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

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:

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.

Thank you

for your

interest