When I was growing up on the farm in the 70’s we only had one TV channel, but for some reason I remember all the shows being great. However, the biggest show in my weekly schedule, and the biggest show in the World at that time, was Happy Days. The most famous character on the show was the black leather cladded “The Fonz” – the coolest guy ever imagined. In one memorable episode they are in the Wisconsin countryside, outside of their home city of Milwaukee, and they run into a bunch of intimidating farm boys. Things look dire but then The Fonz arrives and says something along the lines of “you punks better scram or I am going to rotate your crops!!” and it was with that phrase my life changed. The coolest guy to have ever existed was using an agronomy term to establish his dominance! This started me on the path to becoming an agronomist. Unfortunately, for me it never merged with the path to being cool. I expect that the writer who had inserted that gem into the show’s dialog came from a successful farm.
Crop Rotations is a huge topic to compress into a short article, it comes down to the basic need to add variability into our cropping systems in order for our farms to be successful. There are very few locations on the globe where there is a pure monoculture in nature. It is possible after certain catastrophic events like a fire or volcano, but a monoculture with only fireweed or cheat grass never lasts for long, and soon that void is teeming with a wide variety of species. Even in the high arctic there is an extensive myriad of plants and life on every square meter of the mostly frozen Tundra. This biodiversity is necessary for the whole system to function efficiently and sustainably. When you have many different plants and species growing near one another there is the maximum use of the available resources, and this diversity creates confusion and a lack of consistency preventing pests of all kinds from proliferating. Incidentally, biodiversity is such an important topic now that the International Summit on Biodiversity, called COP15, took place in Montreal earlier in December and it garnered widespread attention and culminated with an agreed framework and national level targets for biodiversity protection.
In farming systems, it is usually impractical and unprofitable to produce several crops on the same acre of land simultaneously so rotating your crops from one production cycle to the next, following a planned sequence, is the best method for adding biodiversity into your cropping system. Historically, rotations were more diverse as it was one of the only tools available to mitigate pests and maximize resources but it became a lost art for many with the advent of commercial fertilizers and pesticides. Now, the diversification of crop rotations is getting attention once again because of the increase in pest resistance from repeated use of the same control methods and the need to use resources such as fertilizer and water much more efficiently.
I am not sure what the rule is called but if you do the same thing over and over then Nature will adapt and reduce the impact of that activity. We have come to learn that this ability for a pest to become resistant is not a surprise or magic, it is a function of biology and math. I farm in Southwest Manitoba and it was the first location anywhere where herbicide resistant green foxtail was discovered back in 1987 (long before the advent of GMO crops). My neighbors just across the fence from our farm experienced a complete failure of control in a herbicide that once killed Green Foxtail easily. It did not matter what rate they used, the speed of the resistance developing was simply related the number of years they had continuously used the “Treflan” herbicide. We were fortunate on our side of the fence in that we had started to use a different mode of action herbicide as soon as it was available a few years earlier. 35 years later the foxtail in those first resistant identified fields appear to still be resistant to Treflan while on our side of the fence Treflan is still effective. This need to add variability should be extended to all the activities in crop production. Prior to inexpensive glyphosate replacing cultivation we had certain weeds like Quackgrass that seemed to get worse if you cultivated in the same fashion each year. We needed to add variability (rotation) to our cultivation program to keep certain weeds at bay.
Many believe that weed and pest resistance is a new phenomenon that is only a result of modern agriculture and in particular genetically modified crops but that is not necessarily true. Pests becoming resistance to their controls can be traced back hundreds of years and to activities as basic as hand weeding. Weeds that became resistant to physical pulling or hoeing developed after generations of hand weeding in the rice paddocks of Southeast Asia. After multiple generations of hand weeding certain weed species were eventually selected to look similar to rice, so it was impossible to distinguish them from the actual crop. Herbicides were still working but hand weeding was no longer effective. The most famous weed that excelled because of the continued hand weeding of rice was Barnyard Grass, a weed that is now very serious on a Global scale (1). If farmers had planted anything besides rice on those fields, even on an occasional basis, then the barnyard grass would have been easy to see and remove and its proliferation would have been kept in check.
A great example of the power of crop rotations is a data set from my native Manitoba. There are almost 9 million cropped acres in the province and the crop insurance program there is managed entirely by the Provincial Ag Department (my previous employer). Virtually all farmed acres are in the crop insurance program so there is a tremendous amount of data there to decipher if you have the resources. In a retrospective study looking back over 10 years, 90 million acres of data, the researchers could see that whenever a crop is planted back unto its own stubble type it presents the poorest yield for that crop. That poorest yield scenario was consistent for all 13 different crops considered in the study. You can also see where the best yields occur after each crop type. The cereal crops yielded best on the broadleaf stubbles and the broadleaf crops generally did best on the cereal stubbles. Almost everything seems to do well on Canola and Flax stubble (low residue crops). This simply proves the intuition that most farmers already have about crop rotations (2).
