Now that planting is over, we look back on how we did at our variable rate management strategies? Did those uniform seeding rates go in as we had intended? That is the value of the as-applied map! Go back to the office download your work into your desktop farm GIS software from your in-cab display and take the time to assess what actually happened out there.
Why is this important? You will need this map at harvest as guidance to go back out and get those uniform rates as separate loads for cost-benefit analysis later. Best to know (a) yes they actually went down the way I wanted them, and (b) your as-applied map is downloaded to another computer and is stored safely for future use back in the field.
What is the purpose of replicated uniform rates? These zones were created from 7 corn years, the process is called normalizing, or multi-temporal yield analysis. After the corn harvest is done, we will analyze the uniform passes by yield zone to see if there was an economic advantage to varying the seeding rate across the field.
At Blythe Brae Farms they have a 40 ft planter, but it is capable of split-planting. Therefore in two passes were we were able to get four 20ft uniform rates applied, in three separate (replicated) locations across the field. These uniform rate pairs were established before going into this field. The operator simply toggles out of the prescription (Rx) map and over to the uniform rates when they are required at a specific location in the field.
What did we learn? Make sure your application map is set to fill the entire field boundary you choose to use this year. This is a small detail in the mapping software, that may not be automatically turned on in the office. In this case we set it to the average conventional seeding rate of 34, 000 seeds per acre. In the interior of the field this would work well if something happened to the guidance system and we needed that default uniform rate. In this field the headlands were fairly uniform, and targeted to 30, 000 seeds / acre. If the operator went outside of the field boundary (e.g. since last year the field was minus a fence row, or the application map didn’t fill the map right to the field boundary) the planter would jump from 30, 000 up to 34, 000 seeds / acre. 20-20 hindsight we would have set the default rate for the headlands to 30, 000 seeds / acre, less work for the planter, and less jumping around. You can always change it back to average conventional rate after the headlands are done.