A more in-depth look into the factors contributing to yield response.

Megan Bourns, Agronomist – On-Farm Network and Daryl Domitruk, Director of Research and Production, MPSG – Summer (June) Pulse Beat 2020

MPSG’s On-Farm Network (OFN) aims to test new products and evaluate management practices in a way that empowers farmers to conduct straight-forward and reliable research on their farms. The OFN structures its investigations as randomized and replicated strip trials, at field scale. Due to their size and the simplicity of comparison in an on-farm trial relative to the intensity of something like small plot research, on-farm trials are typically focused heavily on yield response. Since the OFN’s beginning in 2014, the testing of products and evaluation of practices have been primarily focused on just that — after all, yield is a key driver of the bottom line.

However, as the OFN program has grown and the capacity has expanded, MPSG senses an opportunity to extract even more knowledge from these trials. There’s so much going on in and under the crop — chemical and biological processes that can enhance or detract from the effect a product or practice has on yield. We think farmers are curious to discover hidden interactions that impact their bottom line. Especially interactions that may prove to be unique to their district or overall circumstances. And so, beginning in 2020, MPSG will selectively intensify data collection through collaboration with hand-picked soil and crop experts. You could say we’re moving to address both the what outcome of a product or management practice plus the why answer to how that product or method resulted in the observed yield response.

This year, soybean seed treatment and row spacing trials are a focus for intensification of data collection. A farmer favourite, soybean seed treatment trials have been part of the OFN since 2015, with 41 trials conducted to date. Among those 41 sites, there were only eight locations where seed treatment significantly increased yield compared to untreated soybeans. This result is especially curious since farmers have taken to regarding seed treatment as “insurance” by adding the products and their cost to the crop budget without much thought. The low frequency of yield response begs the question why? Was there too little pest pressure for the treatment to make a difference at most sites? An insurance approach usually means the level of the actual threat is not estimated. Are seed treatments less effective at preserving yield than we may think? Actually, most products do the job they’re developed to do — control or suppress pests. However, that just further stirs curiosity about why we saw so little response. An instrument as blunt as an insecticide-fungicide mix should show some improvement in yield. We need to look deeper.

Through collaboration with researchers, we will be able to determine how effective seed treatments are at reducing seedling root rot pressure, collect data on the range of root rot pathogens that exist in the trials, and gain an understanding of wireworm pressure in the fields where these trials are conducted. Having this in-depth information early in the season will help interpret yield response at harvest.

Soybean row spacing trials are another focus for intensifying data collection. Unlike seed treatment trials that have been conducted for several growing seasons, row spacing trials were a new addition to the OFN suite of research in 2019. In the first year, yield was compared between two row spacings in each trial, with 7.5″ vs. 15″, 10″ vs. 20″ and 15″ vs. 30″ treatments. Out of the seven row-spacing trials conducted in 2019, two sites had significant yield differences, where the narrower row spacing in each trial out-yielded the wider row spacing. A substantial consideration for the effect of row spacing on production is the rate and extent of canopy closure, which influences soil moisture conservation, total sunlight capture, weed and disease pressure. This year, in addition to yield, the OFN will start measuring canopy closure in collaboration with researchers, to assess differences between row spacings. Differences in late-season weed pressure will also be determined.

Another area receiving more scrutiny in the OFN program will be estimates of profitability. While it’s true every farm has different conditions affecting its bottom line, MPSG intends to provide a quick and easy number that farmers can incorporate into their own more extensive calculations of profit. For example, consider row spacing, openers cost money and narrow row spacing results in more iron being pulled through the ground and more fuel consumed. Yet, it may be worth it on many soil types.

Thanks to the farmers who have invested time and effort in on-farm trials, MPSG has amassed a significant bank of practical results. However, like all good research, more questions have arisen. The field-scale and real farm conditions under which these trials are conducted means the questions will keep coming.