Published in Agron J 99:1238-1244 (2007)
DOI: 10.2134/agronj2006.0315
© 2007 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
Peanut
Rotational Effects in Oklahoma Peanut Production
Prospects for Peanut Rotations in the Post-Quota Era
Chad B. Godseya,*,
Jeffrey Vitaleb,
John P. Damiconec,
James R. Sholara,
Jerald Nickelsa and
Jerry Bakerd
a Dep. of Plant and Soil Sciences, Oklahoma State Univ., Stillwater, OK 74078
b Dep. of Agricultural Economics, Oklahoma State Univ., Stillwater, OK 74078
c Dep. of Entomology and Plant Pathology, Oklahoma State Univ., Stillwater, OK 74078
d The Samuel Roberts Noble Foundation, 2510 Sam Noble Pkwy., Ardmore, OK 73402
* Corresponding author (chad.godsey{at}okstate.edu)
Received for publication November 8, 2006.
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ABSTRACT
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The Farm Security and Rural Investment Act of 2002 greatly impacted the southwest (SW) peanut (Arachis hypogaea) growing region. Due to decreased market prices, peanut has lost favor in crop rotations to other crops such as cotton (Gossypium hirsutum L.). Before 2002, a 12-yr peanut rotation study was conducted in Oklahoma to investigate the agronomic benefits and economics of rotating peanut with corn (Zea mays L.), cotton, and grain sorghum [Sorghum bicolor (L.) Moench]. Eight rotations were evaluated in 2- and 3-yr intervals. Incidence of disease, yield, and economic profit were evaluated each year. Twelve years of data indicated rotating peanut every third year with either corn or cotton increased peanut pod yield by 520 and 490 kg ha–1, respectively, compared with the continuous peanut rotation. Two-year rotations of peanut with corn, cotton, or sorghum performed no better than the peanut monoculture. Economic analysis indicates that, even with the removal of the peanut quota system in 2000 and a 50% reduction in peanut prices, the peanut monoculture would still remain the most profitable choice for farmers, generating economic returns of $411 ha–1, but would not be recommended due to increase in disease pressure. Recent increases in cotton yield indicate that a peanut-cotton rotation is the best rotation for southwest producers.
Abbreviations: SW, southwest
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INTRODUCTION
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THE SW PEANUT GROWING REGION (Oklahoma, Texas, and New Mexico) has been significantly impacted by recent legislation that ended the peanut quota system. The Farm Security and Rural Investment Act of 2002 (i.e., the 2002 farm bill) replaced the peanut quota system with a more traditional commodity program similar to corn and wheat (Triticum aestivum L.), which provides only limited price support to peanut producers' (Dohlman et al., 2004). Since the 2002 farm bill was introduced peanut prices paid to producers in the SW have fallen by 39%, from an average of $609 Mg–1 during the 1990s to $364 Mg–1 in 2005 (NASS, 2005). Peanut producers in the SW growing region have responded to the lower peanut prices by shifting out of peanut production (McCorvey et al., 2005). Peanut acreage in the SW growing region has declined by 40% following the 2002 farm bill, from 1,302,200 ha in 2001 to 788,000 ha in 2005, and its share of U.S. peanut production has fallen from 32.5 to 22.3% during that same period (NASS, 2005). Oklahoma peanut producers have been particularly hard hit. Over the past 5 yr peanut acreage has fallen by nearly two-thirds, from 36,450 ha in 2002 to 12,960 ha in 2005 (NASS, 2005).
Economic conditions for peanut producers in the SW were much better under the peanut quota system (Devkota, 2006). Peanut marketed on the quota system held a dominant economic position in the SW region, providing greater returns than alternative crops such as corn, cotton, and grain sorghum. The lucrative nature of the peanut quotas encouraged and enabled producers to specialize in peanut (Katsvairo et al., 2006). Among many peanut producers in the SW region, a peanut monoculture was a common cropping practice (Russo, 2004). The monoculture was a result of the favorable economic returns from the peanut quota system and the lagging profitability of other crops in the region such as cotton and corn.
