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Published in Agron. J. 97:288-293 (2005).
© American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA

Production Papers

Tillage and Nitrogen Application Impact on Cotton following Wheat

P. J. Wiatraka,*, D. L. Wrighta, J. J. Maroisb, W. Koziarac and J. A. Pudelkoc

a Dep. of Agronomy, North Florida Res. and Educ. Center, Univ. of Florida, 155 Research Rd., Quincy, FL 32351
b Dep. of Plant Pathology, North Florida Res. and Educ. Center, Univ. of Florida, 155 Research Rd., Quincy, FL 32351
c Agric. Univ., Inst. of Soil Cultivation and Plant Prod., Mazowiecka 45/46, 60-623 Poznan, Poland

* Corresponding author (pjwiatrak{at}mail.ifas.ufl.edu)

Received for publication June 2, 2004.

   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Tillage and N fertilization influence cotton (Gosspium hirsutum L.) growth and yield. The objective of the study was to evaluate the influence of two tillage systems (conventional tillage [CT] and strip-till [ST]) and four N rates (0, 67, 134, and 202 kg N ha–1) on growth, development, and yield of ‘DP 5409’ cotton following wheat (Triticum aestivum L.). The experiment was conducted at the University of Florida's North Florida Research and Education Center in Quincy, FL, in 1995–1997. Lint yields, plant height, boll no. plant–1, and boll no. m–2 varied across years. With every 1 kg N ha–1 applied to cotton, lint yields increased by 1.74 and 1.53 kg ha–1 in 1996, and 2.76 and 1.76 kg ha–1 in 1997 for CT and ST, respectively. In 1995, maximum lint yields were estimated with 105 kg N ha–1 for CT. Averaged across years, cotton lint yield increase with N application greater than 67 kg ha–1 was not significant and tillage did not influence lint yields. Plant height, boll no. plant–1, and boll no. m–2 generally increased with increasing N rates, except for boll no. m–2 in the ST system in 1995. Greatest boll weight and lint weight boll–1 were obtained with the application of 134 kg N ha–1. Compared with CT, ST reduced boll no. plant–1 and increased boll no. m–2. Tillage did not influence plant height, boll weight, and lint weight boll–1. These results indicate that cotton can be grown successfully in ST and that yields may not increase significantly with rates >67 kg N ha–1.

Abbreviations: CT, conventional tillage • NT, no-till • ST, strip-till


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
NITROGEN AVAILABILITY and quantity are important factors in cotton development and yield (Doss and Scarsbrook, 1969; Oosterhuis et al., 1983). Nitrogen deficiency reduces vegetative and reproductive growth (Gerik et al., 1994); however, high N availability may lead to excessive vegetative development, thus delaying crop maturity and reducing lint yield (Howard et al., 2001). Previous research has shown that N availability is dependant on seasonal changes in soil water content, temperature, soil structure, and organic matter distribution (Radke et al., 1985; Johnson and Lowery, 1985; Ranells and Wagger, 1992; Wagger, 1989). Without N fertilization, cotton may acquire from 25 to 104 kg N ha–1 from soil organic matter N mineralization (Constable and Rochester, 1988).

Nitrogen availability depends not only on applied quantity but also on N mineralization in the soil. Nitrogen mineralization may be reduced due to soil compaction (Hassink, 1995) and low temperature as a result of reduced air flow in conservation tillage (Johnson and Lowery, 1985). However, frequent soil movement in conventional tillage (CT) may increase the N mineralization process (Grace et al., 1993). Azam et al. (1988) and Grace et al. (1993) noted that N fertilization not only increases ammonium N, but also N mineralization in the soil.

Previous crop residues, partly due to the residue quality, affect the optimum N rate for the following cotton crop (Touchton et al., 1995). Brown et al. (1985) and Touchton and Reeves (1988) noted that greater N rates, due to N immobilization, are required for cotton grown after wheat than fallow to obtain the same yields. The use of crop rotation and winter crops may also reduce N leaching potential and degradation of ground water (Touchton et al., 1995). Wood et al. (1991) observed that soil N concentration at the 0- to 40-cm depth was reduced with the establishment of conservation tillage.

