How to make organic no-till work for
field crops in Southern Manitoba?
Caroline Halde, M.Sc.
Ph.D. Candidate and organic farmer from Québec
University of Manitoba, Winnipeg, MB
Organic No-till for Manitoba: The Technical Details
How do I integrate mulch into my cropping system?
In recent years, there has been a growing interest in trying to reduce tillage on organic farms by adapting the mulch production systems widely used by Brazilian no-till farmers since the late 1980s (Bolliger et al. 2006). The Brazilian no-till system with mulches has been adapted to the North American organic grain production conditions to become an "organic rotational no-till system" that reduces tillage by rotating between a green manure established with tillage and a cash crop no-till planted into the green manure mulch.
There are many different ways to adapt the mulch production system to your cropping system. At the Carman Research Station, in Carman, Manitoba, we found that we need to "invest" one full growing season (spring to fall) to grow the green manure that will be used as a mulch. The green manure crop seeded in the spring was rolled in late-summer at the flowering stage using a roller-crimper (Figure 1), in order to produce a thick mulch. This newly created mulch created a physical barrier that suppressed weeds in the fall and the following year. The following spring, a cash crop (flax, spring wheat, etc.) was directly seeded into the decomposing green manure residues (mulch). Plans to build a roller-crimper are available for free download at www.rodaleinstitute.org/our-work/organic-no-till/no-till-rollercrimper-plans.
There have been many successful examples of adaptation of the organic rotational no-till production system in various regions of the United States. In Iowa, a fall rye/vetch and a winter wheat/winter pea mulch has been tested for weed control in organic no-till soybean, corn and irrigated tomato, with the rye/vetch mulch providing the best weed suppression (Delate et al. 2011). In Pennsylvania, organic no-till corn was grown into a hairy vetch mulch and organic no-till soybean into a fall rye mulch, with overall comparable or greater yields than county averages (Mirsky et al. 2012; Mischler et al. 2010a; Mischler et al. 2010b ). A lot of information about the work done at the Rodale Institute, in Pennsylvania, USA, can be found online at www.rodaleinstitute.org/no-till_revolution . Research trials have also been conducted in Illinois with organic soybeans planted into pure fall rye or pure vetch mulch (Davis 2010).
Which species do I need to produce good mulch?
Characteristics of a desirable mulch identified by our research team are:
- High biomass (6-8 t/ha at time of seeding the following cash crop in the spring)
- Slow decomposition rate (for extended weed control into the following year)
- Nitrogen input to the following crop (presence of a legume in the mulch)
A few trials have been conducted with a few different plant species in Carman MB to identify the best mulch. We have tried to combine 2, 3 and 4 plant species together in order to produce the highest biomass of mulch, and we have tried some pure stands of barley, pea and hairy vetch too. The seeding rates that we used are as follows:
- Barley ( 152.3 kg/ha)
- Pea ( 216.4 kg/ha)
- Hairy vetch (51.8 kg/ha)
- Barley (76.1 kg/ha) + pea (108.2 kg/ha)
- Barley (76.1 kg/ha) + oilseed radish (8.1 kg/ha)
- Barley (76.1 kg/ha) + sunflower (5.1 to 8.5 kg/ha)
- Barley (76.1 kg/ha) + hairy vetch (25.9 kg/ha)
- Barley (50.8 kg/ha) + pea (72.1 kg/ha) + oilseed radish (5.4 kg/ha)
- Barley (50.8 kg/ha) + pea (72.1 kg/ha) + sunflower (3.4 to 5.7 kg/ha)
- Barley (38.1 kg/ha) + pea (54.1 kg/ha) + sunflower (2.5 to 4.3 kg/ha) + oilseed radish (4.1 kg/ha)
We had our greatest success using a pure stand of hairy vetch (51.8 kg/ha) and using a mixture of barley and hairy vetch (76.1 and 25.9 kg/ha, respectively). Among all the species of green manures tested, hairy vetch had the special characteristic of not being killed by the crimping action of the roller-crimper, when seeded in the spring. Hairy vetch established slowly in the spring (< 4 t ha -1 of aboveground biomass by mid-summer, in 2010, 2011 and 2012) and was a poor competitor with weeds, but kept growing until the end of October, increasing its biomass and competing with weeds very effectively later in the season.
Another student working with Dr. Martin Entz, Kristen Podolsky, has been working with mulches of field pea and oats, and she found that the field pea/oat mulches did not provide sufficient weed control in no-till conditions in Carman, Manitoba (2-year study in 2011 and 2012).
How much mulch do I need?
Mulches with hairy vetch had the highest mulch biomass in the fall (9 to 11 t/ha) and in the following spring (4 to 8 t/ha) of all the other mulches tested (field pea, sunflower, oilseed radish, and barley). At time of seeding flax into these mulches, biomass of hairy vetch-barley mulches differed greatly over the years. It ranged from 4.1 t/ha dry biomass in spring 2012 to 7.6 t/ha dry biomass in spring 2010; thus, the ability of hairy vetch-barley mulches for control weeds varied over years. As a general rule of thumb, we can conclude that mulches of barley-hairy vetch were found to be efficient in suppressing weeds only when the mulch produced biomass greater than 6 to 7 t/ha. Also, it is interesting to note that high amounts of nitrogen (93-164 kg N/ha) were released over winter from mulches with hairy vetch (pure vetch, or the barley/vetch mixture) and available in form of soil nitrates for the following cash crop.
How do I seed into that thick mulch?