The increased incidence of foliar and soilborne diseases in monoculture peanut practices are well documented in the literature (Melouk and Backman, 1995; Johnson et al., 1999; Jordan et al., 2002). Peanut is susceptible to various pathogens with fungal diseases causing the most wide-spread damage (Chenault et al., 2005). Fungicides are commonly used to protect peanut plants from fungal diseases but are only partially effective, especially in a monoculture environment (Melouk and Backman, 1995). During the past decade there has been a growing awareness that fungicides are insufficient to adequately protect peanut plants over the long term (Johnson et al., 2001). For this reason, crop rotation is recommended to reduce the buildup up of diseases and prevent disease from becoming a problem in peanut production fields (Cox and Sholar, 1995; Sholar et al., 1995). Jordan et al. (2002) in North Carolina observed a decrease in peanut pod yield due to significant buildup of Cylindrocladium black rot (caused by Cylindrocladium parasiticum Crous, M.J. Wingfield, & Alfenas) under a peanut monoculture. In plots where peanut was rotated with corn or cotton in two year rotations, peanut yields were increased by a minimum of 700 kg ha–1 compared with a peanut monoculture.
Rotating peanut with other crops has been found to increase peanut yield (Jordan et al., 2002; Cox and Sholar, 1995; Sholar et al., 1995). The cause of the yield increase resulting from crop rotation is a combination of several agronomic factors including breaking weed, pest, and disease cycles (Ayers et al., 1989). Cox and Sholar (1995) stated that peanut yields could be increased by 30% using a 3 yr rotation that planted peanut once every 3 yr.
Profitability is the primary factor used by producers in selecting a crop portfolio (Tanaka et al., 2002). While rotating peanut with other crops can generate benefits from the rotation effect, the opportunity cost associated with introducing alternative crops into the peanut rotation often exceeds those benefits. Under the quota system there was a high opportunity cost of introducing alternative crops such as corn, cotton, or grain sorghum into the peanut rotation. Peanuts sold under the quota system maintained a significant economic advantage over the other crops. Cotton production, moreover, waned in the 1980s and 1990s as the boll weevil and other pests wreaked havoc on cotton fields throughout the SW region (J.C. Banks, 2006, personal communication). The introduction of Bt cotton in 1996 and a successful boll weevil eradication program, which began in 1999, has increased Oklahoma cotton yields by 15% since the beginning of the eradication program (Gianessi et al., 2002; NASS 2005).
This research documents the results of a long-term peanut rotation study in Love County, Oklahoma. Specifically, this research had the following objectives: (i) determine the effects of crop rotation on peanut pod yield in the southwest peanut growing region, and (ii) evaluate the current economic performance of each peanut based crop rotation in the post-quota era.
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MATERIALS AND METHODS
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A long-term rotation study was established in 1990 and ended in the fall of 2001 at the Noble Research Foundation's Red River Farm in Love County, Oklahoma. Soil type at this site was a Minco fine sandy loam (coarse-silty, mixed, superactive, thermic Udic Haplustolls), which is a common soil in that area for peanut production. The study area had not been planted to peanuts in the previous 14 yr.
Experimental design was a randomized complete block design with four replications. Individual plots were 18.2 by 18.2 m. Eight rotations were evaluated and consisted of continuous peanut (PN), peanut-corn (PN-CR), peanut-corn-corn (PN-CR-CR), peanut-peanut-corn (PN-PN-CR), peanut-cotton (PN-CT), peanut-cotton-cotton (PN-CT-CT), peanut 7 out of 12 yr (rotated with corn 4 times and cotton 1 time), and peanut grain sorghum (PN-SO) (Table 1). Years when peanut was included in the rotation, peanut plots were split. Half of the plot was planted to Spanco (Kirby et al., 1989), a Spanish market type cultivar, and the other half of the plot was planted with Okrun (Banks et al., 1989), a runner market type cultivar. Two different market types of cultivars were selected because of differences in disease resistances and potential differences in pod yield for the region (Godsey et al., 2007). Each year the peanut plots were re-randomized as to which side of the plot was planted to Okrun and which side was planted to Spanco.