Many experiments have shown that cotton yields from conservation tillage systems are lower or similar to yields from CT (Brown et al., 1985; Stevens et al., 1992; Burmester et al., 1993; Hutchinson, 1993), or even greater for conservation than CT (Bradley, 1995; Delaney et al., 1996; Boquet et al., 1997). Strip-till (ST) is the most common conservation tillage system in the southeastern USA, and the system uses a seed-bed preparation implement with in-row subsoil shanks, multiple coulters, and ground driven crumblers that till a band approximately 30 cm wide (Johnson et al., 2001). There are many economic factors favoring cotton production under conservation tillage including decreasing input costs, traffic, labor, fuel, and equipment (Smart and Bradford, 1996). Compared with CT, ST may reduce energy costs by 50% (Burte et al., 1992) and increase revenues by 70% from growing cotton in conservation tillage (Harman et al., 1989). Moreover, greater soil moisture in conservation tillage may help to increase yields (Raper et al., 1994); however, it may also delay maturity and affect yields. Therefore, the purpose of this research was to compare CT to ST and four N rates on growth, development, and yields of cotton grown after winter wheat.


   MATERIALS AND METHODS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Plot Preparation
Field trials with ‘DP 5409’ cotton following wheat were conducted in 1995 through 1997 on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida's North Florida Research and Education Center in Quincy, FL. The soil contained 97 mg kg–1 K, 25 mg kg–1 P, 68 mg kg–1 Mg, 318 mg kg–1 Ca, and 0.5 mg kg–1 NO3–N in the top 15-cm layer. The experiment consisted of two tillage systems (CT and ST) and four N rates (0, 67, 134, and 202 kg N ha–1) in the form of ammonium nitrate (34–0–0 of N–P–K). The CT and ST sections in cotton were imposed following the CT and no-till (NT) sections in wheat, respectively. Conventional sections in wheat were subsoiled, disc-harrowed, and s-tine harrowed. The previous wheat crop (cv. ‘Pioneer 2684’) was broadcast fertilized with 28, 24, and 70 kg ha–1 of N, P, and K, respectively, before planting; and seeded at 101 kg ha–1 in 18 cm row spacing in NT and CT using a Great Plains No-till Drill (Great Plains Mfg., Assaria, KS). At the end of January, wheat was broadcast fertilized with ammonium nitrate at 78 kg N ha–1. The ST and CT sections in cotton followed NT and CT in wheat, respectively. After harvesting wheat for grain, straw was cut with a rotary mower and left in the field. The experimental area was sprayed with glyphosate [N-(phosphonomethyl) glycine] at 3.5 L ha–1 2 wk before planting cotton. Two days before planting, the CT sections were disked, subsoiled, and s-tine harrowed. The rows in ST sections were tilled approximately 0.3 m wide and subsoiled to 0.4 m deep with a Brown Ro-till implement (Brown Manufacturing Co., Ozark, AL). The sections in ST were covered with about 60% wheat plant residues before seeding cotton. Soil conditions were good with adequate moisture while performing tillage operations and seeding wheat.

Plant Culture
Cotton was seeded in ST and CT at a rate of 12 seeds m–1 of row with 91 cm row spacing using a KMC planter (Kelly Manufacturing Co., Tifton, GA) on 22 June 1995, 25 May 1996, and 16 June 1997. Each plot was 3.7 m wide by 6.1 m long and consisted of four rows. The study was sprayed with fluometuron [1,1-dimethyl-3-({alpha}, {alpha}, {alpha}-trifluoro-m-totyl)urea] at 1.1 kg a.i. ha–1 and pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] at 0.9 kg a.i. ha–1 preemergence and direct sprayed with fluometuron at 1.1 kg a.i. ha–1 and MSMA (monosodium salt of methylarsonic acid) at 1.1 kg a.i. ha–1 3 wk later. The N treatment, in the form of ammonium nitrate, was applied at 67 and 134 kg ha–1 4 wk after planting, and 202 kg N ha–1 was divided into 134 kg N ha–1 (applied 4 wk after planting) and 68 kg N ha–1 (applied 3 wk later). 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. The study was defoliated with thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea) at 0.1 kg a.i. ha–1, ethephon (2-chloroethyl phosphonic acid) at 1.15 kg a.i. ha–1, and Agridex (Helena Chem. Co., Collierville, TN) at 2% v/v when 60 to 70% of cotton bolls were open. Cotton was harvested manually 3 wk after defoliation. The time from planting to maturity ranged from 148 to 155 d.

