A field experiment was conducted to study the effect of crop density, establishment methods and split application of N and K on growth and yield of hybrid rice CoRH2 during late Pishanam season (November 2001-April 2002) at Agricultural College and Research Institute, Killikulam in Tambaraparani command area. The experiment was laid out in factorial randomized block design with seven treatments replicated thrice. The treatments consisted of two establishment methods, two plant densities and three methods of split application of N and K. The results revealed significant increase in growth attributes of hybrid rice CoRH2 in seedling broadcasting with 40 hills m-2 viz., taller plants, higher DMP, more number of tiller hill-1 and higher LAI, CGR and yield parameters viz., productive tillers m-1, panicle length, panicle weight, thousand grain weight, number of filled grains panicle-1 and registered higher grain and straw yield of 7206 and 8870 kg ha-1, respectively. With regard to split application of N and K, five splits of N and four splits of K exhibited significantly increased values of growth and yield components and recorded significantly superior grain yield of 6967 kg ha-1.The treatment combination of seedling broadcasting of 40 hills m-2 with five splits of N and four splits of K application registered significantly higher growth and yield parameters, which in turn exhibited higher rice grain yield of 7316 kg ha-1 and maximum net return of Rs. 46,170 ha-1 and the highest B:C ratio of 4.08. Minimum number of man days was utilized with seedling broadcasting of 50 hills m-2 with three splits of N and two splits of K. Energy use was significantly higher under seedling broadcasting with 40 hills m-2 and three splits of N and two splits of K.
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In India rice is cultivated in an area of 42.2 million ha with a production of 110 million tonnes, while China produces 187.45 million tonnes of rice in 33.1 million ha. The productivity of rice in India and China are 2.69 and 5.73 t ha-1, respectively. The increase in rice productivity of China is mainly due to cultivation of hybrids (Ali, 2000). In India the increasing demand for rice grain production has to be met by using limited available resources in a sustainable manner. It is generally felt that a yield plateau has been reached in conventional rice varieties and any further increase in the productivity of rice warrants the breaking of this yield barrier. Hybrid rice offers an opportunity to raise rice yields to higher levels than the present. India is yet to fully exploit the technology which offers a 10-15% yield advantage over the best conventional inbred varieties (Li, 1981; Yang and Sun, 1992). The average yield of hybrid rice is 6 to 7 t ha-1 with a yield advantage of 30% over conventional varieties (Pandian et al., 2001). Invention of commercial hybrid rice and its popularization has prompted agronomic investigations on its establishment and management. Growing hybrid rice is a complex process since agronomic management of hybrid rice differs considerably from that of conventional inbred varieties in many respects. Establishment technique, plant density, nutrient requirement and management, water management etc. need to be standardized to achieve the reported yield potential of rice hybrids of different duration in various environments. Method of establishment is one of the cultural practices, which influence the hybrid rice through its effect on growth and development. Of the several agronomic practices, optimum plant density and fertilizer management are considered as challenges in hybrid rice cultivation. Grain yield of rice per unit area per unit time is dependent on the duration of the variety, its response to plant population and fertilization. Delayed application of N and K, coinciding with flowering could help to realize the potential yield of rice hybrids. However, all these practices have to be scientifically standardized as a location specific study. In this context, the present research was undertaken to evaluate the feasibility, economic advantage of different establishment methods and split application of N and K for Pishanam season in Tambaraparani command area of Tamil Nadu.
MATERIALS AND METHODS
A field experiment was conducted at Agricultural College and Research Institute, Killikulam, Tamil Nadu during late Pishanam season of 2001-2002 to investigate the effect of crop establishment methods and split application of N and K on the yield enhancement of hybrid rice CoRH2. The soil of the experimental field was sandy clay loam in texture, nearly neutral in pH 6.9. The fertility status of the soil was low in available N 173 kg ha-1, high in available phosphorus 27.90 kg ha-1 and medium in available potassium 214.50 kg ha-1.The trial was laid out in Factorial Randomized Block Design and each treatment was replicated thrice. The details of treatments are given below.
