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Nitrogen Rates for Winter Wheat Grown in Different Rotations in Western Oregon

Ron Lewis, Tim VanLeeuwen, Lincoln Volker
with Kevin Sebastian and Russ Karow

Objective

To evaluate the nitrogen requirement of winter wheat grown after different rotational crops in western Oregon.

Growers, Location, Rotation Crop, N rates:

Grower Location Rotation Crop Spring N rates
lb/a Wheat variety

Ron Lewis Amity, OR red clover 0, 50, 100, 150 Madsen

Tim VanLeeuwen Halsey, OR tall fescue 0. 60, 120, 180 Gene

Lincoln Volker Monroe, OR green peas 0, 50, 100, 150 Gene

Lincoln Volker Monroe, OR sweet corn 0, 50, 100, 150 Gene

Wheat crops were established in test fields in the fall of 1993 and test plots were established in the spring with a single application of nitrogen fertilizer at the late tillering stage. Nitrogen was applied with field equipment in either liquid or dry form. Plots ranged in size from 25 to 40 feet wide and 300 to 500 feet long. Three replications were used at all locations. No lodging was observed in any plots. Zero N plots could be visually identified through the remainder of the growing season, but other N rates could not be distinguished. Winter weather was unusually warm and dry and mineralization rates are known to have been quite high. Plots were combine harvested. Grain was weighed in a weigh wagon. Kevin Sebastian, a master student in Crop and Soil Science at Oregon State University, is doing detailed nitrogen budgets for each of the sites.

Data

See Table 1.

Conclusions

From a statistical standpoint, there was a difference in yield between the zero N plots and the first N rate, and at two sites, a difference between the highest and next lowest rate. Middle rates were not different. These data suggest that the first increment of nitrogen may be all that is needed and, given the type of winter weather in 1993-94, even without nitrogen more than 85 bushel per acre yields are possible. Soil test data and economic analysis will further clarify results. Similar trials will be conducted in 1994-95.

**Table 1**. Winter wheat yields in different Western Oregon crop rotations. Preliminary results from field trials - 1994.
N Rate	Yield (bu/a)	Height (in.)	Test Wgt.
*Gene wheat following tall fescue*
0	100	34.4	59.9
60	135	37.2	59.8
120	136	37.0	59.8
180	152	38.0	60.0
Trial Avg.	130.7
PLSD (5%)	15.7
CV	6
P-level	0.00
*Gene wheat following peas*
0	132	38.1	58.0
50	143	37.8	58.2
100	150	37.3	58.1
150	155	37.8	58.1
Trial Avg.	145.1
PLSD (5%)	9.8
CV	3
P-level	0.01
*Madsen wheat following red clover*
0	86	38.1	60.9
50	105	41.3	60.7
100	104	42.3	60.7
150	119	42.3	61.2
Trial Avg.	103.4
PLSD (5%)	15.9
CV	8
P-level	0.01
*Gene Wheat following corn*
0	116	35.9	58.7
50	135	38.2	59.0
100	144	38.9	59.4
150	152	38.3	59.4
Trial Avg.	137.0
PLSD (5%)	7.9
CV	3
P-level	0.00

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Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU