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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #306551
Title: Net returns from terrain-based variable-rate nitrogen management on dryland spring wheat in northern Montana

Author
item Long, Daniel
item WHITMUS, J - Montana State University
item ENGEL, RICHARD - Montana State University
item BRESTER, GARY - Montana State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2015
Publication Date: 4/6/2015
Publication URL: http://handle.nal.usda.gov/10113/6472245
Citation: Long, D.S., Whitmus, J.D., Engel, R., Brester, G.W. 2015. Net returns from terrain-based variable-rate nitrogen management on dryland spring wheat in northern Montana. Agronomy Journal. 107:1055-1067.

Interpretive Summary: Agricultural producers can use variable-rate application technology to vary the rate of nitrogen (N) fertilizer within farm fields. This study was conducted to determine if profit opportunities exist when switching from conventional uniform N application to variable rate N application. Eight experiments were undertaken within farm fields in northern Montana that relied upon field-size N strips and production-scale equipment. An economic analysis was conducted which focused on only those cost and revenue items that change when adopting a new practice. Variable rate nitrogen application was not more profitable than conventional uniform rate nitrogen application in semiarid northern Montana without dollars from federal natural resources conservation programs. The reasons can be traced to modest yields, low response to nitrogen fertilizer, and the inability to define optimum nitrogen rates.

Technical Abstract: Agricultural producers can use variable-rate application technology to vary nitrogen (N) fertilizer within fields. This study was conducted to estimate changes in net returns from implementation of variable-rate N management (VNM) on hard red spring wheat (Triticum aestivum L.). Net return from uniform N management (UNM) traditionally used by producers was compared with that from VNM in eight dryland fields between 1994 and 2004 in northern Montana. Field experiments consisted of a replicated series of four to six N rates applied within strips oriented with the length of each field. Management zones (MZ) were created by dividing fields into upper slopes, south facing middle slopes, north facing middle slopes, and lower slopes. Nitrogen recommendations for management zones were based on soil N testing and expected yields. Grain yield data were obtained using a production-size combine equipped with a yield monitor. Mean grain protein and yield were similar between VNM and UNM. Yield differences were <223 kg ha-1 and averaged only 18 kg ha-1. Grain yield did not differ significantly among N rates within MZ. Net returns from VNM were up to $27.97 ha-1 less than that from UNM in seven of the eight sites, but were profitable if Environmental Quality Incentive Program payments of $34.57 ha-1 were considered as part of net income. Little evidence existed that VNM based on constructed MZ and predetermined N recommendations improves grain yields and profits, or reduces N use in water limited, summer-fallow systems of northern Montana.