P1- Line planting at 25x10 cm (40 hill m-2)
P2- Line planting at 20x10 cm (50 hill m-2)
P3- Seedling broadcasting with 40 hills m-2
P4- Seedling broadcasting with 50 hills m-2
Split application of N and K:
S1- Three splits of N at 50% B, 25% AT, 25% PI and two splits of K at 50% B, 50% PI
S2-Four splits of N at 50% B, 16.5% AT, 16.5% PI, 16.5% H and three splits of K at 50% B, 25% PI, 25% F
S3- Five splits of N at 50% B, 12.5% AT, 12.5% PI, 12.5% H, 12.5% F and four splits of K at 50% B, 25% PI, 12.5% H, 12.5% F
(B-basal, AT-active tillering, PI- panicle initiation, H- heading and F-flowering)
The hybrid CoRH2 is a medium duration (125 days) developed by three line breeding system using cytoplasmic male sterile line, maintainer line and restorer line. The grain is medium slender and white. A seed rate of 20 kg ha-1 was adopted and under line planting seedlings of 25 days old were planted at the rate of single seedling hill-1 by adopting spacing as per the treatments. Seedlings were broadcasted as per the treatments over the field by maintaining thin film of water. The recommended dose of 200:50:50 kg of NPK ha-1 was applied to CoRH2 rice hybrid in the form of urea, superphosphate and potash, respectively. Entire P fertilizer was applied basally and potash and nitrogenous fertilizers were applied in different splits as per the treatments.
RESULTS AND DISCUSSION
Growth components: Among the establishment methods of planting, seedling broadcasting with 40 hills m-2 registered significantly taller plants. The increased height in seedling broadcasting might be due to zero depth of planting resulting in better inducement of root growth for anchorage. This result corroborates with the findings of Matsushima (1979) and Sanbagavalli et al. (1999). Seedling broadcasting method ensures shallow depth of planting of seedlings as compared to line planting. This might be a possible reason to produce more tillers per hill under seedling broadcasting, as deeper planting caused reduction in tillering. Increased plant height and more number of tillers hill-1 resulted in higher DMP. Application of five splits of N and four splits of K was proved as better agronomic method and thus increased the plant height, more tiller number hill-1 and LAI at later stages. The same methods of application of nutrients increased DMP due to higher number of tillers hill-1 and LAI (Table 1). Split application of N and K extended after panicle initiation stage to meet the plant requirement led to the higher values of growth characters. Similar findings were observed by Biswas (1976) and Senthivel and Palaniappan (1985).
Yield components and grain yield: The better yield attributes viz., productive tillers m-2, panicle length, panicle weight, thousand grain weight and filled grains panicle-1 were significantly higher with seedling broadcasting method of planting compared to line planting (Table 2). It confirms the earlier findings of Esther Shekinah and Kandasamy (1998). Stand establishment methods and plant density caused significant variation in hybrid rice grain yield. Among the methods of establishment, seedling broadcasting produced higher grain yield than rest of the treatments. Adoption of 40 hills m-2 with seedling broadcasting method of planting produced significantly higher rice grain yield of 7206 kg ha-1 as compared to other methods and population. A reduction of 240 kg ha-1 grain yield was noticed in transplanting in the similar plant density. Hybrid rice grain yield was significantly lowered with increasing plant density to 50 hills m-2 in both planting methods of broadcasting and line planting. Adoption of line planting with 50 hills m-2 (P2) produced significantly lower grain yield of 6631 kg ha-1.