Plant stand and height, boll number, and yield data were collected from the two adjacent middle rows of each plot. Plant stand was determined by quantifying the number of plants emerged 2 wk after planting. The number of bolls plant–1 was obtained from 20 plants plot–1 at 120 DAP. Cotton bolls were recorded from the first to fifth lateral fruiting position on sympodial (fruiting) branches. Lint yield was calculated based on lint percent in ginned cotton sample from each plot (908 g).

Weather Conditions
Weather data was obtained from the weather station at Quincy, FL (30°36' N lat, 84°33' W long), located at 74.7 m above sea level. Temperature sensors, placed 2 m above ground, were used to display the maximum (Datacom, Fort Walton Beach, FL) and minimum (The Lexsus Service Corp., New York) air temperatures. Soil temperature was recorded at the 0.1-m depth with a soil thermometer (Palmer Wahl, Asheville, NC), and precipitation was recorded with a rain gauge (Frise Engineering Co., Baltimore, MD).

Temperature and precipitation each year provided different conditions for crop development, lint yields, and yield components. Generally, the average monthly temperatures were similar to yearly averages. There was no need for irrigation in 1995 due to adequate rainfall. Lower rainfall in 1996 and 1997 was compensated with irrigation at 102 and 107 mm, respectively, using a lateral-move sprinkler irrigation system. Cotton was irrigated when tensiometer (Irrometer Co., Riverside, CA) readings at the 30-cm soil depth indicated 40 kPa. Yearly precipitation was below the 20-yr average in 1995, but greater than the 20-yr average in 1996 and 1997 (due to irrigation when needed) (Table 1). Overall, the monthly precipitation totals were similar to a 20-yr average during 1995 through 1997 seasons, except low precipitation for May and June in 1996.


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  		Table 1. Average monthly air temperatures and total monthly precipitation at Quincy, FL, from 1995 to 1997.

 
Experimental Design
The field experimental design was a split plot in a randomized complete block with four replications. Tillage was the main plot and N application was the subplot. All data were analyzed using a PROC MIXED model (SAS Inst., 1999). As years were sequential with potentially cumulative effects on soil and plant parameters, years were considered fixed effects. Tillage systems and N applications were considered fixed. Blocks and interactions including blocks were assumed to be random effects. The PROC MIXED procedure of SAS with the LSMEANS PDIFF option was used to compare tillage systems and N applications. The difference between means for tillage and N applications was considered significant at P ≤ 0.05. Single degree-of-freedom contrasts were used to evaluate linear and quadratic effects of N applications on cotton. When a contrast indicated that there was a significant (P ≤ 0.05) linear or quadratic response, then a linear or quadratic regression models, respectively, were fit using PROC REG (SAS Inst., 1999). Pearson correlation coefficients (r) were calculated between lint cotton yield and plant stand and height, boll no. plant–1, boll no. m–2, boll weight, and lint weight boll–1.


   RESULTS AND DISCUSSION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Cotton plant stand was influenced by tillage treatment (Table 2). Greater plant stand, due to emergence, was noted from cotton grown in ST than CT. Johnson et al. (2001) also reported greater cotton stands in ST than CT in some years. However, they also noted less plant stand in ST than CT tillage in other years.


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  		Table 2. Influence of tillage and N rate application on cotton plant stand, height, yields, and yield characteristics; probability of greater values of F of fixed effects; and Pearson correlation coefficients (r) of lint cotton yields with plant characteristics at Quincy, FL, in 1995–1997.

