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
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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.
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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
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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
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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.
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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
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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).
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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
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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. Based on
the results of this study, it appears that at current prices the
annual legumes are a viable substitution or replacement to
commercial N fertilizer in rye–annual ryegrass pastures in
the southern Great Plains and could be of great economic
value if N fertilizer prices rise to exorbitant levels. However, when expected net returns are similar, N fertilizer
application will most likely remain the preferred method
for producers due to greater management efforts associated
with legumes and lack of predictability of legume production. The price of N relative to the price of legume seed
will also affect adoption of this system.
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