Oklahoma State University

Planting Date's Effect on Yield

Planting Date's Effect on Yield

Winter Canola Planting Dates

Mark Boyles and Tom Peeper, Department of Plant and Soil Sciences, Oklahoma State University

We have been recommending that winter canola in Oklahoma should be planted anytime in September, and should be planted before October 1st. However, we have not had much data to back up that recommendation. This past year, we conducted replicated trials at the Northcentral Research Station at Lahoma and the Southcentral Research Station at Chickasha to determine the effect of planting date on growth, winter survival and yield.


The canola at both sites was seeded into a conventionally tilled seedbed using a double disc type seeder which planted 7 rows with 7 1/2 inch row spacing. Each plot was 7 rows wide and 32 feet long. Plots were replicated 4 times at both sites. Each field was fertilized with 200 lbs of 19-19-19 plus 10 pounds/acre of sulfur in the fall and 160 lbs of nitrogen in the spring. The varieties planted were Dekalb DKW 13-86 and Wichita. Seeding rate was 5 pounds per acre. Assure II at 8 ounces per acre was applied on December 3, 04 for volunteer wheat control. Insecticide was applied May 1 for aphid control. Plots were harvested at Lahoma on June 8th and at Chickasha on June 14th. Plots at Chickasha were damaged by severe storms and hail before harvest. After harvesting, the seed from each plot was recleaned before yield was recorded. Yields were adjusted to 10% moisture.


The results from Lahoma are in Table 1. Planting date had a major influence on the size of the plants going into the winter. The canola planted very early had excessive growth and numerous secondary branches on it. Secondary branches are okay, unless you get so many that maturity is delayed. We had excess soil moisture during the winter, and if it had been drier, the early planted canola might have been short on water. Winter kill occurred with the last planting date, which greatly reduced yields. Yields were not significantly different from planting dates ranging from August 31 to September 30. Canola planted on October 22, 2004 did not get enough size on it to prevent winter kill and it had very low yield and delayed maturity. Results from Chickasha were much like Lahoma, with heavy winterkill from the October 22 planting date. We had a late first killing frost in the fall of 2004, so in other years, planting earlier in October might be too late. This data indicates that we probably should be planting between September 10 and September 30 in Oklahoma. We will continue working on determining optimum planting date.

We did not see a difference in winter kill between Wichita and DKW 13-86 at either location. Generally, 4 true leaves are required to avoid winter kill.


Table 1. Effect of planting date on winter canola yields.

Planting Date Cultivar Yield* Test Weight %H2O**

Aug-31-04 DKW 13-86 2664 b 51.5 b 13.1
Aug-31-04 Wichita 3375a 51.9 ab 9.6
Sept-13-04 DKW 13-86 2821 b 52.0 ab 11
Sept-13-04 Wichita 3528a 52.0 ab 9.8
Sept-30-04 DKW 13-86 2604 b 52.3 a 11.6
Sept-30-04 Wichita 3296 a 52.1 ab 10.2
Oct-22-04 DKW 13-86 208 c 49.9 c 13.3
Oct-22-04 Wichita 370 c 48.6 c 12

LSD 0.05   384.4 0.73 1.7
CV%   11.08 0.96 10.06

*Yield = pounds of seed/acre after recleaning, adjusted to 10% moisture.
All plots were direct combined on June 8 th, 2005.
** %H20 = seed moisture after recleaning.
Test weights are pounds / bushel. Winter canola official weight is 50 lbs/bu.
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