Peter Entz
Manager, Seed Products and Agronomy
James Richardson International
Pea production continues to hover around the 2 million acre mark in western Canada. Although the crop was introduced in southern Manitoba, Saskatchewan now dominates the pea acres. A majority of the peas are exported to Europe as a protein source for hog rations.
There have been significant developments in crop inputs over the past years. Today's presentation will focus on these inputs, namely: variety selection, seed treatment/seeding rate, inoculation/the use of nitrogen, weed management and disease management.
Managing crop inputs is simply using sound agronomic and economic decisions to grow a crop profitably. The trick to good management is selecting which crop input to use, and when.
Seed cost may be the largest single expense in pea production. Seeding rates of up to 3 bushels per acres, coupled with seed costs of $12.00/bu (Canadian), quickly add up. The value of the seed is in the genetics being provided and the quality of the seed product.
New varieties have tended to offer better yield, a more desirable seed size and improved agronomic traits. In 1996 and 1997, 16 new varieties were brought to market in western Canada. Newer varieties tend to be genetics imported from Europe. However, the Crop Development Centre at Saskatoon, the Pool; and Ag Canada are starting to bring Canadian genetics back into the market. Regardless of origin, new products have been yielding about 12% better than the check variety Express, which is often the check variety in evaluation trails.
Seed shape and size has improved. Most of the newer varieties have a seed size rated large or very large. Size is important when marketing peas for human consumption. Shape is also important. Other than the block variety Tenor, most varieties have a chance at the human market.
Most newer varieties tend to be more upright in growth, and are therefore easier to swath. None of them match the standability of Carneval, which is still the standard. A new variety Canis tends to be the closest.
Of the varieties registered in 96 and 97, only 3 are leafed varieties. All others are semi-leafless. Semi-leafless plants tend to allow more light to pass through the canopy, making them less competitive with weeds. This may be one reason why the leafed variety Grande is being grown on many no-till fields. Under high disease pressure, semi-leafless plants allow more air movement through the canopy - less potential for disease.
Little improvement in disease resistance is evident with newer varieties. Powdery Mildew (erysiphepolygoni) has resulted in severe yield loss, especially when peas are seeded late. Only the varieties Highlight and Tamor are resistant to this disease. In time, varieties entering the market will all be resistant to this disease. Current varieties are all susceptible to the foliar disease Mycosphaerella blight
(Mycosphaerella pinodes). Yield losses of 50% can occur as a result of this disease. A good source of disease resistance has not yet been identified.
There are several seedling blight, root rots and wilt that affect pea seed or seedlings. As peas increase in your rotation, the potential yield loss associated with seedling diseases also increases. The use of a general fungicide seed treatment has been shown to increase emergence, reduce disease and increase yield. Tests conducted at Agriculture Canada, Morden, indicate that a simple treatment of Thiram (75% thiram) or Vitaflow 280 (14.9" carbathiim and 13.2% thiram) are effective in protecting the seed/seedling from these diseases and can result in yield increases of 10% over untreated peas. The addition of Apron (metalazyl) can complement the activity of Thiram and Vitaflo 280, with the activity of Pythium spp.
The use of a seed treatment may allow you to reduce seeding rates by 10%. When seeding at 3 bushels/acre x S 12.00/bushel, that relates to an additional savings of $3.60/acre.
Seed size varies quite a bit between varieties and seed lots of the same variety. Instead of seeding 2
½ or 3 bushels an acre, peas should be planted based on population - much like corn is. The first step is to determine the weight of 1000 seeds. Table 1 will assist in then determining what that relates to in seeding rate (bu/acre), once you've decided on a target plant population.Table 1. Seeding rate determination based on seed weight and target plant population
Seed Weight Target seeding rated (seeds/m2)
(g/1000 seeds) 50 60 70 80 90
190 1.41 1.69 1.98 2.26 2.54
200 1.49 1.78 2.08 2.38 2.68
210 1.52 1.87 2.19 2.5 2.81
220 1.6 1.96 2.29 2.62 2.94
230 1.71 2.05 2.39 2.74 3.08
240 1.78 2.14 2.5 2.85 3.21
250 1.86 2.23 2.6 2.97 3.35
260 1.93 2.32 2.71 3.09 3.48
270 2.01 2.41 2.81 3.21 3.61
280 2.08 2.5 2.91 3.33 3.75
290 2.16 2.59 3.02 3.45 3.88
300 2.23 2.68 3.12 3.57 4.01
If for example you are seeding a variety that has a seed weight of 290 g/1000 seeds and want to target 70 seeds/m2 as a population, the bushel/acre to seed is 3.02 bu/acre.
