Published July, 2012 RESEARCH Production and Economics of Grazing Steers on Rye–Annual Ryegrass with Legumes or Fertilized with Nitrogen Twain J. Butler, Jon T. Biermacher, Maru K. Kering, and Sindy M. Interrante* ABSTRACT Cool-season legumes have potential to replace N fertilizer in annual cool-season grass pastures, thus improving returns to producers. The objective of this 3-yr study was to compare the performance and economics of stocker cattle (Bos spp.) grazing rye (Secale cereale L.)– annual ryegrass (Lolium multiflorum Lam.) under two N systems. Paddocks were planted in early September 2008 through 2010 and contained rye–annual ryegrass with 112 kg N ha−1 (fertilized so that a total of soil residual N plus fertilizer N would equal 112 kg N ha−1) (RR-N) or contained a rye–annual ryegrass with annual legume mixture (arrowleaf clover [Trifolium vesiculosum Savi], field pea [Pisum sativum L.], and hairy vetch [Vicia villosa Roth]) (RR-Leg). Steers (307 ± 55 kg initial body weight) were weighed every 28 d and stocking rates were adjusted based on forage mass with put-andtake steers. Forage mass, forage allowance, and stocker average daily gain (ADG) and total gain (TG) were measured every 28 d. Results show similar performance between RR-N and RR-Leg systems in grazing days (average 367 d ha−1), ADG (average 1.065 kg per head d−1), and TG (average 390 kg ha−1). While the 3-yr average total cost associated with the RR-N system (US$569.88 ha−1) was greater than the RR-Leg system ($550.57 ha−1), there were no differences in gross revenue (average $815.91 ha−1) or expected net returns (average $255.68 ha−1) between systems. Annual legumes could be a viable replacement for commercial N fertilizer in rye–annual ryegrass pastures although adoption may be limited due to ease of N fertilizer application. CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401. Received 22 Nov. 2011. *Corresponding author (sminterrante@noble.org). Abbreviations: ADF, acid detergent fiber; ADG, average daily gain; CP, crude protein; DM, dry matter; IVDMD, in vitro dry matter digestibility; LR, likelihood ratio; NDF, neutral detergent fiber; NIRS, near-infrared reflectance spectroscopy; PLS, pure live seed; RR-Leg, rye–annual ryegrass with annual legume mixture; RR-N, rye–annual ryegrass with 112 kg N ha−1; TG, total gain. S tocker cattle producers need a consistent supply of highquality forage to maintain consistent animal production, and commercial N fertilizer has traditionally been used to achieve these forage goals. Historically, stocker cattle producers in the southern Great Plains have relied primarily on cool-season annual forages, typically cereal rye and/or winter wheat (Triticum aestivum L.) sown annually with ryegrass, for grazing from fall to spring (Redmon et al., 1995a; Phillips et al., 1996; Rouquette et al., 1997; Kindiger and Conley, 2002; Butler et al., 2006; Hopkins and Alison, 2006; Ball et al., 2007; Beck et al., 2008). In forageonly and dual-purpose production systems, increasing fall productivity has been identified as a key component of enterprise profitability (Redmon et al., 1995a). Rye included in mixed pasture with ryegrass is reported to increase forage availability in early winter and increase total grazing days (Bagley et al., 1988). Producers in the southern Great Plains may be interested in adopting an annual grazing system that uses cool-season legumes in place of conventional N fertilizer, provided that the expected net returns from such a system are greater than or equal to the net returns currently realized under the conventional annual forage Published in Crop Sci. 52:1931–1939 (2012). doi: 10.2135/cropsci2011.11.0611 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA 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. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. 