With grain prices in the basement and crop inputs staying high, many farmers are looking for that one piece of magic to make the whole system work. There is no piece of magic. The system works when all the pieces are put into place and managed. In direct seeding, we often talk about the five pillars; Residue Management, Fertility, Weed Control, Rotations, and Crop Establishment.
Crop Rotations are defined as a planned sequence of crops. The key is the "planned sequence". I have seen rotations that are market oriented or very haphazard. This type of rotations usually end up costing you more money in the long run with either higher inputs or lose of some of the rotation benefits that can be achieved. The crop rotation that is set up will have an impact on residues, weed control and fertility.
Many direct seeders are using a 4-year crop rotation that will have Cereal-Pulse-Cereal-Oilseed. This rotation can be used in all soil zones, as the specific crops that are plugged into the rotation will very according to the region. This rotation has some advantages:
All weeds have a time of year or a specific climatic condition that they germinate and grow best. If we always seed the field closest to home first and the field furthest away last we are selecting for specific weeds on these fields with our seeding habits. One of the best examples of this is Pigmy flower and Yellow Whitlow grass. These weeds germinate as soon as the snow leaves, flower 2 to 3 weeks later, and have produced seed before the end of May. If you always seed this field last, you have allowed these weed to go through their entire life cycle without any disturbance. Using a crop rotation to determine the time of seeding will vary the seeding time on each field as you rotate the crop on that field.
Low residue stubble such as pulse or oilseed stubble should be seeded first as it will warm up sooner and will also dry out quicker due to the lack of residue covering the soil. Higher residue fields, such as cereal stubble, will hold the moisture longer and will also take longer to warm up in the spring, so they can be seeded later and still have adequate moisture to germinate the crop.
Chart#1
When controlling weeds in crop there should be a basic plan. Herbicide rotation should be considered. It is usually cheaper to control broad leaf weeds in a cereal crop and grassy weeds in a broadleaf crop. So this is where the emphasis should be placed. One example is if you have a little bit of Buckwheat in a cereal crop but it may not be economical to spray it out this year. The seed set from those weeds will make it necessary to control the buckwheat in the broadleaf crop the next year. The cost of controlling the buckwheat in a wheat crop is much cheaper than in a pea crop or a chickpea crop where there is no registered control. Residual herbicides should be used to your advantage but require rotation planning and a good set of field records. Don't sacrifice your rotation because you used a herbicide with recropping restrictions that don't fit into your rotation, regardless of how good of weed control it will give you.
Perennial weed control is best achieved with pre-harvest applications of glyphosate. Once again planning your rotation will give you the opportunity to control these tough perennials in the crop you want so harvest and weed staging work together. Many farmers do not like to use pre-harvest in canola because they feel to damage from the sprayer is more than acceptable. Pulses should be a good candidate for pre-harvest, as it will also help dry down the crop for harvest. The problem in pulse crops is when you have high thistle populations, the pulses are not competitive, and where the thistles are, you have no crop at all. Many farmers like to control the perennial weeds before they plant their pulse crops. That leaves cereal crops for the pre-harvest application. But if you are trying for malt barley, the maltsters don't want glyphosate residues on the barley. The crop of choice by many farmers is the other cereal crops and Flax. One additional benefit of spraying Roundup on flax is that it also stops the flax from continuing to grow and the moisture is saved for the next year's crop. Chart #1 shows this basic rotation with seeding dates and time of some weed control. If pre-harvest Roundup is applied to the cereal crop in year 4 for perennial weed control, you can then assess the control in the oilseed crop in year 1 of the chart. If there is still a large number of perennial weeds in the field, you have the option of using a post-harvest Roundup application after crops such as canola or mustard are harvested. These crops are usually cut early in the fall and quite high, leaving many of the thistles leaves on the plant. With fall rains and re-growth showing on the weeds post-harvest is an option that has worked. With perennial weeds, it is more effective to hit them with a Roundup application two falls in a row than to wait for two or three years.
Control of winter annual weeds like stinkweed, flixweed, and narrow-leaved hawksbeard; also need to be part of your rotation plan. Fall 2,4-D is an excellent method of controlling these weeds. In this rotation, there is a fall 2,4-D application following the oilseed and pulse crops. The darker residues of the oilseed and pulse stubble, in addition to the low residues remaining, result in the soil warming up in these fields first in the spring. When the soil warms up earlier, the winter annual weed growth starts earlier as well and often with higher numbers. Therefore, a fall application of 2,4-D is recommended on pulse stubble. However, due to potential residual herbicide damage, fall 2,4-D is not recommended prior to oilseed or pulse crops.
