Research Article

Optimizing Seed Cotton Yield: Exploring the Synergistic Effects of De-topping Stage and Plant Spacing

Muhammad Iqbal1*, Saba Iqbal1, Arbab Jahangeer1, Muhammad Arshad1, Naveed Akhtar2, Ansar Hussain3, Mussarrat Hussain4, Muhammad Shahid5 and Qaisar Abbas4

1Agronomic Research Station Khanewal, Pakistan; 2Agronomic Research Institute Faisalabad, Pakistan; 3Ghazi University, Dera Ghazi Khan, Pakistan; 4Entomological Research Sub-Station, Multan, Pakistan; 5Cotton Research Institute, Multan, Pakistan.

Received | August 02, 2024; Accepted | September 18, 2024; Published | October 21, 2024

*Correspondence | Muhammad Iqbal, Agronomic Research Station Khanewal, Pakistan; Email: Iqbalagronomiist@gmail.com

Citation | Iqbal, M., S. Iqbal, A. Jahangeer, M. Arshad, N. Akhtar, A. Hussain, M. Hussain, M. Shahid and Q. Abbas. 2024. Optimizing seed cotton yield: Exploring the synergistic effects of de-topping stage and plant spacing. Sarhad Journal of Agriculture, 40(4): 1277-1287.

DOI | https://dx.doi.org/10.17582/journal.sja/2024/40.4.1277.1287

Keywords | Cotton, Plant spacing, De-topping timing, Sympodial branches, Seed cotton yield

Copyright: 2024 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Cotton (Gossypium hirsutum L.) is a vital cash crop in Pakistan that provides fiber, oil, and fuel wood, and significantly contributing to farmers’ incomes both locally and globally (Kashif et al., 2022). It performs crucial role in economy (Razzaq et al., 2021) and offers security of livelihood to masses of people across the country (Abbas and Waheed, 2017). Regardless of its importance, cotton production in Pakistan surfaces numerous challenges that hamper its growth and productivity (Razzaq et al., 2021). These challenges are conventional farming methods, pest and disease pressures, water insufficiency as well as climate change (Soomro et al., 2020). To address these concerns, farmers can employ advance farming techniques, integrated pest management practices, water conservation methods and climate-smart agriculture practices and can increase seed cotton yield and quality of produce (Siddiqua et al., 2021). Furthermore, crop yield at farm level is subjected to various aspects such as soil, climate and management practices (Dhaliwal et al., 2022). At farm level, it is vital to adopt amended management practices to boost yield potential of cotton (Ibrahim et al., 2022). One such practice is de-topping that involves removing terminal portion of plant from uppermost node to boost yield. De-topping improves yield by reducing undesired growth, minimizing mutual shading of leaves, increasing light capture, improving nutrient uptake and reducing competition amongst vegetative and reproductive development for nutrients (Dhaliwal et al., 2022). This practice also helps in readdressing plant nutrients to reproductive parts that improves source-sink relationship and promotes better boll development (Bhargavi et al., 2017; Esechie and Al-Alawi, 2002).

Cotton displays an indeterminate growth pattern and has prominent apical dominance (Wu et al., 2023). De-topping is a common practice in China and other cotton-producing regions (Dai and Dong, 2014). This practice disrupts apical dominance and allows a more provision of resources towards reproductive organs which results in increased squaring, flowering, boll formation and ultimately higher lint yield (Li et al., 2006). Additionally, de-topping can help in mitigating issues with sucking pests and bollworm infestations by eliminating fresh growth that might attract pests (Renou et al., 2011). Therefore, implementation of de-topping after plant has reached optimal vegetative growth can enhance cotton production. A study by Dai et al. (2022) has demonstrated that de-topping is an effective practice for improving cotton yield. In another study de-topping at plant height of 75 cm was found to improve yield contributing traits and seed cotton yield (Obasi and Msaakpa, 2005). Similarly, Kataria and Valu (2018) also reported 15 to 21% improvement in yield related parameters and yield of cotton.

