Trapping and maintaining more moisture near the soil surface is likely one of the greatest benefits to be derived from direct seeding in semi-arid regions. Increasing plant-available water reduces dependence on summer fallow, and allows for extended rotations with greater crop diversity. There is a need to evaluate management practices, such as balanced fertility and fertilizer placement, crop specific optimal seeding dates and weed control timing, which together should lead to increased efficiency with which available water is used to produce grain.
There is a need to employ a more holistic approach to nutrient management which requires us to rethink how we approach soil fertility. Rather than focusing on the response of one individual crop to fertilizer applied in one year, there is a need to approach soil fertility from the aspect of soil building and plant health. The development of crop specific nutrient packages, suitable for the various agro-ecological regions, should be our goal. In addition, we need to improve our understanding of tillage effects on the contribution of crop residues, other than legumes, to nutrient availability.
There is a desperate need for some basic information on the impact that tillage has on the severity and longevity of residue borne plant diseases, particularly with oilseed and pulse crops. There is a need to establish a better understanding of the relationship between disease persistence and residue decomposition, considering the diversity of crops currently being grown.
It is our opinion that the lower soil temperatures found with direct seeding should not be a deterrent, except in those cases where the amount of soil disturbance at seeding is low (e.g. disc opener). There is a need to evaluate crop varieties to determine if there are differences in the rate of germination and emergence under cool soil conditions. Advancements in this characteristic would allow for earlier seeding, particularly on fine textured soils where high water holding capacity tends to slow soil warming.
We believe that crop rotations are an integral part of the success of direct seeding, or stated another way, the success of direct seeding is to a large extent dependent on a well managed crop rotation. There is a need to match crop rotations with soil water content, crop residue levels, weed and disease management strategies, and plant nutrition. While rotation research is long-term in nature and may not be responsive to changes in technology, it is our only means of evaluating scientific principles that change slowly over time.
Future research in weed management will have to focus on the
combination, or integration, of technologies that reduce weed
populations as a means of reducing both herbicide use and crop
losses. There is a need to pay more attention to cultural
practices that reduce our dependence on herbicides. An increased
understanding of how we can use weed threshold number in our
decisions to spray or not is an area which requires further
refinement.
Standing stubble traps more snow and can lead to an increase in stored soil moisture at seeding. Cereal and oilseed stubble are far more effective in trapping snow and increasing soil moisture recharge than pulse stubble. While replacing tillage with herbicides for fallow is an effective means of maintaining residue cover for erosion protection, it does not improve soil moisture conservation appreciably over conventional tillage.
Maintaining uniformly tall stubble has been found to be an effective practice for conserving water from snow melt. Snow trapping practices, have on occasion, been reported to result in excessive soil moisture at seeding. This problem occurs most frequently on clay soil textures which go into winter full of water. Standing stubble has also proven effective in reducing wind speed at the soil surface, minimizing its impact on young crop seedlings and reducing water loss by evaporation.
We believe that location and soil specific research and
development is required to establish the proper balance between
stubble height and soil type to optimize moisture conservation,
while avoiding any negative effect of excessive spring soil
moisture on crop establishment.
Even crop residue distribution has been found to be critical
for not only trouble free seeding implement clearance, but to
also act as a uniform barrier to moisture loss by evaporation.
This in turn can help in maintaining uniformly shallow seeding
depth, and facilitate even crop emergence. This is particularly
important with diversification into small seeded crops like
canola, flax and forages like alfalfa, where shallow seed
placement is critical but can prove to be a difficult task on
stubble in semi-arid regions. Where semi-dwarf varieties are
grown, tall stubble means less residue on the soil surface and
higher radiant energy at the soil surface negating the high soil
moisture levels.
Along with their excellent moisture holding capacity, wet clay and silty clay soils can pose certain challenges when direct seeding. These fine textured soils tend to smear when wet, resulting in poor soil flow around the opener and over the seed, preventing proper furrow closure. Seeder opener design becomes critical to ensuring proper seed to soil contact and facilitating germination and crop emergence.
Fine textured soils also have slower drainage, leading to
surface accumulation or ponding of water during spring runoff.
The severity of this problem is almost always a function of soil
water content at freeze-up, with wet soils developing an
impermeable ice layer at the soil surface. When dry, clay soils
usually crack, leading to rapid movement of runoff water deep
into the soil. Beginning zero-till farmers on heavy clay soils
may want to start zero-till after a perennial alfalfa
stand.
Trial and error, in combination with individual experience,
will be required to develop an appropriate strategy for seeding
wet clay and silty clay soils on each individual farm.
