Evaluation of Plant Density and Cotton Genotypes (Gossypium hirsutum L.) on Yield and Fibre Quality

Field experiments were conducted during winter season of 2011-12 and 2012-13 at Tamil Nadu Agricultural University, Coimbatore to study the feasibility of using cotton genotypes under high density planting system and to assess its effect on seed cotton yield, oil content and fibre quality parameters. The experiments were laid out in a strip plot design, replicated thrice. The soil in the experimental site was sandy clay loam with low available nitrogen (182 kg/ha), medium available phosphorus (12.6 kg/ha) and high available potassium (340 kg/ha). The experiment consisted of seven cotton genotypes viz ., Jai, Ranjeet, TCH 1608, SVPR 3, Anjali, Suraj and LH 900 with four spacings viz ., 30 × 30, 45 × 30, 60 × 30 and 90 × 30 cm. Ranjeet planted at the spacing of 30 × 30 cm recorded significantly higher seed cotton yield. The percentage of oil content was significantly higher in Ranjeet genotype than other cotton genotypes. The fibre quality parameters viz ., fibre length, fibre strength, micronaire, elongation percentage were significantly influenced by different cotton genotypes. The oil content and fibre quality was not significantly influenced by plant densities.

Cotton ( Gossypium hirsutum L.) "The king of fibres" is the leading fibre crop in the world.India is the only country where all the four species of cotton are grown among the cotton growing countries of the world.Cotton is an important raw material supplying about 65% requirement of the Indian textile industry.Crop management practices to improve fibre quality while maintaining lint yield have become the focus of intense research.Several studies have reported that lint yield in upland cotton is negatively related to fibre quality (Green and Culp, 1990), that is, cotton plants need to sacrifice fibre quality to improve lint yield.Thus, accessing strategies to improve fiber quality while maintaining yield levels is crucial and this process requires better understanding of the effects of crop management practices on cotton fiber quality.Bednarz et al. (2006) reported lower fibre quality from increased plant density.Cotton is also a good source of edible oil.The cotton seed oil is rich in essential fatty acids such as myristic, palmitic, palmitoleic, steric, oleic and linoleic acid.The deficiency of above acids, leads to narrowing of arteries causing reduced blood supply to the heart.Cotton seed oil will play an important role in meeting the demand of edible vegetable oil in the country (Singh, 2003).Hence, an investigation was initiated to determine influence of different plant densities on the seed cotton yield, oil content and fibre quality of cotton genotypes (Gossypium hirsutum).

Materials and Methods
Field experiments were conducted at Tamil Nadu Agricultural University, Coimbatore during the winter season of 2011 -2012 and 2012-2013.The objectives of this study were to determine the feasibility of using cotton genotypes under high density planting system for cotton production and to assess its effect on seed cotton yield, oil content and fiber quality parameters.Coimbatore is situated in the Western Zone of Tamil Nadu at 11° North latitude and 77° East longitude with an altitude of 426.7 m above mean sea level.The experiment was laid out in a strip plot design, replicated thrice.The soil of the experimental site was sandy clay loam with low available nitrogen (182 kg/ha), medium available phosphorus (12.6 kg/ha) and high available potassium (340 kg/ha).The treatments consisted of seven cotton genotypes viz., Jai, Ranjeet, TCH 1608, SVPR 3, Anjali, Suraj and LH 900 with four spacings viz., 30 × 30, 45 × 30, 60 × 30 and 90 × 30 cm (with plant densities viz., 111111, 74074, 55555, and 37037 plants ha-1, respectively).The crop was sown and raised using the recommended package of practices as per TNAU crop production guide.Defoliant (Dropp Ultra @ 200 ml per ha) was sprayed at 80 % maturity for uniform boll bursting so that one time harvest was done.The oil content was estimated by using the Soxhlet extraction apparatus by the procedure given by Sadasivam and Manickam (1995) .Fibre quality characters were tested using High volume instrument user model: HVI Classic 900.

Seed cotton yield
The seed cotton yield was significantly influenced by cotton genotypes and plant spacing.Among the cotton genotypes, Ranjeet and Jai recorded significantly higher seed cotton yield of 3311 and 3115 kg ha-1, respectively during 2011-12 and were on par with each other Table 1.The cotton genotype SVPR 3 recorded less yield (1510 kg ha-1), which is also comparable with Suraj during 2011-12.Jagannathan and Venkitaswamy (1996) revealed that dwarf compact genotypes responded favourably to a population of 1, 11,000 plants ha-1 on Vertisols.
Comparing the plant spacings, the plant spacing of 30 × 30 cm recorded significantly higher seed cotton yield (3168 kg ha-1) followed by 45 × 30 cm spacing.Lower seed cotton yield was observed with the plant spacing of 90 × 30 cm (1498 kg ha-1) in 2011-12.Ali et al. (2010)  The interaction was significant with cotton genotypes and different plant spacing.In the year 2011-12, plant spacing of 30 × 30 cm in Ranjeet significantly recorded higher seed cotton yield of 4511 kg ha-1 followed by Jai (4378 kg ha-1) and both were comparable with each other.The genotype SVPR 3 at the spacing of 90 × 30 cm registered lower seed cotton yield but was comparable with Suraj and LH 900.The differences in the yield of SVPR 3, Suraj and LH 900 did not differ significantly because they did not cause significant variation with respect to all parameters i.e., growth, physiological and yield parameters.This was also observed by Bhalerao et al. (2008).Venugopalan et al. (2011) found that Gossypium hirsutum genotypes Anjali, PKV 081 and CCH 724 were more amenable to closer spacings i.e. higher planting densities (166000 plants ha-1 ) on rainfed vertisols under Maharastra.Similar trend was observed during 2012-13 also.

