Choosing a pulse variety for a specific location on the Canadian prairies can be a problem because our climate from year to year is so unpredictable. We know that in the long term, the pattern of precipitation and evaporation influences the evolution of the soil and landscape. We have detailed soil maps that reflect fairly closely the effects of the long-term climate. The latest version of the Soil Climatic Zones of Southern Saskatchewan shows seven distinct zones that are more or less laid out in bands starting with the Dry Brown soil zone in the southwest and proceeding to the Grey soil zone in the northeast.
The Saskatchewan pulse industry supports aggressive variety developments for four pulse crops: chickpea, lentil, dry bean and pea. In general, chickpea and lentil can show negative yield and adaptation response to excessively cool and wet environments, while dry bean and pea are more likely to show negative yield and adaptation responses in hot and dry environments. Crop diseases are also highly influenced by the environment.. The problem remains, of course, that for any field in Saskatchewan, the environment in any particular year may be completely different from the long-term climatic pattern that created the soil zone. This is why in the late 1980s (warm and dry cycle) excellent lentil crops were produced in the Moist Black soil zone and why in the 1990s (cool and wet cycle) excellent pea crops were grown throughout the Dry Brown and Brown soil zones. If you are a believer in climatic cycles, and you
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Table 1. General adaptation of pulse crops to the soil zones of Saskatchewan |
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Pulse Crop |
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Soil zone* |
Chickpea |
Lentil |
Pea |
Dry bean |
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Dry Brown |
1 |
2,4 |
2,4 |
6 |
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Brown |
1 |
1 |
2,4 |
6 |
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Dark Brown |
1 |
1 |
1,2 |
2,4 |
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Moist Dark Brown |
3,5,7 |
3,5 |
1 |
2,5 |
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Black |
6 |
3,5,7 |
1 |
2,5 |
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Moist Black |
6 |
6 |
1,7 |
2,5 |
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Grey |
6 |
6 |
1,7 |
6 |
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1 = good; 2 = in wet years; 3 = in dry years; 4 = in cool years; 5 = in warm years; 6 = poor; |
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7 = early maturity beneficial |
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* from Henry and Harder, 1991 |
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forecasting that we are entering a dry cycle, it seems reasonable to predict that all pulse crops will do better one or two soil zones northeast of where they are best adapted. This means, of course, that pea crops would do best in the bush.
Table 1 shows generally where the four pulse crops are adapted in the various soil zones of Saskatchewan. This is a sort of broad-brush analysis of determining which crops fit where. More realistically, at the level of "fine tuning of the system", individual field characteristics such as slope aspect, soil texture and cropping history can play a major role in how well one of these crops will perform. When technical improvements occur in crop production systems, for example, better seeding technology, better weed control, and better varieties, the odds increase that higher productivity can be achieved in a specific environment in relation to the long term environmental trend. And of course, the soil zone tends to have a great influence on which diseases are of prime importance. I will devote the rest of this discussion to fine tuning the legume crop production system with relation to how pulse crop varieties can be expected to perform in different soil zones.
In a conservative assessment of crop adaptation, lentil is best adapted to the Brown, Dark Brown and Moist Dark Brown soil zones. The lentil crop is reaching the mature phase in Saskatchewan, at least for the Laird and Eston market classes. We need market growth to sustain more production of all lentil types with the possible exception of red cotyledon lentil. The range in maturity adaptation of our current lentil varieties goes from late (Laird) to early (Eston). Our long term data base comparing these two varieties shows that Laird performs better as you go southwest from Saskatoon. The later maturity allows more flexibility in response to in-season rainfall. As you move northeast toward the Moist Dark Brown and Black soil zones, the risk factors for Laird lentil increase - higher moisture, particularly after mid-July, means increased risk of ascochyta, increased risk of frost damage, and increased risk of excess vegetative growth at the expense of seed production. The trend works the other way for early maturing varieties like Eston. Whether or not a variety is ascochyta resistant becomes less important in drier regions because the inoculum potential and probability of favourable weather for the disease decreases. CDC Richlea is intermediate in maturity and as a result is probably more widely adapted. This is certainly reflected in its higher yield potential across the lentil production area, based on both small plot trials and grower experience.
So the message in this is that if you want to fine tune your cropping system, ignoring the price fluctuations that can occur among market classes of lentil, the conclusion should be that as you move northeast across Saskatchewan, early maturity should become more important in your lentil cropping decisions. And, as you move southwest, consider that late maturity might be a positive factor because of the bigger window of opportunity for responding to rainfall. In future, our plant breeding system will add flexibility to the system across a wider range of environments. Laird type lentils with earlier maturity are on the horizon. Red cotyledon lentil varieties with extra early maturity are in the pipeline to accommodate an expansion of this market class in the Black soil zone. From now on, most lentil varieties will have ascochyta resistance. In the spring of 1998, the Saskatchewan Pulse Growers will distribute breeder seed of three new ascochyta resistant lentil varieties to Select seed growers in Saskatchewan. These will be 512-2, also knows as CDC Milestone (replacement for Eston), 638-23 (replacement for CDC Richlea), and 578-28 (replacement for Laird).