Water-use efficiency (WUE) is the function used to describe the amount of grain produced per unit of water. This water is the amount found in the soil at seeding, plus that received during the growing season, less that remaining at harvest. Water entering the soil is used either by the crop, lost by surface evaporation, or lost by drainage below the crop rooting zone.
Direct seeding has been shown to increase the water available
to a crop by reducing evaporation from the soil surface, leading
to improved crop establishment and often higher grain yields. The
additional water stored in the soil with direct seeding can only
be used to increase grain yields when combined with proper plant
nutrition and pest management.
Future research needs to focus on developing management
practices, such as balanced fertility and fertilizer placement,
crop specific optimal seeding dates and weed control timing,
which together should lead to increased efficiency with which
available water is used to produce grain. There needs to be a
closer evaluation of the role of deep-rooted annuals (e.g..
sunflower) and winter annuals (e.g.. fall rye and winter wheat)
which have been shown to use more subsoil moisture.
Managing to maintain an adequate and timely source of nutrients for crop yield and quality requires both soil testing to assess soil nutrient supply, and an understanding of crop nutrient removal. The majority of nutrient uptake by a crop occurs prior to head emergence in cereals. The crop roots have extracted all available nutrients from the soil and applied fertilizer, with future uptake coming from mineralization of the soil organic matter during the growing season. Early nutrient uptake is used primarily to increase leaf and stem production, or yield, with late season nutrient uptake going to increasing grain protein, or quality.
One of the problems with our current information on fertilizer
application is that it is based on conventionally tilled, summer
fallow based, production systems. Research results have indicated
lower plant available nitrogen with no-till on a heavy clay soil
at Swift Current and loam textured soil at Scott. While this
lower soil N level did not negatively effect grain yields at
Swift Current, it resulted in hard wheat grain protein that was
1.5% lower than conventional tillage. Similar results were
recorded on a heavy clay soil at Indian Head, with lower soil N
levels in the top 24" for zero and minimum tillage than
conventional tillage. We can speculate that the increased soil
water held in the surface of no-till clay soils is resulting in N
losses by denitrification (saturated soil conditions).
Given that we record increased water stored in direct seeded
fields, while there is often no increase in crop yield, raises
the issue of inadequate correction of nutrient deficiencies. We
may not be taking advantage of this increased soil water because
of nutrient deficiencies. In addition, are higher yielding crops,
and an increased diversity of crops in the rotation, resulting in
deficiencies of nutrients other than N and P?
The release of nutrient from the soil organic matter forms the foundation of what we refer to as "native soil fertility". Soils which originally had high organic matter generally have better nutrient cycling ability than those with low organic matter. Fertilizer application has a large effect on the nutrient cycling capacity of a soil, with long-term judicious use of fertilizer leading to a soil more responsive to added nutrients. Tillage plays a major role in nutrient release from organic matter, with a reduction in tillage leading to a lower release of nitrogen from organic matter.
A multi-location research study, supported by the
Canada/Saskatchewan Green Plan, is evaluating the effects of
tillage, nitrogen rate and previous crop on soil nutrient
supplying power. The research is being conducted to determine if
we need to reconsider the crop response to nitrogen as a function
of tillage systems and previous crop type.
There is a need to better quantify the effect of no-till on
soil nutrient release in different soil types. The goal is the
development of a better soil N test for farmers, one which takes
into account potentially mineralizable N from both legume crop
residues and soil organic matter. The effect of no-till on clay
soils leading to lower plant available nitrogen at seeding
requires investigation. The question should also be asked, what
is happening to the nutrient supplying power of these soils with
a shift in tillage and cropping practices.
There is a need to supply the right quantity and balance of
nutrients, either from the soil or added fertilizer, in order to
improve the crops competitive ability. An adequate and balanced
nutrient supply will assist a crop in dealing with environmental
stress, plant diseases and to a certain extent competition from
weeds.
There is a need to employ a more holistic approach to nutrient
management which requires us to re-think how we approach soil
fertility. Rather than focusing on the response of one individual
crop to fertilizer applied in one year, there is a need to
approach soil fertility from the aspect of soil building and
plant health. Fertilizer management practices must become a
component of crop rotation planning, with the arrangement of
crops and timing of nutrient application to optimize return on
fertilizer investment.