Planting rate for both cultivars of peanut was 160,500 seeds ha–1 and row width was 91 cm. Corn was planted at a density of 74,000 seeds ha–1 in 76-cm rows. Grain sorghum was planted at 185,000 seeds ha–1 in 76-cm rows. Cotton was planted at a density of 86,500 seeds ha–1 in 102-cm rows. All plots were conventionally tilled, which typically included one cultivation with a disc that mixed the surface 10 to 15 cm of soil and one or two passes with a field cultivator that disturbed the surface 7.5 cm of soil before planting. Less than 15% of the soil surface was covered with residue at planting in all plots. A preemergence herbicide was used for all crops and postemergence herbicides were used as needed to control weeds in plots. Irrigations were based on water demands of peanut plots which would have been similar to the other crops (Oklahoma Mesonet, 2007). Visual water stress was minimal for all crops during the growing season.
Fungicide treatments for peanut plots were applied by recommended calendar dates. Chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile, Bravo WeatherStik, Syngenta Crop Protection, Greensboro, NC) was applied alone until 1995 at a rate of 1.26 kg chlorothalonil ha–1 for each application. After 1995, peanut plots were split and half of the Okrun and Spanco plots received either chlorothalonil or tebuconazole {alpha-[2-(4-chlorophenyl)ethyl]-alpha-(1,1-dimethylethyl)-1H-,2,4-triazole-1-ethanol} (Folicur, Bayer CropScience LP, Research Triangle Park, NC) applied at a rate of 0.20 kg tebuconazole ha–1 for each application. After 1995, chlorothalonil based treatments consisted of six applications of chlorothalonil, while Tebuconazole-based treatments consisted of four applications of tebuconazole along with two applications of chlorothalonil. Four rows of each peanut cultivar received chlorothalonil or tebuconazole in each subplot. That left two rows that did not receive any fungicide treatment and were visually rated for disease incidence just before harvest each year. Visual ratings were taken on each individual plot and rated as percentage of the plants/leaves that were affected by Sclerotium rolfsii (southern blight), Rhizoctonia solani (Limb rot), and Sclerotium minor (Sclerotinia blight).
Economic and Statistical Analysis
The peanut rotation data were analyzed using the SAS (SAS Institute, 1998) statistical software package. An ANOVA model of peanut yield was constructed using the PROC MIXED routine. The ANOVA model used crop rotation length, crop rotation (i.e., the crop rotated with peanut), and peanut cultivar as classification factors. The experiment year variable was used as a repeated factor in the model and the four replication plots were included in the model as a random factor. Year was treated as a repeated measure since measurements were taken for yield and disease ratings each year of the study from the same area. The crop rotation length factor included three levels to represent the 2-yr, 3-yr, and continuous cropping systems that were in the study.
The economic returns for the crop rotations were calculated on an average per hectare basis. To compare rotations of differing lengths, the concept of a rotation hectare was used. A rotation hectare considers the proportion of time that each crop is produced in the cropping sequence and assigns the hectare accordingly. Income, variable, and fixed costs are all weighted based on this proportion. For instance, a rotation hectare of PN-PN-CR would contain two-thirds of the income and costs from the peanut enterprise budget and one-third of the income and costs from the corn enterprise budget. The ANOVA model described previously estimated the average yields that were observed over the life of each rotation. For instance, in the PN-PN-CR rotation the ANOVA model estimated average peanut yields in both the first and second years of the rotation, and in the third year for corn. Each rotation was repeated at least four times during the 12-yr study, which provided a sufficient number of rotation cycles for the ANOVA model to fit the data. Because economic conditions have changed significantly since the study was completed, the economic returns were calculated using current prices to reflect changes in the peanut marketing system. Expected prices for each of the crops included in the study were obtained by averaging prices over the past 3 yr, 2003 to 2005. The 3-yr average peanut price was obtained from the Oklahoma Peanut producer association and was found to be $385 Mg–1, about $27 Mg–1 above the loan deficiency payment (L. Vance, 2006, personal communication). Cotton, corn, and grain sorghum prices were obtained from the OSU farm budget survey system, and were found to be $1.16 kg–1, $0.079 kg–1, and $0.081 kg–1, respectively. Average yields for the alternative rotation crops were found to be 1290 kg ha–1 for cotton, 7250 kg ha–1 for corn, and 5100 kg ha–1 for grain sorghum.