1931 system. Legumes tend to have a greater concentration of crude protein (CP) than grasses at a similar growth stage, and legume incorporation into grass pastures often improves digestibility of the forage (Sleugh et al., 2000). Redmon et al. (1998) compared the nutritive values and forage yields of winter wheat alone to that of winter wheat interseeded with either hairy vetch or winter pea [Pisum sativum L. subsp. sativum var. arvense (L.) Poir] when all treatments were supplied with 132 kg N ha−1. They reported greater nutritive values with the inclusion of the legumes but found no differences in forage yields between wheat grown alone or grown with the legumes. Inclusion of arrowleaf clover in a rye–ryegrass pasture may extend the grazing season due to its later maturity (Hoveland and Evers, 1995). Arrowleaf clover is well adapted to southeastern Oklahoma (Miller and Wells, 1985; Ball et al., 2007). It is one of the most popular and widely used forage legumes in southeastern Oklahoma, and it is generally used with bermudagrass [Cynodon dactylon (L.) Pers.], tall fescue {Festuca arundinacea Schreb. [syn. Schedonorus arundinaceus (Schreb.) Dumort]}, and small grains for pastures and hay, resulting in high-quality forage for stockers and cow–calf operations (Caddel and Redmon, 1995). Fixed N not used by legumes in legume–grass binary pastures, decomposition of legume tissue and nodules, and recycling of N in urine and dung increases the availability of soil N (Heichel and Henjum, 1991), which can be used by companion grass species. An increase in proximity of legume and grass roots to each other increases the likelihood for N transfer between species to occur (Ta and Faris, 1987; Giambalvo et al., 2011). However, the amount of N transferred from legumes to grasses grown in association has not been easily quantified due to large background fluxes affecting net effect measurements and the fact that excluding one species from the system fundamentally alters the system (Høgh-Jensen, 2006). Pirhofer-Walzl et al. (2012) reported white clover (Trifolium repens L.), red clover (Trifolium pratense L.), and alfalfa (Medicago sativa L.) transferred 9 kg N ha−1 to perennial ryegrass (Lolium perenne L.) and Festulolium (×Festulolium Perun with Lolium multiflorum Lam. and Festuca pratensis Huds. as parents) when grown together in a mixture with no N fertilizer applied. In a grazing study with dairy cows, Ledgard (1991) reported that white clover transferred 54 to 102 kg N ha−1 yr−1 belowground to ryegrass. Elgersma et al. (2000) reported white clover transferred an average of 49.5 kg N ha−1 yr−1 to perennial ryegrass. Dahlin and Stenberg (2010) reported that 15N dilution and direct 15N transfer methods measured an average of 38 and 26 kg N ha−1, respectively, transferred from red clover to perennial ryegrass. However, Morris et al. (1990) reported that in a 2-yr field study, the amount of N transferred from arrowleaf clover to annual ryegrass was less than 5 kg N ha−1 for check treatments receiving no N fertilizer. 1932 Under conventional grass-only pastures, sufficient high-quality forage has been obtained with application of synthetic N fertilizers. Grass production is dependent on N, and high N fertilizer cost is an important factor affecting the profitability of cow–calf and stocker-cattle operations. Therefore, as fuel and N fertilizer prices increase, the economics and sustainability of stocker cattle production systems are of increasing concern. Incorporating legumes into cool-season grass pastures may offer an alternative source of N, thereby reducing production costs and potentially increasing enterprise profits. Despite reports from other parts of the United States, data on a systematic investigation comparing grazed annual cool-season grass systems under conventional N fertilizer to that with forage legumes as the N source in the southern Great Plains is limited. The objective of this study was to compare the agronomic and economic performance of a conventional cereal rye–annual ryegrass with 112 kg N ha−1 (RR-N) to a rye–annual ryegrass with annual legume mixture (RR-Leg) for stocker cattle production in the southern Great Plains. MATERIALS AND METHODS The experiment was conducted over three grazing seasons (2008/2009, 2009/2010, and 2010/2011) at the Samuel Roberts Noble Foundation’s Headquarter Farm located in south central Oklahoma (34°10′ N, 97°10′ W; elevation 266 m). The soil type of the experimental site was a Heiden clay (fi ne, montmorillonitic, thermic Udic Chromusterts) with average pH of 6.7 and organic matter of 34 g kg−1. At the beginning of the study, the average soil P, K, Ca, and Mg were 26, 138, 3207, and 652 mg kg−1, respectively. The experiment was a completely randomized design with three pasture