Recommended Adjustments for When Wheat Planting is Delayed - UNL CropWatch, Sept. 27, 2013

Recommended Adjustments for When Wheat Planting is Delayed - UNL CropWatch, Sept. 27, 2013

September 27, 2013

Wet fields

Figure 1. Washed out field near the UNL High Plains Ag Lab near Sidney. After being dry much of the summer, areas of the Panhandle received as much as 8 inches of rain in the last three weeks, leaving fields too wet to plant during the optimum period for winter wheat. For some fields this will be the third planting.

Map of recommended seeding dates for winter wheat in Nebraska

Figure 2. Recommended seeding dates for Nebraska winter wheat.

How can you compensate for yield loss from delayed winter wheat planting due to recent rain in the Nebraska Panhandle?

The Nebraska Panhandle has experienced patchy but heavy rain in the past two to three weeks. For example, the High Plains Ag Lab near Sidney received 8 inches of rain the last three weeks of September. The situation was similar in other parts of the southern and northern Panhandle. The last storm dropped nearly 3 inches of rain in one day in the Alliance area. Some fields are too wet to plant within the optimum seeding dates (Figure 1). A few wheat fields, which were already planted, may have to be replanted due to erosion in the fields. The rain has also delayed dry bean harvest, which indirectly pushes irrigated wheat planting back.

How late can you plant winter wheat?

Several factors determine optimum planting dates. In the Panhandle the dates depend on elevation. Producers can determine the ideal date for each field by knowing the elevation. Using a starting point of September 15 for 3,500 feet, add one day for each 100-foot decrease and subtract one day for each 100-foot increase in elevation. The map (Figure 2) is a guide rather than an absolute deadline. Each producer should make changes to ensure the planting dates fit the conditions of his or her farm.

What will be the yield loss?

In the Panhandle the yield loss due to delayed planting can be 5-20% depending on how late it was planted. (For more information see NebGuide 2211, Planting Winter Wheat in Dry Soil.)

What adjustments can be made in order to compensate for yield loss?

One or more of the following steps can be used to compensate for most of the yield losses:

  • Use narrow row spacings. A 5-8 inch row spacing is suggested over a 10-15 inch spacing. If you use a wider spacing, increase seeding rate by 1.5 times.
     
  • Increase the per-acre seeding rate to:

— 10-15 lb (150,000-225,000 seeds) for dryland (non-irrigated) winter wheat and
— 15-20 lb (225,000-300,000 seeds) for irrigated winter wheat

for each week after the optimum date for your farm (based on elevation). If no-till seeding into row crop stubble more than one week later than the optimum seeding date, the seeding rate should be 90-120 lb (1,350,000-1,800,000 seeds) per acre. Optimum seeding rate is 18 plants per foot of row for dryland (10- to 14-inch row spacing) and irrigated (6- to 8-inch row spacing). Optimum seeding rates for the Panhandle range from 600,000 to 900,000 viable seeds per acre for dryland and 1,000,000 to 2,500,000 viable seeds per acre for irrigated, which will be in ranges of 30-60 lb and 90-180 lb per acre, respectively, depending on seed weight and germination percent. Total seeds per acre are more critical than the pounds per acre. Therefore, calculate seeding rate in pounds per acre based on seed weight, row spacing, and germination percent of the seed lot. Use Tables 1 and 2 as guides to estimate seeding rate. (See details in NebGuide G2211.)


Table 1. Examples of converting seed/lb to lb of seed/acre for plant population density (PPD), maintaining 18 plants/linear foot at four row spacings.


Row spacing 6-inch 8-inch 10-inch 14-inch
PPD* (million seed/acre) 1.570 1.180 0.940 0.670
Number of seed/lb -- lb seed/acre --
10,000 157 118 94 67
12,000 131 98 78 56
15,000 105 79 63 45
18,000 87 66 52 37

Table 2. Examples of converting 100 lb seed/acre to lb viable seed/acre after calculating seeds/lb desired.

  Percent Germination
  75 80 85 90 95
lb seed /acre -- lb viable seed/acre --
60 lb 80 75 71 67 63
90 lb 120 113 106 100 95

 

  •  Apply phosphorus with the seed. Use 20 lb phosphorus where no phosphorus is needed and increase by 20% for every 20 lb per acre that would have been applied based on soil tests. (See September 6, 2012 CropWatch for other considerations.)
  • Use certified treated seed.

Additional Resources

Dipak K. Santra, Extension Alternative Crops Specialist, Panhandle Research and Extension Center
Karen DeBoer, Extension Educator, Kimball, Banner, and Cheyenne Counties
John Thomas, Extension Educator, Box Butte County
Robert Klein, Western Nebraska Cropping Systems Specialist, West Central REC