Crop enterprise production costs were developed from the management practices employed in the Red River Farm long-term peanut rotation field study. Input levels on seeding, fertilizer, herbicide, fungicide, and insecticide treatments were held fixed throughout the study in each of the crop rotations. Operating and fixed costs, such as machinery and labor, were obtained from the OSU Farm Budget Service to reflect actual farm conditions in the peanut growing region (Doye et al., 2004). The variable and fixed production costs were updated to 2006 price levels. Unpaid labor expenses and management were not factored into the crop enterprise budget costs.
Break-even price analysis was conducted to determine the range of price combinations that would create equal returns between the peanut monoculture and a rotation. The economic returns were also subjected to sensitivity analysis, which accounted for the low levels of peanut disease pressure found during the study and for recent changes in cotton production. Cotton is now a more productive and profitable crop in the southwest peanut growing region than it was during the peanut rotation study. The introduction of Bt cotton and the eradication of the boll weevil have pushed up cotton yields by 34%, from 860 to 1100 kg ha–1, since the end of the peanut rotation study in 2001 (J.C. Banks, 2006, personal communication). The peanut study was conducted under conditions of low to moderate disease pressure (discussed above), but in areas where disease pressure, particularly S. minor were present, peanut production costs were $179 ha–1 higher (Doye et al., 2004). This raises peanut production costs from $1156 to $1335 ha–1. The higher cotton yields and peanut production costs were factored into the economic returns in the sensitivity analysis.
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RESULTS AND DISCUSSION
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Peanut Yield
A significant crop rotation main effect was observed when averaging peanut yield for all of the years when peanut was included in a rotation (P > t = 0.01). In general, peanut pod yield increased as the time span between peanut crops in a rotation increased (Table 2). Higher peanut yields were observed with 3-yr rotations compared with the PN monoculture over the 12-yr period. When PN-CR-CR and PN-CT-CT were compared with the PN system, peanut yield was increased by 520 and 490 kg ha–1. Peanut yields for 2-yr rotations were similar to the PN system. One unexplainable observation was the PN-PN-CR rotation, which had similar peanut yield compared with the 3-yr rotations that included peanut only once in the rotation. No crop rotation x peanut variety interaction was detected, nor did the two peanut cultivars tested yield differently (data not shown).
When considering individual years when peanut occurred in every rotation, a significant crop rotation main effect was observed in 1995 but not in 2001 (Table 2). Trends in peanut yield were similar to the 12-yr average; the 3-yr rotation had higher yields compared with 2-yr rotation and the PN monoculture.
Increase in peanut yield observed in this study was similar to results reported by Jordan et al. (2002). They found that including corn or cotton in a rotation with peanut significantly increased peanut yield compared with a monoculture peanut system.
Soilborne Disease and Fungicide Effects
Overall, minimal soilborne disease was observed for the duration of the experiment. This was probably a result of no peanut crop being grown at this site 14 yr before when the study was established in 1990. Even though disease pressure was not extreme, a significant main effect for foliar treatment was detected when yields were averaged from 1995 to 2001 (P > F = 0.01). Four applications of tebuconazole along with two applications of chlorothalonil increased pod yield by 410 kg ha–1 compared with six applications of chlorothalonil alone when averaged across year and crop rotation. Increase in yield from application of tebuconazole resulted in increased gross revenue of $55 ha–1 (P > F = 0.01). No significant effect was observed for cultivar and no interaction was observed for cultivar and fungicide treatment.
