Yields put in perspective

Ray Mueller
Now Media Group


Following a year during which Wisconsin's corn growers have enjoyed a record high average yield of 165 bushels per acre, Extension Service corn agronomist Joe Lauer is sharing a few ideas he'd like them to consider for the 2016 crop year and beyond.

Speaking at the Extension Service's annual Agronomy Update meetings during the first full week of January, Lauer reviewed the production achievements of 2015, which he attributed to very close to 30-year averages on growing season temperatures and rainfall and the absence of extreme weather conditions. The only exception he cited was a July windstorm that damaged corn in Wisconsin's southern tiers of counties.

At the Extension Service's 14 variety test plots for corn, 15 grain corn hybrids and 14 corn silage hybrids broke into the top 50 for all-time yields in those plots, Lauer reported. Only two of those plots had grain yields lower than the 10-year average, he pointed out.

History of corn yields

Lauer took a look at history to track the continual increase in corn yields. The first official statistics credited Wisconsin with an average yield of 29 bushels per acre in 1866, he noted.

New record high average yields were established in 28 of the subsequent 150 years, including 6 new record highs in the last 22 years, Lauer observed. There were several periods of major increases, including with the introduction of hybrid corn in the 1930s and then again with the unveiling of transgenic traits starting in 1996.

Lauer also credited earlier planting dates and the per acre increases of plant population for the yield increases. He cited field surveys during the past 35 years in Wisconsin, Iowa, Illinois, Minnesota, and Indiana, which found that the average increase in per acre plant population approaching harvest was up by more than 300 plants per year during that period — an overall total increase of nearly 11,000 plants per acre.

Economic challenge

Anticipating that 2016 will be a year of economic challenge for corn growers, Lauer is encouraging them to consider several practices and decisions that could reduce their production input costs. Among them are choosing between conventional corn hybrids and the great majority that have one or more transgenic traits and the amount of tillage of land on which corn is grown.

Regarding the growing of corn hybrids with transgenic traits, Lauer invited growers to examine Table 3 of the corn section in the 2015 variety test results. That table lists 27 different transgenic trait groupings and compares the grain and silage yields of each group (minimum of 50 entries in the trials) with the overall trial averages.

With an eye on seed costs, Lauer advises all growers to consider a hybrid that has the minimum of the trait for controlling the European corn borer. Beyond that, he said the need for additional traits should be linked to the environmental conditions or management practices. And focus on buying only the hybrids that placed in the top 20 percent of those entered in the state's trial plots, he stressed.

Conventional hybrid views

Citing the placings that a handful of conventional hybrids earned in the top 10 for both grain and silage yields in some of the trial plot zones in the state, Lauer said growing one or more of them can be a good choice. In the 2015 trial plots, the 383 conventional hybrid entries posted a grain yield average of 1.1 bushels per acre above the overall trial average, he reported.

That was a continuation of a three-year trend, which emerged after the conventional hybrids had lagged the overall trial averages by as much as 7 to 10 bushels per acre in the previous five to seven years, Lauer observed. Because the trial plots are designed to identify genetic differences between the hybrids, he explained that all of the hybrids in them are given the same management input — unlike the practices on many farms.

What's not in doubt is that 'the traits do their jobs,' Lauer remarked. But he advises corn growers to select and pay for only the traits they need, depending on what insects they encounter and what their weed control practices are.

Refuge in a bag

With the continued federal requirement that growers have non-transgenic hybrids as a certain percentage of their acres, seed companies have developed the refuge in a bag concept (RIB — which is included in the hybrid name), Lauer pointed out. To comply with the regulations, the RIB hybrids have a 3, 5, or 10 percent mix of hybrids with differing traits.

How those mixes might affect yields and other factors has been studied at 10 sites during the past three years, Lauer reported. The results have been quite favorable, indicating virtually no difference in yields, moisture, and test weights, he said.

The only noticeable difference, which was tabulated at four sites, was a yield reduction of 7 to 18 bushels per acre with refuge plants, Lauer stated. What was more important, however, was the absence of any major difference in the comparisons of the RIB and the hybrid base, he explained.

Reducing tillage

Lauer realizes that he is treading on some unfriendly turf with his suggestion that corn growers greatly reduce the amount of tillage on a number of their fields. If nothing else, they would realize savings on 'fuel and steel' by cutting back on tillage.

A major national study conducted from 1980 through 2013 found that conventional tillage boosted corn yields by an average of 5 percent — as did trials at four sites in Wisconsin from 1978 to 1984, Lauer conceded. But he asked growers to realize the fuel, machinery, and labor costs that were needed to make that happen.

Crop rotations alone have a beneficial effect that's similar to that of conventional tillage, Lauer pointed out. He referred to a study at Monmouth, IL on a rotation of corn and soybeans to confirm that point.

Data from trial plots in Wisconsin from 1994 through 2013 is showing corn yield increases based on an annual rotation with soybeans compared to conventional tillage, Lauer reported. He added, however, that conventional tillage is needed in most cases to maintain yields with the continuous growing of corn.

'But I want to place the idea of less tillage in your head,' Lauer commented. He agreed that the warming and drying of soil in the spring is definitely a drawback to reduced tillage in many cases.

Field management

In the past, the reasons for conventional tillage included the control of weeds and preparation of a seedbed, Lauer observed. But with the widespread use of herbicides to control weeds and better quality planting equipment, those reasons for tillage no longer exist on many farms, he stated.

But the effects of reduced tillage don't become evident for quite a few years, Lauer emphasized. For that reason, he urged growers to exercise patience if they change their tillage practices.

An anecdotal example of this occurred following nearly a five-inch rainfall in September of 2015 at the Marshfield experimental farm, where the land which was not being tilled was ready for equipment travel several days before that being conventionally tilled, he reported.

Organic material

Lauer also mentioned the importance of adding organic material to the soil in conjunction with reduced tillage. To a question about the role of cover crops in contributing to that goal, Lauer shared doubts about the practicality of doing that on a significant portion of Wisconsin's crop acres.

The typical harvest timetable for corn silage, soybeans, and grain corn does not allow enough growing season time for many of the cover crop species, Lauer pointed out. That leaves mainly the acres from which wheat was harvested as the prime candidate for cover crops, he said.

For protecting the soil from erosion, Lauer stated that the late season growth of weeds could help on that point. Regarding the introduction of organic material to the soil, he said that the proper management of crop residue would accomplish that.

Lauer invited corn growers and crop consultants to keep themselves informed by checking the corn.agronomy.wisc.edu website regularly or logging onto the associated social media venues.