- G. Schell, Ecological Services for Planning Ltd., Guelph, Ontario
(Tech. Transfer Report Summaries)
View / Download Final Report [1394 KB pdf]
Associated SWEEP/LSP Research
Completed: July, 1992
erosion, erosion control, conservation technology, rainfall simulation,
Universal Soil Loss Equation, cover crops, conservation tillage, phosphorus,
run-off, no-till, conventional, reduced tillage, manure, aeration tillage,
residue cover, slope.
Rainfall simulations were conducted in 1989, 1990 and 1991 on twenty-two
occasions at fourteen different farms. A wide range of conservation farming
systems, involving different tillage, cover crop and manure management systems,
were evaluated in terms of runoff and soil and phosphorus losses resulting
from a simulated rainstorm.
The rainfall simulations took place on research plots set up within ongoing
TED studies, following consultation with the TED research contractor and
the farmer cooperator. Runoff and erosion data were collected within one
set of replications set up under the main research trials.
The erosion control offered by aeration tillage, reduced tillage (using
a chisel plow or offset disk) and zero-tillage systems was evaluated, and
compared against a conventional (moldboard plow) tillage system. At some
sites, the erosion control provided by cover crops of red clover, rye, barley,
annual ryegrass, hairy vetch or oilseed radish was compared against treatments
where the only surface residue cover was from the previous main crop. The
susceptibility of soils to erosion and phosphorus losses following applications
of raw and composted beef manure, and liquid swine manure was also examined.
The runoff and erosion data provided by the rainfall simulations were
highly variable at many of the sites. However several trends emerged from
the research. In most cases, the conservation tillage systems resulted in
reduced runoff and erosion rates. Aerway tillage shows promise as an effective
management tool for high residue cropping systems. It leaves sufficient
residue on the surface to reduce the amount of soil detachment and erosion
due to rainfall, and does not appear to lower the infiltration rates in
comparison with moldboard plow tillage, as indicated by runoff volumes.
Furthermore, it can be pulled in tandem with the planter, providing secondary
tillage with relatively little soil disturbance.
Reduced tillage systems tended to lessen the amount of sediment loss
due to the simulated rainstorm, in comparison with moldboard plow tillage.
In most cases, the degree of control over sediment losses was proportional
to the amount of residue cover remaining on the surface and the amount of
disturbance to the soil surface by the tillage operation.
Many cover crop systems were tested by rainfall simulation. When they
were growing, or had been killed but not disturbed by tillage, they provided
nearly complete surface cover and appeared to be equally effective in controlling
soil erosion. After spring cultivation and planting, some cover crops, most
notably hairy vetch, appeared to provide lasting erosion control benefits,
possibly due to soil structural improvements and persistent surface residue.
Other cover crops, in particular oilseed radish, provided no lasting erosion
control benefits. In general, the residue from cover crops with more fibrous
plant growth was more persistent and effective in controlling soil erosion.
Applications of raw and composted beef manure in summer onto perennial
forages and applications of liquid swine manure in summer and spring did
not affect erosion rates or phosphorus losses in comparison with similar
treatments where manure was not applied. However, when poultry manure was
applied in the fall and incorporated by aerway tillage only, soluble orthophosphate-P
losses by rainfall simulation were very high (3.6 mg/m2) in comparison
with losses of 0.13 mg/m2 when the manure was incorporated by
Several factors contributed to high variability or possible non-treatment
related differences in the rainfall simulation results. Soil cracks on some
plots caused major reductions in runoff. Due to the experimental set-up,
the slopes of some treatments were significantly different than the slopes
of the treatments to which they were being compared. Nevertheless, many
of the rainfall simulations provided excellent results and demonstrated
that reductions in soil and phosphorus erosion can be achieved by the adoption
of conservation farming measures.
(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank,
The purpose of this study was to use rainfall simulation to evaluate
the relative effectiveness of the different conservation and erosion control
technologies tested in the TED program of SWEEP.
Rainfall simulation was conducted during the summers of 1989-91 on fourteen
farms. On- farm research on these areas was initiated, previous to this
study, to evaluate the effectiveness of one of the following: conservation
tillage, residue management, nutrient management and cover crops. Sample
design followed the replications and comparisons established in the TED
projects. Rainfall simulation methods established by the Ontario Institute
of Pedology were adopted for the study. Benchmark soil conditions were sampled
for soil particle size, moisture content, organic matter content and initial
concentrations of available phosphorus. One metre square run-off plots were
placed, to collect run-off, and was sampled for water volumes, sediment
loads, sediment P and soluble phosphorous concentrations.
Mean values of each treatment for before and after rainfall conditions
were analyzed using the Duncan multiple range test. The results of the rainfall
simulation were found to be highly variable and definite conclusions regarding
the effectiveness of specific conservation treatments was difficult to ascertain.
However, certain trends in the data were observed. For example, as expected,
conservation tillage systems yielded less run-off and soil loss. The higher
the residue level - the lower the run-off. The investigators found that
cover crops with fibrous rooting (e.g. hairy vetch) were more effective
at erosion control.
Variability in the data was attributed to variation in the slope and
soil conditions between plots on each farm.
The identification of the need to test the relative efficiency of several
conservation technologies at controlling soil loss and run-off was a positive
step: any on-farm conservation agronomy research should be subjected to
standardized objective evaluation. There are several problems relating to
the use of rainfall simulation:
Topographic position and soil type were not used rigorously as criteria
for the establishment of the on-going TED study sites. This does not only
make the design of original studies suspect but raises serious questions
about the design of this study. If observations across treatments were
not made on similar site (soil and slope position) conditions, the subsequent
flow of logic from observations to conclusions and recommendations is
The Universal Soil Loss Equation (USLE) was referred to in the treatment
of the literature but was not used as a model to help verify the appropriateness
of specific sites chosen for the simulation work. If this had been done
it would have indicated the relative potential influence of the variation
of LS and K factor-values on predicting soil loss for the TED study areas.
It is not readily apparent that spatial influences on run-off were
considered in the design. The potential for aggregation of detachment,
sheet and inter-row erosion was not accounted for with one metre square
plots within treatments. Further, the influence of micro-topography over
a larger area was not addressed. In addition, the effectiveness of cover
crops in early spring would have been more appropriately tested in March
It is difficult to place confidence in those results, where physical
conditions were not similar between treatments.
SWEEP Report #12 - Choice and Management of
Cover Crop Species and Varieties for Use in Row Crop Dominant Rotations
SWEEP Report #27 - Cereal Cover Crop Study
SWEEP Report #38 - Management of Farm Field
Variability. I. Quantification of Soil Loss in Complex Topography. II. Soil
Erosion Processes on Shoulder Slope Landscape Positions
SWEEP Report #58 - Manure Management in Conservation
Future Research: ( ) indicates reviewers suggestion for
priority, A - high, C - low.
(C) Better standards, with particular emphasis on design and field variability,
for evaluating conservation technologies with rainfall simulation should
be developed. Research toward this end should be supported.
Thursday, May 19, 2011 04:05:19 PM