Slow Release Nitrogen for Furrow Irrigated Wheat Brad Brown Extension 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 application Spread out the workload Cheaper N

Late winter top-dressed urea is more effective than early fall preplant incorporated urea in 2 out of 3 years: N ImmobilizationDenitrification LeachingVolatilization from plant Excessive vegetative growth Phytotoxicity

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 compaction NH 3 volatilization Phytotoxicity of high N rates Higher 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

Objective : To evaluate preplant slow release polymer-coated urea N for furrow irrigated SWW wheat

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: NrateUreaESN(.15)(.50)

Preplant slow release polymer coated urea does have a place in the furrow irrigated wheat system if reasonably priced.

Thank you for your interest