replicates (0.81 ha) of two N treatments. All paddocks were planted annually with a mixture of ‘Maton II’ cereal rye plus ‘Marshall’ annual ryegrass. The N source treatments were (i) conventional N fertilizer (urea-ammonium sulfate blend; 34–0–0) applied at a rate of 58 to 74 kg N ha−1 so that a total of soil residual N plus fertilizer N would equal 112 kg N ha−1 for each paddock before planting in each September (RR-N) and (ii) inclusion of a cool-season forage legume mixture of ‘Apache’ arrowleaf clover, ‘Specter’ and ‘Secada’ field peas (P. sativum L.), and ‘AU Merit’ hairy vetch (RR-Leg). Specter field pea is winter-pea type with excellent freeze tolerance while Secada field pea is a spring-pea type that produces greater biomass in autumn but then winter kills. Broadleaf weeds were controlled the year before initiating the experiment by using 2,4-D [2,4 dichlorophenoxyacetic acid] at a rate of 1.1 kg a.i. ha−1 (Butler et al., 2008) while no herbicides were used during the 3 yr of this study. Paddocks were prepared by chiseling in June, followed by tillage with an offset disk in July, and followed by a tandem disk in August. All paddocks were fertilized with P according to soil test recommendations in September of each year with either triple super phosphate (0–46–0) for the RR-Leg paddocks or diammonium phosphate (18–46–0) in the RR-N paddocks at the rate of 21 kg P ha−1 (47 kg P2O5 ha−1). Paddocks were planted in early WWW.CROPS.ORG CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 September of each year using a no-till drill (Great Plains Mfg., Inc.) equipped with two seed boxes. In the RR-N treatment, rye and annual ryegrass were sown at a rate of 106 and 20 kg pure live seed (PLS) ha−1, respectively. In the RR-Leg treatment, rye, annual ryegrass, field peas, hairy vetch, and arrowleaf clover were sown at a rate of 67, 10, 22, 11, and 4 kg PLS ha−1, respectively. Arrowleaf clover was purchased pre-inoculated while field peas and vetch were inoculated using a vetch and/or pea inoculum (Nitragin C, EMD Crop Bioscience). The larger seeds (rye, peas, and vetch) were mixed together and planted using the grain box while annual ryegrass and arrowleaf clover were planted together using the legume box of the no-till drill. In 2009, paddocks were replanted in early October with rye and annual ryegrass due to stand loss resulting from fall armyworm (Spodoptera frugiperda J.E. Smith) damage. Animal Assignment, Data Collection, and Processing Paddocks were evaluated on 28-d intervals for estimations of forage mass, forage allowance, and average daily gain (ADG) of steers. Forage mass was determined using a double-sampling technique. The indirect estimate of forage mass was the settling height of a 0.1-m 2 aluminum disk meter, and the direct measurement was clipping forage in the same 0.1-m 2 area to a 3-cm stubble. The disk was calibrated monthly by taking direct and indirect measurements at 20 0.1-m 2 sites that represented the range of forage mass on the six experimental units. Clipped forage samples were dried in a forced draft oven set at 50°C to a constant weight for 3 to 4 d and weighed. Before drying, forage samples were separated by hand into species components (rye, annual ryegrass, vetch, peas, and arrowleaf clover). The dry weights of all components were summed to represent forage mass. Prediction equations were developed by regressing actual forage mass on disk height. Separate prediction equations were developed for RR-N and RR-Leg treatments. At each sampling date, 20 disk height measurements were taken at randomly selected locations per paddock. The average height was entered into the calibration equation to predict forage mass. Hand-plucked samples were used to estimate nutritive value of the grazed portion of the canopy. Samples were taken every 28 d at 40 random locations per paddock, and herbage representing the grazed portion of the canopy was removed. Hand-plucked samples were separated by species, dried in a forced draft oven at 50°C for 3 to 4 d, and ground in a Wiley mill (Thomas-Wily Laboratory Mill, Thomas Scientific) to pass a 1-mm screen. Each species was analyzed for CP, acid detergent fiber (ADF), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD) concentrations using the Foss 6500 near-infrared reflectance spectroscopy (NIRS) instrument. The samples were scanned using Foss ISIScan software (Infrasoft, 2003) and prediction equations developed by the NIRS Forage and Feed Testing Consortium (Hillsboro, WI). The NIRS calibration equation parameters (mean, standard error of validation, and r 2) for nutritive values of rye, ryegrass, and legumes are presented in Table 1. These equations were then used to predict CP, ADF, NDF, and IVDMD concentrations for all samples. Each year, grazing was initiated when forage mass was sufficient (>2.0 Mg dry matter [DM] ha−1) and was terminated when forage mass was limiting (<1.0 Mg DM ha−1) or when forage nutritive value was so low as to limit animal gains (Redmon et al., 1995b; Beck et al., 2008). The goals for maintaining sufficient forage mass were to manage pasture quantity and quality to maximize total gain (TG), to avoid forcing the steers to graze low quality forage, and to avoid within-year variation in forage allowance among experimental units. In the 2008/2009 season, grazing was initiated on both rye–annual ryegrass systems on 12 Nov. 2008 and was terminated on 22 Jan. 2009 due to low forage mass. In the 2009/2010 season, grazing was initiated on both rye–annual ryegrass systems on 13 Nov. 2009 and was suspended due to low forage mass on 5 Feb. 2010. Grazing resumed on the RR-N system on 26 Mar. 2010 and on the RR-Leg system on 9 Apr. 2010. Grazing was terminated on both systems on 3 June 2010. In the 2010/2011 season, grazing was initiated on both rye–annual ryegrass systems on 11 Nov. 2010 and was suspended on 6 Jan. 2011 due to low forage mass. Grazing resumed on both systems on 1 Mar. 2011, and was terminated on 12 Apr. 2011. Paddocks were continuously stocked with a variable stocking rate using preconditioned Angus and Angus × Brangus steers (307 ± 55 kg initial body weight) of local origin. Each year, two “tester” steers were randomly assigned to each paddock and grazed the paddock for the duration of the experiment that year. Additional “grazer” steers were added or removed from the paddocks periodically in an attempt to equalize forage allowance across paddocks (Vendramini et al. (2006) and 2007). Steers were weighed every 28 d, and stocking adjustments were made as needed to approximate 1.0 kg forage DM kg−1 steer live weight. Stocking rate ranged from 4.2 to 6.5 animals ha− 1 for the RR-N system and 4.3 to 6.4 animals ha−1 for the RRLeg system. Average daily gain was calculated from the initial and fi nal weights of the tester steers that were measured at 0800 h following a 16-h fast without feed or water. Total gain was calculated by multiplying the ADG of the tester animals by the total number of grazing days for each system. Table 1. Near-infrared reflectance spectroscopy calibration equation parameters for nutritive values of rye, ryegrass, and legumes from the 2008 through 2011 growing seasons in Ardmore, OK. Forage component Rye Ryegrass Legumes † Crude protein Mean SEV† ———— g kg−1 ———— 208 5 208 5 207 6 Acid detergent fiber r2 0.99 0.99 0.96 Mean SEV ———— g kg−1 ———— 257 9 257 9 324 18 Neutral detergent fiber r2 0.97 0.97 0.91 Mean SEV ———— g kg−1 ———— 456 12 456 12 409 18 r2 0.98 0.98 0.95 In vitro dry matter digestibility Mean SEV ———— g kg−1 ———— 891 13 891 13 796 21 r2 0.96 0.96 0.89 SEV, standard error of validation. CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 WWW.CROPS.ORG 1933 Economic Analysis The relative economic value for each forage system was determined by calculating the difference between the expected values for revenues and the costs for each system. Because the goal of the study was to compare the economics of conventional N fertilizer with the inclusion of annual forage legumes as the N source, full detailed enterprise budgets were developed to account for all the costs that differed between the two systems. Costs included tillage and seedbed preparation, seed purchase and planting, fertilizer management, weed management, and interest on operating expenses, including the opportunity cost of owning stocker cattle during the grazing period. Costs for each system were calculated using the 3-yr average quantities of inputs multiplied by expected market prices for the region for each input used by each system. The expected regional market prices of $1.21 kg−1 of actual N (46–0–0) and $3.00 kg−1 of P