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Spring Crop Choice (Wheat and Oat) Influence on Winter Wheat Yield

Ray Olson
with Paul Peterson and Lawrence Brown, Spokane Co. Extension; Baird Miller, Ron McClellan and Stewart Wuest, WSU

Objective

Compare yields, N carryover, and economics of spring wheat and oats, and determine their influence on winter wheat yields, erosion, and profitability of the rotation.

Location: Rockford, WA
Annual precipitation: 17 inches
Soil series: Larkin silt loam
Field history: Winter wheat 92

Treatments

Previous crop:

Spring wheat
Spring oat

Comments

We are reporting the initial spring wheat and oat yields and residual soil N levels after the spring wheat and oat crops. The winter wheat yields are following either spring wheat or oats. The plots run up and over a ridge and are 30 by 650 ft. Yield data is from a 12 by 650 ft swath. Soil Samples, taken from each end of the plots, were combined for each treatment.

The soil N carryover was not different between spring wheat and oat. The N rates applied to the following winter wheat was 60 lb N/ac following the spring wheat, and 90 lb N/ac following the spring oats. The higher N rate following the spring oats was necessary to compensate for N tie up by the greater amount of oat residue.

Data

**Yield of spring wheat and oat,** lb/ac
Previous Crop	Rep 1	Rep 2	Rep 3	Average
Spring wheat	2010	1789	2100	1970
Spring oat	4066	4166	4691	4308

Residue of the previous crop following harvest in 1993, lb/ac

Previous Crop Rep 1 Rep 2 Rep 3 Average

Spring wheat 5162 2238 3782 3727a

Spring oat 2003 2634 3579 2739a

LSD (5%) 4728

CV 41.6%

Inorganic N to three feet, lb/ac, 7 Oct 93

Previous Crop North end South end Average

Spring wheat 43 55 49a

Spring oat 40 64 52a

LSD (5%) 76.2

CV 12%

Yield of winter wheat, bu/ac

Previous Crop Rep 1 Rep 2 Rep 3 Average

Spring wheat 32.3 29.9 29.3 30.5a

Spring oat 31.3 35.3 32.6 33.1a

LSD (5%) 8.1

CV 7.3%

Test weight of winter wheat, lb/bu

Previous Crop Rep 1 Rep 2 Rep 3 Average

Spring wheat 56.66 52.96 53.14 54.25a

Spring oat 56.06 54.78 54.33 55.06a

LSD (5%) 3.12

CV 1.6%

Grain protein of winter wheat, %

Previous Crop Rep 1 Rep 2 Rep 3 Average

Spring wheat 12.99 13.83 14.13 13.65a

Spring oat 13.48 14.00 13.77 13.75a

LSD (5%) 1.07

CV 2.2%

All crop residue following winter wheat harvest, lb/ac

Previous Crop Rep 1 Rep 2 Rep 3 Average

Spring wheat 3311 3738 4518 3856a

Spring oat 4540 3878 5017 4478a

LSD (5%) 1379

CV 9.4%

Conclusion

There was no consistent trend in the amount of the previous crop residue harvested in 1993. Under the droughty conditions of the 1994 growing season, there were no significant differences in the winter wheat yields following spring wheat or spring oat. The winter wheat test weights and grain protein percentage was not affected by the previous crop. The total crop residue (winter wheat residue + previous crop residue carried over from the previous year) was also not significantly different between the previous crop treatments.

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