A Web-Based Calculator for Estimating the Profit Potential of Grain Segregation by Protein Concentration

Published in Agron. J. 105:721–726 (2013) doi:10.2134/agronj2012.0353 Available freely online through the author-supported open access option. Copyright © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. G protein concentration (GPC) is an important non-grade-determining factor that influences the U.S. dollar value of the dark northern spring (DNS) subclass of hard red spring wheat (Triticum aestivum L.). Prices are quoted at Portland, OR, in relation to a standard grade, which is no. 1 DNS wheat at a GPC of 140 g kg–1. Typically, a bonus, or premium, is added to the price of wheat for each 2.5 g kg–1 change in GPC above this standard, whereas a discount is subtracted from the price for each 2.5 g kg–1 in protein below this standard. Discounts are weighted more than premiums. For example, in 2012, premiums were US$14.70 to US$29.40 Mg–1 above 140 g kg–1 GPC, whereas discounts were US$36.75 Mg–1 below 140 g kg–1 (December 2012 average cash grain bids for DNS wheat, Pacific Northwest Grain Market News, search.ams.usda.gov/mndms/2013/01/ LS20130111WPNWGRAIN.PDF). Many studies have shown that farm fields are spatially variable in GPC due to differences in environmental conditions including soil fertility (Reyns et al., 2000; Delin, 2004), topography (Fiez et al., 1994), plant-available water (Stewart et al., 2002), and the previous year’s cropping inputs (Fiez et al., 1994; Long et al., 2008). In practice, because of time constraints and the assumption that the wheat is homogenous, growers tend to bin the grain together that is produced in a farm field. By mixing the grain together, conventional harvesting systems diminish the ability of growers to capture premiums for high-quality grain found within fields. Grain segregation by protein content has been proposed to maximize revenues in markets that offer protein premiums (Stafford, 1999; Thylén and Rosenqvist, 2003; Meyer-Aurich et al., 2008). Segregation can be accomplished on the farm by harvesting different zones of grain quality within a field and delivering the grain from each zone separately to the elevator (Tozer and Isbister, 2007). It can also be achieved by sampling each hauling vehicle for GPC at the elevator and using this information to segregate the grain into different batches (Herrman et al., 2002). The first approach requires prior knowledge of harvesting zones, grain quality and yield differences between zones, and price schedules to ascertain whether grain segregation would be profitable. The second approach usually requires the GPC and yield for different fields within a harvesting region as needed to plan the organization of grain segregation in anticipation of buyer specifications for grain with a specific protein content (Le Bail and Markowski, 2004). A third possibility is the use of near-infrared (NIR) spectroscopic techniques pioneered by Norris (1964). Optical NIR sensors have been implemented for combine harvesters to map GPC within farm fields (Stafford, 2000). These “in-line” systems have the ability to rapidly and accurately measure GPC in a process stream during harvest. On-combine accuracies have been reported to be within 5.7 g kg–1 GPC for winter wheat (Maertens et al., 2004), 6.6 g kg–1 GPC for DNS wheat (Long and Rosenthal, 2005), 3.1 g kg–1 GPC for soft white winter wheat (Long et al., 2008), and 4.5 g kg–1 for Australian hard spring wheat (Whelan et al., 2009). ABSTRACT