were used in the study. Seed prices of $0.55, $0.55, $1.72, $5.03, and $7.10 kg−1 PLS for rye, annual ryegrass, peas, vetch, and arrowleaf clover were used, respectively. Regional custom rates for N and P application ($14.81 ha−1) and seedbed preparation operations (chiseling [$26.45 ha−1], offset disk [$28.66 ha−1], cultivating [$24.25], and no-till drilling [$26.45 ha−1]), were used (Doye and Sahs, 2010). An annual interest rate of 7.5% was used to calculate the opportunity cost of capital during the growing season. Value-of-gain was determined using the 2012 futures prices for January and June quoted by the Chicago Board of Trade and adjusted to reflect the Oklahoma City National Stockyard regional price using Beef Basis.com (Crosby et al., 2005). A value of $2.09 kg−1 was used for both rye–annual ryegrass systems to place value on TG produced per hectare by stocker cattle. Sensitivity analysis (Anderson et al., 1977; Biermacher et al., 2009a; Biermacher et al., 2009b) was conducted to determine how robust the results are to changes in the prices of N and legume seed. Statistical Analysis Data on forage mass, forage allowance, and animal performance were subjected to analysis of variance using PROC MIXED (SAS Institute, 2002). Rye–annual ryegrass system, evaluation date, and their interactions were considered fi xed effects while year and replicate were considered random effects. Year was considered a random effect to make inferences across years with variable amounts of precipitation. Significance was determined at p ≤ 0.05. The PDIFF function of the LSMEANS procedure was used to compare means. Differences among rye–annual ryegrass system means were based on F tests. For responses measured multiple times per year, evaluation date was treated as a repeated measure. Value of gain, gross revenue, total cost, and net return for each rye–annual ryegrass forage system were analyzed using random-effects mixed models, with year and replication modeled as random effects, and rye–annual ryegrass system modeled as a fi xed effect (SAS Institute, 2002). The statistical models for the economic variables applied the autoregressive (AR1) spatial power covariance structure to account for temporal autocorrelation in data collected across years. Individual paddocks were used as local subjects within all analyses, as they represented the units in the study that received the specified rye–annual ryegrass 1934 N system over the course of the study. The null hypothesis of no year random effect was tested with the likelihood ratio (LR) test and rejected at p ≤ 0.0001 for all dependant variables analyzed. The LR (λ) is obtained as a ratio of the maximum likelihood value obtained when the mixed model is analyzed with and without the random constraint associated with study site and year. The LR depends on the restricted and unrestricted models and under regularity, the test statistic (−2lnλ) follows a chi-squared distribution with degrees of freedom equal to the number of restrictions imposed (Greene, 2005). RESULTS AND DISCUSSION Weather The total amount and seasonal distribution of precipitation affected the results (forage mass, grazing days, ADG, and TG) of this experiment. The growing season defined as September through May was extremely dry during the 2008/2009 season (Fig. 1), which was 48% below the 30-yr average (740 mm). Season 2009/2010 received 100% of the normal precipitation. Season 2010/2011 was moderately dry and received 27% below the normal 30-yr precipitation. Minimum and maximum monthly temperatures during the growing seasons of all years were consistent with 30-yr average temperatures (data not shown). Seasonal Forage Mass and Allowance There were no N source × evaluation date interactions for forage mass (p = 0.9) or forage allowance (p = 0.6). There was no effect of N source on rye–annual ryegrass system forage mass (p = 0.2; average 1.2 Mg ha−1) or forage allowance (p = 0.9; average 0.7 kg of forage per kg of animal live weight) when measured every 28 d throughout the grazing season over 3 yr. The variation in forage mass at each 28-d period during the study allowed adjustment of stocking rate by removing or adding steers to each grazing system (Redmon et al., 1995b; Beck et al., 2008). There were seasonal differences in forage mass (p < 0.0001) and forage