with 13 plants has an average population of 180,336. This is found by using the factors in the table and multiplying 13 x 13,872.
Good Enough or Try Again?
No matter the method, once you have taken the appropriate measurements it’s time to make your decision. Is the stand good enough or is it time to replant and give it another try? After measurements are taken, then estimate yield potential. This estimate is based on population and planting date.
For fields planted in the normal window, research over the years at ISU found that final uniform soybean stands in the range of 100,000 to 125,000 plants per acre were “good enough.” In fact, having final populations above those typically didn’t result in yield increases great enough to be economically important when the added seed cost was considered.
If you are below the range and replanting is being considered, there are several charts you can reference. These will help you assess the yield potential of later planted soybean stands.
Generally, replanting should be considered if uniform stands are less than 75,000 plants per acre when planted mid-May or earlier, or less than 50,000 to 60,000 plants per acre when planted late May into June.
Replanting can be a tough decision. There are several factors that should go into making the replant choice. First, you must gather all proper measurements to determine yield. A simple, cost-effective way to do this is the hula hoop method. After determining all measurements and figuring potential yields, it is time to make your decision. Will you replant or are you content with your stands?