Amongst various production factors, planting geometry plays a crucial role, particularly as a cost-effective input (Pinnamaneni et al., 2021). Achieving right plant density is essential for high yields, as insufficient plant density can lead to resource wastage, while excessive density can hinder growth of individual plant (Munir et al., 2015). Humidity, wind movement, moisture availability and radiation interception are affected by plant density (Heitholt et al., 1992). This change in crop microclimate further affects the height of canopy, branching of plant, behavior of fruiting, maturity of crop and ultimately yield (Heitholt et al., 1992). Proper density of plants also improves irrigation as well as fertilizers use efficiencies of crop (Abbas, 2000). Additionally, crop geometry influences yield by affecting rooting patterns and moisture extraction (Reddy and Reddy, 2011). The highest yields are achieved when plant populations enable individual plants to reach their full potential (Hussain et al., 2021). Plant geometry has been shown to significantly impact various growth characteristics, yield attributes and overall cotton yield (Ghule et al., 2013; Waghmare et al., 2018).

Despite lots of research conducted on de-topping and plant spacing in previous years, however optimal timing and plant spacing for de-topping in cotton remained unclear. Further research is needed to explore the interaction between de-topping stage and plant spacing to determine most effective combination for maximizing seed cotton yield. Therefore, this study aimed to optimize cotton production by examining the influences of de-topping and plant spacing on seed cotton yield. This study investigated how de-topping at various growth stages influenced yield and how this interacted with plant spacing. By identifying the optimal timing for de-topping and the most productive plant arrangement, this research was aimed to provide valuable recommendations for cotton farmers. These improved practices can empower them to maximize seed cotton yield and enhance their agricultural output.

Materials and Methods

Experimental site, design and treatments

This field study was executed at research area of Agronomic Research Station, Khanewal, Pakistan, situated at a latitude of 30º18’ 35.95’’ N, a longitude of 71º59’ 40.14’’ E, and an elevation of 454 m, for two years; 2019 and 2020. Climate of this region is arid with sandy loam soil. The chemical properties of the soils were as; a pH of 8.6, EC 4 ds cm-1, nitrogen (N) content 0.06%, phosphorous (P) content 6.90 ppm and K content 206.70 ppm. Two factors were studied in this experiment i.e., plant spacing; 30, 23, 15 cm and de-topping; de-topping at 90, 105 and 120 DAS. The experiment was set up in the field using a net plot size of 8.0 × 3.5 m and three replications in accordance with randomized complete block design (RCBD).

Crop husbandry

Following wheat harvesting, land preparation involved two cultivations, followed by one planking. The entire crop received fertilization: 247 kg ha-1 N as urea, 99 kg ha-1 P as single superphosphate (SSP), 94 kg ha-1 K as sulfate of potash (SOP), 12 kg ha-1 zinc sulfate (33%), and 6 kg ha-1 boric acid (17%). During seed bed preparation, the entire amount of P, K, zinc sulfate, and boric acid was applied to the soil, whereas N was given in four equal splits (at sowing, squaring, flowering, and boll formation). Nitrogen was applied in furrows immediately after irrigation. Beds with dimensions of 75 cm on the bed top and 75 cm in the furrow were made using a tractor-drawn bed shaper. Cotton was planted at a seed rate of 15 kg ha-1 using test variety named; MNH-1050. Sowing was performed manually on both sides of the bed using dibbling method maintaining plant-to-plant distance as per treatment. To manage weeds, a pre-emergence herbicide, Pendimethylene (Stomp), was sprayed immediately after sowing at a rate of 2457 ml ha-1. Crop was gap filled at six days after sowing (DAS) whereas thinning was performed at 25 DAS. A total of fourteen irrigations were scheduled, with the first irrigation applied at 4 DAS, followed by the 2nd, 3rd, and 4th irrigations at 7-day intervals. Subsequent irrigations were administered at 12-day intervals as per the crop’s requirements, with irrigation applied in furrows. Three pickings were conducted during each growing season.

Observations

At maturity, twenty plants from each treatment were randomly labeled to record yield-related variables. Using the meter rod, the plant height was calculated in centimeters. Sympodial branches of these labelled plants were counted and noted. Likewise, bolls per plant of these labelled plants was counted and noted. For each replicate, 50 bolls from each treatment were taken, weighted using a weight balance, and then averaged to record the average boll weight. Whole plot was picked and weighted using weight balance (electric compact scale: GT-500) to record seed cotton yield of each treatment in kilogram, afterwards convert into kilogram per hectare by employing unit method and noted.

