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Crop Rotations

Performance of Peanut and Cotton in a Bahiagrass Cropping System

^a Univ. of Florida, 155 Research Rd., Quincy, FL 32351
^b Auburn Univ., Wiregrass Reg. Res. & Ext. Center, P.O. Box 217, Headland, AL 36345

^* Corresponding author (katsvair{at}ufl.edu)

Received for publication December 1, 2006.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Yields for peanut (Arachis hypogaea L.) and cotton (Gossypium hirsutum L.) have reached a plateau in the southeastern USA (SE). This, coupled with environmental concerns and increased production costs, prompt the need to find alternatives to the limited peanut/cotton rotation currently used. Bahiagrass (Paspalum notatum Fluegge) was introduced to the current peanut/cotton cropping system to evaluate its effect on peanut and cotton performance. Our objectives were to compare crop yields in a conventional rotation of cotton-cotton-peanut vs. a bahiagrass–bahiagrass–peanut–cotton rotation under irrigated and nonirrigated conditions. Field studies were conducted in Quincy, FL, on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) from 2000 to 2004. During 2–3 yr of the study, peanut yields were 900 kg ha^–1 greater (averaged across irrigation treatments) following 2 yr of bahiagrass compared with following 2 yr of cotton under both irrigated and nonirrigated conditions. Root biomass was greater for cotton in the bahiagrass rotation compared with cotton in the conventional rotation. The greater root biomass, however, resulted in rank growth and cotton in the bahiagrass rotation yielded the same as cotton in the conventional rotation. It appears potential exists for greater cotton yield in the bahiagrass rotation once effective management practices have been identified.

Abbreviations: CT, conservation tillage • SE, southeastern USA • SMK, sound mature kernels • TDK, total damage kernels • TK, total kernels • TSMK, total sound mature kernels

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
STAGNANT YIELD, depressed commodity prices, and the attraction of environmentally friendly crop production have resulted in a growing interest in the use of perennial grass-based peanut/cotton production practices in the SE. Historical data show that cotton and peanut yields have been stationary for the past 15 yr (USDA-NASS, 2005) while production costs have maintained a steady upward trend. A growing, but still limited, body of research has shown that use of sod-based production systems is an effective way to improve crop yield and maintain overall sustainability of the cropping systems (Katsvairo et al., 2006a; Sulc and Tracy, 2007; Russelle and Franzluebbers, 2007; Russelle et al., 2007; Allen et al., 2007; Franzluebbers, 2007). The potential benefits of bahiagrass sod rotation include increased yield, improved soil and plant health, environmental stewardship, risk reduction, and better economic returns. However, most of these benefits have either not been conclusively proven or the results tend to be inconsistent.

Peanut yield increases in bahiagrass rotations have been attributed mainly to reduced pest pressure following the nonhost crop (Toth, 1998; Brenneman et al., 2003; Katsvairo et al., 2006b) and improvements in soil conditions (Katsvairo et al., 2007). Brenneman et al. (2003) reported increased peanut yields in 5 of 7 yr when peanut followed bahiagrass compared with the traditional planting of peanut following cotton. Similarly, White et al. (1962), Dickson and Hewlett (1989), and Hagan et al. (2003) reported increased peanut yields in bahiagrass-based peanut rotations in Georgia, Florida, and Alabama, respectively. However, Hagan et al. (2003) reported cases of no yield differences between peanut in a bahiagrass rotation and continuous peanut in some years. With five to eight routine pesticide applications per crop on the half million hectares of peanut grown in the SE, reduction in pesticide use resulting from lower pest populations could increase the profitability of peanut farming.

Few reports document the effects of bahiagrass on cotton yields. In one of the earliest publications on bahiagrass/cotton rotations, Long and Elkins (1983) reported greater cotton yield after bahiagrass in some years but also reported reduced yields in other years. They attributed this outcome to improved soil nutrient and moisture uptake as a result of a bigger rooting system following the bahiagrass. In some years, however, the authors encountered rank growth in the sod rotation which resulted in boll rot and insect damage, causing reduced cotton yields.

Most growers minimize the duration of bahiagrass in the rotation due to low income potential during this phase of production. Subsequently, knowledge of the time span needed for sod crop establishment and the length of beneficial effects on following crops is essential for planning and budgeting purposes. But opinions differ for the answers to these questions. For example, as little as 1 yr of bahiagrass in the rotation resulted in increased peanut yields (Norden et al., 1980), but higher yields of subsequent crops were obtained in longer grass rotations (Brenneman et al., 2003; Hagan et al., 2003). Norden et al. (1980) reported improved peanut yields for up to 5 yr when preceded by bahiagrass, while Brenneman et al. (2003) reported a peanut yield benefit that lasted for only 2 yr.