Chart # 1 shows the timing of all the practices I have been mentioning. However, when I start plugging specific crops into this rotation I will change some of the timings:
If peas are my pulse I will seed them first, even though they are on cereal stubble mainly because peas can tolerate cool soils and require a lot of moisture to germinate. When they are seeded early, there is usually two weeks before they emerge. This is an opportunity to do a post- seeding, pre-emergent burnoff. Quite often in a Low Disturbance system, if the broadleaf weeds are controlled at this time, there is very little new germination. As a result, there may not be a need to use any in-crop broadleaf weed control, provided that all the tough to kill broadleaf weeds that were in the cereal crop the previous year were controlled. This may not always work, but when you build it into your rotation system you reap the benefits when it works.
If I were using a Roundup Ready Canola as my oilseed crop, I would also seed it early and not use the zero incorporated granular herbicide. The reason for planting this type of canola early is that I don't need to wait for the first flush of weeds to emerge before I apply my Roundup burnoff. I can spray Roundup at any time the weeds are there and not hurt the crop. By seeding early I can also make use of the moisture and avoid the July heat
It was once believed that there would be worse disease in a direct seeded crop than in conventional till and that the disease would stay around on the field longer because the straw is decomposing at a slower rate. At Indian Head Research Station, Dr. Karen Bailey showed that disease was defiantly worse on a direct seeded field that had no crop rotation. This was wheat on wheat and the tan spot and septoria were worse on the direct seeded field compared to the conventional till wheat on wheat stubble. When she looked at wheat on oilseed or pulse stubble the degree of disease infestation was the same whether the field was direct seeded or in conventional tillage.
Dr. Bailey rated a number of factors as to how they affect disease:
Of all the factors the one that will have the biggest impact on disease that we have control over is rotation.
Some of the diseases that were a problem this year may not be controlled by rotations but rotations may have an impact on their severity.
Ergot
Ergot is caused by a fungus that can infect all cereals and grasses. It is usually more severe in rye and it is seldom found in oats. The ergot fungus survives from year to year as sclerotia that have fallen to the ground or as sclerotia sown with seed. The incidence of ergot varies from year to year and it depends upon how closely the spore release coincides with the flowering period of susceptible plants.
If you had ergot in a cereal field last year you know that you will have sclerotia in the soil because they are lighter than the grain and many of them blew out of the combine with the chaff. We can't avoid ergot with rotation because the spores will blow in with the wind from the field borders but we may be able to reduce its severity by not planting a cereal crop on that field next year. Ergot sclerotia can only survive one year in the soil so the oilseed-cereal-pulse-cereal rotation will help reduce infection.
Sclerotinia
Sclerotinia has a similar life cycle as ergot but the sclerotia stay viable in the soil for a longer period of time. The crop rotation of oilseed-cereal-pulse-cereal will not reduce the incidence of sclerotinia significantly as it is recommended that we have a 4-year break in having a host crop in rotation. All pulse and oilseed crops can be a host. Sclerotinia does usually not affect flax but it can be a host that will allow for the disease to remain on that field. We don't have enough crop selection to choose from to avoid Sclerotinia. We can improve our rotation with the inclusion of a winter cereal that will create a 5-year rotation from our 4-year rotation. Our rotation would now be oilseed-cereal-winter cereal-pulse-cereal. This rotation would give us two years of no host for sclerotinia. This will not eliminate the disease from the rotation but it will help.
If we continue to look at this 5-year rotation as to its weed control options we find it has some benefits there as well.
Chart #2
Chart #2 is similar to Chart #1 but this time I have included some specific crops and added winter wheat as my 5th crop. Many farmers have been seeding winter wheat on canola stubble but some also have been seeding it on barley stubble. The advantage of barley stubble is the increase in straw cover helps insulate the soil so we are not completely dependant on snow cover for the survival of the winter wheat. Many time all the weed control that is required for winter wheat is a fall application of 2,4-D to control the winter annuals. The winter cereals get off to a very early start in the spring so the need for in crop weed control may not be needed. Don't assume that you don't need in-crop weed control. Field scouting is required and you may need to spot spray for weeds like wild oats.
If you like to get into longer-term rotations to assist in weed control and disease management some farmers are looking at including forages in rotation. One example may be:
Year 1 - Smart canola under seeded with alfalfa (use pursuit to control weeds in canola and give some residual weed control in alfalfa stand).
Year 2 to 5 - Alfalfa - This will help break disease and weed cycles.
Year 5 - remove alfalfa with glyphosate sprayed prior to second cut while there is good re-growth.
Year 6 - seed competitive cereal crop that can be sprayed with a broadleaf herbicide to control alfalfa (oat may be good as there should be very few wild oats).
Continue with annual crop rotations for a few years. You may want to include a roundup ready canola in the rotation if dandelion or other perennials have developed while the land was in alfalfa.
As you can see even though I have set out a basic rotation, once specific crops are identified, some of the practices change. There is no perfect rotation or recipe that will work for all conditions. However, taking the time to plan your rotation may reap you some benefits. Any increase to production that is achieved from additional management, is all profit. There is no input cost to management besides the time you put into it. Like everything else, the more you put into it the more benefit you receive from it.