Weather conditions

Figure 1 is presenting the weather of the experimental area during both growing seasons; 2019 and 2020. In the year 2019, during growing period the maximum temperature noted was 47ºC though in 2020 the maximum temperature noted was 45ºC. Moreover, in the year 2019, during growing period the least temperature noted was 14ºC whereas in 2020 it was 12ºC. In case of rain fall, total rainfall noted in growing period of 2019 was 290 mm while it was 196 mm in 2020.

 

Statistical analysis

Fisher’s analysis of variance was utilized to evaluate the data using STATISTIX 8.1 statistical software (Statistix, analytical software, Statistix; Tallahassee, FL, USA, 1985-2003) (Steel et al., 1980). Means were compared using the Least Significance Difference (LSD) test at the 5% probability level.

Results and Discussion

The experiment results underscored the substantial effects of plant spacing, timing of de-topping, and their interaction on various yield contributing traits of cotton over two years. Plant spacing was identified as a critical factor for improving cotton canopy structure and enhancing photosynthetic efficiency (An et al., 2022) and it is also an integral component of production technology of cotton. Absorption of light, availability of moisture, and movement of wind are the factors which are effects by plant density which in turns affect structure and height of plant, development of bolls, maturity of crop and ultimately productivity of crop (Fahad et al., 2021). High plant populations reduce the space between plants within rows, potentially leading to crowding stress that can limit yield (Bernhard and Below, 2020). Increasing row spacings can alleviate crowding, improve plant-to-plant spacing, and reduce competition for light, water, and nutrients (Tollenaar and Wu, 1999; Bernhard and Below, 2020). Relationship among cotton productivity and plant density has been explored in numerous studies (Bondada and Oosterhuis, 2001; Wei et al., 2022). Additionally, de-topping cotton after a significant vegetative growth stage has been shown to promote the growth of existing sympodia and enhance the formation of new sympodia. This increase in sympodia and bolls is crucial for maximizing seed cotton yield. The significant differences observed in the study highlight the importance of optimizing these agronomic practices to improve cotton production.

Plant population (plants ha-1)

In both year, plant population was significantly (P≤0.05) affected by plant spacing however was non-significant for time of de-topping (Table 1). Higher plant population was noted when cotton was planted at 15 cm plant spacing whereas least was noted where cotton was planted at 30 cm plant spacing (Table 1).

 

Table 1: Influence of plant spacing and De-topping on yield and yield components of cotton.

Treatments

Plant population (ha-1)

Plant height (cm)

Sympodial branches per plant

Bolls per plant

Average boll weight (g)

Seed cotton yield (kg ha-1)

2019

2020

2019

2020

2019

2020

2019

2020

2019

2020

2019

2020

Plant spacing (cm)

15

87178A

86385A

78A

85A

10C

11C

11C

11 C

2.35C

2.31 C

2111B

2200 C

23

57771B

57741B

68B

83B

13B

14B

15B

16 B

2.74B

2.73 B

2183A

2522 B

30

35536C

35150C

63C

81C

16A

16A

20A

23 A

3.52A

3.62 A

2214A

2965 A

LSD 0.05

216

127

1.8

0.2

0.06

0.5

0.07

0.3

0.07

0.08

68

91

Time of De-topping (Days after sowing)