 
A year x tillage x N application interaction was observed for cotton plant height (Table 2). Generally, N application increased plant height in all 3 yr for CT and ST (Fig. 1). Cotton plant height increased by 0.07 and 0.13 cm in 1995, 0.08 and 0.18 cm in 1996, and 0.18 and 0.17 cm in 1997 for every 1 kg N applied to cotton grown in CT and ST, respectively. Averaged across years, tallest cotton plants were noted with the application of 202 kg N ha–1 (Table 2). Hutmacher et al. (1996) also noted taller plants with increased N application compared with treatment without N or 60 kg N ha–1. Our research, averaged across years, showed no significant difference between tillage systems for plant height (Table 2). These results agree with Lascano et al. (1994), who did not observe a significant difference between ST and CT cotton for plant height. Overall, plant height varies across years and increases with increasing N rates on cotton.



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  		Fig. 1. Influence of N application on plant height of cotton under two tillage systems at Quincy, FL, from 1995 to 1997. ***Significance at the 0.001 probability level.

 
An interaction of year x tillage x N application existed for the boll no. plant–1 (Table 2). Greatest boll no. plant–1 was observed with the application of 107 kg N ha–1 in CT, while the boll no. plant–1 increased by 0.02 with every 1 kg N applied to cotton under ST in 1995 (Fig. 2). Boll no. plant–1, with every 1 kg N applied to cotton, increased by 0.05 and 0.013 boll plant–1 in 1996, and 0.02 and 0.013 boll plant–1 in 1997 for CT and ST, respectively. The boll no. plant–1, due to greater plant stand (data not shown), was generally less in 1997 compared with other years. Averaged across years, greatest boll no. plant–1 was obtained with 134 and 202 kg N ha–1 (Table 2). Boll no. plant–1 was greater for CT than ST. These results agree with Wright et al. (1998), who noted greater boll no. plant–1 with the application of 134 and 202 kg N ha–1 compared with lower N rates. Generally, increasing N rate on cotton increased boll no. plant–1 and greater boll number, due to less plant stand and consequently expending fruiting branches with bolls, was observed in CT than ST.



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  		Fig. 2. Influence of N application on boll no. plant–1 of cotton under two tillage systems at Quincy, FL, from 1995 to 1997. **, ***Significance at the 0.01 and 0.001 probability levels, respectively.

 
A year x tillage x N application interaction was noted for the boll number m–2 (Table 2). In 1995, a quadratic plateau was obtained for the boll no. m–2 of cotton grown in CT and ST (Fig. 3). According to this plateau, maximum boll no. m–2 was estimated with the application of 95.8 kg N ha–1 for CT, while maximum boll number for ST was expected with 92.8 kg N ha–1 applied to cotton. In 1996, with every 1 kg N ha–1 applied to cotton, the boll no. m–2 increased by 0.07 in CT. However, no plateau boll no. m–2 was achieved for ST in 1996. In 1997, an increase of 0.13 and 0.09 boll m–2 was noted with every 1 kg N applied to cotton in CT and ST, respectively. Averaged across years, greater boll number was obtained with N application than without, but no difference was found among N rates (Table 2). Reddy and Rao (1970), however, noted greater boll no. m–2 with increased N application on cotton. We noted greater boll no. m–2 from ST than CT when averaged across years (Table 2). Similarly, Pettigrew and Jones (2001) observed greater boll no. m–2 from cotton grown in conservation than CT. Overall, the boll no. m–2 increased with increasing N rates in cotton and greater boll no. m–2, due to better plant stand, was obtained from ST than CT.



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  		Fig. 3. Influence of N application on boll no. m–2 of cotton under two tillage systems at Quincy, FL, from 1995 to 1997. NS, not significant at the 0.05 probability level; **, ***Significance at the 0.01 and 0.001 probability levels, respectively.

 
Cotton boll weight and lint weight boll–1 were influenced by N application (Table 2). Greater boll and lint weights were obtained with the application of 134 kg N ha–1 compared with other N rates. Wright et al. (1998) also noted an increase in boll weight with increased N application on cotton. No differences for boll and lint weights were observed between tillage systems (Table 2). However, Pettigrew and Jones (2001) observed greater boll weight from cotton grown in conservation than CT. Generally, these results indicate that increasing N application up to 134 kg N ha–1 in cotton increase the weight of cotton boll and lint weight boll–1, regardless of tillage system employed.