|Table 1:||Effect of establishment methods and split application of N and K on growth attributes of CoRH2 rice hybrid|
|Table 2:||Influence of crop establishment methods and split application of N and K on yield components of CoRH2 rice hybrid|
|Table 3:||Grain yield (kg ha-1) and Straw yield (kg ha-1) of CoRH2 rice hybrid as influenced by establishment methods and split application of N and K|
Increased nutrient availability, better solar radiation distribution and less competition for growth were the possible reasons for getting superior yield under seedling broadcasting in late Pishanam season. Split application of N and K had significant positive influence on grain yield. With regard to split application of N and K, five splits of N and four splits of K recorded higher yield attributes and rice grain yield. Four splits of N and three splits of K registered higher straw yield, which was on par with five splits of N and four splits of K (Table 3). Fractional application of N and K after panicle initiation and flowering stages synchronizing with the crop demand may lead to conducive translocation of more amount of carbohydrates to sink, which produced superior yield attributes under five splits and four splits, respectively. Combined application of N and K was found to be the better method of fertilizer application and reflected by more number of productive tillers, filled grains panicle-1, higher thousand grain weight, panicle weight, panicle length and lesser chaffy grains. These results are in accordance with Mondal et al. (1989). The interaction effect between stand establishment methods and split application of N and K was found significant. The higher grain yield of 7316 kg ha-1 was registered in the treatment with line planting at 20x10 cm (50 hill m-2) and five splits of N and four splits of K. The lower grain yield of 6582 kg ha-1 was associated with P2S1 which was on par with P2S2 (6640 kg ha-1).
Labour requirement: The quantity of labour requirement was worked out for the treatmental operations along with the weeding to assess the total man days/woman days required for each treatment.
|Table 4:||Effect of stand establishment methods and split application of N and K on labour requirement (man days ha-1) and energy budget of rice (MJ ha-1)|
|*Data not statistically analyzed|
|Table 5:||Economics (Rs.ha-1) of rice hybrid CoRH2 as influenced by establishment methods and split application of N and K|
|*Data not statistically analysed|
In general, seedling broadcasting employed less number of labourers of 36 man days ha-1 for planting than line planting (52 man days ha-1). Adoption of seedling broadcasting economized the labour requirement in transplanting to the tune of 30.76% over line transplanting. Among the split application of N and K, three splits of N and two splits of K (S1) required 6 man days ha-1, four splits of N and three splits of K(S2) required 8 man days ha-1 and five splits of N and four splits of K (S3) required 10 man days ha-1 in both establishments. The data on total labour requirement revealed that adoption of seedling broadcasting of 50 hills m-2 with three splits of N and two splits of K (P4S1) resulted in less labour requirement of 63 man days ha-1, followed by P3S1, P4S2 (65 man days ha-1) P3S2, P4S3 (67 man days ha-1) and P3S3 (69 man days ha-1). Line planting of 40 hills m-2 with five splits of N and four splits of K (P1S3) required more labourers of 89 man days ha-1(Table 4).
Energy use: Adoption of seedling broadcasting with 40 hills m-2 and three splits of N and two splits of K (P3S1) recorded higher energy use efficiency (5.61). Though the energy input requirement was lower under this treatment, increased total dry matter positively influenced the energy use efficiency. On the other hand, line planting of 40 hills m-2 with five splits of N and four splits of K registered lower energy use efficiency, which was mainly due to higher energy input requirement coupled with lower output. Similarly, the energy use efficiency in various lowland rice systems was also reported by Patel et al. (1994) and Bhuvaneswari (1998) (Table 4).
Economics: The net return showed considerable difference in various treatments. Higher net income was realized with seedling broadcasting. Seedling broadcasting of 40 hills m-1 with five splits of N and four splits of K (P3S3) recorded higher net return and B:C ratio (4.08) due to increased gross return. Reduction in cost of cultivation with seedling broadcasting method resulted more benefit than line planting (Table 5). The results are in accordance with Ponnuswamy et al. (2000) and Kathiresan and Narayanasamy (2000).
The present study concludes that seedling broadcasting of 40 hills m-2 with five splits of N and four splits of K to late Pishanam season rice, is a viable crop establishment method and nutrient management package for getting higher income, B:C ratio through higher yield with higher Nitrogen use efficiency under Tambaraparani command area of Tamil Nadu.