Agronomist Notes
Seeding progress was rapid this week as conditions were favorable. The majority of my clients are 50%- 80% completed and one client is 100% finished. I have been busy seeding my own crop and have learned many lessons along the way. I’ve always been the one driving around with a sharp stick prodding my clients, secretly hiding my frustration when progress is slower than I would like. Well, here I am seeding my own canola on May 20th, which is much later than I would like and there’s more. The half hour job turns into 4 hours each day, little fixes turn up with each fill and we don’t typically get seeding until noon although we start at 7 am. Good times!
I have a deeper appreciation for what my clients do after experiencing what they go through on a hourly/daily basis. I’ve joked in the past that if ever you need parts, you’ll probably need them on a long weekend when everything is closed and the nearest parts source is a six hour round-trip away. Well, we had the pleasure of experiencing that very scenario and had to improvise to make due. In spite of all the long days, frustrations with breakdowns and fix-it jobs, old and new equipment setup, calibration and orientation, seed and fertilizer pickup and delivery, and everything in between, I have truly enjoyed my experience and my wife is nervous of what I’m considering next! Expansion… perhaps.
The crops seeded the first week of May are emerging with canola at the cotyledon stage and wheat and barley at the one leaf stage. With the wet soil conditions, we need to be on the lookout for wireworm damage and emergence issues with soil crusting or compaction. This week’s issue will take a deep look at the effects of soil compaction and wireworm description, damage and control.
Agronomy
What are the Consequences of Soil Compaction
Soil compaction can have both desirable and undesirable effects on plant growth.
Desirable Effects
Slightly compacted soil can speed up the rate of seed germination because it promotes good contact between the seed and soil. In addition, moderate compaction may reduce water loss from the soil due to evaporation and, therefore, prevent the soil around the growing seed from drying out. A moderate amount of compaction can increase root branching and secondary root formation, allowing roots to more thoroughly explore the soil for nutrients. This is especially important for plant uptake of non-mobile nutrients such as phosphorus. Air drills have been designed specifically to provide moderate compaction with planter mounted packer wheels that follow seed placement.
Undesirable Effects
Excessive soil compaction impedes root growth and therefore limits the amount of soil explored by roots. This, in turn, can decrease the plant's ability to take up nutrients and water. From the standpoint of crop production, the adverse effect ofsoil compaction on water flow and storage may be more serious than the direct effect of soil compaction on root growth.
In dry years, soil compaction can lead to stunted, drought stressed plants due to decreased root growth. Without timely rains and well-placed fertilizers, yield reductions will occur. Soil compaction in wet years decreases soil aeration. This results in increased denitrification (loss of nitrate-nitrogen to the atmosphere). There can also be a soil compaction induced nitrogen and potassium deficiency. Reduced soil aeration affects root metabolism and there can also be increased risk of crop disease. All of these factors result in added stress to the crop and, ultimately, yield loss.
Research from North America and Europe indicates that crops respond to soil compaction. In a dry year, at very low bulk densities, yields gradually increase with an increase in soil compaction. Soon, yields reach a maximum level at which soil compaction is also optimal for the specific soil, crop, and climatic conditions. However, as soil compaction continues to increase beyond optimum, yields begin to decline. With wet weather, yields are decreased with any increase in compaction.
What Causes Soil Compaction
There are several forces, natural and man-induced, that compact a soil. This force can be great, such as from a tractor, combine or tillage implement, or it can come from something as small as a raindrop. Listed below are several types of soil compaction and their causes.
Raindrop impact - This is certainly a natural cause of compaction, and we see it as a soil crust (usually less than 1/2 inch thick at the soil surface) that may prevent seedling emergence. Rotary hoeing can often alleviate this problem.
Tillage operations - Continuous cultivation or disking at the same depth will cause serious tillage pans (compacted layers) just below the depth of tillage in some soils. This tillage pan is generally relatively thin (1-2 inches thick), may not have a significant effect on crop production, and can be alleviated by varying depth of tillage over time or by special tillage operations.
Wheel traffic - This is without a doubt the major cause of soil compaction. With increasing farm size, the window of time in which to get these operations done in a timely manner is often limited. The weight of tractors has increased from less than 3 tons in the 1940's to approximately 20 tons today for the big four-wheel-drive units. This is of special concern because spring planting is often done before the soil is dry enough to support the heavy planting equipment.
Minimal Crop Rotation - The trend towards a limited crop rotation has had two effects: 1) limiting different rooting systems and their beneficial effects on breaking subsoil compaction, and 2) increased potential for compaction early in the cropping season, due to more tillage activity and field traffic.
Myths About Soil Compaction
There are two wide spread myths about compaction; 1) freeze-thaw cycles will alleviate a majority of soil compaction created by machinery, and 2) what compaction "Mother Nature" does not take care of, deep tillage or subsoiling will alleviate.
Freeze-Thaw Cycles
Although soils are subject to annual freeze-thaw cycles and freeze to depths of 3 feet or more, only the top 2-5 inches will experience more than one freeze-thaw cycle per year. The belief that freeze-thaw cycles will loosen compacted soils may have developed years ago when compaction would have been relatively shallow because machinery weighed less and grass and legumes were grown in the rotation.