The placement of nitrogen fertilizer remains a major issue amongst producers practicing a one pass, direct seeding system. Many producers avoid preseeding band application of fertilizer to prevent excessive soil disturbance and drying of the seedbed. While seed placement of nitrogen fertilizer remains a viable option to producers in the southern prairies, the higher rates require for optimum yields in the Parkland require a greater seed and fertilizer spread, and more soil disturbance than most direct seeders are interested in. The expansion of oilseed and pulse crop acreage has increased the potential for fertilizer damage, as these crops do not have the same tolerance for seed row nitrogen as has been recorded for cereals. Regardless of location, the tolerance to seed placed fertilizer is a function of soil type, moisture conditions, crop type, nitrogen form and seed - fertilizer spread.
There is a need for a better information base on the impact of fertilizer placement options, such as preseeding banding, precision banding at seeding, seed placement, surface broadcast application, post-seeding spoke and coulter injection, etc. We need to improve our understanding of how each of these nitrogen fertilizer management strategies influences N use efficiency, N losses, soil moisture conservation and residual nutrient responses. It is our opinion that this information will allow for informed decisions to be made which suit individual production systems.
The development of openers has increased the opportunity for
precision placement of multiple nutrient bands (NPKS) while
direct seeding. However, we have little understanding of either
the interaction between nutrients within these bands, nutrient
uptake by crops, or impact on grain yield or quality.
It is our opinion that there is a need to evaluate the issue
of nutrient balances, particularly when high target yields are
combined with precision placement of multiple nutrient bands. The
development of crop specific nutrient packages, suitable for the
various agro-ecological regions, should be our goals. It may very
well be that beyond a certain level, we will have to separate the
nutrients, in either/both space and time, to optimize uptake
efficiency by a crop.
Legume crop residues have the potential to improve the
nutrient supplying power of soils. Long-term research from the
Swift Current Research Station, where a continuous wheat-lentil
rotation was practiced for 15 years, indicates lentils in the
rotation produced superior wheat grain protein and improved soil
N levels. While no wheat yield benefit was measured in the Swift
Current trial, major cereal yield increases have been recorded on
both conventional and zero till pea stubble in the Parkland at
Melfort. It is important to note that little or no yield benefit
from pulse crop stubble was measured during dry growing seasons,
indicating that only when moisture was abundant were grain yield
increases recorded. However, there are numerous reports of fields
recently broken from perennial alfalfa supplying most of the N
requirements of the next two grain crops.
The previously mentioned Green Plan study (see nutrient
mineralization), assessing the impact of previous crop residue
type on crop response to fertilizer N, will improve our
understanding of tillage effects on the contribution of crop
residues to nutrient availability. While we have established
considerable information on the positive effects of legumes,
there is a need to assess other cereals and oilseeds for both
positive and negative impacts on the nutrition of succeeding
crops in rotation.
Plant pathologists usually begin a presentation on disease management by telling us that the year-to-year variability in plant disease levels are a function of three factors:
a) The host crop - for a disease to have any effect on yield the crop being grown must be susceptible.
b) The disease spores - for a disease to have any impact their must be spores around on previous crop residues, or blown-in from adjacent stubble, to infect the growing crop.
c) The environment - having a disease susceptible crop and an abundance of disease spores still requires that there be the proper moisture and temperature conditions for the spread and infection to occur.
It is important to remember that all three of these factors
must be present for a negative impact of plant disease to reduce
crop yields. Growing a resistant variety, or more commonly
adverse environmental conditions, will usually prevent any yield
loss from occurring. It is important to keep this concept in mind
when either evaluating your fields for disease, or developing
disease management strategies for your particular crop
rotation.
Research conducted at both Indian Head and Swift Current indicate that tillage system used for crop production has far less of an impact on cereal disease levels than does environmental or crop rotation effects. While an increase in leaf spotting disease has been recorded for no-till relative to conventional tillage, the opposite has been observed for root disease.
There are several documented examples of how precision placement of fertilizer, close to the seed row at seeding, can reduce the impact of plant disease, particularly root disease. This precision placement is far less important when cereals are grown on oilseed or pulse crop stubble, indicating a large effect of crop rotation on disease control. Along with placement, the balance of nutrients, and its early season uptake by the seedlings, have been suggested as factors influencing this positive crop response.
Crop rotation, in combination with disease free seed and
proper plant nutrition, is likely the most effective means of
minimizing crop yield loss to disease. The role of rotation and
agronomic management in preventing disease loss in crops
increases as we move from the semi-arid Brown and Dark Brown soil
zones to the sub-humid Black and Grey soil zones.
There is a desperate need for some basic information on the
impact that tillage has on the severity and longevity of residue
borne diseases, particularly with oilseed and pulse crops. There
is a need to establish a better understanding of the relationship
between disease persistence and residue decomposition. The use of
small plot research trials for disease evaluation must be
compared with large field survey results, in order to determine
if accurate assessments can be made from small plots. If not, we
need to develop field scale assessment methods which will provide
us with the information on management impacts on plant disease.
