September 14, 2007

Figure 1. Recommended planting dates for Nebraska winter wheat.

With good rainfall in many areas of the state and the high price for winter wheat, there is an increased interest in seeding winter wheat this fall. If you're seeding winter wheat after harvesting a crop this fall, it's likely that you're planting after the suggested dates for seeding (see Figure 1). Other factors such as rainfall and trying to destroy a stand of downy brome or jointed goatgrass also can delay seeding. Several changes can be made to help compensate for the delayed seeding. 

Late seeding is usually classified as at least a week or more after the suggested date. Usually yields start to decline if planting is more than two weeks late, but in some situations it may even outyield winter wheat planted earlier, especially if wheat was planted much before the suggested dates. This can be attributed to disease and insect problems and the use of extra soil water in the fall.

Use narrow row spacings. When planting after the recommended date, narrower row spacings of 5-8 inches are preferred over 10- to 15-inch row spacings. If you use a wider spacing, such as from using a 15-inch planter, consider seeding twice with the second pass at a slight angle to the first. Use one-half the seeding rate each time. This works only with disc drills as hoe drills move a lot of soil and bury much of the seed from the first pass.

Increase the seeding rate. Late seeding usually results in less root and tiller development. A general recommendation is to increase the seeding rate 10 to 15 pounds (150,000-225,000 seeds) per acre per week after the suggested seeding date for your area. The maximum seeding rate for rainfed wheat is 120 pounds (1,800,000 seeds) per acre or limit the maximum to about twice the seeding rate used for seeding at the suggested date for your area.

For irrigated wheat the recommended seeding rate is 90 pounds (1,350,000 seeds) per acre if planted at the suggested seeding date. Increase the seeding rate 15 to 20 pounds (225,000-300,000 seeds) per acre for every week after the suggested seeding date to a maximum of 180 pounds (2,700,000 seeds) per acre.

Also, when no-tilling wheat into row crop stubble, seeding rates are usually increased by as much as 50% even when seeded up to 10 days before the suggested seeding date. When planting occurs more than one week after the suggested seeding date, the seeding rate should be 90 to 120 pounds (1,350,000-1,800,000 seeds) per acre for rainfed. With irrigated wheat, increase the seeding rate the same up to the maximum listed earlier.

Figure 2. Effect of seeding rate on performance of seed and dual placement methods of phosphorus application at three locations.

Apply phosphorus with the seed. When seeding wheat late, phosphorus placed with the seed helps improve yield (see Figure 2). Use 20 pounds phosphorus where none is called for by soil tests and increase other phosphorus rates which are over 20 pounds by 20% for late seeded winter wheat.

The normal superphosphates and ammonium phosphates generally have a negligible effect on wheat stands because of the low salt content of phosphorus fertilizer compared to nitrogen fertilizer, the low concentration associated with narrow rows (5-12 inches), and the generally high rates of seed used. The seeding mechanism for applying phosphorus fertilizer with the seed is not critical unless the producer applies additional nitrogen at the same time. Do not apply over 15-20 pounds of nitrogen per acre with the seed. Also, do not use 12-0-0-26.

If equipment is not available, some have mixed 11-52-0 or 18-46-0 with the winter wheat seed. A good mix is important. I prefer to use 11-52-0 with its lower nitrogen content. There are two things to be aware of when doing this: 

1. the fertilizer may cause more wear to the drill and
2. always check to see if you are satisfied with the mix by test drilling on top of the ground so you can observe the distribution of winter wheat seed and fertilizer.

Use certified treated seed. Both of these qualities increase the success with winter wheat. The seed treatments need to thoroughly coat the seeds to give good results and should be applied with seed treating equipment.

Robert N. Klein
Extension Cropping Systems Specialist
West Central REC, North Platte