Cotton enjoys a predominant position among all cash crops in India and has retained its unique fame as “King of Fibres” and “White Gold” because of its higher economic value among all cash crops in India. It is grown mainly for its fibre used in the manufacture of cloth for mankind. In recent years, cotton clothing being preferred to the synthetic ones due to the increasing health consciousness among the people. Besides fibre, cotton is also valued for its oil and cotton seed cake. Also, it likely to play a key role in paper, particle board and cardboard industries. With the advanced technology, short fibre or fuzz or linter can now be used to make excellent grade paper like currency paper, linoleum, cellophane, rayon’s, photographic film, dynamic and moulded plastics.

The early estimate of USDA indicates that India has displaced China and became the leading producer of cotton and also maintaining the largest area under cotton besides being second largest exporter of cotton next to United States [1]. In India, the production increased from a meager of 169 kg lint per hectare during 1980-81 to a high of 523 kg lint per hectare in 2015-16. However, the productivity of cotton in India is still far less than other cotton growing countries of the world viz., Australia (2038 kg ha^-1), Turkey (1620 kg ha^-1), Brazil (1524 kg ha^-1), China (1484 kg ha^-1), USA (1476 kg ha^-1) and Egypt (737 kg ha^-1) (Anon., 2015). In Karnataka, cotton occupies an area of 5.07 lakh hectares with a production of 18 lakh bales and a productivity of 604 kg per hectare [2].

Indian farmers have been widely accepted Bt-cotton technology due to the inbuilt technology of bollworm management. Despite of heavy inroads of hybrids, especially Bt cotton hybrids occupying as much as 95 per cent of the total area under cotton cultivation in India, the seed cotton yield per unit area is still far below than many other cotton growing countries of the world. Among the various factors responsible for the low cotton yield in the country, low plant population and use of common potential varieties are of primary importance. Under these conditions adaption of HDPS in cotton is more relevant to India in general and Karnataka in particular. The ongoing cotton breeding research in various cotton research centres in the country and at UAS, Raichur has led to the evolution of promising compact cotton genotypes that have the advantage of short sympodial branches with reduced inter-nodal length giving morphological feature of compressed habit and clustered boll habit. Among the three non-Bt, early maturing compact with short sympodial genotypes (Anjali, C1412 and CCH-7245), the genotype Anjali recorded significantly higher seed cotton yield and boll weight (2513 kg ha^-1 and 3.4 g, respectively) over C1412 genotype (1922 kg ha^-1 and 3.0 g, respectively) while it remained on par with CCH 7245 genotype (2349 kg ha^-1 and 3.3 g) [3]. Decrease in the number of functional leaves, leaf area and dry matter accumulation per plant with increase in plant population density from 1,11,111 plants ha^-1 to 2,22,222 plants ha^-1. Similarly, increase in plant density decreased the number of the boll, boll weight and yield per plant. Whereas, increase in plant density increased the economic and biological yield per unit area [4, 5].

            Keeping these points in view, field investigation under irrigated condition was carried out to know the suitable potential genotype and optimum planting geometry to get a sustained higher yield under the HDPS system.

  MATERIAL AND METHODS

            A field experiment entitled “Growth, yield and economic performance of compact cotton genotypes grown under high-density planting system in the irrigated ecosystem” were conducted at College of Agricultural, UAS, Raichur during Kharif 2016-17 and 2017-18 on medium black soil, neutral with low available nitrogen, medium in phosphorus, rich in potassium. The climatic condition during the experimental period was favorable and regular irrigation was provided to crop during both the years at later part of crop growth stages i.e, from 60 DAS to till first picking.