An interaction of year x tillage x N application was observed for lint cotton yields (Table 2). Maximum lint cotton yields were estimated with 105 kg N ha–1 applied to cotton under CT in 1995 (Fig. 4). The same year, however, no plateau yield was achieved for cotton yields in ST. With every 1 kg N applied to cotton grown in CT and ST, lint cotton yields increased by 1.74 and 1.53 kg ha–1 in 1996, and 2.76 and 1.76 kg N ha–1 in 1997, respectively. Averaged across years, lint yields were less for treatments without than with N application (Table 2). However, no difference was observed among treatments with 67, 134, and 202 kg N ha–1 for lint cotton yields. In reviewed literature, the optimum applied rate of N on cotton varied from 35 to 135 kg N ha–1 (Howard and Hoskinson, 1986; Lutrick et al., 1986; Maples and Frizzell, 1985; Phillips et al., 1987; Thom and Spurgeon, 1982; Touchton et al., 1981). To obtain maximum yield, cotton should receive 91 to 225 kg N ha–1, but optimum N rate would be 14 to 51 kg N ha–1 less than the rate giving a maximum yield (Constable and Rochester, 1988). Our results were similar to Wright et al. (1998), who found that lint cotton yields were greater with 134 and 202 kg N ha–1 compared with the treatment without N fertilization. However, they noted greater lint yields with the application of 134 kg N ha–1 than 67 kg N ha–1. Our results showed no difference between tillage systems when data was averaged across years (Table 2). Burmester et al. (1997) also showed that yields from conservation and CT may vary across years. Furthermore, Matocha and Barber (1992), and Smart and Bradford (1996) noted that different tillage and fertilization have a direct effect on cotton yield. Our results agree with Rhoads et al. (1997), who showed that yields of cotton grown in ST were similar to yields obtained from CT. On the contrary, cotton yields may be greater from conservation than CT (Brown et al., 1985; Keeling et al., 1989; Delaney et al., 1996). The results of this study indicate that N application increases lint yields, however, rates >67 kg N ha–1 may not significantly increase lint cotton yields.



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  		Fig. 4. Influence of N application on yield of cotton under two tillage systems at Quincy, FL, from 1995 to 1997. NS, not significant at the 0.05 probability level; ***Significance at the 0.001 probability level.

 
According to Pearson correlation coefficients, lint yields were correlated with plant height (r = 0.63), boll no. plant–1 (r = 0.37), boll no. m–2 (r = 0.94), and lint weight boll–1 (r = 0.43) (Table 2). Morrow and Krieg (1990) also noted a correlation between lint yields and boll no. m–2 (r = 0.94). These results also agree with Reddy and Rao (1970), who showed high yield increases with increased number of bolls m–2. These 3-yr results indicate that lint cotton yields depend mostly on the number of bolls m–2.


   CONCLUSIONS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Plant height, boll no. plant–1, boll no. m–2, and lint cotton yields varied from year to year, but generally increased with increasing N application on cotton grown in CT and ST. Boll no. m–2, however, decreased with N application on ST in 1995. According to a quadratic regression, maximum lint yields were expected with 105 kg N ha–1 applied in CT in 1995. In 1996 and 1997, a linear plateau was achieved for lint yields. Greatest boll weight and lint weight boll–1 were obtained with the application of 134 kg N ha–1. The plant stands explains the differences between tillage systems for boll no. m–2 and boll no. plant–1. The boll no. m–2, due to better plant stand, was greater for cotton grown in ST than CT. With less plant stands for CT than ST, the branches in the CT grew out into the open spaces in the canopy and put more bolls on sympodial branches. Therefore, the total number of bolls plant–1 was greater for the treatment with less stands and cotton yields were similar for two tillage systems. Early planting date in 1996, compared with 1995 and 1997, resulted in greater cotton boll no. m–2 and lint yields. However, the tillage and N rate effects on cotton seeded in 1996 were similar to other years. The results of this study indicate that cotton can be grown successfully in ST and generally plants react positively to N application. However, rates >67 kg N ha–1 may not significantly increase lint yields. With increasing N application, greater lint yields were primarily due to increased boll no. m–2.


   NOTES
TOP
 NOTES
ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
This research was supported by the Florida Agric. Exp. Stn. and approved for publication as Journal Series no. R-10283.


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





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