Incidence of disease for cultivars is presented in Table 3. Southern blight was the only soilborne disease that was observed in 1995. In 2001, limb rot and sclerotinia blight was observed but was highly variable between blocks. Observations indicated that a difference existed between cultivars in incidence limb rot (P > F = 0.01). Okrun appeared to have a greater incidence of limb rot compared with Spanco. This is not surprising since Okrun is considered highly susceptible to all three of these diseases, especially southern blight and sclerotinia blight (Melouk, 2005). For both cultivars, the tebuconazole-based fungicide treatment had reduced the percentage of plants infected with limb rot compared with chlorothalonil (Table 3). Significant differences were not detected between rotations. While the effects of crop rotation on limb rot were not significant, there was a trend for increased limb rot following the cotton rotations. Rhizoctonia solani has a wide host range and is a primary cause of seedling disease in cotton (Brown and McCarter, 1976).
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Table 3. Incidence of disease for Spanco and Okrun cultivars in rotations in 1995 and 2001 when peanut occurred in every rotation.
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Economic Evaluation
The economic results found that the peanut monoculture, PN, produced significantly higher economic returns than any of the alternative cropping rotations considered in the study (P > t = 0.05). The PN monoculture generated an economic return of $411 ha–1, which was at least $166 ha–1 higher than any of the other crop rotations (Table 4). In general, the peanut cotton rotations had the highest economic returns among the peanut rotations. The exception was the PN-PN-CR rotation, which produced an economic return that was not significantly different (P > t = 0.05) than either the PN-CT or the PN-CT-CT rotation (Table 4). Among the remaining rotations, PN-SO had significantly higher economic returns than either the PN-CR or PN-CR-CR rotations (P > t = 0.05). The only rotation that had negative returns was the three year peanut-corn rotation, PN-CR-CR, which had a return of $–40 ha–1 (Table 4).
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Table 4. Average gross revenue, costs of production, and net economic returns in the Red River Farm peanut rotation study, Love County, Oklahoma, 1990–2001.
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Peanut returns were significantly higher (P > t = 0.05) in the rotations where peanut was grown in only 1 out of 3 yr, PN-CR-CR and PN-CT-CT (Table 5). By keeping peanut out of production for two consecutive years, the economic return for a single year of peanut was increased from $411 to $612 ha–1 for the PN-CR-CR rotation, and from $411 to $602 ha–1 for the PN-CR-CR rotation (Table 5). Peanut returns in each of the 2-yr rotations (PN-CR, PN-CT, and PN-SO) were not found to be significantly different from the PN monoculture. The results indicate that peanut would need to be out of rotation for at least 2 out of the 3 yr to capture any significant economic benefits from crop rotation.
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Table 5. Estimated economic returns above fixed and variable costs for six alternative crop rotations from the Red River Farm peanut rotation study.
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The benefits from rotating peanut with other crops were offset by the low economic returns of the rotation crops in the off years when peanut was not produced. Cotton was the only crop that generated a positive economic return, $46 ha–1 (Table 5). The other two rotation crops, corn and grain sorghum, had negative returns of $–366 ha–1 and $–160 ha–1. In the PN-CT-CT rotation, for instance, the benefits from rotation resulted in an increase of $191 ha–1 in economic returns for the first year compared with the PN monoculture. In each of the subsequent 2 yr, however, the PN-CT-CT would have its economic returns lowered by $365 ha–1 compared with the PN monoculture. The corn rotations had even more significant losses. The first year of the PN-CR-CR rotation increased economic returns by $201 ha–1 over the PN monoculture, but in the second and third years of the rotation economic returns were reduced by $777 ha–1.
Although the PN monoculture remains as the most profitable cropping practice, the recent changes in the peanut marketing system have substantially reduced the break-even prices of the rotation crops (Fig. 1
). Under the peanut quota marketing system, peanuts were sold at the farm gate for $681 Mg–1, but since quotas were removed in 2002 the peanut price has fallen to $369 Mg–1. These changes in peanut prices, coupled with a modest increase in cotton prices of $0.10 kg–1, have moved peanut and cotton prices closer to the break-even price line as illustrated in Fig. 1. The break-even cotton price of cotton in the PN-CT-CT rotation has been reduced from $2.61 to $1.48 kg–1. With cotton prices at $1.16 kg–1, it would only take an increase of $0.32 kg–1 in cotton prices for the break-even price to be reached. The break-even price for the peanut-corn rotations have been reduced as well. The PN-CR rotation now has a break-even price of $0.15 kg–1, down from $0.292 kg–1 that prevailed during the rotation study (1990–2001).
