The decision does not have to be between conservation or profit; a blend of tillage options within a system may allow for both.
Corn producers
have successfully adjusted cropping practices for years, trying to weigh input
costs, environmental concerns and profit potential into the mix. In considerations
over reduced tillage, some of the flexibility in decision making was at risk
if you ascribed to either of two theories that became particularly popular
in the late 1980s. They were: 1) no-tillage systems improve with time; yields
may be reduced in the initial years but soil structural improvements will
foster improved no-till results in subsequent years; and 2)…(which sort
of follows automatically) once you get started into a no-tillage system, doing
occasional tillage for some crops may reduce no-till success for other crops
in following years.
Concerns over the validity of these claims fostered a long-term project at
Woodstock (funded by OCPA and under the direction originally of Tony Vyn and
now being conducted by Bill Deen of the University of Guelph). The aim of
this study is to examine yield limitations in a corn-soy-wheat rotation that
could be caused by short duration no-till or by a lack of continuity in a
tillage system. The site was established in 1995 and has all crops (corn,
soybeans and winter wheat) present each year.
| Table 1. The impact of tillage system continuity on crop yields. Yields are 5-year averages 1996-2000. Woodstock, Ontario. Loam Soil | |||
| Tillage System |
Corn
|
Soybean
(bu/ac) |
Wheat |
| 1. Moldboard (all crops) |
169 |
44 |
76 |
| 2. Chisel (all crops) |
169 |
45 |
77 |
| 3. No-till (all crops) |
162 |
44 |
75 |
| 4. Chisel (corn)No-till (soys and wheat) |
168 |
46 |
76 |
| 5. Chisel (soys) No-till (corn and wheat) |
164 |
45 |
75 |
|
|
|||
| Least Significant Difference (P=0.05) |
4.6 |
1.5 |
2.4 |
| B. Deen, K. Janovicek, University of Guelph and T. Vyn, Purdue University | |||
Table 1 outlines
the crop yield results as summarized for the first five years of the trial.
You will note that a no-till system employed each year did result in corn
yields that were less than either moldboard or chisel systems. However, this
continuous no-till system produced soybean and wheat yields that were not
different from chisel or moldboard systems. That there were more problems
with no-till corn than no-till soys or wheat is not surprising news. To address
this problem, the study compared a system where you insert the chisel plow
once every three years prior to corn, and leave the no-till system in place
for the other two years in the rotation. The results are indicated in Table
1 – tillage system number#4: Chisel (corn)/No-till (soys and wheat). The study
indicates that such a system can improve corn yields with no detrimental effect
on the subsequent no-till soybean and wheat yields compared to the continuous
no-till system.
| Table 2. The impact of tillage system continuity and length of time in no-till on corn yields in 2001. Woodstock, Ontario. Loam Soil. | |
| Tillage System |
Corn
Yield (bu/ac at 15.5%) |
| Moldboard
(all crops) (continuous since 1995) |
119 |
| Chisel (all
crops) (continuous since 1995) |
137 |
| Chisel (corn) No-till (soys and wheat) |
133 |
| No-till
(corn and wheat) Chisel (soys) |
138 |
| No-till
(all crops) (continuous since 1995) |
127 |
| No-till
(all crops) (continuous since 1998) |
127 |
| No-till
(all crops) (2001 only) |
120 |
|
|
|
| Least Significant Difference (P=0.05) |
not
significant |
| B. Deen and K. Janovicek, U. of Guelph | |
Some may argue
that the six-bushel increase in corn yields doesn’t warrant adding the
tillage to an otherwise no-till system. I would agree completely in cases
where fields are highly sloping/erodible, organic matter contents are chronically
low, or where soil drainage generally lets you plant no-till corn successfully,
and on time, most years. However, for situations where poor soil drainage
often hampers no-till corn planting, where previous crop residues are high,
and where manure management demands tillage - it may be the only option. This
research points to the fact that growers who do occasional (rotational) tillage
to overcome some of these obstacles may successfully no-till in other years
within the rotation.
The other
aspect of this study was establishing a series of plots that switched to no-till
at various points within the life of the study. That is, one series of plots
was no-till from the beginning (1995), another set was converted to no-till
in 1998, and a third set was no-tilled for the first time in 2001. Table 2
outlines corn yields from this long-term site in 2001 and shows the various
treatments in terms of their length of time in no-till as well as the other
rotational tillage systems discussed earlier. Unfortunately, the very dry
conditions at Woodstock this past year made the site, normally fairly uniform,
quite variable. A statistical approach to interpreting the numbers in Table
2 indicates that random chance alone could have easily created the trends
(if indeed there are any) that were observed. Fortunately, this study is scheduled
to continue until 2004 and thus will allow for further evaluations on the
effects of tillage system continuity.