Many planters on the market today are capable of variable rate seeding. The software used to generate the prescriptions can complete the task in its entirety in just a few minutes. Most monitors make it almost seamless to execute. But how do you know what rate is right for each area? Earlier this month we posted about the data that goes into creating a good VR map, today we will focus on how to populate the zones.
Understanding Field Variability
When creating the map, all variability is relative within the field boundary. Often we talk about ranking the areas or zones that we define as significantly different in our field by productivity. It may be more useful to number or name the zones arbitrarily and focus on what makes them different rather than better or worse than the other zones. Could it be fertility, drainage, or something else that can be managed? Often our productivity ranking can change depending on the growing season Mother Nature gives us, so focusing on what makes each zone different can help you be a more effective manager of each zone.
Plant-type Impact on Population
Once you have zones identified and understand why they are different, you need to consider the product you’re placing in that field. Understanding how different products respond to different populations is not something that should be overlooked when generating your rates. For corn many factors contribute to the plant's ability to withstand competition but ear type is an easy first indicator. If the ears tend to flex, backing populations down gives the plant more room to express its natural ability to yield. If your hybrid is more of a fixed-ear type, pushing population may be more beneficial especially in your higher organic matter areas. In addition to ear-type, root structure and plant height are other things to consider for your rates. For soybeans, looking at the plants’ body type including height and if it is more of a straight-line or bushy plant can impact your decision. In addition to that, considering the disease package may impact your population depending on how you plan to manage diseases.
Finding the Right Rate
Many growers use variable rate seeding as an opportunity to get more aggressive in specific areas of their field, both high and low, ending up with an average population similar to what they would have flat-rate planted. A general rule of thumb is that in more productive areas we increase plant populations in corn and decrease in soybeans. In more productive areas soybeans may get too tall and lodge whereas corn can use those more productive soils to put more energy into the ear. Things that need to be considered are areas that suffer productivity due to flooding, compaction, or other common issues. Knowing whether that area should have more seed or less seed to compensate for those struggles is a field-by-field decision that also includes consideration of the hybrid or variety and the time of year we get in the field to plant.
Managing all of these variables can seem overwhelming, especially when plans change once the planters get rolling which is almost guaranteed to happen. It may be beneficial to have a plan in place for switching hybrids or crops. It can be very time-consuming to initially come up with a VR plan but the same zones can often be used for multiple years. Remember that how you manage your field impacts yield data so noting in your future yield data that you used a script may be beneficial to take into consideration when you sit down to evaluate your zone for the following year.
Now that you’re all set on your VR scripts, are you ready to throw variable hybrids into the mix?
What maps or services have you used to generate VR seeding maps? Leave a review or comment below!