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Carver, Brett

Edwards, Jeff

Horn, Gerald

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OKLAHOMA CDDPEFIATIVE £XTENSIDN SERVICE PSS-2157 { Impact of Grazing on Wheat Grain Yield Jeff Edwards Small Grains Extension Brett Carver Wheat Breeding Gerald Horn Beef Cattle Nutrition and Management Background Oklahoma farmers and ranchers have relied on wheat pasture to diversify income, spread risk, and increase profit-ability for more than 1 00 years. Questions regarding the impact of grazing on subsequent wheat grain yield have always been on the minds of producers. OSU research has shown that the effect of grazing on wheat grain yield can be minimized by removing cattle by the first hollow stem stage of growth, and there is a significant wheat grain yield penalty for grazing past this point (OSU Fact Sheet PSS-2147). This leaves the question, however, how much does grazing decrease wheat grain yield when cattle are removed in a timely fashion? To help answer this question the OSU Small Grains Extension Program conducted side-by-side grazed and non-grazed wheat variety trials at the Wheat Pasture Research Unit near Marshall, Oklahoma from 1991 to 2011 (harvest years). All plots were sown at 120 lb/acre using conventional tillage methods. Pre-plant nitrogen fertilizer was applied at quantities necessary to produce 3,000 lb/acre fall forage fol-lowed by 50 bu/ac grain yield. Weed and insect pests were managed according to OSU Extension guidelines. Stocker steers were place on the grazed plots by mid November each year and grazing was terminated by the first hollow stem stage of growth. Non-grazed plots were excluded from the larger research pasture (approx. 20 acres) by electric fence. Research Results From 1991 to 1998 (harvest years) grazed and non-grazed plots were both sown in early September. Data from 1994 - 1996 were removed due to insufficient fall growth to allow grazing by cattle. When grazed and non-grazed plots were both sown in early September, wheat yield reduction from grazing ranged from 2 to 8 bu/ac (Table 1 ). Grazing increased grain yield of early-sown plots by 3 bu/ac in 1992. While not typical, it is not unusual for grazing to increase the grain yield of early-sown wheat. The abundant fall growth associated with early-sown wheat is critical for forage production, but when left ungrazed it also increases crop moisture use, likelihood of insect infestations, and foliar disease incidence and severity. Oklahoma Cooperative Extension Fact Sheets are also available on our website at: http://osufacts.okstate.edu Table 1. Effect of grazing on wheat grain yield when grazed and non-grazed plots were both sown in early September. Year Grazed Non-grazed Difference --------------bu/ac-------------1991 12 14 2 1992 37 34 -3 1993 26 29 3 1997 18 20 2 1998 52 60 8 Average 29 31 2 From 1999 to 2011 we compared dual-purpose and grain-only wheat production systems. In this comparison, dual-purpose plots were sown in early September and grain-only plots were sown in mid October. Wheat grain yield reduction associated with grazing ranged from 4 to 14 bu/ac (Table 2). Similar to the 1991 1998 data, grazing increased grain yield 3 out of 13 years from 1999 to 2011; however, increases in grain yield in the latter comparison were likely the result of insufficient growth in the grain-only plots. Table 2. Effect of grazing on wheat grain yield when dual-purpose and grain-only plots were sown in Sep-tember and October, respectively. Year Dual purpose Grain only Difference --------------bu/ac---------- ---1999 33 43 10 2000 44 42 -2 2001 38 44 6 2002 45 49 4 2003 53 50 -3 2004 39 51 12 2005 16 30 14 2006 22 28 6 2007 16 30 14 2008 54 63 9 2009 8 21 13 2010 44 36 -8 2011 18 29 11 Average 33 40 7 Division of Agricultural Sciences and Natural Resources • Oklahoma State University Implications for Producers The combination of earlier-Septemberplanting and graz-ing by cattle typically reduce the grain yield of dual-purpose wheat. In our studios, grazed wheat yielded approximately 6% loss than non-grazed wheat sown at the same time, and dual-purpose wheat yielded approximately 18% less than grain-only wheat when systems were compared. The differ-ence between these two values (12%) indicates that early sowing accounts for approximately 2/3 of the yield penalty associated with dual-purpose wheat production and grazing accounts for approximately 1/3. This comparison indicates that once a producer has made the decision to sow wheat in early September, much of the yield penalty associated with dual-purpose management has already been incurred. Yield loss from dual-purpose management is not absolute. In our study grazing increased wheat grain yield approximately 20% of the time. Increases in grain yield from grazing are likely in early-sown wheat when grazing reduces water use and foliar diseases of wheat. Similarly, dual-purpose wheat can outperform grain-only wheat when winter conditions prevent adequate tillering of October-sown wheat. Wheat grain yield is only one component influencing the profitability of the dual-purpose wheat production enterprise, and the data presented in this fact sheet are insufficient to make determinations as to the overall profitability of dual-purpose or grain-only production systems. These data do, however, provide guidelines that can be used in budgeting or in determining appropriate wheat pasture rental rates. Cattle graze dual-purpose plots near Marshall, OK. Grain-only plots in the rear were excluded from grazing by electric fence. Oklahoma State University, in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Di.sabilitic.s Act of 1990, and other federal Jaws and regulations, does not discriminate on the basis of race, c.olor, national origin, gender, age, religion, disability, or status as a veteran in any of rts pohc!eS, pract1ces. or procedures. This includes but is not lim1ted to adm1ss1ons, employment, financial ard, and educational services. Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Robert E Whitson, Director of Cooperative Exten-sion ~ervice, Oklahoma State University, Stillwater, Oklahoma. This publication is printed and issued by Oklahoma State University as authorized by the Vice President, Dean, and Director of the Drvision of Agricultural Sciences and Natural Resources and has been prepared and distributed at a cost of 20 cents per copy. 1211 GH. PSS-2157-2 

Impact of grazing on wheat grain yield

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Impact of grazing on wheat grain yield

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