Reducing Tillage in Organic Agriculture on the Canadian Prairies
I. Vaisman and M.H. Entz
Department of Plant Science, University of Manitoba, 66 Dafoe Rd, Winnipeg MB, Canada R3T 2N2
Contact: [email protected]
Table 1. Termination treatments for the green manure crop of peas and oats in Study 1.
Introduction
In organic crop production, tillage is often used to terminate and
incorporate green manures, and also as a major tool for weed control.
However, tillage has been shown to decrease organic matter and can lead
to more erodible soil (Teasdale et al., 2007). Zero tillage cropping systems,
on the other hand, have been shown to have higher soil organic matter,
cation exchange capacity, and water holding
A
capacity as compared to tillage systems
(Teasdale et al., 2007). Organic farmers are
therefore faced with the challenge of
managing green manures in a way that can
maintain
overall
soil
health,
while
minimizing weed populations.
In response to this challenge, the Rodale
Institute developed the roller crimper
(Teasdale, 2007). The roller crimps crop
stems and lays the crop flat, eventually
drying and killing the plant. The residue left
on the soil surface creates a barrier that
can suppress weeds and reduce water
evaporation. The residue also contributes to
soil organic matter. The roller crimper can
therefore help reduce tillage in organic
agriculture.
B
Fig 1. A) the roller crimper can be
mounted to the back of a tractor. B) the
blades on the roller crimper crimp crop
stems.
Treatment
Jul 07
Aug 07
Sept 07
1
Roll
Roll
Roll
Oct
Roll
07
May
08 *
2
Roll
Roll
Roll
Roll
Till
4 Rolls + 1 till
3
Roll
Roll
Roll
Till
Till
3 Rolls + 2 till
4
Roll
Roll
Till
Till
Till
2 Rolls + 3 till
5
Roll
Till
Till
Till
Till
1 Roll + 4 till
6
Till
Till
Till
Till
Till
0 Roll + 5 till
-
Total
4 Rolls + 0 till
4 Rolls + 1 Till
Roll = one pass with the roller crimper, Till = one pass with a tandem disc
* Before seeding of wheat
Fig 3. The roller crimper in action
rolling a green manure crop of peas
and oats
Study 2:
In the summer of 2007, three different
legumes were grown separately as
green manures: chickling vetch
(Lathyrus sativus), hairy vetch (Vicia
villosa), and Indian Head black lentil
(Lens culinaris Medik.). At flowering,
each green manure was terminated
under two different treatments, tillage
and reduced tillage (Table 2). In the
spring of 2008, Hard Red Spring Wheat
(cv. HR5602) was seeded into the
different treatments. Soil samples were
taken at seeding to measure nitrate
levels.
Study 2:
Crop
Treatment
July 2007
Oct 2007
Tillage
Till
Till
Chickling
Vetch
Reduced tillage
Roll
Till
Tillage
Till
Till
Hairy
Vetch
Reduced tillage
Roll
Till
Tillage
Till
Till
Reduced tillage
Roll
Till
Lentil
Roll = one pass with the roller crimper, Till = one pass with a tandem disc
To assess the use of the roller crimper for green manure termination in
organic agriculture on the Canadian prairies:
Results and Discussion
Study 1: To compare the rolling versus tillage of a green manure and the
effect in the subsequent year on nitrogen availability, soil water and wheat
yield.
Study 1:
Materials and Methods
Field trials were conducted over two years on organically managed land at
the Carman Research Station in southern Manitoba, Canada. The region is
characterized by a continental climate and receives a mean annual rainfall
of 409 mm.
Study 1:
In the summer of 2007, a pea (Pisum Sativum) and oat (Avena sativa)
intercrop was grown as a green manure. Beginning at pea flowering, the
green manure was terminated by six different levels of tillage intensity
(Table 1). In the spring of 2008, Hard Red Spring Wheat (cv. HR5602)
(Triticum aestivum) was seeded into the different treatments. At seeding,
soil samples were taken to measure nitrate levels in the soil profile down to
120cm. Soil moisture was measured with a neutron probe down to 120 cm.
Nitrogen
Nitrate levels were not
significantly affected by
crop or tillage intensity
(P>0.05).
Yield
Wheat yield was not
significantly affected by
crop or tillage intensity
(P>0.05) (Fig 5).
Fig 5. Yield of hard red spring wheat grown after three
different green manure crops terminated under tillage and
reduced tillage.
Conclusions
Study 1:
ƒ Using the roller crimper to terminate green manures provided the
same amount of nitrogen to the subsequent wheat crop as tillage.
Use of the roller crimper did not conserve water and had no effect on
water available to the subsequent wheat crop. Wheat yield was not
affected by tillage intensity.
Nitrogen
Tillage intensity did not have a
significant effect on nitrate
concentrations in the soil (P>0.05). The
average nitrate concentration across
all six treatments was 212 kg/ha.
Study 2:
ƒ Chickling vetch, hairy vetch, and lentil provided the same amount of
nitrogen and wheat yield regardless of tillage intensity.
Moisture
Tillage intensity did not have a
significant effect on water content in
the soil (P>0.05). The average moisture
content across all six treatments was
33.52 cm3/cm3.
The roller crimper has the potential to replace tillage of green
manures while still providing adequate nitrogen and wheat
yield.
References
Yield
Tillage intensity did not have a
significant effect on wheat yield
(P>0.05) (Fig. 2). The average yield
across all six treatment was 3704
kg/ha.
Fig 4. Pea and oat residue are visible on the surface of
the soil in the spring of 2008. Treatment 2 is on the left
and treatment 1 is on the right
Table 2. Termination treatments for the green manure crops in Study 2.
Objectives
Study 2: To compare different legume species for their potential as green
manures in a low tillage system.
4 Rolls + 0 Till
Teasdale, J.R., Coffman, C.B., Mangum, R.W. (2007). Potential long-term benefits of no-tillage and
organic cropping systems for grain production and soil improvement. Agronomy Journal, 99,12971305.
Fig 2. Yield of hard red spring wheat grown after a green manure
crop terminated at different tillage intensities.
Acknowledgments
The authors gratefully acknowledge the expert technical assistance of Mr. Keith Bamford and funding from the Canadian
Wheat Board, Manitoba’s ARDI program and the Organic Agriculture Centre of Canada