Control

60056

59855

88A

97A

11D

12C

14D

15 D

2.86C

2.77 C

1933D

2127 D

75

60154

59873

56E

67E

10E

12C

12E

14 E

3.02A

2.87 B

1821E

2082 D

90

60270

59712

63D

77D

16A

16A

20A

21 A

2.61D

2.89 AB

2559A

3165 A

105

60163

59699

68C

83C

14B

14B

16B

18 B

2.92BC

2.94 A

2335B

2813 B

120

60165

59656

73B

91B

13C

14B

15C

17 C

2.94B

2.95 A

2198C

2624 C

LSD 0.05

-

-

1.3

0.5

0.2

0.5

0.2

0.5

0.07

0.06

69

111

Plant spacing × Time of de-topping

15

Control

86953a

86663 a

94a

103a

8j

9i

10j

10 k

2.27g

2.13 k

1702ij

1918 h

75

87055a

86727 a

64f

68n

7k

9i

9k

8 l

2.40f

2.25 jk

1656j

1627 i

90

87282a

86253 b

72e

76k

14e

13ef

15g

13 hi

2.20g

2.49 hi

2547b

2884 c

105

87370a

86216 b

76d

83h

11h

12g

13h

12 j

2.43ef

2.27 j

2430bc

2378 ef

120

87229a

86067 b

83c

95c

9i

10h

11i

11 k

2.47ef

2.39 i

2220def

2191 fg

23

Control

57926b

57738 c

88b

96b

12g

13f

15g

13 ij

2.77d

2.55 gh

2120fg

1867 h

75

57935b

57750 c

54i

64o

10i

14e

13h

14 h

3.03c

2.63 fg

2003gh

2126 g

90

57955b

57744 c

59g

79j

16c

16bc

18d

19 e

2.53e

2.98 d

2312cd

3273 ab

105

57683bc

57739 c

66f

84g

14e

15d

17e

17 f

2.67d

2.79 e

2298d

2795 c

120

57357c

57738 c

71e

92e

13f

15d

16f

16 g

2.70d

2.70 ef

2179ef

2546 de

30

Control

35289e

35164 d

81c

93d

15d

16cd

18d

20 d

3.53b

3.63 b

1975h

2597 d

75

35472de

35142 d

49j

69m

13f

14ef

16f

19 e

3.63ab

3.73 ab

1805i

2493 de

90

35575de

35139 d

57h

74l

19a

20a

28a

30 a

3.10c

3.20 c

2819a

3337 a

105

35436e

35142 d

61g

82i

16b

17b

19b

25 b

3.67a

3.77 a

2276de

3265 ab

120

35909d

35164 d

65f

86f

16c

17b

19c

24 c

3.67a

3.77 a

2196def

3134 b

LSD 0.05

461

295

2.2

0.9

0.4

0.8

0.4

0.9

10

0.1

119

191

 

Means sharing same case letter do not differ significantly at p ≤ 0.05.

 

In case of interaction between plant spacing and time of de-topping, during 2019, higher plant population was noted in all those de-topping treatments where cotton was planted at 15 cm plant spacing although least was noted in the de-topping treatments where cotton was planted at 30 cm plant spacing (Table 1). However, during 2020, higher plant population was noted where cotton was planted at 15 cm plant spacing and de-topped at 75 DAS as well as in control treatment whereas least was noted in the treatments where cotton was planted at 30 cm plant spacing and de-topped at 75, 90, 105 DAS as well as in control.

Results of this study revealed that plant spacing significantly affected plant population in both years, with the highest plant population noted at the closest spacing of 15 cm and the lowest at 30 cm. This pattern is consistent across both years, indicating that closer plant spacing results in a denser plant population. Lesser plant population in wider row spacing as well as higher plant population in narrow row spacing has also been reported by many researchers (Zaman et al., 2021; Haarhoff and Swanepoel, 2022).

Plant height (cm)

In both years, plant height was significantly (P≤0.05) affected by plant spacing, time of de-topping and interaction between plant spacing and time of de-topping (Table 1). In case of plant spacing, higher plant height was noted when cotton was planted at 15 cm plant spacing whereas least was noted where cotton was planted at 30 cm plant spacing (Table 1). In case of time of de-topping, higher plant height was noted when cotton was not de-topped (control) whereas least was noted when de-topping was performed at 75 DAS (Table 1). Regarding interaction between plant spacing and time of de-topping, during 2019, higher plant height was noted in treatment where cotton was planted at 15 cm plant spacing and no de-topping was performed (control) whereas least was noted where cotton was planted at 30 cm plant spacing and de-topped at 75 DAS (Table 1). During 2020, higher plant height was noted in treatment where cotton was planted at 15 cm plant spacing and no de-topping was performed (control) whereas least was noted where cotton was planted at 23 cm plant spacing and de-topped at 75 DAS (Table 1).

