I had made it to the sermon portion of our Sunday church service. The Brewers had played extra innings on the west coast the night before so my ability to stay coherent was being somewhat challenged. However, sleeping is difficult on hard pews and my wife is of the opinion that shut-eye in church is not a good example to set for the kids (like going to bed before the end of the 5th inning is being a good role model?).
I read all the interesting stuff in the morning’s church bulletin and so my attention shifted to the sermon. The pastor was talking about making choices in life and he quoted a line from some movie that had meaning and substance; it’s the kind I never watch. He said, “The right thing to do and the hard thing to do are usually the same thing.”
I got to thinking about how true that statement is in so many of life’s daily decisions. It certainly is true in crop production. We learned that lesson early in Wisconsin’s agricultural history when during the 1800’s farmers took the road of all-out wheat production. In fact, one-sixth of all U.S. wheat was grown here.
Over a period of years, soils were depleted of nitrogen; diseases overwintered and thrived in the crop; and chinch bugs acted like they were in…well…chinch bug heaven. Around 1870, settlers from New York who had previous experience milking cows decided dairying might be a bit more profitable than five bushels of wheat per acre. It seemed to work out OK.
I’m sure that growing one crop on every acre, every year, was the easy thing to do in the mid-1800’s, but it wasn’t the right thing to do. The same rules apply today. A lot of research money and time has been spent on quantifying this simple fact: one crop is not so good, a two crop rotation is better, and a three or more crop rotation is best. Sometimes the reasons for this certitude are easy to explain, sometimes not.
Generally speaking, when one crop is grown after itself, 10 to 15 percent of the yield potential can be written-off in the second year. We’re learning that some of that yield loss can be explained by soil microorganisms with names too long to fit in this column, but we also know that many weeds, insects, and diseases thrive when given the chance in consecutive years. So in addition to giving up yield, it’s historically been the case that we need to spend more money on fertilizer and chemical inputs to get less bushels or tons.
One of the real strengths of Wisconsin’s agriculture is that we have diverse cropping systems. There are perennial forage crops that fuel the dairy industry. Both wheat and vegetable crops are also routinely grown as third rotational crops.
The vulnerability of growing a single crop is readily apparent, but now there are good examples of pests that are evolving and adapting to cause headaches in even the two crop corn-soybean rotation. The western corn rootworm variant and northern corn rootworm extended diapause are prime examples.
Growing multiple crops in rotation isn’t necessarily the easy thing to do, but it is the right thing to do for preserving our natural resources, having success in controlling pests, and for long term farm profitability. We have had a long history to learn this. However, we have had a much shorter history in Wisconsin to learn and experience the long run impacts of employing the same pest management system on single or multiple crops.
Plant biotech traits to control weeds or insects, as great as they are, can easily lead us down a road of “systems monoculture” if they are not used appropriately.
Evidence of pest management system abuse is starting to become more prevalent. There are now 14 weed species with documented glyphosate resistance in the U.S. Wisconsin has fared somewhat better than many states with only two documented resistant populations: giant ragweed (2010) and horseweed (2012).
Also troubling is the recent documentation in several Midwest states of field-evolved resistance to the Cry3Bb1 protein by western corn rootworm. Cry3b1 is the active protein in YieldGuard Bt corn hybrids.
In most cases where weed or insect resistance is proven, the cause can be traced to the repeated use of the same control strategy for multiple years. It’s important to note that these situations were not caused by the technology per se, but rather by people who made poor management decisions in respect to using the technologies.
History has taught us that easier monoculture cropping systems ultimately lead to failure. Using the same effective pest control system year after year may also seem like the easy thing to do; but long-term is it the right thing to do?
Mike Rankin, Crops and Soils Agent, UW Extension-Fond du Lac County