Deep Tillage/Subsoiling
While deep tillage (greater than 10 inches) is capable of shattering hard pans created by wheel traffic, it has not been proven to increase yield consistently or for long periods of time. In Midwestern studies where plots with established compaction were split with a deep tillage treatment (14-16 inches), corn yields were either unaffected or reduced slightly (10 bushels per acre) compared to the non-subsoiled plot.
Source: http://www.extension.umn.edu/distribution/cropsystems/components/3115s02.html
Preventing Soil Compaction
Soil compaction can be prevented by a number of measures:
- Scheduling farm operations to avoid traveling across fields when they are wet.
- Reducing the number of trips across an area.
- Maintaining good ground coverage and high organic matter in the soil (organic matter promotes aggregation of soil particles, increasing porosity).
- Minimizing livestock traffic in wet areas.
- The addition of manure, compost and other organic materials can improve soil structure, helping resist compaction.
Wireworm Description Damage & Control
Now is the time to begin scouting fields with histories of wireworm damage. Wireworms can spend roughly four years of their life cycle as larvae in the soil. Wireworms prefer cool, moist soil and tend to be actively mobile in the top 6 inches of the soil. Early in the growing season, they are attracted to the carbon dioxide produced in the germination process and will come to the surface to feed on emerging plants. This is the time when they will cause the most damage to crops, usually by shredding below ground plant tissue.
Source: Canola Council of Canada
Description
Wireworms are slender, cylindrical, hard-bodied insect larvae reaching up to 4 cm (1 1/2in.) in size. They are usually copper-brown but when newly molted they can be soft-bodied and white. Adult wireworms are beetles that have the ability to flip themselves upright when placed on their backs, making an audible click as they do, giving them their name "click beetles."
Wireworm (larvae) and click beetle (adult).
Scouting Techniques
Soil samples can be sieved to find any wireworms present in the field. Samples can be collected using a post-hole auger and a series of soil sifting screens or by marking out areas 50 cm x 50 cm (20 in. x 20 in.) and sieving the soil to a depth of 15 cm (6 in.). Repeat in different areas of the field to determine an average number of larvae per square metre (sq. yd.).
Damage
Sometimes, wireworm damage is confused with cutworm damage. Remember that, with wireworms, the plant is wilted and discolored but remains attached to the root. With cutworms, the plants are usually cut off completely at or near the soil surface.
Economic Thresholds
An action threshold of about 32 wireworms per square metre (sq. yd.) is often recommended. If wireworms are found at this or a higher density, seed treatment is usually warranted in following years.
Control Tips
Control of wireworms is through seed treatments applied prior to planting. Cruiser®, containing the active ingredient thiamethoxam, is currently the only registered seed treatment for control of wireworms. Commercial seed treaters can only apply it with closed system facilities.
Some agronomists recommend that growers treat seed for 2 consecutive years after breaking sod to reduce the problem to a non-economical level. This should be done only if the risk of an infestation is high.
If wireworms are found in an emerging crop, there is no 'quick fix'. Often, the damage occurs or is seen too late to reseed the damaged patch. Also, the loss in yield does not justify the cost of re-seeding. The best plan is to consider what action may be necessary for the following year.
Source: Saskatchewan & Manitoba Agriculture
For more information on wireworms, refer to the following links:
http://www.gov.mb.ca/agriculture/crops/insects/fad28s00.html
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm2509?opendocument
http://www.ext.nodak.edu/extpubs/plantsci/pests/e188-1.htm
Market News
CWB World Crop & Weather Highlights
The following link will provide you crop and weather information from 17 major grain producing countries. This information is maintained by the Canadian Wheat Board and provides timely information on crop progress and weather conditions.
Link: http://www.cwb.ca/public/en/farmers/weather/maps/#
Ukraine Wheat: Yield prospects for all major crops remain generally favorable despite persistent spring dryness that has reduced soil moisture in many areas of Ukraine. Recent precipitation has replenished surface moisture in most areas of Ukraine, but additional rain in May and June will be necessary to recharge subsurface moisture reserves and maintain the current yield outllook.
Source: USDA
China Winter Wheat and Rapeseed: Unusually mild winter temperatures caused China's 2007/08 winter wheat and rapeseed crops to emerge from dormancy well ahead of schedule and grow abnormally fast, weakening their resistance to extreme weather. The mild winter also created ideal conditions for insects and plant diseases to thrive.
Source: USDA
European Union Wheat: Despite recent rain, there are fears that yields in some areas – N Germany, parts of France, Bulgaria and Rumania have already been adversely affected and we still have two to three months to go until harvest.
Source: USDA
European Union Rapeseed: Despite the potential record oilseed rape crop across Europe the market prices remain supported by the firmness in the other oilseeds markets, palm oil prices hit new contract highs and the US soya oil market also remains firm.
Source: USDA
Canola Futures
As you can see on the chart below, canola futures is pushing towards its fourth high since late February, and may start to push upward from of its sideways trading range. This is a result from increased commercial demand and a renewed bullish sentiment from the funds. However, the strong Canadian dollar may keep a lid on a move higher. The long and short-term market indicators report a weak to average buy signal at this point. SL
