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© 2007 Plant Management Network.
Accepted for publication 18 May 2007. Published 15 August 2007.

Comparing the Growth, Weed Control, and Yields of Cotton on Two Tillage Systems in the Southeast

Pawel J. Wiatrak, Department of Entomology, Soils, and Plant Sciences, 64 Research Road, Edisto Research and Education Center, Clemson University, Blackville, SC 29817; David L. Wright, Department of Agronomy, and James J. Marois, Department of Plant Pathology, 155 Research Road, North Florida Research and Education Center, University of Florida, Quincy 32351

Corresponding author: Pawel J. Wiatrak. pwiatra@clemson.edu

Wiatrak, P. J., Wright, D. L., and Marois, J. J. 2007. Comparing the growth, weed control, and yields of cotton on two tillage systems in the Southeast. Online. Crop Management doi:10.1094/CM-2007-0815-01-RS.

Abstract

Tillage practices influence weed control and cotton (Gossypium hirsutum L.) growth. The objective of this 3-year field study was to evaluate the influence of two tillage systems [conventional (CT) and strip-till (ST)] on Stoneville (cv ‘ST 474’) cotton. Significant year by tillage interactions were observed for plant emergence and density, and weed cover at 30 days after treatment (DAT) application. Greater plant density (18.9 vs 11.5 plants per 10 ft²) was observed, due to greater plant emergence, under CT than ST in 2002, while there was no difference between tillage systems in 2000 and 2001. Weed cover at 30 DAT was greater under ST that CT tillage (14.5 vs 9.3%) in 2001, whereas no difference between tillage systems was detected in 2002. Averaged across years, plant height and plant index at 60 days after planting (DAP) were greater from CT than ST. However, weed coverage at 60 DAP, boll number on the first position, and total boll number per plant were greater from ST than CT when averaged across years. Similar lint cotton yields obtained from both tillage systems indicate that despite plant reductions under ST compared to CT, cotton can be successfully grown under ST in the Southeast.

Introduction

Concern about soil erosion, water quality, and decreasing soil productivity has stimulated interest in alternative cotton production systems designed to minimize these problems (8). Triplett and Dabney (12) stated that conservation tillage reduces soil erosion and sustains crop productivity. Strip tillage is the most common conservation tillage system in the southeastern US, and the system uses a seedbed preparation implement with in-row subsoil shanks, multiple coulters, and ground-driven crumblers that till a band ~12 inches wide (6). Planter units may be mounted on the tillage implement or as a separate operation. Adoption of conservation tillage may help to increase yields of cotton produced in Florida due to less erosion and moisture conservation. Based on research in Tennessee and Texas, greater cotton yields were obtained from reduced tillage than from conventional tillage (CT) (1,4).

Tillage system can affect the density and spectrum of weed populations with broadleaf species being dominant in CT and annual grasses being major weeds in conservation tillage (2). Poor weed control can be a limiting factor in the adoption of conservation tillage (11) and can cause significant economic losses (10). Derksen et al. (3) noted that the success of conservation tillage depends on the development of agronomically and economically viable weed management systems. Therefore, the objective of this study was to evaluate weed control and cotton growth and yields under strip tillage (ST) and CT.

Trials Comparing Weed Control and Cotton Yield under ST and CT

Field trials with cotton were conducted from 2000 to 2002 on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida, North Florida Research and Education Center near Quincy, FL. The winter oat cover crop [feed oats drill-seeded at 2 bu/acre using a Great Plains No-till drill (Great Plains Mfg. Inc., Salina, KS)] experimental area was sprayed with glyphosate (Roundup Ultra) at 1 lb ai/acre two weeks before planting. One week prior to planting, the experiment was broadcast fertilized with 22, 20, and 55 lb/acre of N, P, and K, respectively. The CT and ST were performed two days prior to planting cotton. In CT, plots were disked using a disk-harrow, sub-soiled to a depth of ~15 inches using a chisel plow, and s-tine-harrowed. The ST consisted of using a Brown Ro-till implement (Brown Manufacturing Co., Ozark, AL) to subsoil the rows ~15 inches deep and create a 7-inch wide seedbed. Cotton was planted using a Monosem air planter (A.T.I., Merriam, KS) at 4 seeds/ft of row on 29 May 2000, 11 May 2001, and 12 April 2002. Each plot (24.0 ft wide by 32.5 ft long) consisted of 8 rows with 36-inch row spacing.