We have been seeding a few different cash crops (spring wheat, flax, sunflower) into the mulches using a disk-drill seeder. We seed when the mulch is dry, to facilitate the cutting of the mulch by the disks. A group of agrologists from France came to visit us in Carman in 2010, and they told us that were having a lot of trouble with their seeder (different disks?) that did not cut the mulch. However, we have never encountered any problem with seeding into thick dry mulches at the research station. We have posted a video online of our technician seeding a field of organic flax into mulches using our disk-drill seeder. You can find it online at: www.umanitoba.ca/outreach/naturalagriculture/video/zerotill_seeding.html.
What kind of yields can I expect?
Spring wheatSpring wheat yields reached 2.5 t/ha (37 bu/ac) and 3.9 t/ ha (58 bu/ac) in 2011 and 2012, respectively, in organic no-till production with mulches containing hairy vetch. Yields obtained in these research plots were comparable to the average regional yields of 2.4 t/ha (36 bu/ac) in 2011 and 3.2 t/ha (48 bu/ac) in 2012. Mulches with pure stand hairy vetch did similarly to mulches with a mixture of barley and hairy vetch. Spring wheat yielded poorly (1-2 t/ha, 15-30 bu/ac) in other mulches without hairy vetch (e.g. barley-sunflower-oilseed radish mixture).
Other work considered the agronomic performance of herbicide-free no-till production systems (with mulch) compared to those of herbicide-free tilled systems. In 2009, flax yields in the tilled systems (2.3 t/ha or 37 bu/ac) were significantly higher than in the no-till treatment (2.0 t/ha or 32 bu/ac). However in 2010, flax yield in the no-till treatment (1.8 t/ha or 29 bu/ac) was significantly higher than in the tilled treatment (1.1 t/ha or 18 bu/ac).
In conclusion, the successful adaptation of the organic rotational no-till system to the growing conditions of Southern Manitoba reduced the need for tillage for a period of 1.5 to 2 years in organic spring wheat production. Mulches of barley-hairy vetch were found to be effective at suppressing weeds only when the mulch produced high biomass, greater than 6 to 7.1 t ha-1. Large yield penalties were observed after 2-to-3 years of maintaining the no-till system without herbicide. Yield penalties were associated with the establishment and proliferation of perennial weeds and with low soil N mineralization.
Challenges and problems we've encountered, and what we’ve tried in order to resolve these issues
Specific weed problem: dealing with wild oats
In 2011 and 2012, we had difficulties with wild oats in one of our fields at the Carman Research Station. The reason why the wild oats were present is because wild oats seeds were seeded in that field more than 15 years ago in order to conduct an experiment on weed seed dispersal (Shirtliffe and Entz 2005). Unfortunately, I inherited this field for my research! I have learned a few things: it is better to deal with the wild oats problem (grow perennials for 2-3 years with frequent mowing, do a fallow year with frequent tillage, etc.) before attempting to switch to organic no-till field crop production.
Poor establishment of the green manure (mulch)
In spring 2011, the green manure of barley and hairy vetch did not establish well. That spring was very wet, and we had problems controlling wild oats (see previous comment), so a poor establishment of the green manure led to low mulch biomass and low weed control level by the mulch the following year.
Weed population shifting to perennial weeds
Because we stopped tilling the soil, our weed population switched from summer annual weeds (redroot pigweed, foxtail, wild buckwheat, etc.) to p erennial weeds, such as dandelion (Taraxacum officinale) and Canada thistle (Cirsium arvense). The proliferation of perennial weeds affected yields when no tillage or herbicides were used for more than a 2 to 3 year period (medium-term continuous no-till). Sheep were introduced in fall 2012 as an alternative for perennial weed control. We are waiting for the snow to melt to be able to observe the results of the sheep grazing!
Problems with using hairy vetch
Here is a list of some problems that we have encountered with hairy vetch:
- Slow establishment
- Hard seed coat – It is preferable to scarify the hairy seed seeds before seeding.
- Expensive seed
- Does not always die over winter
- Disease (?): Some farmers in Quebec have reported having some mortality of hairy vetch plants when growing hairy vetch for seed (over 2 years).
Bolliger, A., Magid, J., Carneiro Amado, T. J., Neto, F. S., dos Santos Ribeiro, M. F., Calegari, A., Ralisch, R., and de Neergaard, A. 2006. Taking stock of the Brazilian "zero-till revolution": a review of landmark research and farmers' practice. Advances in Agronomy. 91:47-110.
Davis, A. S. 2010. Cover-crop roller-crimper contributes to weed management in no-till soybean. Weed Science. 58:300-309.
Delate, K., Cwach, D., and Chase, C. 2011. Organic no-tillage system effects on soybean, corn and irrigated tomato production, and economic performance in Iowa, USA. Renewable Agriculture and Food Systems. 27(1):49-59.
Mirsky, S. B., Ryan, M. R., Curran, W. S., Teasdale, J. R., Maul, J., Spargo, J. T., Moyer, J., Grantham, A. M., Weber, D., Way, T. R., and Camargo, G. G. 2012. Conservation tillage issues: Cover crop-based organic rotational no-till grain production in the mid-Atlantic region, USA. Renewable Agriculture and Food Systems. 27(1):31-40.
Mischler, R. A., Curran, W. S., Duiker, S. W., and Hyde, J. A. 2010a. Use of a rolled-rye cover crop for weed suppression in no-till soybeans. Weed Technology. 24:253-261.
Mischler, R., Duiker, S. W., Curran, W. S., and Wilson, D. 2010b. Hairy vetch management for no-till organic corn production. Agronomy Journal. 102(1):355-362.
Shirtliffe, S., and Entz, M. 2005. Chaff collection reduces seed dispersal of wild oat by a combine harvester. Weed Science. 53(4):465-470.
This page created April 2013.