allowance (p < 0.0001). Forage mass and forage allowance were greater early in November (1.9 Mg ha−1 and 1.2 kg kg−1, respectively) and December (2.2 Mg ha−1 and 1.0 kg kg−1, respectively) and gradually decreased as the grazing season progressed through June (0.7 Mg ha−1 and 0.4 kg kg−1, respectively). Steers were removed from the paddocks when forage mass became limiting (<1.0 Mg DM ha−1) or forage quality declined sharply (<120 g CP kg−1) (NRC, 1996; Beck et al., 2008). Although there was no effect on seasonal forage mass, to estimate the contribution of the different species of grasses and legumes to the total forage mass in both rye–ryegrass systems, forage mass values were separated by species, and data was evaluated by month for each system. In the RR-N system, rye and ryegrass tended to contribute equally to forage mass in the autumn through early spring, after which rye made little contribution to the system for the remainder of the grazing season (Fig. WWW.CROPS.ORG CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 Figure 1. Monthly rainfall (mm) for the 2005/2006 to 2009/2010 growing seasons at Ardmore, OK, compared to the 30-yr average. 2A). The grasses and legumes tended to contribute equally to forage mass from 12 November through 7 January (Fig. 2B). As the growing season progressed through the spring, ryegrass and vetch tended to be the greatest contributors to forage mass until 23 April, after which ryegrass contributed more than the other species to total forage mass. Redmon et al. (1998) reported 2-yr average contribution to wheat–legume forage yield during March, April, and May of 46, 35, and 54%, respectively, for hairy vetch and 29, 27, and 40%, respectively, for winter pea. Bagley et al. (1988) reported arrowleaf clover made up 28% of the forage mass in rye–ryegrass–arrowleaf clover pasture in Louisiana averaged across 2 yr from December through May. In the current study, however, arrowleaf clover contribution was only 5% of the forage mass when averaged across 3 yr from 12 November through 3 June, with its greatest numerical contribution of 15% occurring on 23 April (Fig. 2B). While not consistently statistically different, peas tended to contribute more numerically to total forage mass in the autumn than vetch while vetch was a greater numerical contributor than peas in the spring. Based on visual observations in the field, cattle appeared to avoid grazing peas in the autumn and vetch until late in the spring. Forage Nutritive Value To evaluate the nutritive values of the different species of grasses and legumes in both rye–ryegrass systems, chemical composition measurements were separated by species and data was evaluated by month for each system in a manner similar to the contribution of the different species CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 of grasses and legumes to the total forage mass. Rye and ryegrass in both systems generally had similar nutritive values (p > 0.05) for most of the grazing season, with the exception of late spring when rye was fully matured and of poorer nutritive value than ryegrass (Table 2). In most cases, the legumes had greater nutritive than the grasses (p < 0.05). Forage nutritive value of both rye–ryegrass systems tended to be greater early in the grazing season and after paddocks were rested (1 March) and decreased over time. In general, CP and IVDMD concentrations tended to decline and ADF and NDF concentrations tended to increase with time due to plant maturation (Beck et al., 2008). When averaged across all years and evaluation dates, the legumes generally had greater nutritive values than the grasses (Table 2). In the RR-N system, nutritive value between rye and ryegrass was similar with the exception of greater NDF associated with rye than ryegrass. Although varying over time, CP and IVDMD concentrations were adequate (~120 g CP kg−1and ~700 g IVDMD kg−1) on most evaluation dates for steers to gain weight until the end of May or early June (NRC, 1996; Beck et al., 2008). Animal Performance Steer ADG varied during the grazing season (p < 0.0001), with lesser ADG occurring at the end of the grazing season (Fig. 2A and B). This reduction of animal performance was probably the result of reduced forage allowance and declining forage nutritive value as rye and ryegrass went