Current Crop Topics

The latest information on crop management and agronomy issues in field and horticultural crops in Manitoba.

 


General Agronomy

 Seed Placed Fertilizer Cautions for Canola
This spring has brought many questions about seedplaced fertilizer rates for canola.  Several factors are causing concern:
·         Drier soils – which increase the risk of seed toxicity
·         Desire to apply sufficient P to meet crop removal – since many fields have seen decreasing P levels due to high yield.  P removal is about 1 lb P2O5/bu, so high yield potential fields are looking at high P replacement rates.
·         Increased use in low disturbance, low seedbed utilization (SBU) drills.  Many new openers are arriving on the scene, which are “close-to-seed” sidebanding for which one may need to consider as seedplaced.
·         Desire by growers to reduce seeding rates for cost savings.  Most research studies investigating seedplaced fertilizer injury were seeded at some 150 seed/m2, about double what some farmers are now targeting.
More detailed analysis on situation at Seed-placed -fertilizer-for-canola.pdf
More topics on soil fertility can be found on Manitoba Agriculture's Soil Fertility webpages.

Can Sidebanded Nitrogen Cause Injury in a Dry Year?

With a lack of seedbed moisture, there are justified concerns about seedplaced fertilizer injury to canola and other crops.  How safe is sidebanded nitrogen? Research studies by  Dr. Cindy Grant documented considerable canola stand thinning when high rates of sidebanded urea or UAN solution were applied.  Agrotain (AT) served to reduce stand injury, but is no longer supported for this use by the manufacturer. 
 
Points:
·         Stands were thinned at even modest N rates, on a clay loam soil.  At high rates stands were reduced to 50%
·         Crop growth compensated for reduced stands and generally produced as good a yield as the Agrotain protected stands, except at the highest rate.
More detailed analysis and discussion at Can-sidebanded-nitrogen-cause-injury.pdf 
More topics on soil fertility can be found on Manitoba Agriculture's Soil Fertility webpages.
 
Spring Preplant Banded nitrogen Too Hot for Corn in Dry Springs!
There is no single best way to fertilize corn in Manitoba.  The 4 most common N application methods are spring broadcast and incorporated, fall banded, banded at seeding and preplant banded.
In a dry spring like 2018,  broadcasting and incorporating fertilizer before seeding, risk drying out the seedbed.  Many farmers, especially on clay-textured soils prefer not to disturb their seedbed in the spring and so prefer to fall band their N.  And although spring preplant banding is a very efficient way to place nutrients for a corn crop, it comes with some particular cautions - thinning and seedling injury.  More detailed information at spring-preplant-banded-nitrogen-hot-for-corn-in-dry-spring.pdf 
More topics on soil fertility can be found on Manitoba Agriculture's Soil Fertility webpages.

 
Volatilization of surface applied urea/UAN
Surface broadcasting of nitrogen (N) fertilizers has become popular to increase operational efficiency – increasing the speed of seeding and reducing risk of seed injury.  But, in a dry spring with limited rain prospects, growers may choose not to till and avoid further drying out seedbeds.  Then growers must consider the risks of nitrogen volatilization loss and take precautions when risk is high.
Volatilization of ammonia (NH3) from urea or the urea portion of UAN (28-0-0) affected by several factors volatilization-surface-applied-urea.pdf
More topics on soil fertility can be found on Manitoba Agriculture's Soil Fertility webpages.