Chickpea: the hot pulse crop in Saskatchewan, or is it the pulse crop for Saskatchewan in hot years? The summer of 1997 was excellent for chickpea production. Growers had reasonable yields, high quality and no disease. The combination of seed demand plus some commercial sales kept prices up to a reasonable level. So we will go into the spring of 1998 with virtually unlimited supplies of seed for both kabuli and desi types. What will happen? The number of acres seeded to chickpea will at least double (conservative estimate).
Chickpea adaptation in Saskatchewan is best in the Brown and Dark Brown soil zones. Chickpea is highly indeterminate with a rooting depth similar to spring wheat. This means that if the soil does not dry out by the end of the growing season, the plants will stay green and continue to grow until moisture reserves are depleted or until the plants freeze. So, as you move northeast in Saskatchewan, chickpea becomes less adapted. As you move northeast, the risk of early frost relative to maturity increases, so it becomes more difficult to produce top quality. At this stage in the development of the crop, chickpea may receive a market discount as a feed, so quality is a major consideration.
The maturity factor is especially important for kabuli types in comparison to desi types. Kabuli chickpea is large-seeded and this raises the seeding cost considerably. Most kabuli chickpea varieties are later than most desi varieties. In most regions where chickpea is grown, the crop is seeded in winter and then harvested in late spring or early summer as soil moisture reserves disappear. In our limited experience with kabuli varieties, yield increases with earlier maturity at every location where chickpeas are grown. So the message is, grow the earliest maturing ascochyta resistant kabuli you can find. Right now the choice is to Dwelley, Sanford and B-90. Dwelley is late everywhere, so adaptation problems will start sooner with this variety as you move northeast. Sanford is a little earlier so it has slightly wider adaptation. B-90 is the earliest, the most widely adapted, and the highest yielding. It also has the smallest seed. For desi chickpea, the situation is very simple. Myles is the only ascochyta resistant variety available.
About 50 Select seed growers received a small allocation of CDC Yuma (tested as line 92037-26) in the spring of 1997. This variety is earlier than Sanford, has similar seed size and in all our testing so far, has higher yield potential. CDC Yuma has the normal fern leaf foliage type. Because the seed increase ratio of chickpea is low (10:1), large quantities of certified seed of CDC Yuma will not be available until the spring of the year 2000.
Field pea is the pulse crop with almost unlimited variety choice, or is that too much choice. Over the past several years, the field pea crop has expanded to almost every part of Saskatchewan. Variety choice for field pea starts with assessment of market potential. The feed market absorbs most of the production, so if the decision to grow pea is based on expectations of feed prices, variety choice should be based on yield potential and seed size. In Saskatchewan, all pea varieties are compared to the yellow pea variety Grande. Because of the large number of varieties available, choosing a field pea variety becomes more difficult.
It is usually best to consider pea variety choice on the basis of market class. At the moment, the dominant market class is the yellow field pea, used for both human consumption (whole or split) or feed. Within this class of pea, varieties are rated for seed coat breakage. In general, the larger the seed, the greater the potential for seed coat breakage during seeding, threshing and post-harvest handling. The human market also recognizes the amount of green tinge in the seed coat of yellow cotyledon pea. Some varieties are more prone to green tinge, and the potential for this problem increases in the cooler environments. In the warmer, sunnier zones of Saskatchewan, green tinge may be bleached out.
Green cotyledon pea is the second largest market class. In general, green pea varieties yield less than yellow pea varieties, so the incentive to grow green pea must be influenced by the potential to receive a premium based on colour and uniformity. Green peas for human consumption are graded on the amount of bleaching. This quality trait is highly dependent on the variety and the environment. The variety with the best bleaching tolerance is Princess, followed by Radley and Keoma. Most other varieties tend to bleach more. The conditions that promote bleaching are the combination of moisture and bright sunlight. In 1997, most of the green pea crop in Saskatchewan received an inch or more of rain in early August, just when the seeds were maturing. This rainfall was followed by very warm sunny weather. The result? A shortage of food quality green peas for export, causing a premium price scenario. So how do you choose a green pea variety? If you want to grow green peas for premium, it is important to consider your ability to manage harvest at the correct stage to minimize bleaching. As you move northeast, the potential for warm sunny weather in August decreases, so variety choice becomes more flexible. As you move southwest, variety choice based on potential for bleaching becomes more important.
The current specialty pea markets include marrowfat, maple, forage, and some others that may be used in birdfeed mixtures. Marrowfats are graded on size and colour, so if your environment is unsuitable for green pea production because of high risk of bleaching, it will be even more unsuitable for marrowfat types. For maple types, the main current problem is that almost all current production is based on a variety from New Zealand called Whero. It has long vines and is late maturing. This makes it high risk in the northeast because it collapses early and matures late. In the southwest, Whero may sometimes have a problem because soil moisture becomes depleted. It is important to seed this variety early everywhere it is grown. Forage pea varieties characteristically have small seeds and long vines with normal leaves. They tend to be later maturing, so early seeding is critical everywhere.