Approximately 30% of land planted to peanut and 15% of land planted to cotton in the SE is irrigated. Irrigation reduces year-to-year variation in yield caused by sporadic droughts. In Georgia, irrigation increased cotton yields by 350 kg ha^–1 (Bednarz et al., 2000). Another Georgia study reported that irrigated peanut tends to be grown more frequently in crop rotations than nonirrigated peanut because of the high capital investment in peanut production (Lamb et al., 1993). However, rotational benefits are more likely to be observed under irrigated than nonirrigated conditions (Lamb et al., 1993). Further work is needed to evaluate the feasibility of the sod-based peanut/cotton production systems under both irrigated and nonirrigated conditions.

For bahiagrass to be adopted in peanut/cotton cropping systems, it must be compatible with conservation tillage (CT), a common cultural practice in the SE (National Crop Residue Management Survey, 2002). Farmers in the SE also utilize winter cover crops primarily to increase the organic matter content and protect the soil from erosion. Sod-based rotations can be used in conjunction with CT to obtain maximum benefits from the cropping systems (Reeves, 1994, 1997) and can complement cropping with cover crops such as rye (Secale cereal L.), winter wheat (Triticum aestivum L.), and oat (Avena sativa L.).

The current peanut and cotton production system in the SE is a two-crop rotation system. Diversification of this cropping system has been shown to sustain soil health and improve yields. The objectives of this study were to determine if the inclusion of bahiagrass in the peanut/cotton rotation could improve peanut and cotton yields and quality.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
A 4-yr irrigation x rotation study was initiated in 2000 at the University of Florida's North Florida Research and Education Center in Quincy, FL (84°33' W, 30°36' N). The 1.75-ha experimental site was planted to cotton in the summer of 1999 and was fallow during the following fall and winter. Before 1999, the field had been in a CT/winter cover cropping sequence for several years. Soil tests in the fall of 1999 indicated a pH of 5.4, 36 mg kg^–1 P, 117 mg kg^–1 K, and 116 mg kg^–1 Ca, based on the Mehlich-1 extraction procedure (Mehlich, 1978).

Treatments were arranged in a strip plot experimental design (also called split-block) with three replications (Little and Hills, 1978). The use of a lateral move irrigation unit imposed the necessity for the strip-plot treatment layout. Three strips, each 128 m long by 45.7 m wide, were utilized and each of the strips consisted of alternating irrigated and nonirrigated treatments (Fig. 1 ). The irrigation unit stayed in the same area all 4 yr of the study. Irrigation was applied when tensiometer (Irrometer Co., Riverside, CA) readings at the 30-cm soil depth indicated 40 kPa. Crop rotation subplots were 45.7 m long by 18.3 m wide (20 rows) and subplots were aligned perpendicular to the irrigated and nonirrigated strips. Crop rotations studied were a cotton-cotton-peanut rotation, which is the conventional rotation used by growers in the region, and a bahia-bahia-peanut-cotton rotation. All phases of the rotations were present in all years (Table 1). In the conventional rotation, the first and second year of cotton were also compared. Bahiagrass sod was grown for 2 yr before planting peanut to ensure good ground coverage and vigorous growth of the bahiagrass.

View larger version (15K): [in this window] [in a new window]   Fig. 1. Treatment layout for two irrigation systems and three rotations in Florida, 2003 and 2004. Irrigation constitutes the main strip. Rotation constitutes the substrips.

View this table: [in this window] [in a new window]   Table 1. Crop sequence for bahiagrass, peanut, and cotton, during 2000 to 2004.

Cotton
In April of each year and on a date that was 2 to 3 wk before cotton planting, plot rows were strip-tilled using a Brown Ro-till implement (Brown Manufacturing Co., Ozark, AL). In 2000, cotton cultivar Paymaster PM 1500 BG/RR was used, while in 2001 to 2004, cultivar Deltapine DP 458 BR was planted. All plantings were made from late April to early May with a Monosem pneumatic planter (ATI Inc., Lenexa, KS) at 144,000 seeds ha^–1. Phorate {(0,0-diethylS-[(ethylthio) methyl] phosphorodithioate} was applied in-furrow for insect control at a rate of 6.72 kg a.i. ha^–1. Insecticide applications of Methyl Parathion (0,0-Dimethyl 0-p-nitrophenyl phosphorothioate) at 0.17 kg a.i. ha^–1 and tank mixes of Dicrotophos (Dimethyl phosphate of 3-hygroxy N,N-dimethyl-cis-crotonamide) at 0.42 kg a.i. ha^–1 + tracer (Spinosyn A and Spinosyn D) at 0.07 kg a.i. ha^–1 were made to control plant bugs (Lygus lineolaris L.) and southern green stink bugs (Nezara viridula L.). Starter fertilizer (5–10–15) at a rate of 560 kg ha^–1 was band applied adjacent to each row at planting. Cotton was sidedressed with 200 kg ha^–1 34–0–0 at square initiation. The study was sprayed with fluometuron [1,1-dimethyl-3-(, , -trifluoro-m-totyl)urea] at 1.1 kg a.i. ha^–1 and pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] MSMA (monosodium salt of methylarsonic acid) at 1.1 kg a.i. ha^–1 to control weeds. Early season cotton plant densities were determined when cotton was 10 cm tall by counting the number of plants in an 18.3-m length of the two harvest rows in each plot. At first bloom, plants were broadcast sprayed with mepiquat chloride (N, N-dimethylpiperidinium chloride) at 18.5 g a.i. ha^–1 to control height.

