Early season, The Bean Report

The Bean Report – April 17, 2024

APRIL 17, 2024

Risk of Greater than Expected Herbicide Carryover

Many residual herbicides are broken down by microbial activity. This requires adequate soil moisture and warm temperatures to occur. In-season rainfall is the most important factor affecting breakdown of residual herbicides and they can remain in the soil longer if less-than-normal rainfall is received. As a result, the risk of greater-than-expected herbicide carryover may be interpreted from precipitation maps of the previous growing season (June 1 to Sept 1 and mid-June to mid-September).

Use these maps with caution as rainfall events in the 2023 season were sporadic and localized. Many areas had little or no rainfall for the majority of the summer, and microbial activity would have been greatly reduced during this period. If possible, use rainfall data (timing and amount) specific to your fields to help determine risk. Refer to the current Guide to Field Crop Protection for a list of residual herbicides and always read the label for specific re-cropping restrictions.

Pulse and soybean crops are particularly sensitive to some herbicides. In-season, you may notice injury symptoms pop up following a rain. The moisture releases herbicides from soil particles into the soil solution which can then be taken up by crop roots and cause injury.

Dry Bean Nitrogen Rates: On-Farm Network Results

Six on-farm trials have tested nitrogen (N) rates ranging from 0 to 140 lbs N/ac applied in navy, pinto and black beans from 2019-2023.

These dry bean fields have not been inoculated, yet often have had more than 15 nodules/plant. The exception has been with black beans in southwest Manitoba where nodulation has generally been low. As nitrogen rate has increased in these trials, nodulation has decreased. 70 lbs N/ac applied appears to be a tipping point regarding nodulation, where rates above 70 lbs N/ac have resulted in a decline in nodule numbers.

In terms of yield response, four out of six on-farm trials saw an increase in yield with increasing nitrogen rates while one trial in 2020 saw a significant decrease in yield with increasing N rates (p<0.10). Broadly speaking, applying 70 lbs N/ac increased yield by 8 to 17% at half of these on-farm trials. Environment also played a key role in how dry beans responded to N rates applied.

Looking at the economics of these trials in terms of return on nitrogen investment ($/ac), there were no significant increases in profit with increasing N rates. This means that yield increases were not large enough to provide a consistent return on nitrogen investment as N rates increased.

While these on-farm trials were on-going, N rates were also under investigation in two small-plot studies with 1) Kristen MacMillan, UM-MPSG Agronomist-in-Residence at Carman and Portage (2017-19) and 2) Dr. Ramona Mohr, AAFC at Brandon, Carberry and Melita (2021-22).

  1. Optimizing Nitrogen Rates for Pinto and Navy Beans (Small-plot Trials at Carman, Portage 2017-19) →
  2. Full Research Report: Nitrogen and Phosphorus Management for Black and Pinto Beans in Southwestern Manitoba (2021-2022) →

Participate in an On-Farm Network trial in 2024!

What’s involved in hosting an on-farm trial?

You establish the trial using your equipment by following a randomized and replicated trial layout we provide. Strips typically run the length of the field, excluding headlands and are at least as wide as one combine pass. You manage the trial the same as you would the rest of the field. We provide support at trial establishment and harvest. We scout the field regularly and collect relevant data throughout the growing season. In the fall, you receive a short report summarizing analyzed trial results and economics.

What’s the time commitment of hosting one of these trials?

It starts with a conversation, what are you interested in testing? From there, the two main time commitments are at trial establishment (either at seeding or spraying, depending on the trial) and at harvest. Some trials are easier and quicker to establish than others. At harvest, each strip needs to be individually unloaded and weighed. This can add an extra 1 to 2 hours to your traditional field harvest.

Trial types include investigating seeding rates, row spacings, double vs. single inoculant, single vs. no inoculant, seed treatments, fertilizer rates, fungicide applications and biological products. Want to test something else on your farm? Let us know!

Residue Management

Stubble Type (Crop Sequence)

What’s the best crop to plant before growing soybeans, peas and dry beans? We can look to MASC data to see historic yield responses to planting these crops following various previous crops.

For soybeans, yield responses have been greatest following winter wheat, spring wheat or navy beans. For peas, yield responses have been greatest following canola or soybeans, and navy beans report yield increases of more than 110% following potatoes, corn or spring wheat.

The following results from individual research projects provide some insight into how to best manage previous crop residues.

Before Growing Soybeans

From 2017 to 2021, six tillage treatments (fall tilled, fall burned, short standing stubble with and without straw and long standing stubble with and without straw) were evaluated before growing soybeans at Brandon, Carberry and Indian Head.

Direct-seeded soybeans yielded the same or greater than the tilled and burned treatments. Tall standing stubble also resulted in similar or greater yields than shorter stubble. Removing wheat straw before seeding soybeans resulted in similar or greater yields than chopping and returning the straw. Days to emergence among tillage treatments varied by one day or less on average. Soil temperatures at seeding varied by 1 to 3°C among treatments and tillage and burning commonly resulted in drier soils.

Seeding into corn residue can be particularly challenging. From 2015 to 2016, four on-farm trials compared four different tillage strategies (conventional double disc, vertical till high disturbance, vertical till low disturbance and strip till. Among these different treatments, there was no effect on soybean emergence or plant stand 75% of the time. While there were no yield differences due to the different tillage treatments, economic analysis indicated time and cost savings in favour of strip till.

Before Growing Peas

Research at Carman and Roblin (2020-2024) has been ongoing investigating the combination of preceding crop, tillage vs. direct seed and phosphorus fertilize rate and placement on pea yield. Stay tuned for results from this project soon!

Before Growing Dry Beans

From 2017 to 2020, pinto beans were planted into four crop residues (wheat, canola, corn and pinto beans) that had been split into tilled and direct seeded treatments.

Preceding crop did not affect pinto bean yield, but there was greater grassy weed pressure following corn than wheat and root rot severity was the greatest in beans following beans.

Direct-seeded pintos yielded 10-17% greater than pintos in tilled stubble at two site-years, likely due to moisture conservation benefits. Grassy weed densities were also greater in tilled residue treatments.


Production Guidelines

Review agronomy-focused production guidelines and recommendations that provide an overview of field selection, seeding, crop nutrition, pest management and harvest.

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