In the testing system for registration of field pea varieties in western Canada, we recognize that variety performance can be categorized by two main climatic zones - cool and wet (Zone 1) and warm and dry (Zone 2). After harvest, trials are separated into two groups based on the climate experienced at that location. In Saskatchewan, sites in the Brown and Dark Brown soil areas are usually included in Zone 2. The Zone 1 area of adaptation is usually the Black, Moist Black and Grey soil zones. In the Zone 1 regions (cool and wet), early maturity becomes a major factor in variety choice. In Zone 2 areas, tolerance to heat and drought become more important, and late maturity is not necessarily a penalty.
Disease is also a consideration for choice of pea varieties. Now that the pea crop is widely distributed, so are the two major pea disease - Mycosphaerella blight and powdery mildew. Mycosphaerella blight is more problematic in cool and wet environments. If the disease starts to develop in the lower canopy in June, the disease can reach the destructive phase in July. Lower stem infection leads to excessive lodging, stem rot and yield reduction. From the standpoint of variety resistance, no discussion is necessary because none of the varieties have good tolerance to the disease. The best ratings on the scale are fair, which really doesn't amount to much. Powdery mildew is an unusual disease because it is favored by dry conditions. For example, it regularly shows up in the winter nursery in Arizona, where it virtually never rains. Powdery mildew is always a bigger problem in dry climatic cycles. Dew and moisture in the lower canopy followed by warm sunny days cause the disease to develop very rapidly in July. The earlier the disease shows up, the higher the potential for economic loss. Good resistance is available, but few breeders have used it so far. The yellow pea varieties Highlight and AC Tamor are the only two available. This situation will change over the next few years when a new slate of resistant varieties becomes available from several breeding programs.
Regional and registration yield trials conducted throughout Saskatchewan in the past 4 years clearly indicate that the best regions of adaptation for dry bean are the irrigation districts around Lake Diefenbaker, and the Black soil zone. The Moist Dark Brown soil zone is suitable in years when it rains in late July or early August. In the Moist Black soil zone, dry bean crops can be grown in years with above average temperature and if a killing frost does not occur before mid-September. Of all the pulse crops, dry bean has the largest potential market and probably the fussiest market in terms of seed size, seed colour and seed condition. The feed market discounts dry bean, so growers should pay particular attention to adaptation.
Dry bean is the pulse crop for which variety performance is most erratic from location to location and from year to year. This is because both temperature and day length influence the rate of development of the crop. Performance can only be judged by testing in a range of environments. From the perspective of crop maturity, the current variety list shows a range of flowering dates and maturity. Once again, early maturity becomes a larger factor as you more northeast into the Black soils. One other consideration for dry bean is that the crop matures more rapidly in response to more heat units, so as you move southeast within the Black soils, some environments have higher heat units. The other method to fine tune the location for bean crops is to try to choose a field that benefits the crop. South facing slopes and lighter textured soils add more heat units to the growing season for dry beans.
The dry bean crop is developing in Saskatchewan with two distinct agronomic systems. In the irrigation districts, where the potato crop is expanding, row crop systems like those used in Alberta and Manitoba are now well established. Use of irrigation usually delays maturity of dry bean crops by a week. In these areas, growers should pay close attention to maturity ratings, because in many years frost can affect both yield and quality of late maturing varieties. In general, late maturing varieties have higher yield potential, but this must be measured against the potential for frost damage and quality loss caused by late maturity.
The other agronomic system for dry bean production in Saskatchewan is based on using seeding and harvesting techniques similar to those used in lentil production: direct seeding into stubble, narrow rows, and harvesting by swathing or by direct combining. For this system it is essential that varieties have good pod clearance characteristics In Saskatchewan coop and regional trials, each variety is rated for the percentage of pods that completely clear the cutterbar (assumed to be 5 cm from the ground). Pod clearance should be the prime consideration for growers wishing to try out this crop. We are trying to develop varieties that combine earliness with good pod clearance and high yield. This is not an easy task in the short term, but the breeding programs based in western Canada are making good headway.
Pulse crops are mostly sold on the basis of visual quality, and each pulse crop has multiple market classes. Varieties should be chosen on the basis of productivity and marketability within specific markets. Once that marketing decision is made, it is possible to reduce risk by choosing a particular pulse variety for a particular location in Saskatchewan. Keeping in mind how the various soil zones developed over time provides some good insight into how much consideration should be given to early maturity and disease resistance. Choosing pulse crops on the basis of drought tolerance becomes more important as you move southwest in Saskatchewan. Choosing varieties of specific pulse crops on the basis of early maturity and resistance to fungal diseases becomes increasingly important as you move northeast.