The study was broadcast sprayed with fluometuron (Cotoran 4L) at 0.98 lb ai/acre and pendimethalin (Prowl 3.3 EC) at 0.8 lb ai/acre pre-emergence, fluometuron at 0.5 lb ai/acre + Monosodium Acid Methanearsonate (MSMA) at 0.8 lb ai/acre over-the-top when cotton plants were at the 3- to 5-node stage. Additionally, cotton was post-direct sprayed with Monosodium Acid Methanearsonate at 0.8 lb ai/acre + diuron (Direx 4L) at 1.3-ft plant height. Supplemental N at 60 lb/acre was applied to cotton 27 DAP. Plants were defoliated with thidiazuron (Dropp) at 0.36 lb ai/acre + ethephon plus cyclanilide (Finish) at 1.2 lb plus 2.3 oz ai/acre, respectively + Agridex - non-ionic surfactant (Helena Chemical Co., Memphis, TN) at 1 pt/acre 3 weeks prior to picking. The application volume and pressure were 15 GPA and 25 PSI for herbicide application, and 25 GPA and 30 PSI for defoliant application, respectively. Cotton seed and lint were harvested from 4 rows per plot with an International 782 spindle picker (International Harvester Co., Chicago, IL) on 3, 15, and 18 November in 2000, 2001, and 2002, respectively.

Percent weed cover was assessed with the visual rating scale from 0 to 100 with 0 having no cover and 100 having complete weed cover at 30 and 60 days after last (post-direct) herbicide application. Most common weeds in both tillage systems were: sicklepod (Cassia obtusifolia), dayflower (Commelina Communis), purple nutsedge (Cyperus Rotundus L.), morningglory (Ipomea ssp.), and pigweed (Amaranthus ssp.). Plant density and height, and boll number per plant were recorded from the two adjacent middle rows of each plot. Plant density was determined by quantifying number of plants in two 32.5-ft long rows at 14 DAP. Based on 10 randomly selected plants per plot, plant height and node number were recorded at 60, 90, and 120 DAP, and number of bolls per plant was obtained at 120 DAP. For the total number of bolls per plant, cotton bolls were recorded from the first to fifth lateral fruiting position (data from the second to fifth position are not shown) on sympodial (fruiting) branches. The plant index was calculated from dividing the plant height in inches by plant node number. Lint yield was calculated based on lint percentage in ginned composite cotton sample from each plot (2.0 lb).

The experimental design was a randomized complete block with four replications. Years and tillage treatments were considered fixed effects. Blocks and interactions including blocks were assumed to be random effects. The PROC MIXED procedure in SAS (SAS Institute Inc., Cary, NC) with the PDIFF option was used to compare tillage systems. The difference between means for tillage systems was considered significant at P ≤ 0.05.

Effect of Tillage on Cotton and Weed Control

Year Χ tillage interactions were observed for cotton plant density and emergence (Table 1). Plant density and emergence were greater for CT than ST in 2002, while no difference between tillage systems was noted in 2000 and 2001. The results from 2002 agree with Johnson et al. (6), who reported greater cotton density in CT than ST in some years. However, they also noted lower plant density in CT than ST in other years. Generally, plant density is sometimes less than desirable in ST due to plant material left on the soil surface and therefore lack of good soil-seed contact and therefore lower emergence.

Table 1. Effect of conventional (conv.) vs strip tillage on plant density and emergence, weed cover, boll number per plant, and lint yield of Stoneville 474 cotton grown from 2000 to 2002 at NFREC near Quincy, FL.

 ^x DAP = days after planting.

 ^y DAT = days after last herbicide application.

 ^z LSMEANS within a row to compare tillage systems followed by the same letter are not different at the 0.05 probability level.

— indicates data not collected in 2000.

An interaction of year Χ tillage was found for weed control at 30 DAT application (Table 1). Greater weed cover was noted in ST than CT in 2001 due to less weed control in ST, while tillage did not influence weed control in 2002. Averaged across years, less weed control and therefore greater weed cover was observed under ST than CT at 60 DAT. However, Johnson et al. (6) noted greater weed control in ST compared to CT. Our results indicate that weed control may be similar or greater in CT than ST.

Plant height was influenced by tillage system at 60 DAP (Fig. 1). Averaged over years, taller plants were observed for CT than ST. Tillage did not influence plant height at 90 and 120 DAP (Fig. 1) and node number between 60 and 120 DAP (data not shown). However, Lascano et al. (7) reported greater height of cotton under ST than CT, and Triplett et al. (13) noted more nodes on cotton grown in conservation tillage than CT. Cotton plant index was greater under CT that ST at 60 DAP while difference was not detected between tillage systems at 90 and 120 DAP (Fig. 2). Moreover, plant height and node number increased for the period from 60 to 120 DAP, while plant index was similar over time. Overall, our results showing taller plants at 60 DAP for CT than ST and similar node number for tillage systems contradicted to results obtained by Lascano et al. (7) and Triplett et al. (13), respectively.