The results demonstrated that both plant spacing and de-topping time significantly affected plant height. Plants sown at 15 cm spacing were consistently taller than those at wider spacing, indicating that closer spacing might promote vertical growth (Shrestha et al., 2021). The increased height in closer spaced plants can be attributed to competition for light, which encourages vertical growth as plants strive to outgrow their neighbors (Zaman et al., 2021). These findings align with those of Sharma and Kumar (1989), Sharma (1998), and Ali et al. (2009), who observed that closer plant spacing led to increased plant height. This height increase was attributed to the elongation of internodes as plants sought to access more solar energy at higher canopy levels. De-topping time also played a crucial role, with the tallest plants noted in the control (no de-topping), followed by later de-topping times (120 DAS and 105 DAS), while the shortest plants were noted with early de-topping (75 DAS). This trend was consistent across both years, suggesting that delaying de-topping allows for greater vertical growth (Nayak et al., 2023). The interaction effects further emphasized that the combination of 15 cm spacing and no de-topping resulted in the tallest plants, highlighting the combined influence of these factors on plant height (Khubna et al., 2021).

Sympodial branches per plant

In both years, sympodial branches per plant was significantly (P≤0.05) affected by plant spacing, time of de-topping and interaction between plant spacing and time of de-topping (Table 1). In case of plant spacing, higher sympodial branches per plant was noted when cotton was planted at 30 cm plant spacing whereas least was noted where cotton was planted at 15 cm plant spacing (Table 1). In case of time of de-topping, during 2019, higher sympodial branches per plant was noted when cotton was de-topped at 90 DAS whereas least was noted when de-topping was performed at 75 DAS (Table 1). During 2020, higher sympodial branches per plant was noted when cotton was de-topped at 90 DAS whereas least was noted when de-topping was performed at 75 DAS as well as in control (Table 1). Regarding interaction between plant spacing and time of de-topping, during 2019, higher sympodial branches per plant was noted in treatment where cotton was planted at 30 cm plant spacing and de-topped at 90 DAS whereas least was noted where cotton was planted at 23 cm plant spacing and de-topped at 75 DAS (Table 1). During 2020, higher sympodial branches per plant was noted in treatment where cotton was planted at 30 cm plant spacing and de-topped at 90 DAS whereas least was noted where cotton was planted at 15 cm plant spacing and de-topped at 75 DAS and control (Table 1).

The sympodial branches per plant was highest at the widest spacing (30 cm) and lowest at the narrowest spacing (15 cm), suggesting that wider spacing promotes the development of lateral branches. This increase in fruit branches per plant at lower planting densities (wider spacing) is likely owing to more space for growth of plant and reduced competition (Ibrahim et al., 2022). These findings are consistent with observations by Sharma (1994, 1998), Singh and Singh (1998), and Mukharjee (1999), who reported that wider plant spacing enhances branch development by improving photosynthetic efficiency. Additionally, de-topping at 90 DAS consistently gave in the highest number of sympodial branches across both years, with 105 DAS and 120 DAS showing intermediate results, and the lowest number of branches noted at 75 DAS. Since cotton has an indeterminate growth habit, de-topping after the appropriate vegetative stage encourages the growth of existing sympodial branches and the formation of new ones (Brar et al., 2000). Furthermore, de-topping inhibits vertical growth, which subsequently promotes lateral growth and branching (Alam et al., 2024). Rathore and Gumber (2015) also found that de-topping increases the number of sympodial branches by breaking apical dominance and promoting the development of lateral fruiting branches. The interaction effects showed that the combination of 30 cm spacing and 90 DAS de-topping yielded the highest number of branches as wider spacing enabled plant to grow better due to low plant to plant competition for resources and higher photosynthetic efficiency (Ibrahim et al., 2022) and de-topping after attaining suitable vegetative growth enabled plant to allocate the photosynthates for the development of sympodial branches instead of allocating resources on vertical growth (Alam et al., 2024).

Bolls per plant

In both years, bolls per plant was significantly (P≤0.05) affected by plant spacing, time of de-topping and interaction between plant spacing and time of de-topping (Table 1). In case of plant spacing, higher bolls per plant was noted when cotton was planted at 30 cm plant spacing whereas least was noted where cotton was planted at 15 cm plant spacing (Table 1). In case of time of de-topping, higher bolls per plant was noted when cotton was de-topped at 90 DAS whereas least was noted when de-topping was performed at 75 DAS (Table 1). Regarding interaction between plant spacing and time of de-topping, higher bolls per plant was noted in treatment where cotton was planted at 30 cm plant spacing and de-topped at 90 DAS whereas least was noted where cotton was planted at 15 cm plant spacing and de-topped at 75 DAS (Table 1).

