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No need to switch to shorter-day soybeans

May 9, 2014, Ontario – Soybean planting has been delayed this spring, but Horst Bohner notes there is no reason to consider switching to shorter-day varieties in the latest Ontario field crop report from OMAF. 

Wheat fields continue to struggle from winterkill and slow growth (in the tillering stage) in the lower heat unit regions to the north, reports Peter Johnson. Nitrogen applications continue in this area as field conditions allow. In the south west, nitrogen application is complete, and advanced wheat has entered the rapid growth stage. The growing point has started moving up in the plant (GS 30-31). This is at least 10 days behind the normal stage of the wheat crop for this calendar date. Weed control is now critical, as weeds present at GS 30 can reduce yields. Annual weeds have germinated in these warmer regions, with ragweed, smartweed, wild buckwheat etc. all being reported, many at high levels. With thin stands, this is not a good year to forgo weed control. Winter annuals have already bolted, making control of these weeds extremely difficult. Do not wait on underseeded clover staging for weed control: clover is tolerant to registered herbicides at all early stages of growth.

Spring cereal planting has struggled to get underway in earnest with cool, wet conditions. Frost seeded cereals are at the 2 leaf stage. As the calendar moves later, remember that 6 row barley tolerates late seeding better than the other spring cereals.

Check your alfalfa stands, advises Joel Bagg. Winterkill and winter injury continue to be reported across much the province, including many areas where winterkill is not normally an issue. Assessment cannot wait until after the corn is planted, since dealing with winterkilled forage stands may alter the crop rotation significantly (refer to Check Alfalfa Stands This Spring and Make A Plan).

The best option is often to replace the winterkilled stand by seeding a new forage stand in a new field in the crop rotation. Corn following the winterkilled alfalfa can take advantage of the nitrogen credit and 10 to 15 per cent rotational yield benefit. Direct seed, or use a companion forage crop, such as cereals or cereal-pea mixtures. Some farmers attempt to repair large patches by no-tilling in red clover and/or Italian ryegrass. These species are difficult to dry for hay, but can make quality haylage. If an alfalfa stand is uniformly thin or weakened but the grass content is good, an application of nitrogen can significantly increase yields and protein (Apply Nitrogen To Grass Stands To Increase Yields). Do not interseed alfalfa into an established alfalfa stand due to autotoxicity and disease risks.

Very little canola planted to date, reports Brian Hall. Late planted canola can still have optimum yields. Yield will depend on the temperature at flowering. Swede midge risk is higher so monitor the crop every three days after emergence and implement best management practices. All canola should be scouted regularly for flea beetle. Harvest of late planted canola may experience delays due to fall weather increasing the risk of shatter. Late harvesting will delay the winter wheat planting.

Soybean planting has been delayed this spring compared to the last few years, according to Horst Bohner, but should not be considered late. The middle of May has generally been one of the best times to seed soybeans. There is no reason to consider switching to shorter-day varieties.

As much as 25 per cent of Ontario fields are now below minimal levels for potassium to achieve maximum economic yields. Applying potassium in the spring before planting will increase yields. A number of Ontario studies over the last few years have shown that broadcast P and K provides up to 5 bu/ac more in low testing fields. The response was similar to banding fertilizer through the planter compared to broadcast. Any field with less than 100 ppm soil test K will suffer, especially in dry years. Liquid starter fertilizer can also be used but generally increases yield only by 2 to 3 bu/ac in low testing fields. There is little response to any form of fertilizer in fields with sufficient soil test values.

Glyphosate burndowns should be applied five to seven days before planting to ensure adequate translocation into perennial weeds. If annual weeds are the target, a three-day pre-plant interval is adequate.

Corn planting progress to date has been very slow, notes Greg Stewart. Switching away from full season hybrids should be not be considered until May 15 in short season areas (less than 2800 CHU), May 20 to 25 in areas rated at 2800-3200 CHU and May 30 in areas over 3200 CHU (all CHU ratings are based on May 1 start date). When suitable soil conditions are present for planting producers should consider not delaying planting in order to apply pre-plant nitrogen or incorporate herbicides.

May 12, 2014  By OMAF


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