Averaged across years, tillage influenced the number of bolls on the first position and the total number of bolls (Table 1). Greater number of bolls on the first position and total number of bolls per plant was obtained from ST than conventionally tilled cotton. Tillage did not influence boll number per plant from the second to the fifth position (data not shown). Results obtained by other scientists are not consistent. Triplett et al. (13) also reported that cotton plants under conservation tillage had more bolls per plant compared to CT. However, Stevens et al. (9) showed that the conventionally tilled cotton produced more bolls than cotton in reduced tillage, while Hicks et al. (5) found no differences among tillage treatments for boll number per plant. Generally, tillage may influence the number of bolls, which may be either similar or greater under ST than CT due to plant density.

Lint yields were not influenced by tillage system (Table 1). These results agree with Johnson et al. (6) who also noted that yields of cotton did not differ between ST and CT. However, Paxton et al. (8) reported similar or greater cotton yields from reduced tillage than CT. Overall, our 3-year results showed no difference between tillage systems for lint yields.

Conclusions

Plant density, emergence, and weed control at 30 DAT varied between years. Generally, higher plant density (due to greater emergence under CT), weed control, and plant height can be expected from CT than ST. Due to less plant population in ST, greater boll number on the first position and total number of bolls per plant may be observed under ST than CT. Our research showed similar results for plant height at 90 and 120 DAP, node number from 60 to 120 DAP, and plant index at 90 and 120 DAP, boll number from the second to the fifth position, and lint yields when both tillage systems were compared. Data from this trial indicate that despite some plant reductions due to lower emergence under ST, cotton compensated by producing more bolls per plant and therefore produced comparable yields to CT. Also, despite lower weed control, compared to CT, cotton can be successfully grown in ST.

Disclaimer and Contribution Number

Mention of trademark, proprietary product, or vendor does not constitute or warranty of the product by Clemson University or University of Florida and does not imply its approval to the exclusion of other products or vendors that may also be suitable.

South Carolina Agricultural Experiment Station Technical Contribution No. 5296.

Literature Cited

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2. Clements, D. R., Benoit, D. L., Murphy, D., and Swanton C. J. 1996. Tillage effects on weed seed return and seedbank composition. Weed Sci. 44:314-322.

3. Derksen, D. A., Blackshaw, R. E., and Boyetchko, S. M. 1996. Sustainability, conservation tillage, and weeds in Canada. Can. J. Plant Sci. 76:651–659.

4. Harmon, W. L., Michels, G. J., and Wiese A. F. 1989. A conservation tillage system for profitable cotton production in the Central Texas High Plains. Agron. J. 81:615-618.

5. Hicks, S. K., Wendt, C. W., Gannaway, J. R., and Baker, R. B. 1989. Allelopathic effects of wheat straw on cotton germination, emergence, and yield. Crop Sci. 29:1057–1061.

6. Johnson, W. C., Brenneman, T. B., Baker, S. H., Johnson, A. W., Sumner, D.R ., and Mullinix, B. G., Jr. 2001. Tillage and pest management considerations in a peanut-cotton rotation in the southeastern coastal plain. Agron. J. 93:570-576.

7. Lascano, R. J., Baumhardt, R. L., Hicks, S. K., and Heilman, J. L. 1994. Soil and plant water evaporation from strip-tilled cotton: Measurement and simulation. Agron. J. 86:987–994.

8. Paxton, K. W., Lavergne, D. R., and Hutchinson, R. L. 1993. Conservation tillage vs conventional tillage systems for cotton: An economic comparison. Pages 95–99 in: Proc. of the South. Conserv. Tillage Conf. for Sustainable Agric., 15-17 June 1993. P. K. Bollich, ed. Monroe, LA.

9. Stevens, W. E., Johnson, J. R., Varco, J. J., and Parkman, J. 1992. Tillage and winter cover management effects on fruiting and yield of cotton. J. Prod. Agric. 5:570–575.

10. Swanton, C. J., Harker, K. N., and Anderson, R. L. 1993. Crop losses due to weeds in Canada. Weed Technol. 7:537–542.

11. Triplett, G. B., Jr. 1985. Principles of weed control for reduced-tillage corn production. Pages 26-40 in: Weed Control in Limited Tillage Systems. A. F. Weise, ed. Weed Sci. Soc. Am. Monogr. 2, Champaign, IL.

12. Triplett, G. B., and Dabney, S. M. 1995. Long term crop responses to conservation tillage. Pages 93–96 in: Proc. of the South. Conserv. Tillage Conf. for Sustainable Agric., 26–28 June 1995. Jackson, MS.

13. Triplett, G. B., Dabney, S. M., and Siefker, J. H. 1996. Tillage systems for cotton on silty upland soils. Agron. J. 88:507–512.