from vegetative to reproductive growth stage as well as increasing ambient temperatures from autumn through late WWW.CROPS.ORG 1935 A B Figure 2. Species composition of rye–annual ryegrass–N (A) and rye–annual ryegrass–legume (B) at monthly evaluation dates across 3 yr and three replicates (n = 9). Average daily gain (ADG) on rye–annual ryegrass treatments at monthly evaluation dates across two N systems, 3 yr, and three replicates (n = 18) for the 2008 through 2011 growing seasons in Ardmore, OK. †Forage mass means followed by the same letter within month do not differ by the LSMEANS test (p > 0.05) (SAS Institute, 2002). spring. When pooled across 3 yr, ADG was similar (p = 0.9) between the RR-N (1.06 kg d−1) and RR-Leg (1.07 kg d−1) systems (Table 3), which is similar to reports of others. Islam et al. (2011) reported the ADG of rye–ryegrass fertilized with 112 kg N ha−1 averaged 1.05 kg d−1 in a 5-yr study. Beck et al. (2005) reported in a 3-yr study (1999–2002) that steers grazing winter wheat–cereal rye and annual ryegrass had a mean ADG of 1.18 and 1.07 kg d−1 during the fall and winter, respectively. In another study from 2003 to 2006 in Arkansas by Beck et al. (2008), mean ADG of steers grazing a mixture of winter wheat–cereal rye versus monoculture annual ryegrass during the fall and spring grazing was 0.88 and 0.84 kg d−1, respectively. Bagley et al. (1988) reported 1936 greater steer ADG on ryegrass–arrowleaf clover pastures (1.0 kg d−1) than on ryegrass fertilized with 34 kg N ha−1 (0.9 kg d−1) in Louisiana over 4 yr although the difference was only 0.1 kg d−1. Total gain did not differ (p = 0.3) between the RR-N (407 kg ha−1) and RR-Leg (373 kg ha−1) systems (Table 3), which is similar to other research. Islam et al. (2011) reported that rye–ryegrass TG averaged 491 kg ha−1 but ranged from 130 to 844 kg ha−1 depending on the year and amount of precipitation. In Louisiana over 4 yr, Bagley et al. (1988) reported no difference in TG on steers grazing ryegrass–arrowleaf clover pastures (582 kg ha−1) and those grazing ryegrass fertilized with 34 kg N ha−1 (522 kg ha−1). WWW.CROPS.ORG CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 Table 2. Chemical composition of forage samples collected at monthly evaluation dates across 3 yr and three replicates (n = 9) for the 2008 through 11 growing seasons in Ardmore, OK. Grazing system Rye–ryegrass–legume Component † CP conc. ‡ ADF conc. § Rye–ryegrass–N ¶ NDF conc. IVDMD conc. CP conc. −1 Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch Arrowleaf clover Peas Rye Ryegrass Vetch † ———————————————————————————————————— g kg 12 Nov. 310 a# 153 ab 181 c 871 d 238 b 192 ab 269 b 920 c 298 a 134 b 308 ab 976 a 257 b 197 a 325 a 959 ab 297 a 145 ab 174 c 938 bc 10 Dec. 255 a 176 bc 227 c 863 d 226 b 200 ab 288 b 880 cd 219 bc 182 b 362 a 954 a 189 c 220 a 347 a 911 bc 277 a 156 c 206 c 914 b 7 Jan. 252 a 193 ab 215 c 868 bc 213 b 238 a 334 b 840 c 214 b 196 ab 391 a 920 a 183 c 206 ab 365 ab 911 a 250 a 182 b 246 c 886 ab 29 Jan. – – – – 177 c 325 a 444 a 755 b 189 bc 245 ab 440 a 863 a 232 ab 249 ab 442 a 886 a 254 a 189 b 237 b 886 a 1 Mar. 308 ab 172 abc 183 b 870 c 321 ab 145 c 197 b 937 ab 312 ab 186 a 370 a 947 a 293 b 183 ab 375 a 915 b 349 a 154 bc 171 b 930 ab 2 Apr. 265 a 222 ab 268 c 816 c 260 a 184 b 261 c 892 a 189 b 257 a 472 a 846 bc 215 b 222 ab 394 b 893 a 291 a 196 b 251 c 866 ab 23 Apr. 250 a 222 b 276 b 795 a 229 a 200 b 296 b 853 a 142 b 304 a 540 a 760 a 135 b 295 a 500 a 789 a 231 a 254 ab 323 b 813 a 21 May 196 a 283 c 360 c 746 a – – – – 48 c 446 a 738 a 534 b 96 b 355 b 584 b 713 a 191 a 300 c 363 c 761 a 3 June 140 a 359 b 435 c 677 a – – – – 51 b 454 a 750 a 536 b 78 b 430 a 652 b 662 a 142 a 427 ab 514 c 593 ab Mean 249 ab 215 bc 260 cd 822 b 232 b 214 bc 302 c 868 a 191 c 251 a 464 a 841 ab 191 c 247 ab 418 b 868 a 264 a 197 c 251 d 871 a NDF conc. IVDMD conc. ———————————————————————————————————— – – 313 a 267 b – – – 168 a 198 a – – – 370 a 352 a – – – 952 a 938 a – – – 223 a 209 a – – – 180 a 190 a – – – 371 a 335 a – – – 951 a 936 a – – – 194 a 181 a – – – 198 a 211 a – – – 407 a 387 a – – – 918 a 894 a – – – 252 a 254 a – – – 198 a 188 a – – – 406 a 378 a – – – 931 a 913 a – – – 302 a 341 a – – – 198 a 151 a – – – 386 a 342 a – – – 940 a 936 a – – – 164 b 236 a – – – 270 