Finally, we need to continually communicate with plant breeders
on the role that shifting tillage practices have on the selection
for disease resistance.
Attaining good crop establishment when seeding stubble fields
can potentially be a problem in dry springs in all areas of the
prairies. The improved surface moisture conditions achieved with
direct seeding should improve crop establishment by reducing soil
drying. Excessively wet soil conditions can pose problems on clay
and silty clay soils in achieving effective seed to soil contact,
with subsequent dry periods having a negative effect on crop
establishment. Provided that shallow planting, and good
seed-to-soil contact were achieved, no difference was recorded
between conventional, minimum and zero tillage seeding systems in
the establishment of wheat, flax and peas at Indian Head. In
drier production regions, direct seeding may prove to be the only
means by which small seeded crops like canola and flax can be
established when stubble cropping.
Spring soil temperatures are lower with direct seeding. Research conducted at the Conservation Tillage Productivity Centre near Minto Manitoba revealed that while initially lower, the soil exposed while direct seeding with a hoe type opener resulted in rapid warming of the seed placement zone of direct seeded fields. However, when using a no-till disc drill the low soil disturbance resulted in little exposed soil and little soil warming. These lower soil temperatures are less of a concern in the semi-arid Prairie than the Parkland. However, using spring wheat as an indicator crop, no difference was recorded in crop establishment rate between conventional, minimum and zero tillage at Indian Head. The hoe type opener used at Indian Head supports the results from Manitoba on soil disturbance and soil warming. Any crop establishment differences recorded were more often related to either crop rotation or the type and amount of residue present.
Research conducted at Beaverlodge and Lacombe, Alberta has
identified distinct variability between pea varieties to
germinate and emerge at different soil temperatures. In addition,
certain strains of rhizobium inoculant grow faster under cool
soil conditions. The goal of this ongoing research is to match
fast emerging pea varieties with rhizobium strains which will
allow for early nodule formation under cool soil conditions,
increasing the germination, vigor and disease tolerance of a
direct seeded pea crop.
The effect of cold soil conditions on crop establishment can
often be exaggerated by poor management practices such as deep
seeding, poor quality seed, improperly spread crop residues, or
excessive seed placed fertilizer. While most producers new to
direct seeding are anxious to take advantage of the ability to
seed shallow into abundant surface moisture, excessive seed
placed fertilizer continues to pose the greatest problem to crop
establishment. The high level of interest in a one-pass seed and
fertilizer system requires that producers evaluate those side
banding openers available on the market with their specific soil
and machine conditions in mind.
It is our opinion that the lower soil temperatures found with
direct seeding should not be a deterrent, except in those cases
where the amount of soil disturbance at seeding is low, and/or
very early seeding is practiced. There is a need to evaluate crop
varieties to determine if there are differences in the rate of
germination and emergence under cool soil conditions.
Advancements in this characteristic would allow for earlier
seeding, particularly on fine textured soils where high water
holding capacity tends to slow soil warming. Producers are
encouraged to conduct their own on-farm testing of double shoot
openers for direct seeding, finding those which best suit their
specific soil and machine conditions. Remember, in order to
optimize the crop response to available water and inputs, every
effort should be made to minimize the stress on a germination and
emergence.
It is completely safe to say, based on research trials across Canada and around the world, that a crop rotation is helpful, in some cases critical, to making no-till succeed. It also appears that no-till enhances rotation benefits, not just those of legumes, but other crops such as winter crops, annual forages and perennial forages. In short, we believe that crop rotations are an integral part of the success of direct seeding, or the success of direct seeding is to a large extent dependent on crop rotation. Some specific examples include:
In the semi-arid region of Saskatchewan recently initiated research has revealed significant promise for the pulse crops lentil, chickpea and field pea when grown on stubble under relatively favorable growing conditions. In addition, a positive wheat yield advantage was obtained on pulse crop stubble over that of wheat stubble. While the advantages of low N fertilizer cost and good stubble yields have heightened interest in pulse crops in the Brown soil zone, high seed cost, weed control challenges and little or no snow trapping potential are distinct disadvantages. The superior weed control options available for oilseeds, and its good snow trapping potential, make early seeded canola a good option.