Putting together a suitable crop rotation schedule should increase production and reduce costs, but finding the most suitable rotation is not easy. One type of rotation is never suitable for all farms in a region, each one has to be researched and tested for the specifics of your farm, which means that its rotation may be different compared to the farm next door. Those differences may not have anything to do with agronomy, it may be that one farm has access to more labor than the other – allowing for more intensive managed crops like dry beans or potatoes. Even within a farm, certain fields will have different rotation priorities depending on the specifics of that field. On my own farm there are fields that have higher levels of saline salts compared to other fields. On the “salty” fields I will plant barley and canola in the rotation more often (they are the most salt tolerant crops). Then on my fields that have less topography and fewer stones, I will plant dry beans and soybeans more often. I will not plant sunflowers on the fields beside wetlands because the birds will eat the sunflowers while they nest in the wetlands. Even within the fields themselves, I will sometimes rotate to different crops in those specific problem areas depending on the year. For instance, in a large saline spot, I will plant barley instead of wheat but in the following year I will plant all the field acres to canola. There are literally a million things to consider when creating crop rotations for your farm.
So where do you start? The first thing you should do is take inventory of all relevant aspects of your farm: the soil types, the available water (dryland and irrigated), the storage capability and planned capability, your equipment, your labor situation, your growing environment (what are the heat unit ratings for your farm?). Then you need to check to see where the markets are at for any potential new crop that might be considered. In the South, where Fall Line is trying to encourage farmers to use winter crops in the rotation that are new to the region, the biggest obstacle is finding local markets for these new crops. A generation ago Saskatchewan was a province that almost exclusively grew wheat, but now it leads the world in the export of 10 or more different crops (3). As Chickpeas, lentils, dry peas, and more crops started to be grown in that province in the 1990’s the processors and markets quickly followed. However, production needs to hit a critical mass for that to start but you as an innovating farmer could be the one that helps develop the market as well? It was often the Saskatchewan farmers themselves that worked together to create new markets for their new crops.
Now that you understand the resources of your farm and each field, and you have identified some potential markets for any new possible crop, the next step would be to list the major obstacles you see in maximizing production on your farm. Next, you want to identify the things that are holding you back from achieving greater efficiency and/or higher production. Then plan your rotations to try and address those specific problems. You also want to develop rotations that avoid future problems but you need to start with addressing the problems you see in the present. Are you always late in getting your seeding finished? Then maybe consider crops with different seeding times (spring and winter crops). Is harvest a real bottle neck? Then once again consider crops that spread out the harvest season as well (maybe include sunflower and corn). This may be obvious, but if certain diseases and pests are becoming difficult to manage then find a way to rotate away from those susceptible crops, but having a good rotation already implemented should delay this problem in the first place.
The Dakota Lakes Research farm in Pierre, South Dakota has done some of the most widely referenced crop rotation research anywhere. Their research on zero-till, unique cropping systems and the interactions of Crop Rotations have been translated into many different languages and is known Worldwide. They have some great resources for helping farmers evaluate and create suitable crop rotations (4). Dakota Lakes talks about crop “Rotational Intensity” where the use of the soil water is carefully considered. If a field is consistently too wet then the current crop rotation lacks Intensity and crops that can utilize the extra water need to be incorporated (alfalfa, corn, etc.). Obviously, the reverse is important as well where fields that are often too dry are probably suffering from a rotation that is too intense. Alternating between high intensity and low intensity helps protect against variable weather conditions. It is also important to note than when you make a change to your farming system, like switching to zero-till, then the crop rotation needs to be re-evaluated as well. Zero-till will always provide more soil water compared to a heavy cultivation system, so cropping decisions need to be adjusted accordingly. To quote Dakota Lakes extension material: “Crop rotation intensity means growing a combination of crops that will match soil water use with crop water use under your local climatic conditions” (4).