The jury is still out on what is the desired plant population. It is fair to say that there should be between 50-60 plants/m2 to optimize yield. Assuming a germination of 80% and 10% loss due to seed damage and disease, that would relate to a seeding rate of 80 seeds/m2.
In trials I have been involved in, it has been difficult to assess what the optimum plant population should be. Just this year at a site near Carman, MB, yield peaked with a population of 20 plants/m2 ) Table 2). In 1996, the data varied greatly by location. Under drier conditions, the more the merrier. Under very moist conditions, more plants, related to greater loss due to disease. For my peace of mind 70 plants/m2 with a seed treatment seems to strike a balance.
Table 2. The effect of seeding rate on height, lodging and yield of field pea, variety Eiffel.
Treatment Seed rate Actual plant stand Height Lodging Yield
(seeding rate) (kg/ha) (plants/m2) (inches) (0-9)* (bu/ac)
June 13 July 17 July 30 Sept 3
1 . 20 seeds/m2 56 19 31 1 44
2. 30 seeds/m2 84 20 34 3 54
3. 40 seeds/m2 112 38 33 1 51
4. 50 seeds/m2 140 40 34 2 54
5. 60 seeds/m2 168 60 35 2 51
6. 70 seeds/m2 196 65 35 3 56
7. 80 seeds/m2 224 76 35 3 53
8. 90 seeds/m2 252 83 37 4 49
9. 100 seeds/m2 280 88 36 3 51
10. 110 seeds/m2 294 92 35 4 56
* O=no lodging-, 9=flat as a pancake
Inoculating pea seeds with the appropriate strain of rhizobia bacteria has proven itself as a good management practice. Still there are many questions. The ones, I have heard most often are: 1. Should I apply additional nitrogen? 2. Do I need to inoculate fields with, a history of pea production? 3. Are granular inoculant worth the extra money?
The nitrogen issue is fairly straight forward in my mind. If you, want to put down a lot of N, grow canola. A few pounds of nitrogen at planting may give that desired "pop up" effect, but I would not recommend any more than 20 lbs/acre. The additional nitrogen will only inhibit effective nitrogen fixation by the plant (Table 3).
Table 3. The effect of additional nitrogen and inoculant on nodulation, flowering and yield. of field pea (Carman, 1997)
Inoculant Actual
Nitrogen added Nodules/plant % flowering Yield
(lbs/acre) June 13/June 6 (July 8) (bu/acre)
1. MBR 0 13 27 20 74
2. SOIL IMPLANT 0 27 32 23 N/A
3. PEAT 0 24 47 25 69
4. NONE 0 36 41 28 67
5. MBR 20 19 22 25 66
6. SOIL IMPLANT 20 17 36 30 73
7. PEAT 20 17 41 35 71
8. NONE 20 16 26 30 62
9. MBR 40 9 28 25 72
10. SOIL IMPLANT 40 9 22 20 67
11. PEAT 40 7 22 18 69
12. NONE 40 9 22 15 66
MBR=NicroBioRhizogen granular clay inoculant applied at 8 kg/ha
SOIL IMPLANT=Liphatech granular peat inoculant applied at 5.6 kg/ha
PEAT=Rhiz up peat based inoculant
The addition of 40 lbs/acre of nitrogen did not affect final grain yield, while slowing down the nodulation of the pea roots and somewhat delaying flowering. Nodulation was not greatly affected by formulation of the inoculant. Yields were always lower with the inoculate plants.
Inoculation of fields with a history of pea production is still recommended. The root will usually form nodules grown on most fields, but not all nodules are effectively fixing nitrogen. By ensuring the best strain of rhizobia is introduced each time peas are grown, ensures the most effective and efficient nitrogen fixation. The use of granular inoculants may be a tool you can use to manage these fields. A lower rate of inoculant may be desired on fields with a recent history of pea production.
