Sept. 3, 2010

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

• Use narrow row spacings. When seeding after the recommended date, narrow row spacings of 5-8 inches are preferred over wider spacings of 10-15 inches. If you use a wider spacing, such as from a 15-inch seeder, consider seeding twice with the second pass at a slight angel to the first. Use one-half the seeding rate each time. This works only with disc drills; hoe drills move a lot of soil and will 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) 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 into row crop stubble, seeding rates are usually increased by as much as 50% even when seeded during the suggested seeding dates. When seeding 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 1. Effect of seeding date on performance of seed and dual placement methods of phosphorus application at three locations and seeding dates.

   

• Apply phosphorus with the seed. When seeding wheat late, phosphorus placed with the seed helps improve yield (Figure 1). 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 fertilizers 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 to place fertilizer in the seed furrow, 11-52-0 or 18-46-0 can be mixed with the winter wheat seed. A good mix is important and fertilizer dealers can usually do this for you. I prefer to use 11-52-0 with its lower nitrogen content. With this method, check to see if you are satisfied with the mix by test drilling on top of the ground so you can observe how well the winter wheat seed and fertilizer are mixed. Be aware that with this method, the fertilizer may cause more wear to the drill. Also, fertilizers can absorb water so take precautions against this.
   
• Use certified treated seed to increase planting success. The seed treatments need to thoroughly coat the seeds to give good results and should be applied with quality seed treating equipment.

Robert Klein
Extension Western Nebraska Crops Specialist