Plots were defoliated at 2% v/v with tank mixes of ethephon (2-chloroethyl phosphonic acid) at 1.15 kg a.i. ha^–1, thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea) at 0.056 kg a.i. ha^–1, and ethephon (2-chloroethyl phosphonic acid) at 1.15 kg a.i. in mid-September to October each year and determined when 60 to 70% of cotton bolls were open. The plots were harvested with a spindle picker (Case International, Model 1822, Phoenix, AZ) in October or November of each year. A 1-kg subsample of seed cotton from each plot was ginned to determine percentage lint content and seed yield. Cotton quality was not determined in 2002.

Cotton Root Biomass
Cotton roots were sampled after the crop reached physiological maturity in October. The roots were carefully dug, using shovels and spades, from three sample areas (1 m long by 0.5 m wide) in each rotation plot. Roots were dug to the depth of the natural compaction zone plus 10 to15 cm into the compaction layer. The difficulty of digging into the compaction zone limited sampling depth. The roots were carefully washed to remove all soil and organic debris, then oven-dried and weighed. Cotton root biomass was not determined in the first-year cotton in the conventional rotation in 2003.

Peanut
Peanut ‘Georgia Green’ was planted using a Monosem pneumatic planter (ATI Inc., Lenexa, KS) planter at 20 seeds m^–1 of row in mid to late May of each year. Chlorothalonil (tetrachloroisophalonitrile) at 0.841 kg a.i. ha^–1, pyraclostrobin (carbamic acid, [2[[[1-(4-chlorophenyl)-1Hpyrazol-3 yl]oxy]methyl] phenyl] methoxy-methyl ester at 0.2196 kg a.i. ha^–1, and tebuconazole, alpha- [2-(4-chlorophenyl) ethyl]-alpha-(1,1-dimethyylethyl)-1H-1,2,4-triazole-1-ethanol at 0.227 kg ha^–1 were applied to control soil-borne and foliar diseases. Weeds were controlled using metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] at 0.09 a.i. L ha^–1, pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitro-benzenamine] at 0.93 a.i. L ha^–1, and GramoxoneMax (paraquat, 1,1'-dimethyl-4,4'-bipyridinium ion) at 0.32 L a.i. ha^–1. The peanut crops were not fertilized.

Peanut crops were dug in mid-September to early October each year using a KMC (Kelly Manufacturing Co., Tifton, GA) digger/inverter and were allowed to air cure for three days. Windrows were then threshed with a 5000 Express peanut picker (Gregory Manufacturing Co., Lewiston Woodville, NC). A 500 g pod subsample from each plot was graded for sound mature kernels (SMK), total sound mature kernels (TSMK), other kernels, total damage kernels (TDK), total kernels (TK) and hulls. Grade values are expressed as percentage of total subsample weight based on specifications from the USDA Grading Service (USDA, 2006a).

Oat
An oat cover crop was planted at a rate of 67 kg ha^–1 using a Great Plains No-Till Drill in late November to early December of each year after cotton and peanut harvest. Before oat planting, cotton stalks were shredded with a rotary mower. Oat cover crops were not fertilized or cultivated, and were killed with glyphosate N-(Phosphonomethyl) at 1.15 kg a.i. ha^–1 prior to reaching maturity in April of each year and before planting of cotton or peanut.

Environmental Data
Air temperature and precipitation were recorded hourly at a weather station located at the experimental site. Growing degree days (GDD) were calculated only for cotton from daily maximum and minimum temperatures as GDD = [(T_max + T_min)/2] – 15.5, where T_max = daily maximum (if T_max > 30°C, then T_max = 30°C) and T_min = daily minimum (if T_min < 15.5°C, then T_min = 15.5°C (Russell and Webb, 1976).

