Top Crop Manager

Precision Ag
Split nitrogen applications a good idea this year

May 2, 2014, Ontario – This is the year to try a split nitrogen application, writes Peter Johnson in the latest field crop report from OMAF. 

Winter kill and slow growth continue to plague the wheat crop. Provincially, estimates continue at 15 per cent replant, but localized areas may lose 40 per cent or more of the crop. Only 10 per cent of the wheat crop rated good-excellent. The balance will have reduced yield potential due to holes and weak spots in the fields. Growth continues at a snail’s pace, making field evaluations difficult in counties to the north. Conversely, wheat in Eastern Ontario looks quite good, having escaped the icing conditions that often plague that region.

The majority of the nitrogen is now on the wheat crop, with N applications just getting underway further north and east (10 per cent). Many growers insist on waiting on nitrogen applications until they can make the call on replant. This is the worst possible management decision, as early nitrogen is critical to help marginal wheat crops tiller and have good early growth. Most growers have chosen to go with a single application of nitrogen, although split nitrogen applications are gaining ground. If there was ever a year when split applications made sense, it is 2014.

Winter annuals are bolting in the south, and control is becoming very difficult. This is the challenge of weed control when weeds are not controlled in the fall. Annual weeds are beginning to germinate, with early annuals already at the first true leaf stage.

Very few spring cereals have been planted to date. Soil conditions have remained too wet in the shorter season areas that typically grow spring cereals.

Check your alfalfa stands! Winterkill and winter injury reports are coming in from across the province. This includes areas of central and western Ontario, such as Perth and Waterloo counties, where alfalfa winterkill is normally considered a low risk. Winterkill in eastern Ontario appears to be about average, but is more severe closer to the St Lawrence. Winterkill is more common in some of the higher risk older stands, flat heavier clays, and fall harvested stands. Environmental risk factors this winter included the wet late-fall that reduced winter hardening, water ponding and icing, extreme cold temperatures, and crown and root disease. A cool, wet spring has delayed green-up and spring seeding, further complicating how to manage the situation.

Alfalfa fields should be scouted for winterkill by digging plants and assessing roots and crowns for plant health. It is especially important to monitor fields that showed signs of stress last year, fall harvested fields, and fields that are slow to green-up. Using a shovel, dig alfalfa roots and use a knife to cut open the root and crown. Watch for root rots, brownish discolouration, spongy texture and lack of secondary roots and nodulation. Plant health is often more significant than plant density to a successful yield. The minimum number of healthy plants per square foot should be 12 to 20 for first year stand, eight to 12 plants for second year stands and five plants for a third year or older stand. Refer to Check Alfalfa Stands This Spring and Make A Plan.

If winterkill is identified early enough, the best option is often to simply replace the winterkilled stand by seeding a new forage stand in a new field in the crop rotation. A direct seeding can be done, or by using a companion forage crop such as cereals or cereal-pea mixtures. Corn can follow the winterkilled alfalfa to take advantage of the 112 kg/ha (100 lbs/ac) nitrogen credit and the 10 to 15 per cent rotational yield benefit. If an alfalfa stand is uniformly thin or weakened but the grass content is good, an application of nitrogen can significantly increase yields and increase protein levels. Unless the stand was just seeded the preceding year do not try to repair a stand by interseeding alfalfa into an alfalfa stand because of autotoxicity and disease. Where winterkilled areas are large and patchy, some farmers attempt to repair these areas by no-tilling in red clover and/or Italian ryegrass. These species are difficult to dry for hay, but can make high quality haylage. Refer to Forage Options When Alfalfa Winterkill Strikes.

Very little corn planting progress to date. 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.

Spring tillage options should be focused on creating a fine, shallow seedbed. Some reminders: run light (proper inflation pressure in all tires), run level (keep tillage tools level front to back), run shallow (aim for tillage depths in the two- to four-inch range, depending on soil moisture and tillage tool) and run smooth (set harrows properly and aim for one pass seedbed preparation where possible). Vertical tillage tools can be effective at shallow tillage. Caution should be used in running consecutive passes with these tools as traffic impacts may create soil compaction that is not loosened by the tillage pass.

May 2, 2014  By OMAF


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