            The experiment was laid out in split-plot design with three compact cotton genotypes viz., G₁: SCS-1206, G₂: DSC-99, G₃: Suraj as main plot treatments and three planting geometries viz.,  S₁: 60 cm x 10 cm (1,66,666 plants ha^-1), S₂: 75 cm x 10 cm (1,33,333 plants ha^-1) and S₃: 90 cm x 10 cm (1,11,111 plants ha^-1) as sub plot treatments along with the conventional system of cotton cultivation with Bt cotton hybrid ATM at a recommended spacing of 90 cm x 10 cm (uneven control) 

RESULTS AND DISCUSSION

Genotypes

            Among the different compact cotton genotypes, G₁: SCS-1206 recorded significantly higher seed cotton yield (2886 kg ha^-1 on pooled basis) and substantially lower seed cotton yield was recorded with genotype G₂: DSC-99 (2486 kg ha^-1). This difference in seed cotton yield was mainly attributed to the significant difference in yield components viz., seed cotton yield per plant,  boll weight and number of bolls per plant (25.98 g, 3.73 g and 12.82, respectively on pooled basis) and which was further due difference in growth attributes viz., plant height, number of sympodial branches per plant, dry matter accumulation in reproductive parts and total dry matter production per plant (121.54 cm, 12.72, 57.70 g and 126.72 g, respectively on pooled basis) and also due to significant difference in absolute growth rate, crop growth rate leaf area duration and leaf area index (1.54 g plant^-1, 20.76 g m^-2 day^-1, 124.32 days and 5.08, respectively on pooled basis). Similar results were also reported by the other workers [3, 6, 7, 8, 9]

Table 1. Growth attributes of compact cotton under high density planting system and cotton grown under conventional system

Planting geometry     

The difference in seed cotton yield due to different planting geometry was evident. Among different row spacings, a closer spacing of S₁: 60 cm x 10 cm recorded significantly higher seed cotton yield (2896 kg ha^-1 on pooled basis) when compared with the medium row spacing of S₂: 75 cm x 10 cm (2758 kg ha^-1 on pooled basis) and wider row spacing of S₃: 90 cm x 10 cm (2472 kg ha^-1 on pooled basis). Whereas, yield attributes viz., number of bolls per plant, boll weight and seed cotton yield per plant (13.98, 3.88 and 26.16 g, respectively on pooled basis) were significantly higher under wider row spacing of S₃: 90 cm x 10 cm, which was mainly due to significant difference in growth attributes viz., number  sympodial branches per plant, dry matter accumulation in reproductive parts, total dry matter production per plant and absolute growth rate (14.50, 58.07 g, 133.05 g and 1.65 g plant^-1 day^-1 respectively, on pooled basis) which was mainly due to more ground area available for individual plants. Further, other growth parameters viz., crop growth rate, leaf area duration and leaf area index (22.12 g m^-2 day^-1, 126.12 days and 5.24, respectively on pooled basis) recorded were significantly higher under closer row spacing of S₁: 60 cm x 10 cm. Significantly higher seed cotton yield in closer row spacing was attributed to higher plant population per unit area even though the growth and yield attributes were lower when compared to recorded under medium and wider row spacings and an increase in the number of plants per unit area could be compensated for the decrease in yield components per plant under narrow spacing. Significantly superior seed cotton yield observed was mainly due to higher number of harvested bolls and higher plants population per unit area as supported findings of the other workers [4, 5, 10, 11, 12, 13].

Table 2. Growth attributes of compact cotton under high density planting system and cotton grown under conventional system

  Interaction effect

            The interaction effect of compact cotton genotypes and planting geometries were found significant. Among the different combinations, the interaction of genotype G₁: SCS -1206 with a row spacing of S₁: 60 cm x 10 cm recorded significantly higher seed cotton yield (3096 kg ha^-1 on pooled basis) when compared to the rest of the treatment combination. However, it remained at par with the genotype G₁: SCS-1206 with a row spacing of S₂: 75 cm x 10 cm (2949 kg ha^-1 on pooled basis) and genotype G₃: Suraj with a row spacing of S₁: 60 cm x 10 cm (2923 kg ha^-1 on pooled basis). Further, cotton grown under conventional system with Bt cotton hybrid ATM at a recommended spacing of 90 cm x 60 cm recorded significantly lower seed cotton yield (2314 kg ha^-1 on pooled basis) when compared with all the treatment combinations of cotton grown under HDPS except with the combination of genotype G₂: DSC-99 with a row spacing of  S₂: 75 cm x 10 cm (2525 kg ha^-1 on pooled basis) and genotype G₂: DSC-99 with a row spacing of  S₃: 90 cm x 10 cm (2263 kg ha^-1, on pooled basis). A decrease in yield under the conventional system of cotton cultivation when compared to HDPS was attributed to the increase in area per plant has not compensated for an increase in yield per plant per unit area. The results are in line with the findings of the other workers [14, 15].