Statistical Analysis
All data were analyzed using SAS general linear models procedures (SAS Institute, 2002). Irrigation main effects were confounded with block effects. As a result, they cannot be discussed from a statistical significance standpoint, but can be discussed using means and standard errors. However, irrigation x rotation interactions are appropriate for discussion. Although the study started in 2000, the rotations did not complete the first cycle until 2002, so only data from 2002 to 2004 are presented. The year-to-year variances for peanut and cotton yield and peanut grade were not homogenous, therefore separate analysis for each year is presented. Mean separation for main effects and interactions were obtained by Fisher's protected LSD, as described by Little and Hills (1978). Effects were considered significant in all statistical calculations if P 0.05.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Weather conditions differed among the three growing seasons (Table 2). The 2002 growing season was the driest and also had the highest GDD for cotton. Total irrigation amounts of 188, 114, and 127 mm were applied to all three crops (cotton, peanut, and bahiagrass) in the irrigated treatment in 2002, 2003, and 2004, respectively. July of 2004 was dry and had rainfall below the 30-yr average. The year 2004 was also marked by three hurricanes, resulting in lodged plants and lost lint yield.

View this table: [in this window] [in a new window]   Table 2. Monthly precipitation and growing degree days (GDD) for cotton from 2002 to 2004 growing seasons.

Peanut in the bahiagrass rotation produced greater yields than did peanut in the conventional rotation in both irrigated and nonirrigated treatments in 2003 and 2004, but not in 2002 (Table 3). In 2003, peanut yield under irrigation was 320 kg ha^–1 greater than the nonirrigated peanut when averaged across rotations. The yield difference may have been due to the low precipitation in September of 2003 (Table 2) during the end of pod fill. This made irrigation necessary during this growth period and resulted in the higher yields in the irrigation treatment. There was no rotation x irrigation interaction.

Peanut Grades
Each year, SMK and TSMK were generally higher for peanut in the bahiagrass rotation across both irrigated and nonirrigated conditions (Table 4). Number of TDK varied by year. When the differences between rotation treatments were significant, they were greater in the conventional rotation. These findings are consistent with those of Norden et al. (1980), who reported a reduction in kernel damage in peanut after bahiagrass. The year 2003 produced the best quality when SMK (65%), TSMK (72%), and TK (80%) were highest and percentage hulls lowest (Table 4). With the exception of September 2003, the more uniform rainfall distribution for that year likely caused the improved peanut grades.

View this table: [in this window] [in a new window]   Table 4. Peanut quality for two crop rotations from 2002 to 2004.

The positive effects of the sod rotation on cotton may vary with site, climate, crops, and soil conditions. Long and Elkins (1983) reported higher cotton yields in a sod rotation on soils with low fertility. The soils at our experimental site have a higher percentage of silt in comparison with most cotton growing areas of Florida. On the basis of these results, there is a need to refine some of the cultural practices of cotton production to adapt them to a bahiagrass-based cropping system. A reduction in N rates in the bahiagrass-based rotation for subsequent trials may be necessary. For example, on the deeper clay soils of the Mississippi Delta, growers reduced N rates by at least 20% for cotton after bahiagrass and still maintained high yields (M.W. Ebelhar, 2004, personal communication).

Cotton Quality
Unlike yield, many cotton fiber characteristics had significant rotation and year effects (Table 7). Improved cotton quality was observed in 2004 compared with 2003 for length (2.87 vs. 2.76 cm), strength (308.6 vs. 281.2 kN m kg^–1), and uniformity (82.65 vs. 81.87%). No interactions were observed for quality parameters between years, irrigation, or rotations. With the exception of uniformity, quality factors including micronaire, length, staple, and strength did not show any response to rotation under both irrigated and nonirrigated conditions in 2003.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Inclusion of bahiagrass in the traditional peanut/cotton cropping systems increases the diversity of the cropping system. Peanut in the bahiagrass rotation yielded greater than peanut in the cotton rotation in 2 of 3 yr under both irrigated and nonirrigated conditions. Peanut in the bahiagrass rotation had improved grade quality characteristics, most notably SMK and TSMK. Unlike peanut, rotating cotton with bahiagrass did not improve cotton lint yield. Even though cotton yield did not increase, cotton plant growth was improved with a larger root biomass in the bahiagrass rotation compared with the conventional rotation. Additionally, rank growth was observed for cotton in the bahiagrass rotation and it was surmised that this was the yield-limiting factor. These data suggest a need to learn how to manage the cotton under the sod system. Nitrogen application rates may need to be reduced when cotton follows bahiagrass to reduce excessive growth. Bahiagrass can either be grazed by cattle, sold as seed or baled and sold as hay for an income.

	ACKNOWLEDGMENTS

 
This study was supported in part by Cotton Inc., Peanut Checkoff, USDA Special Projects, and Florida Northwest Water Management District. Special mention is made of Brian Kidd, Iwona Jarczykowska, and Cynthia Davis Holloway for help with conducting the field and laboratory work.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Mention of a trademark, proprietary product, or vendor does not constitute a guarantee of warranty for the product, and does not imply its approval to the exclusion of other products or vendors that may be suitable.

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TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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