Oil content
The cotton genotypes significantly influenced oil content.The percentage of oil content was significantly higher in Ranjeet (24.7 and 24.5 % in 2011-12 and 2012-13, respectively) than other cotton genotypes followed by LH 900, Suraj and Jai and were comparable with each other.Lower oil content was recorded by SVPR 3, Anjali and TCH 1608 and they were on par with each other

Lint Index, Seed Index and Ginning percentage
The quality parameters differed significantly due to genotypes.The lint index was significantly higher in Ranjeet (6.19 and 6.14 in 2011-12 and 2012-13 respectively) followed by Jai and TCH 1608 and were comparable with each other in both the years.Comparably lower lint index was registered by LH 900, Anjali and Suraj in both years of study Table 3.
The genotypes Ranjeet, TCH 1608 and Jai recorded higher seed index.Significantly lower seed index was registered by Anjali, LH 900 and Suraj and were on par among themselves in both the years of study Table 3.The genotype TCH 1705 , which is morphologically similar to the genotype TCH 1608 recorded higher lint and seed index in Coimbatore under irrigated condition (AICCIP, 2013).
No significant difference was observed with regard to different plant spacings on lint and seed index Table 3.The ginning percentage was neither significantly influenced by both cotton genotypes nor by plant densities Table 3.

% span length
Higher 2.5 % span length was recorded with Jai (30.18 and 29.58 in 2011-12 and 2012-13, respectively), which was comparable with TCH 1608,  (2006) reported that there is no significant difference was observed in micronaire values between plant densities of wider row spacing 38 cm and 76 cm but significant difference was observed with the 19 cm row spacing in Texas.

Uniformity (%)
The cotton genotype, Suraj recorded significantly higher values of fibre strength (20.13 and 22.05 g tex-1 in the year 2011 -12 and 2012-13) but was comparable with Jai in 2012-13 Table 4.The fibre strength was not significantly influenced by different plant densities.

Micronaire
Among the cotton genotypes, significantly finer fibres were observed with Anjali, Suraj, SVPR 3 and TCH 1608 and they were on par among themselves Table 4. LH 900 recorded significantly higher micronaire value followed by Jai.The genotype CSH 3075 registered lower micronaire value closely followed by CCH 12, RS 2718, GTHV 09, and GTHV 04 under irrigated conditions of Coimbatore (AICCIP, 2013).The plant densities did not significantly No significant difference was observed with cotton genotypes and plant spacings on uniformity ratio Table 4. Jost and Cothern (2000) opined that the fibre uniformity with decrease in row spacing due to lack of photosynthate production or less available moisture.

Elongation percentage
The elongation percentage was significantly influenced by cotton genotypes Among the cotton genotypes, significantly higher elongation percentage was recorded by Anjali (7.15) but was comparable with SVPR 3, Jai and TCH 1608 in the year 2011-12 Table 4.
In 2012-13, Anjali registered significantly higher elongation percentage and was on par with SVPR 3. The elongation percentage was significantly lower with the cotton genotypes Suraj, Jai and LH 900 and were comparable among themselves during both the years of study.In the present study the increase in plant density did not influence the quality parameters.Molin and Hugie (2010) also reported that the quality parameters like Micronaire, fibre length, strength, and uniformity were not affected by increasing population density in Silty loam soils of Stoneville.

Conclusion
Among cotton genotypes, Ranjeet planted at the spacing of 30 × 30 cm recorded significantly higher yield.Irrespective of plant densities, Ranjeet recorded significantly higher oil content, lint and seed index.Finer fibre with higher elongation percentage was recorded with Anjali.The cotton genotypes, Jai and Suraj recorded significantly higher values of both fibre length and fibre strength.Ginning percentage and uniformity ratio was not significantly influenced by cotton genotypes and plant density.

Table 1 . Effect of plant densities on seed cotton yield (kg ha-1) in G.hirsutum genotypes
revealed that significantly Singh et al. (2012)12)ld was obtained with narrow spacing 15 cm followed by 30 cm than 45 cm row spacing in silt loam soil in Pakistan.Similar results were reported byDelaney et al. (2002);Brodrick et al. (2012)andSingh et al. (2012).

Table 3 . Effect of plant densities on ginning percentage, lint Index and seed Index in G.hirsutum genotypes
Tenacityinfluenced the micronaire values.Clawson et al.