Laura Schmidt, MSc, PAg, Western Production Specialist, MPSG – Fall/Winter (December) Pulse Beat 2020
We kicked off the growing season with plenty of moisture in the bank and a bit of a mess to tidy up from last year’s harvest — including some standing crop. Spring had a cold, slow start delaying planting dates.
Peas and faba beans didn’t mind the cooler temperatures, but we ended up with a wide range of planting dates for those crops, from early May to early June. Soybean planting was, for the most part, pushed later. Combined with running into tight deadlines and a shortened growing season window, many acres designated for soybeans were swapped out for other crops like canola.
Struggling through the Soil
Soil crusting, smearing and side-wall compaction from the wet conditions proved challenging for crop emergence. Soybean and dry bean seedlings had yellow, swollen and crooked hypocotyls from trying to grow around soil clods. A general observation was that more seedlings could grow through the crust if seeding rates were higher.
Saline areas of the field were apparent again in our saline-intolerant pulse and soybean crops. Each year we waste expensive seed, fertilizer and pesticides in these barren, marginal areas of the field. It may be time to start thinking about these saline spots as areas we need to crop independently from the rest of our pulse or soybean crop. The best thing we can do to manage these areas and stop their expansion further into the field is to have something tolerant growing and drawing salts down, and soybeans and pulses are just not the answer here.
What are better options? Soil sample to determine the scope of the problem and define the areas of the field affected. Once you have an idea of the salt values in those areas, grow something tolerant to those levels, and maybe even consider a cover crop following harvest.
Competitive Pulse Plant Stands
Giving peas a strong start is the foundation of their success and while scouting this year, we saw a range of pea plant stands. Achieving a good stand (350–400,000 plants/ac) maximized yield potential, ensured good standability at harvest and offered weed suppression. Peas really aren’t competitive with weeds until the canopy closes, and a higher density stand achieves that much quicker. Lower density pea plant stands were more likely to produce branches to compensate for open spaces.
Weed control was an issue in dry beans once again, and here again, I believe competitive plant stands are key to make sure we’re not putting so much strain on our herbicide regime. A recently wrapped up project in Manitoba evaluated plant population, row spacing and variety effects on dry bean yield and weed suppression during wet (2015/16) and dry (2017/18) years. Watch for the results of this research in the next issue of Pulse Beat – The Science Edition.
Extremes of Moisture
June brought extremes of moisture to several areas in the province. The monsoons hit mid-western and south-eastern regions of Manitoba, while desert-like conditions continued to prevail in the Interlake. In the west, we were reminded that peas don’t like wet feet or standing water and are susceptible to root rot in those conditions. Well-drained fields with coarser soil textures performed better here. Soybeans that weren’t drowned out bounced back readily, displaying their ability to tolerate excess moisture once again.
Overall, more moisture in 2020 resulted in some very successful crops. Soybeans grew tall with excellent yield potential. We spotted four-bean pods in several fields — something we hadn’t seen in the last couple of years. Dry beans, peas and faba beans were also very successful this year.
Pea Fungicide Paid in Much of the Province
While this moisture increased our yield potential, it also meant we had a year to justify fungicide applications in many fields. The decision to spray was more easily made in peas than dry beans. In peas, you could wait until you saw disease symptoms start to show up in the lower canopy to make the call, while dry bean fungicide is purely preventative, and you need to make that decision based on the forecasted conditions. For peas and dry beans, fungicides protected the yield potential that was there this year.
An unfortunate result of early-season storms was that bacterial blight showed up in pea canopies right around the time of fungicide application. Mycosphaerella (Ascochyta) blight and bacterial blight in peas look very similar as they progress. This means we need diligent scouting as peas flower, and really need to get down into the canopy to search for the purple freckles of mycosphaerella before they turn into the lesions that are often mistaken for bacterial blight.
Using this checklist may mean multiple visits to the same field to watch for disease progression and weather changes. But this is also an opportunity to assess nodulation and check for other pests, like pea aphids that like to hang out in the upper stipules and flowers around this time.
On the other hand, we ask ourselves again, is soybean fungicide really necessary? We’ve now been asking this question for seven years in the On-Farm Network (OFN). So far, ten sites out of 66 have had a significant yield improvement from soybean fungicide (in 2015, 2017 and 2018). We have significant results, but do they make economic sense?
If we assume an average cost of $15/ ac for fungicide application and a soybean price of $10.50/bu, we’d need to see a yield increase of 1.4 bu/ac to break-even. Six sites have had significant yield increases above this, meaning of the 66 trials to-date, we’ve seen a positive, economic benefit to fungicide only 9% of the time. Something else to note is that three of those six sites were also soybeans the previous year, increasing the disease loads in those fields.
2020 was arguably conducive for disease development, yet not one of the seven OFN soybean fungicide trials resulted in a significant yield response. The fungal diseases we aim to control with fungicide (septoria brown spot and white mould) just have not been yield-limiting in our growing conditions to-date.
But that doesn’t mean we shouldn’t pay attention to soybean diseases. We’ve been keeping an eye out for emerging diseases through the annual soybean disease survey. This year, we identified many of the usual suspects (bacterial blight, septoria brown spot, downy mildew and northern stem canker). Interesting finds for me this year included Cercospora leaf blight, which resembles sun bronzing, and late-season Alternaria infection, which looks like premature plant ripening. Neither of these diseases are typically yield-limiting.
Details of Desiccation
This year, many farmers paid close attention to their desiccation decisions in peas and dry beans, as consumers and buyers have become increasingly cautious around these late-season chemical applications. This meant diligent scouting for the appropriate timing of 30% seed moisture in the least mature areas of the field — where bottom seeds rattle in pods, colour change has occurred in middle pods and the top, greenest pods have an orange peel-like texture and seeds within split evenly rather than squash when under pressure. At MPSG, we’re working to create detailed fact sheets that illustrate what 30% seed moisture looks like to better support farmers in this area.
September 8 brought a hard frost across much of western Manitoba, followed by a light frost the next evening in the central and eastern regions. Many soybeans in the west were still filling pods (R6) and were susceptible to yield and quality loss as a result. As these fields were harvested, percent greens were quite high. Earlier-planted and earlier-maturing soybeans ranged from R7 to R8 and were unharmed by the frost.
Some fields were harvested in stages to separate the quality of more mature areas from those hit harder by the frost, and some were put into storage, anticipating some colour change to occur in the bin.
This served as an important reminder to match your variety selection with your maturity zone, based on the probability of when a hard, killing frost will occur.
Dry Harvest Conditions
Harvest turned out to be pleasantly different from the last few years, with many farmers wrapping up in time for Thanksgiving, thanks to drier conditions. Despite the drier fall, we’re sitting at better soil moisture conditions going into winter than previous years across the province.
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