Table 3. Yield attributes and yield of compact cotton genotypes under high density planting system and cotton grown under conventional system

Economics

            Among the different compact cotton types, genotype G₁: SCS-1206 and G₃: Suraj recorded significantly higher net returns (₹ 81,346 and 75,434 ha^-1 respectively on pooled basis) and BC ratio (2.73 and 2.60, respectively on pooled basis). At the same time the genotype G₂: DSC-99 recorded significantly lower net returns (₹ 63,508 ha^-1 on pooled basis) and BC ratio (2.35 on pooled bases). Among different planting geometries, a closer row spacing of S₁: 60 cm x 10 cm recorded significantly higher net returns (₹ 80,865 ha^-1 on pooled basis) and BC ratio (2.69 on pooled basis) and it was found at par with medium row spacing of  S₂: 75 cm x 10 cm (₹ 75,732 ha^-1 and 2.61, respectively on pooled basis). While, wider row spacing of S₃: 90 cm x 10 cm recorded significantly lower net returns and BC ratio (₹ 63,692 ha^-1 and 2.38, respectively on pooled basis). Among different interactions of cotton grown under HDPS, a combination of genotype G₁: SCS-1206 with row spacing of S₁: 60 cm x 10 cm recorded significantly higher net returns and BC ratio (₹ 89,736 ha^-1 and 2.87 , respectively on pooled basis) and found on par with the combination of genotype G₁: SCS-1206 with a spacing of S₂: 75 cm x 10 cm (₹ 84,263 ha^-1 and 2.80, respectively on pooled basis) and genotype S₃: Suraj with a row  spacing of S₁: 60 cm x 10 cm (₹ 82,064 ha^-1 and 2.71, respectively on pooled basis). Significantly lower net returns and BC ratio (₹ 54,379 ha^-1 and 2.18, respectively on pooled basis) was observed with the combination of genotype G₂: DSC-99 with a row spacing of S₃: 90 cm x 10 cm. Cotton grown under the conventional system with Bt cotton hybrid ATM with a recommended spacing of 90 cm x 60 cm recorded significantly lower economic values (₹ 53,522 ha^-1 and 2.09, respectively on pooled basis) when compared with the cotton grown under HDPS. This result was supported by findings of the other workers [14, 15].

Table 4.     Gross returns (₹ ha^-1), net returns (₹ ha^-1) and benefit cost ratio of cotton as influenced by genotypes and planting geometries under high density planting system

CONCLUSIONS

            In this research work, among the different compact cotton genotypes, the genotype SCS-1206 recorded significantly higher seed cotton yield (2886 kg ha^-1 on pooled basis). Among the different planting geometries, a closer spacing of 60 cm x 10 cm recorded significantly higher seed cotton yield (2896 kg ha^-1 on pooled basis). Among the different combinations, the interaction of genotype SCS -1206 with a row spacing of 60 cm x 10 cm recorded significantly higher seed cotton yield (3096 kg ha^-1 on pooled basis) when compared to the rest of the treatment combination. Cotton grown under the conventional system with Bt cotton hybrid ATM at a recommended spacing of 90 cm x 60 cm recorded significantly lower seed cotton yield (2314 kg ha^-1 on pooled basis). Thus, cotton cultivation under high-density planting system with suitable compact cotton is an economically viable technology for farmers of India as an alternate means for getting higher yields compared to conventional cultivation.

REFERENCES     

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