We continuously crop a 5000 acre grain farm at Shellbrook, 1/2 hour west of Prince Albert, in the Parkland area. The soil type varies from loamy sand to clay loam. Average rainfall for our area is 10-14 inches during the growing season. Quite often our crops suffer frost damage due to the short growing season.
In 1996 we grew wheat, oats, barley, winter wheat, fall rye, and canola as traditional crops; peas and faba beans as specialty crops; as well as alfalfa and slender wheat grass for seed. In the past we have experimented with sunflowers, lentils, canary seed, caraway seed, buckwheat, oilseed radish, and fall-seeded canola.
My first experience with direct seeding was in 1990 when I was a member of the Agriculture Development and Diversification Board (ADD Board), and we were promoting zero till. We planted a quarter section of peas into unmanaged-residue wheat stubble. Germination was a problem in the chaff rows, and thistles were also a problem. However we were pleased with the overall results; and since 1993 have converted all of our acres to zero till.
When farming conventionally quackgrass and thistles were weed pests that could not be controlled using the cultivator. Other main weed pests were wild millet , pigweed, buckwheat, and lambs quarters. Since switching to zero-till these weeds are not as much of a threat, if they are closely monitored. There has been a shift in weed persistency; cleavers and hemp-nettle are now major weed problems. Following a cold wet spring, wild oats can be a problem.
In addressing the topic of weed control on our farm, I will go through our crop production procedure, mentioning the weed control involved during each stage. This will include residue management, seed and seeding equipment. post-emergent weed control, fertilization, and rotation.
Residue management starts in the fall prior to seeding. We straight cut all of our crops except for the Argentine canola, faba beans, and some barley. On our TR96 combines, we modified the straw chopper by enlarging the deflector fins and replacing the original hammers with heavier ones to create a full 25 foot straw spread, the width of the straight cut header. This year the TR98 combines proved to have a very aggressive straw chopper, so modifications were unnecessary. We did add chaff spreaders as we had on the TR96's. In 1993 and 1994, we harrowed after combining with a heavy harrow in order to achieve extra residue spread. This year, using TR98 combines, we found that only fields which were combined tough needed to be harrowed.
I choose short straw varieties of wheat and barley for the heavier land and reserve the longer straw varieties for the lighter land in order to better manage excess residue. By managing residue, we can seed shallow with precise seed placement.
All of our seeding is done with a Flexi-Coil air drill with 3 inch spoons, 31/2 inch packer wheels on 12 inch row spacing. Shallow seeding allows quick germination which discourages weed competition. On-row packing produces good seed to soil contact and leaves the soil in between the rows fluffy, a poor environment for weed growth. Although this leaves a fairly rough field finish, the furrows are smoothed out by harvest from plant mass and rains.
For all crops we plant only high quality seed which has been tested for germination and vigour. I prefer hybrid Argentine canola because it has a very strong seedling vigour characteristic, allowing it to compete with weeds in the early growing stage. Seedling shallow with good quality seed and proper fertilization leads to a crop that emerges quickly and competes against weeds.
We determine our fertilizer requirements by having the fields soil tested. Phosphorus, sulfur, potash, micronutrients, and 20 lbs of nitrogen are applied in the three inch seed row. The remaining nitrogen is applied as top dressing at the four leaf stage for cereals and prior to bolting in canola. We do this using a Terragator at rates varying from 50 to 80 lbs of actual N. Top dressing can be done economically, quickly and allows us the flexibility to adjust nitrogen rates according to moisture conditions. Although top dressing with nitrogen is believed to foster weed growth, we have not found that to be the case. We have gained in crop yields and wheat protein content by top dressing.
Prior to converting to zero-till, pre-emergent herbicides were used extensively. I had used trifluralin extensively for millet control since 1976, resulting in trifluralin resistant millet problems. The millet then had to be controlled with another group of chemicals. Since we've been zero-tilling, the millet pressure has not been as great because of the unfavourable seedbed for millet germination. Where a millet problem appears, we now use a post-emergent herbicide such as Poast or Assure on peas and canola, or Achieve or Horizon on wheat. Realizing that any weed can develop a resistance to a chemical, we conscientiously use a herbicide rotation.
With zero-till, fields that are to be seeded to canola and peas, we use a pre-harvest application of Roundup if thistles and/or grass are a problem. In the spring, the fields are made ready for canola using a pre-seeding burn off with a 1/2 litre per acre of Roundup. A tank mix of Assure and Muster give us satisfactory grass and broadleaf weed control in canola. Although Muster is not registered for cleavers, we have experienced satisfactory control of this weed.
Weeds adapt to their environment. For example, the more a dandelion on the lawn is mowed during the summer, the shorter it grows. By late summer, the flower grows to the height of the mower cut. However, if it is left alone, it will grow eight inches tall. Weeds in field are the same. If we treat them the same way all the time, year in and year out, we will find we have some resistance in those weeds. A significant weed control measure to prevent weed adaptation is rotations.
The first rotation is crop rotation. Not only does crop rotation reduce crop disease problems, but also exerts different pressures on the weeds. Rarely is wild oats a problem in fall rye or winter wheat due to early spring crop competition. Cleavers seam to flourish in peas and lentils because there is less crop competition. By rotating crop types, the weed species can be controlled. On our farm we don't have a definite crop rotation, but we consider the weed populations and try to alternate a broadleaf crop (canola, peas, faba beans, etc.) between cereal crops. If we do see cereals in succession, we alternate the type of cereal. For example, oats on fall rye stubble, barley on wheat or oats stubble.
The second rotation that we consider is seeding dates. We alternate the seeding dates of any field from one year to the next. For example, if we seed the home quarter first this year, then next year we may seed it half way through the seeding season or maybe seed it last. This produces an inconsistent environment for the weeds and discourages habitual growth of a specific weed type. We also grow winter cereal crops which provides a radical environmental change for weeds.
To Summarize, these are the practices we incorporate to control weeds on our zero-tilled farm:
1: Residue management to evenly spread residue for even seeding and crop germination.
2: Quality seed and good seed to soil contact with on-row packing.
3: Optimum fertilization.
4: Post-emergent herbicide control.
5: Crop and seeding date rotations.