The trend in the bolls per plant showed that of the sympodial branches, with the highest count at 30 cm spacing and the lowest at 15 cm. This pattern aligns with findings by Hussain et al. (2000) and Alfaqeih et al. (2002), who noted that an improvement in bolls per plant was directly related to a higher number of sympodial branches. Additionally, Iqbal et al. (2010) suggested that the increased number of bolls with wider plant spacing could be the result of lesser competition among plants, as wider spacing allows for better water and nutrient uptake, leading to more sympodial branches (Zaman et al., 2021). This, in turn, results in a higher bolls per plant. Furthermore, the increase in boll number could also be due to improved assimilation and translocation of photosynthates, facilitated by better light interception in plants with wider spacing (Iqbal et al., 2012). In addition to that in wider spaced plants the plant roots can grow better so that they can absorb nutrients better hence the plant grow’s better (Khubna et al., 2021). Likewise de-topping at 90 DAS again resulted in the highest number of bolls, followed by 105 DAS and 120 DAS, with the fewest bolls at 75 DAS. Vekaria et al. (2020) also reported an increased boll per plant as a result of de-topping compared to no de-topping. Vani et al. (2021) observed that removing the shoot apex shifts growth from the vegetative stage to the reproductive stage and improves boll number by increasing nutrient availability. This is because the removal of the shoot apex alters the distribution of nutrients, enhancing uptake (Pandey et al., 2021). Therefore, nutrient availability significantly affects the bolls per plant in cotton (Vani et al., 2021). Additionally, removing the shoot apex reduces apical dominance and promotes the growth of lateral shoots, which increases boll number (Swapna and Singh, 2008). Ohta and Ikeda (2016) and Ohta (2017) found that after removing the shoot apex, the number of bolls increased significantly due to better availability of photosynthetic products and nutrients. These findings are consistent with Pandey et al. (2021), who reported the highest bolls per plant following shoot apex removal compared to plants without apex removal. The interaction effects highlighted that the combination of 30 cm spacing and 90 DAS de-topping was optimal for boll production. These findings suggest that wider spacing and appropriately timed de-topping can enhance boll development, potentially leading to higher yields.

Boll weight (g)

In both years, average boll weight was significantly (P≤0.05) affected by plant spacing, time of de-topping and interaction between plant spacing and time of de-topping (Table 1). In case of plant spacing, higher average boll weight was noted when cotton was planted at 30 cm plant spacing whereas least was noted where cotton was planted at 15 cm plant spacing (Table 1). In case of time of de-topping, during 2019, higher average boll weight was noted when cotton was de-topped at 75 DAS whereas least was noted when de-topping was performed at 90 DAS (Table 1). During 2020, higher average boll weight was noted when cotton was de-topped at 75, 90, 105 and 120 DAS as compared to control (Table 1). Regarding interaction between plant spacing and time of de-topping, higher average boll weight was noted in treatments where cotton was planted at 30 cm plant spacing and de-topped at 105 and 120 DAS whereas least was noted where cotton was planted at 15 cm plant spacing and no de-topping was performed (Table 1).

Plant spacing and de-topping time significantly influenced the average boll weight. The highest average boll weight was observed at 30 cm spacing, followed by 23 cm, and the lowest at 15 cm. The increased boll weight at wider spacings is likely due to reduced competition among plants, leading to more efficient resource use (Zaman et al., 2021). These results are consistent with findings by Alfaqeih et al. (2002) and Shah et al. (2017), who reported that wider spacing increased both the number of branches per plant and boll weight due to decreased competition. Additionally, lower plant density was associated with a higher number of heavier bolls per plant, while higher plant density led to a reduction in both boll quantity and weight (Bednarz et al., 2007). De-topping at 75 DAS yielded the highest average boll weight in 2021, while in 2022, the highest weights were observed at all de-topping times compared to the control. This because of the reason that due to de-topping the vertical growth is inhibited and photosynthates are mostly allocated to the developing bolls (Zaman et al., 2021). Studies have shown that increase in average boll weight owing to de-topping is because by removing the top portion of the plant, the plant’s resources are concentrated on remaining bolls instead of producing more vegetative growth, allowing for larger and heavier bolls to develop (Dai et al., 2022). The interaction effects revealed that the combination of 30 cm spacing and de-topping at 105 and 120 DAS produced the heaviest bolls. These results indicate that wider spacing and delayed de-topping enhance boll weight, contributing to overall yield.

