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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)