The evaluation of crop sequence in the Dark Brown soil zone at Scott has revealed some significant advantages to alternating cereal, oilseed and pulse crops. Cereals generally yield 5-15% higher on oilseed than cereal stubble, while yielding 5-25% more on pulse stubble. These results are similar to those obtained from a study on Black and Grey soils in northeastern Saskatchewan, as well as a review of long-term Manitoba Crop Insurance yield data. In addition, crop rotations with a mix of cereal, oilseed and pulse crops provide for greater year-to-year yield stability than cereal monoculture, because changes in climatic conditions result in different responses for each crop.
Continued efforts are required to fine tune the production practices for new crops in rotation. For example, while field pea and canola are well established in many regions of the prairies, yield variability from farm-to-farm, in any given year, can be very large. The full impact on grain yields of disease levels, poor nodulation, insect pest damage, nutrient supply, etc. all require our continued attention if we are to gain the full benefit from a diversified rotation.
One area which has received some preliminary evaluation is the
use of short-term forage crops in zero-tillage rotation. The
challenge of seeding and termination of forage crops has resulted
in them being treated more as a long-term crop in rotation.
Currently, farmers use up to six tillage operations as part of
the termination of a perennial forage and prior to seeding an
annual crop. However, given the rapid decline in forage stand
productivity after the initial 2-3 years, they are well suited to
more frequent rotation. Seeding alfalfa and forage grasses in a
zero-till system can enhance stand establishment in dry
conditions. Direct seeding grain crops into chemically terminated
forage is feasible provided that dandelion problems can be
addressed. In addition, the deep rooted nature of most forage
crops allows for deeper exploitation of the soil profile,
alleviating any potential leaching of nutrients below the annual
crop root zone, improving the structural suitability of heavy
clay soils to direct seeding, and enhancing the overall rotation
water-use efficiency.
We believe that there is substantial opportunity to improve
crop production efficiency by developing appropriate rotation
management practices. The three keys to successful crop rotations
are DIVERSITY, DIVERSITY AND DIVERSITY. There is a need to match
crop rotations with soil water content, crop residue levels, weed
and disease management strategies, and plant nutrition. Are there
residue management practices which will minimize weed and disease
losses on crops in rotation, while enhancing the nutrient and
moisture conserving potential? While rotation research is long
term in nature and may not be responsive to changes in
technology, it is our only means of evaluating scientific
principles that either don't change or change slowly over
time.
It has been reported that about 50% of the world's agriculture work force is involved in weed control, likely at the other end of a hoe of some kind. In agriculture we are working against nature by growing one harvestable plant type where an abundance used to grow. As a result, the focus of farmers around the world has been to optimize the yield of their selected crop while minimizing the negative impact of competition from unwanted plants, better known as weeds.
Research conducted at Indian Head and in East central Saskatchewan has revealed that environment has by far the largest influence on the type and amount of weeds present. This is followed by crop rotation, individual crop and finally tillage system. In general, spring germinating annual weeds tend to decrease in number with a shift to direct seeding, while winter annual and wind blown perennial weeds tend to increase in number. Volunteer crops tend to persist for more years with direct seeding, increasing the importance of alternating crop species type and year-to-year weed control focus. Problems with foxtail barley in monoculture wheat systems in southwestern Saskatchewan, and dandelion in more humid regions, has resulted in a number of farmers introducing some "discreet tillage" into their direct seeding production system. The immediate advantage of this limited tillage in controlling these perennial weeds should not detract from the positive benefits being derived from the long-term direct seeding program.
A number of recent developments are going to have a profound
impact on weed management strategies for all farmers. Herbicide
resistant crops, in particular those linked with nonselective
herbicides, have the potential to almost eliminate weed control
problems with certain crops. Where the decision to grow canola
was often limited due to "weedy fields", seeding a herbicide
tolerant canola could potentially remove any weed control
limitation. Alternatively, herbicide resistant weeds are becoming
increasing more common throughout the prairie provinces. While
no-till farmers are not experiencing any greater a problem with
herbicide resistant weeds than producers using conventional
tillage, both must continue to develop and adopt weed and
herbicide management strategies which minimize the opportunity
for resistance to develop. Preharvest application of Roundup has
also had a profound impact on several troublesome perennial
weeds. As Doug Derksen has pointed out to all of us, by shifting
the time at which we subject the problem weeds to herbicide
treatment, we introduce a completely new control
measure.
Future research in weed management will have to focus on the combination, or integration, of technologies that reduce weed populations as a means of reducing both herbicide use and crop losses. There is a need to pay more attention to cultural practices that reduce our dependence on herbicides. An increased understanding of how we can use weed threshold number in our decisions to spray or not is an area which requires further refinement. Continued monitoring of weed population shifts is critical to our understanding of how new technology and management practices are impacting on our current and emerging weed management challenges.