Seed cotton yield (Kg ha-1)

In both years, seed cotton yield was significantly (P≤0.05) affected by plant spacing, time of de-topping and interaction between plant spacing and time of de-topping (Table 1). In case of plant spacing, higher seed cotton yield was noted when cotton was planted at 30 and 23 cm plant spacing whereas least was noted where cotton was planted at 15 cm plant spacing (Table 1). In case of time of de-topping, during 2019, higher seed cotton yield was noted when cotton was de-topped at 90 DAS whereas least was noted when de-topping was performed at 75 DAS (Table 1). During 2020, higher seed cotton yield was noted when cotton was de-topped at 90 DAS whereas least was noted when de-topping was performed at 75 DAS and control (Table 1). Regarding interaction between plant spacing and time of de-topping, during 2019, higher seed cotton yield was noted in treatments where cotton was planted at 30 cm plant spacing and de-topped at 90 DAS whereas lowest was noted in treatment where cotton was planted at 15 cm plant spacing and de-topped 75 DAS (Table 1). During 2020, higher seed cotton yield was noted in treatments where cotton was planted at 30 cm plant spacing and de-topped at 90 DAS whereas lowest was noted in treatment where cotton was planted at 15 cm plant spacing and de-topped 75 DAS (Table 1).

Seed cotton yield was significantly affected by plant spacing and de-topping timing. The highest yields were achieved at 30 cm and 23 cm spacings, while the lowest yield was observed at 15 cm. According to Shrestha et al. (2021) and Khubna et al. (2021), higher plant densities led to increased plant competition, resulting in taller plants with fewer branches, more lodging, and reduced pod and seed production, ultimately decreasing seed yield compared to lower densities. Additionally, de-topping at 90 DAS consistently produced the highest yields, followed by 105 DAS and 120 DAS, with the lowest yield at 75 DAS. This is due to de-topping breaking apical dominance and redirecting resources to reproductive organs, resulting in more squares, flowers, bolls, and lint yield (Li et al., 2006; Dai et al., 2022). Similar increases in lint yield and yield components with de-topping have been observed in both full-season cotton under single cropping (Ren et al., 2013; Li et al., 2018) and short-season cotton under double cropping (Yu et al., 2022). The interaction effects showed that the combination of 30 cm spacing and 90 DAS de-topping produced the highest yields, particularly in 2022. These findings underscore the importance of optimizing both plant spacing and de-topping time to maximize cotton yield. These results showed that closer spacing supported higher plant density, which may influence other growth parameters and overall yield.

Conclusions and recommendations

The experiment demonstrated that both plant spacing and de-topping time are critical factors affecting cotton growth and yield. Closer plant spacing (15 cm) promoted higher plant population and plant height, while wider spacing (30 cm) enhanced the number of sympodial branches, bolls, and average boll weight, leading to higher seed cotton yield. The optimal de-topping time appeared to be 90 DAS, which consistently resulted in higher yield related parameters and yield. Hence it is concluded that to maximize the seed cotton yield the cotton plants should be planted at 30 cm plant spacing and de-topped at 90 DAS.

Acknowledgements

The research was the part of Annual program of work of Agronomic Research Station, Khanewal. The authors acknowledge the Agriculture Department, Government of Punjab, Pakistan, for providing the financial support to carry out this research study.

Novelty Statement

This study addressed the gap in cotton agronomy by exploring the combined effects of de-topping and plant spacing on seed cotton yield. However de-topping has been known in some cotton-producing regions but its optimal timing and interaction with plant spacing was unclear. By systematically examining de-topping at various growth stages and different plant densities, this research identified the most effective combination for maximizing yield.

Author’s Contribution

Muhammad Iqbal: Wrote the paper

Saba Iqbal: Handled experiment execution, data collection, analysis, and co-wrote the paper.

Arbab Jahangeer: Worked on proofreading, data tabulation, and graphs.

Muhammad Arshad: Removed plagiarism.

Naveed Akhtar, Ansar Hussain, Mussurrat Hussain, Muhammad Shahid and Qaisar Abbas: Contributed to proofreading and editing.

Conflict of interest

The authors have declared no conflict of interest.

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