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Fig. 1. Break-even price lines for peanut-cotton (PN-CT and PN-CT-CT) and peanut-corn rotations (PN-CR and PN-CR-CR). The straight lines in each graph represent break-even price combinations. These are points at which returns from the PN monoculture are equal to the returns from a given rotation. The area under the break-even price line represents points where the PN monoculture has a higher economic return than the corresponding peanut rotation. The opposite is true above the break-even line, where the peanut rotation has a higher return than the PN monoculture.
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DISCUSSION
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The findings of this research, that PN-CR and PN-CT rotations generate higher peanut yields than PN monoculture, are consistent with findings from peanut rotation studies in the southeast (SE) growing region. In Alabama, Georgia, and North Carolina, peanut rotated with either corn or cotton reduced soil and plant disease and provided significantly higher peanut yields than yields from continuous peanut plantings. Hagan et al. (2003) found that in Alabama both 2- and 3-yr corn-peanut rotations performed better than the peanut monoculture, but that the peanut-cotton rotation required a 3-yr rotation before the rotation yields were higher than the peanut monoculture. Brenneman et al. (2003) found in Georgia that 3-yr peanut-corn and peanut-cotton rotations had yields that averaged 648 and 643 kg ha–1, respectively. Jordan et al. (2002) found in North Carolina both higher yields from 2-yr rotations of peanut-corn and peanut-cotton than under continuous peanut, as well as higher economic returns. Consistent with the previous research, the peanut-cotton rotation generated the highest economic returns among the rotation crops. The North Carolina findings were different, however, in that the peanut monoculture did not generate the highest earnings. The peanut-cotton rotation outperformed the peanut monoculture by $1423 ha–1, and the peanut-corn rotation was found to have returns $1166 ha–1 higher than the peanut monoculture.
In areas where peanut disease pressure is significantly higher than the observed pressure during the study, the break-even cotton and corn prices would be reduced by as much as $0.20 and $0.02 kg–1, respectively (Table 6). This would still leave the break-even cotton price for the PN-CT-CT rotation $0.13 kg–1 above the 2006 cotton price, and the PN-PN-CR rotation $0.05 kg–1 above the 2006 corn price. Even in high disease pressure areas the PN monoculture would remain as the most profitable. The recent advances in cotton technology, which have pushed cotton yields up by 34%, would reduce the break-even cotton price from 1.48 to $1.19 kg–1 for the PN-CT-CT rotation. This brings the break-even cotton price for the PN-CT-CT rotation to within $0.03 kg–1, or 2.6%, of 2006 cotton prices. The only situation where the PN monoculture would not be the most profitable would be under the updated cotton yields and in areas of high disease pressure. Under this scenario, the break-even cotton price for the PN-CT and PN-CT-CT rotations would be 1.13 and $1.05 kg–1, both less than the 2006 cotton price of $1.16 kg–1.
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Table 6. Break-even price analysis for peanut-cotton and peanut-corn rotations under alternative peanut disease pressure (Sclerotinia) and updated cotton yields.
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CONCLUSIONS
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Crop rotation with corn or cotton grown 2 out of 3 yr was important to maintain the highest peanut yields. Increased peanut yield from rotation in the southwestern peanut growing region will help producers in the region maintain high yields and reduce disease buildup. When considering the economic return for the entire crop rotation, the PN system had the highest economic return, even though peanut yield was reduced in this system compared with rotational systems. Further work needs to be done to determine the long-term sustainability of such a system. With recent increases in cotton yield in the region and suitability of cotton to the southwestern climate, a peanut-cotton rotation may be the best economic rotation for southwest peanut producers.
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REFERENCES
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TOP
ABSTRACT
INTRODUCTION