a 230 a – – – 514 a 400 a – – – 826 a 883 a – – – 131 a 138 a – – – 330 a 272 b – – – 595 a 461 b – – – 731 a 817 a – – – 63 b 140 a – – – 414 a 305 b – – – 712 a 533 b – – – 566 b 776 a – – – 61 b 117 a – – – 429 a 371 b – – – 728 a 601 b – – – 552 b 718 a – – – 205 a 214 a – – – 234 a 223 a – – – 455 a 398 b – – – 868 a 887 a – CP, crude protein. ‡ ADF, acid detergent fiber. § NDF, neutral detergent fiber. ¶ # ADF conc. IVDMD, in vitro dry matter digestibility. Means within evaluation date and column followed by the same letter do not differ by the LSMEANS test (p > 0.05) (SAS Institute, 2002). CROP SCIENCE, VOL. 52, JULY– AUGUST 2012 WWW.CROPS.ORG 1937 Table 3. Expected values for costs of inputs, value of gain, total cost, animal response (grazing days, average daily gain, and total gain), gross revenue, and net return to land, labor, and management by grazing system. Grazing system Economic variable Seedbed preparation, $ ha−1 Establishment cost, $ ha−1 Nitrogen fertilizer cost, $ ha−1 Phosphorus fertilizer cost, $ ha−1 Pest management, $ ha−1 Interest on operating capital, $ ha−1 Total cost, $ ha−1 Average initial grazing date Average termination date Steer grazing days, d ha−1 Average daily gain, kg per head d−1 Total gain, kg ha−1 Value of gain, $ kg−1 Gross revenue, $ ha−1 Expected net return, $ ha−1 Rye– Rye– ryegrass– ryegrass– N legumes p value 88.89 152.72 97.04 63.70 16.35 151.21 569.88 15 Nov 30 Mar 384 1.06 407 88.89 235.36 – 63.70 16.35 145.68 550.57 15 Nov 30 Mar 349 1.07 373 0.2 0.9 0.3 2.09 851.46 281.58 2.09 780.35 229.78 0.3 0.4 0.02 Grazing Days The number of grazing days did not differ (p = 0.2) between the RR-N (384 d ha−1) and RR-Leg (349 d ha−1) systems (Table 3). Islam et al. (2011) reported that the number of grazing days for rye–ryegrass fertilized with 112 kg N ha−1 averaged 448 d ha−1 but ranged from 161 to 734 d ha−1 depending on the year and amount of precipitation. However, Bagley et al. (1988) reported that steers grazed ryegrass–arrowleaf clover pastures in Louisiana more days than ryegrass plus N over 4 yr, although this difference was based on only one additional day of grazing (149 and 148 d, respectively). Based on this data, the legume system appears to have potential as an alternative to N fertilizer. Economics Estimates of average production costs, gross revenue, and net return to land, labor, overhead, and management are reported in Table 3. In this 3-yr study, total annual cost was greater (p = 0.02) for the RR-N system than for the RR-Leg system ($569.88 and $550.57 ha−1, respectively). However, gross revenue and expected net returns did not differ (p = 0.3 and p = 0.4, respectively) between the RR-N ($851.46 and $281.58 ha−1, respectively) and RR-Leg ($780.35 and $229.78 ha−1, respectively) systems. Islam et al. (2011) reported that rye–ryegrass fertilized with 112 kg N ha−1 had a net return of $278.59 ha−1, which is very similar to these findings. Bagley et al. (1988) reported that, when the cost of N fertilizer was equal to the cost of arrowleaf clover seed, there was no difference in cost of gain over 4 yr in Louisiana between ryegrass–arrowleaf and ryegrass plus N fertilizer ($0.15 and $0.16 kg−1, respectively), although their cost of gain 1938 did not include ownership costs of the animals. Sensitivity analysis revealed that the net return for the two systems would be equal when the price of N reached $1.90 kg−1. If the price of N is held at $1.21 kg−1, the prices of vetch, peas, and arrowleaf clover would have to decline by 40% in order for the profit of the RR-Leg system to equal that of the RR-N system. Because arrowleaf did not contribute a significant amount to biomass, sensitivity analysis was run excluding the arrowleaf clover seed cost, and it was determined that expected net returns ($262.56 ha−1) still did not differ from the RR-N system ($281.58 ha−1) CONCLUSIONS This paper summarized 3 yr of data comparing the production and economics of beef steers grazing rye–annual ryegrass fertilized with 112 kg N ha−1 to rye–annual ryegrass planted with annual legumes (peas, vetch, and arrowleaf clover). The legume and N treatments within the rye– annual ryegrass systems did not differ in forage mass, forage allowance, ADG, TG, or expected net returns. 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