 
Assessing Winter Wheat Survival
Temperatures are getting warmer and many producers are thinking about their winter wheat crop and how it survived the winter.  There are three common ways to assess winter survival:
1. Sod Extraction Method – A producer can extract several ‘sods’ from the field with a shovel.  Warm up the sods inside while keeping the soil moist.  In 5 to 7 days, assess the crowns for new root growth which indicates the plant has survived. 
2. Bag Test Method – This method was developed by Ducks Unlimited in North Dakota and involves five easy steps:
1) Dig or chisel plants out of the soil without damaging the crown.
2) Rinse the soil off the crown and roots.
3) Using scissors, trim off the roots and leaves and all but one inch of stem above the
                  crown.
4) Put the crowns in a Ziploc bag and puff some air into it before sealing.
5) Keep at room temperature and observe every 2 days.  Repeat the rinsing and air
                 every 2 days. 
Plants that are alive will extend leaves and grow new white roots.  If new growth is not observed after 6 days, consider the plant dead.  There is a good YouTube® video illustrating this method at: https://www.youtube.com/watch?v=soCj2OsLJ_w&feature=youtu.be
3. The Wait for Spring Growth Method – This method requires producers wait until the crop breaks dormancy and new root growth commences out in the field; this could take until mid-May in some years depending on spring weather conditions.  This method does still require producers dig up plants within the field as brown, dried leaves do not necessarily indicate winter injury, and green overwintering leaves are not a sure sign that the crop has survived.  To properly assess, dig up some plants, rinse the roots with water and examine the crown for the development of new white roots.  If new roots are developing, and the crown appears white and healthy, the plant is likely in good condition. 
Regardless of method used to assess winter survival, producers should still scout their winter wheat fields to determine plant stands.  It has occurred where plants will green up and then slowly go ‘backwards’ and eventually die; there are enough nutrients in the crown to allow the plants to green up, but if winter injury occurred, it can cause vascular damage so that the nutrients that are left cannot move, or root rot diseases can move in and kill the plants.  So don’t scout the field once and assume all is okay. 
Looking for more information?
The Winter Cereal Survival Model and real-time soil temperatures at four locations in Manitoba can be found at:  https://www.wheatworkers.ca/wcsm.php 
Interested in underseeding Red Clover in Winter Wheat? There is extensive information at:  https://www.gov.mb.ca/agriculture/crops/soil-fertility/underseeded-red-clover-in-winter-wheat.html
 
 
Changes to wheat variety classifications will impact spring seeding intentions
As of August 1, 2018, 25 Canada Western Red Spring (CWRS) varieties and 4 Canada Prairie Spring Red (CPSR) varieties will be moved into the Canada Northern Hard Red (CNHR) class.  Prior to putting seed in the ground, consult the Canadian Grain Commission’s variety designation list to see if the variety you are planning to grow will be changing classes before harvest.  The complete list of varieties transitioning to CNHR is available at:  https://www.grainscanada.gc.ca/consultations/classes-en.htm
The modernization of the wheat class system revised the parameters of the CWRS and CPSR classes to ensure that wheat varieties in these classes met strict quality guidelines.  The varieties transitioning from CWRS and CPSR to CNHR do not meet the quality parameters of their current class.  The CNHR wheat class was created to allow farmers more flexibility in the wheat varieties they grow while preserving the quality of the CWRS class.  Wheat varieties in the CNHR class such as Faller, Prosper, and Elgin ND, have slightly lower protein than CWRS wheats but are higher yielding.        
 
 
Factors to Consider with Herbicide Carryover
 Plantback or re-cropping restrictions for residual or extended control herbicides are an important crop rotation consideration. Soil moisture is an important consideration.  In addition, soil texture, organic matter and pH can influence the degradation of any herbicide. Re-cropping intervals are also be impacted by use rates and time of application, so always read the label for specific re-cropping instructions. Check Manitoba Agriculture’s current Guide to Field Crop Protection for detailed information on re-cropping restrictions (Page 78).
With lower than normal rainfall amounts in many areas in 2017, risk areas have been developed based on precipitation amounts received during the period from June 1 - September 1, 2017.  Producers in the normal risk areas should follow label directions to determine what crops they may plant, but may still have localized areas that are susceptible to extended carryover due to the low in season rainfall. Producers in the extreme, very high risk and high risk areas should contact the manufacturer of the residual herbicide for rotational crops supported by that company. Producers in the moderate risk areas that also have low organic matter or have soil pH less than 6.5 or greater than 7.5 should also contact the manufacturer of the residual herbicide used previously.
 
It is important to have rainfall records for each field in order to determine localized risk. Herbicide residues can be managed, but it requires good record keeping, planning and knowing which herbicides leave residues.