Granular inoculants are an interesting option of inoculating peas. Granular formulations have been used for decades in North America. Whether to use granular inoculants in peas, is not a question of does it work, but do you have the equipment to handle the product and is it worth the extra cost. A separate delivery system is required to meter out the granular product. That is, a third tank on air seeder or some type of velmar or grass seed attachment to the seeder. This is more or less an engineering or budgeting issue.
The benefit of granular inoculants is essentially convenience. And as a farmer, you need to determine a value for that convenience. However, granular inoculants offer other benefits. It allows you to vary, the rates of the inoculant. Usually, rate was determined by what stuck to the seed, not an accurate calibration. Granular inoculants may offer the ability to place inoculant where it is most effective.
Peas are very uncompetitive with weeds. The selection of herbicides to control weeds tended to be limited. With the registration of Pursuit (imazethapyr) and Odyssey (imazemox + imazethapyr) and the use of pre-harvest RoundUp the year previous, weed control is no longer as big an issue. Pre-harvest RoundUp is used primarily for the control of Canada Thistle, as in-crop treatments provide only poor Canada Thistle control.
The issue may not be weed control, but justifying the expense of the weed control products. Pursuit needs to be tank mixed with a germicide (Post or Assure) to strengthen its efficacy on grasses. Odyssey is a stand-alone product, which costs about $25.00/acre. An economical approach to weed control would be the products Sencor and MPCA Sodium Salt. More economically priced, they offer less crop safety and kill fewer weeds. To justify the use of better herbicides, higher yields need to be achieved.
A discussion on weed control can not limit itself to the herbicide package of the day. Cultural practices such as growing peas after a cereal crop where you have "cleaned up" the field is important. If weed pressure is expected to be high, seeding at a higher seeding rate (increasing 20% of normal) and/or selecting a leafed variety will produce a more competitive crop.
Mycosphaerella blight and Powdery mildew are the two main diseases to consider in-season.
Mycosphaerella blight is the most common foliar disease of field peas in western Canada. Yield losses with this disease can be as high as 50%. The fungi can be seed, stubble and soil borne. Infected plant materials tends to be the primary source of infection. The disease becomes visible as tiny, brownish/purple spots on the leaf. These spots will then be noticed on other plant parts, including the pod. Once the disease is present it is easily spread through the splashing action of rain. Dr's Allen Zue and Tom Warkentin of Ag Canada in Morden have done extensive work on developing both fungicide and genetic resistance for this pathogen.
The use of Bravo (chlorothalonil) is effective and economical when the disease pressure is heavy. Application at the early flowering stage may be most effective as a single treatment. This timing is before any symptoms are usually visual. Bravo is a protectant, so a second application may be necessary at mid-late flower.
The use of certified seed and only growing peas in a 1 in 4 year rotation are currently the best cultural practices to implement. Resistant varieties are not likely in the future.
Powdery Mildew is a widespread fungal disease that becomes evident in late maturing pea crops. The disease overwinters on plant residue and ascospores are blown around by the wind. They affect pea plants by a secondary growth of a fine, white powdery mildew that soon covers the entire plant. The disease is favoured by dew without rain. The disease can be controlled by planting resistant varieties (Hightlight and AC Tamor) or the use of sulfur product (Kumulus - 80% sulfur) applied when the disease is first noticed and then every 7-10 days following, if necessary. Early planting is the best way to manage this disease. Often plants will exhibit this disease very late in the season. Fungicide application at this time is not economical.
The value of each input has to be considered against the overall yield potential of the crop and what each input will contribute to that yield. To oversimplify the situation , the following table attempts to prioritize the use of these crop implants.
Crop lnput Priority Remark
Weed contro/herbicide 1 Everything else is secondary, if you have a polluted field
Inoculant 2 even at $ 10.00/acre it's the cheapest N available
Variety 3 10% boost in yield
Seed treatment 4 For fields with history of peas
Foliar fungicide 5 Only economical under severe disease pressure
Nitrogen 6 Save your N for canola