Corn & Small Grain Management

Wheat Nitrogen Algorithm Development

Components of the algorithm

Equations for the Virginia Tech Wheat Algorithm

 

The Virginia Tech wheat algorithm uses an exponential equation for Yield Potential, b but includes a minimum ref area value, and adds GS 25 N: a rate application offset term.

www.grains.cses.vt.edu/wheat_algorithm.htm

VA Wheat Soft Red Winter

(1) Maximum Yield Potential. Not environmental potential, but realistic for a whole-field yield

(2) Response Index
NDVI_Hi = Peak of Reference Strip (Best Spot)
NDVI_Lo = Low point of field (Poor Spot)

(3) Yield Potential without additional N

(4) Conditional: computed value up to the MaxYield value.

(5) Qty of Nitrogen to apply [kg].

A value is entered also as a maximum cap Assumes 134 kg/ha (120 lb/ac) max N need in Spring less GS 25 application rate

(6) Rate of N applied in first Spring top-dress application (Growth Stage 25). (This controls the minimum N rate to be prescribed by the algorithm)

 

k a

function multiplier

YP0 eq: Crop Algorithm specific

k b

Exponent multiplier

YP0 eq: Crop Algorithm specific

k c

additive factor

YP0 eq: Crop Algorithm specific

GS_25N

 

Rate of N applied in first Spring top-dress application (Growth Stage 25). (This controls the minimum N rate to be prescribed by the algorithm)