During years when soybeans are harvested later than expected or environmental conditions delay field work, winter wheat planting is rushed and can sometimes even be skipped in the rotation. When planting later than the recommended planting dates, even more care should be taken to ensure yield potential is not lost.
Planting Date
In general, delaying plantings past the recommended planting window can cost a producer from 0.6 to 1.1 bu/day. It is best to strive to plant around the optimum dates (See Figure 1), although field conditions obviously play the biggest factor.
BEST MANAGEMENT PRACTICES
Variety Selection
Variety selection does not play as big of a role when planting late as it does when planting early. In general, choose a variety that has a good disease package and is known to overwinter well. Certified seed is also recommended because of the guaranteed quality standards.
Seed Treatment
It is essential that later planted seed is treated with a fungicide such as: Vibrance Quattro, Cover 2, etc. These will help to protect the crop from various seed and soil prone fungal diseases.
Plant Population
When planting later, the wheat plant has less time available to develop roots and tillers. Increasing seeding rates can help, to an extent, overcome this decease of growth and maintain yield potential. The weather in the fall and early winter will greatly determine if the increased seeding rate will actually pay off.
In general, wheat should be seeded at 1.5 million seeds/acre when seeded at the optimum timing (this can vary slightly depending on the variety). Increase this rate by 200 000/ week delayed to a maximum of 2.2 million seeds/acre. Be sure to account for the seed size when setting the planter (see chart).
Seeding Depth
When planting later it is recommend to plant shallower. It is generally recommended to plant from 1- 1.5”. When planting is delayed, a shallow planting allows the plants to emerge faster and gives more time for growth. This increase in growth needs to be weighed against the potential for more winter injury due to the shallow root system. To strike a balance between the risks a depth of 1” is a good target to shoot for.
Fertilization
Winter wheat requires a small amount of nitrogen for good fall development. Generally speaking, the wheat crop can get all the nitrogen it needs in the fall from P sources such as MAP or MESZ, as well as scavenge nitrogen from the soil when planted after a legume crop like soybeans or edible beans.
In addition to nitrogen, other nutrients are essential for late wheat planting. Wheat has a higher requirement for phosphorus than corn or soybeans. Phosphorus plays a very important role in winter survival and can help the plant tiller in the fall. Dry or liquid fertilizer starters can and should be applied with the seed in-furrow if your planting setup allows it. Rates of up to 120 lbs of MAP can be applied in furrow; higher rates can also be applied and worked into the soil to cover the crop removal or help to raise the soil test level. Research has shown that there is a major benefit to having P down as a starter for winter wheat, even in medium or higher testing soils.
Potassium is also very important. Though major uptake occurs close to flowering, fall is a great time to apply sources of potassium like Muriate of Potash (0-0-60). Potash should be applied at higher than crop removal when test levels are lower to build up the soil. When test levels are higher, rates should match the expected crop removal for your yield goal to maintain your soil quality.
Weather
In the end, weather factors are the most important in determining if later plantings will retain good yield potential. Following these best management practices will help to protect your yield. Watch the forecasts and make a decision as close to the actual planting date as possible. It is strongly recommended to revisit these fields in spring around green up to assess winter kill and populations to determine if the crop should be kept.
References: http://www.ag.ndsu.edu, http://www.ontariosoilcrop.org/docs/v4cer3.pdf, http://msue.anr.msu.edu, OMAFRA