Use Response-to Scores to Guide Agronomic Decisions

  • Apr 10, 2019
Mid-season cornstalks
Response-to scores can help you better match the hybrids you choose to your management style and farm environment, which allows you to allocate your crop inputs budget more precisely. For the last eight years, WinField United has measured and recorded the response of various hybrids to population, nitrogen and continuous corn. In the last four years, response to fungicide has been added to the mix.
In 2018, we field-tested 240 hybrids from CROPLAN®, DeKalb®, NK®, Mycogen® and Pioneer® for response to population (RTP), response to nitrogen (RTN) and response to continuous corn (RTCC). We tested 225 hybrids from the same manufacturers for response to fungicide (RTF). The yield response ranges highlight the importance of understanding how the hybrids you pick react to different management practices to optimize yield potential.
2018 Answer Plot® Response-to Insights Summary
Response-to test Yield response range
Response to Population1 -3.8 to 20.8 bushels per acre
Response to Nitrogen2 58.4 to 119.4 bushels per acre
Response to Continuous Corn3 6.9 to 29.8 bushels per acre
Response to Fungicide4 -3.5 to 39.5 bushels per acre
Planting a hybrid with a high RTN score, for example, yielded up to nearly an additional 120 bushels per acre. Those are bushels you may be leaving in the field. Here are some practical ways you can use response-to scores to your advantage.
Response to Population (RTP)
Some hybrids respond more favorably to being planted at high populations than others. For example, if you are planting on your home farm, have good tile drainage and adequate fertility, and want to experiment with high management and pushing populations, planting a hybrid that tolerates high populations can potentially give you a larger yield potential response and more plants per acre.
If you have another farm that’s a long way from home, is on rented ground with lower fertility levels, has sandier or rockier soil that’s droughty and where corn plants usually dry up in August, you’d want to plant a lower-population hybrid. This allows you to maintain yield at low populations and in a low-yield environment. But if you do get decent rains in August and some good mineralization to boost fertility, even a lower-population hybrid could flex its ear more and you could still capture some top-end yield.
Response to Nitrogen (RTN)
If you’re planting a high-RTN hybrid this year, make sure you apply in-season nitrogen or are top-dressing those hybrids first. If you put all of your nitrogen on prior to or at planting, you might assume that’s enough for the year. However, if you have above-average rainfall during May and June, and you do a pre-sidedress nitrate test or take a tissue sample that indicates you’re low on nitrogen, make sure you’re applying additional nitrogen in-season on your high RTN hybrids first.
But again, if you’re planting on rented ground with low natural fertility and low organic matter that doesn’t supply as much nitrogen naturally through mineralization, selecting a low-RTN hybrid is generally a better choice.
Response to Continuous Corn (RTCC)
With low commodity prices and a 2017 that was particularly bad for white mold, many fields that in a normal corn/soybean rotation would be back to soybeans in 2019 may have better luck with corn. If you’ve made the economic decision to plant corn-on-corn, a hybrid with a high RTCC score that can tolerate the added disease potential of that environment is a good choice. Hybrids with a higher RTCC score also tend to tolerate colder soil conditions better than those with a lower RTCC score and have better emergence potential, even in tougher environments. If you are planting soybeans on corn/soybean rotation fields this season, be sure to scout diligently and employ ag technology tools to spot any disease pressure early and apply a fungicide if needed.  
Response to Fungicide (RTF)
When spraying a fungicide, you need as much of that fungicide as possible to get deep into the plant canopy, where it can be effective. The problem is, many nozzles generate smaller droplets, and some of the very small droplets are so light they can drift away or evaporate before they reach a leaf.
Having an adjuvant like MasterLock® in the spray tank can help improve spray coverage to the target. Particularly with tasseled corn or soybean plants with many leaves and branches, using MasterLock is a great way to dramatically increase the percentage of spray droplets that ultimately hit the mark. Research has shown a 5.7-bushel-per-acre average yield increase in corn when MasterLock was used in the spray tank along with a fungicide, compared to using a fungicide alone.5
Take advantage of response-to data
WinField United invests a substantial amount of time, energy and resources into testing for and determining response-to scores. We take pride in the quality of our data, how it’s collected and analyzed, and that we’re representing a large portion of the seed industry by testing multiple brands. Use this data to help you be an even better farmer and improve your yield and ROI potential, and see our data in action this summer at an Answer Plot® event near you. Talk with your trusted advisor about how to take advantage of an Answer Plot event and how response-to data can help you manage your corn crop to its fullest potential.

1. National average yield difference between 30,000 and 37,500 plants per acre.
2. National average yield difference non-limited and limited nitrogen applications; rates varied by soil type and location.
3. National average yield difference between first-year and corn-on-corn rotations.
4. National average yield difference between fungicide application at V5/R1 and untreated control.
5. WinField United, 14 studies, 8 states, all fungicides, 2012–2017.
© 2019 WinField United. Answer Plot®, CROPLAN®, MasterLock®  and WinField® are trademarks of WinField United. 
DeKalb® is a trademark of Monsanto Technology LLC.
NK® is a trademark of Syngenta Group Company.
Mycogen® is a trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow.
Pioneer® is a trademark of E. I. du Pont de Nemours and Company or its affiliates.