Then once you have addressed the optimum Crop Intensity for your farm the next category is Crop Diversity. Crop rotation diversity means growing a combination of crops that compliment each other as much as possible to mitigate disease, weeds, and pests, and to maximize production and profitability (4). It is useful to aggregate crops into four different categories to do this exercise:
Cool Season Grasses: wheat (spring and winter), durum, barley, oats, rye
Warm Season Grasses: corn, sorghum, millet, sudangrass (the “C4” grasses)
Cool Season Broadleaves: field pea, flax, canola, mustard, potatoes, alfalfa
Warm Season Broadleaves: safflower, sunflowers, chickpea, soybeans, dry beans, cotton
These four groups are simply guidelines and in different regions this list may change. For instance, cotton is a warm broadleaf but has a pretty small region of adaptability. A great place to start with these four groups on the Plains is a cool season grass in year 1 (e.g., Winter Wheat), a warm season broadleaf in year 2 (e.g., Soybeans), a warm season grass in year 3 (e.g., Corn) and then a cool season broadleaf in year 4 (e.g., Canola). Then you check again to see if that rotation fits your intensity needs (does it match water use with availability?), then you revisit if those crops can fit into the infrastructure and equipment on your farm, and then you check to see if you can market all those crops effectively? In certain regions you could lump all the broadleaves together and consider them to be equal in a rotation and then rotate any broadleaf with Warm Season grasses in year one and cool season grasses in year 3, for instance. Other amalgamations of these groups might be appropriate for other regions?
There are also legumes in the broadleaf groups and for some, legumes could be considered a separate group too. Many people assume that a legume crop will supply ample Nitrogen to its following crop because it has “fixed” Nitrogen at levels greater than its own needs. However, in my 40+ years of experience, while legumes are great to include in a rotation, their benefit to the subsequent crop is usually not much beyond the fact they are a broadleaf crop. If you think you can lower N fertilizer significantly on N thirsty crops because you planted a legume the year before then you should be careful. Depending the jurisdiction, you will see published expected N credits from dry peas being 40 lbs/ac down to 0 lbs/ac available to the subsequent crop. With Dry Beans a zero N credit is usually expected for the subsequent crop. What I am basically saying here is that a proper rotation can only take things so far and while it helps basic agronomy, it doesn’t replace it.
There is also a school of thought that proposes “stacked rotations” may work best on some farms. A stacked rotation is where you have two grasses in a row and then two broadleaves in a row. The reasoning is that having 2 full years between growing the same type of crop again allows for more of the disease hosts and pests to completely die down before introducing new host plants again. I have done this on my farm a few times and it worked fine, but I do not think it was a significant improvement under my conditions. There is also the vitally important consideration of pesticide use on any specific crop and the need to rotate your pesticide groups to prevent resistance. If you are planting all glyphosate resistant corn, canola and soybeans in that 4-year rotation I suggested then you are going to have resistance problems, it is not a question of “if” but “when”. This important topic can be addressed in future articles. There is also the consideration of livestock in your crop rotation. There are many ways to incorporate livestock into your cropping system: with the main ones being grazing crop residues or regrowth and/or grazing a planted pasture or cover crop in between commercial cash crops. Suffice it to say adding livestock does add a great deal of variability to your farm and almost always enhances the farm’s entire production and efficiency but this requires a whole new level of management and infrastructure so it is not for everyone. Incorporating livestock in your cropping system is a topic we can save for a future date as well.
With all this to consider where do you go next? Visiting with your neighbors about their experiences will be extremely helpful in getting to what might work best on your farm. Local extension people and professional agronomists will be helpful, and attending meetings and fields days at local research facilities should work too. Then there is also the potential of simply observing the natural eco-system in your community. If you are in a tall grass prairie region then you have more moisture and heat at your disposal than if your farm is in the short grass prairie eco-system. If your farmland was cleared from hardwood trees then ample moisture should be at your disposal. However, with all that being said it will be the other farmers in your community that will have the most practical information for your operation. I know farmers that consider hunting season in planning their crop rotation or baseball/hockey season too. They want cropping systems that do not interfere with those other “seasons”. These are valid considerations for those farmers and are examples of just how many factors need to be weighed on each farm. One last thing I will share from my 40+ years of farming and being an agronomist, is that I do not think you can be successful if you are simply trying to follow last year’s best prices in your cropping plans. Once you have an effective rotation in place changing things to chase the markets is likely going to hurt in the long run. Your diverse rotation will pay off in ways you cannot anticipate at any given moment, you must simply accept that diversity will prevail in the long run. It always prevails in Nature. On my farm we did not know that herbicide resistance was developing across the fence, but we were trying to “mix things up” way back then, and here we are 35 years later where a herbicide is still effective for us but is useless 100 meters away.
(1) https://source.wustl.edu/2019/09/hiding-in-plain-sight/
(2) https://www.masc.mb.ca/masc.nsf/mmpp_crop_rotations.html
