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Slow Release Nitrogen for Furrow Irrigated Wheat
Brad BrownExtension Soil and Crop Management Specialist
2010 Idaho Nutrient Management Conference
Shoshone, ID
March 9, 2010
Historically:
Preplant N was favored by the industry
To avoid an extra applicationSpread out the workloadCheaper N
Late winter top-dressed urea is more effective than early fall preplant incorporated urea in 2 out of 3 years:
N Immobilization DenitrificationLeaching Volatilization from plantExcessive vegetative growthPhytotoxicity
NRCS 590 Nutrient Management Standard discourages early fall preplant applied N due primarily to risk of nitrate leaching to shallow ground water.
Winter Top-dress risks:Increased compactionNH3 volatilizationPhytotoxicity of high N ratesHigher application costs
(labor, fuel, equipment)
Ideal preplant N source for furrow irrigated winter wheat
• One application to minimize application costs
• Avoiding excessive N effects on yield
• Provide some late season N release for grain filling
• Minimize volatile N losses
Treatments
N rates: 60, 120, 180 lb /A
N sources: ESN, Urea, Mix (50:50)
N Timing: Early fall preplant,
Late fall top-dress,
Late winter top-dress
Preplant slow release ESN
• Increased plant height, N utilization, yield, protein, grain N and apparent N recovery compared to preplant dry urea
• Was no more effective than late winter top-dressed urea.
Late Winter Topdressed ESN
• Reduced plant height, flag leaf Chlorophyll and yield relative to topdressed urea.
• Did not release sufficient N for optimal vegetative growth and yield.
Preplant Economic Analysis
Assume ESN is $.15 or $.50 more/lb than urea, equal application costs, wheat is $4/bu:
Nrate Urea ESN (.15) (.50)
60 543 584 32 11
120 581 635 36 -6
180 621 650 11 -52
Preplant slow release polymer coated urea does have a place in the furrow irrigated wheat system if reasonably priced.