Pakistan Journal of Biological Sciences

Year: 2007 | Volume: 10 | Issue: 18 | Page No.: 3205-3209
DOI: 10.3923/pjbs.2007.3205.3209

Effect of Planting Density on Agronomical Characteristics of Rice (Oryza sativa L.) Varieties in North of Iran

Hamid Reza Mobasser, Morteza Mohseni Delarestaghi, Ali Khorgami, Davood Barari Tari and Hamid Pourkalhor

Abstract: In order to study the effects of plant density on agronomical characteristics of rice varieties a field experiment was carried out in field of Ghaemshahr Azad University in 2006. This experiment was laid out in split plot in basis of Randomized Completely Block Design with three replications. Main factor was rice variety in three levels (Hashemi Tarom, Fajr, Neda) and minor factor was planting density (Including 10x8.3, 10x10, 12.5x10, 16.6x10, 16.6x15 and 25x20 cm or 120, 100, 80, 60, 40 and 20 plant m^-2, respectively). Results showed that planting density had significant effect on plant height, total spikelets, total tillers, fertile tillers, panicle per m², grain yield and harvest index. Days number till to 50% flowering stage and growth period length were maximum in Neda variety. Also these characteristics were not influenced by different planting densities. Maximum plant height and maximum panicle length were obtained in Hashemi Tarom variety and minimum of these characteristics were produced in Neda variety. Plant height was decreased significantly with increase of planting density.

Keywords: yield, plant density, Rice and morphology

INTRODUCTION

Rice (Oryza sativa) is one of the most important crops in Iran. It is the largest crop in terms of area and production in north of Iran (Hatami, 2002). Rice is the dominant staple food for many countries in Asia and the Pacific, south and north America as well as Africa. In Asia more than 2 billion people obtain 60 to 70% of their calories from rice (Dowling et al., 1998). World rice production must increase by approximately 1% annually to meet the growing demand for food that will result from population growth and economic development (Horie et al., 2004). The crop plants growing depends largely on temperature, solar radiation, moisture and soil fertility for their growth and nutritional requirements. An unsuitable population crop may have limitation in the maximum availability of these factors. It is, therefore necessary to determine the optimum density of plant population per unit area for obtaining maximum yield. There have been extensive studies on the relationship between yield and plant density in rice under nonstressed conditions. The relationships varied with different planting systems in rice production. In transplanted culture systems, maximum grain yield can be reached at a plant density of about 200 plant m^-2 (Nguu and De Datta, 1970; Akita, 1982). In drill-seeded 161 and 215 plant m^-2, which can be achieved with seeding densities between 90 and 112 kg ha^-1 (Huey, 1984). In continuosly flooded, direct water flooded cultural systems that are common in some countries, a broad range of plant densities between 221 and 451 plant m^-2 (Miller et al., 1991). A compensatory relationship between yield components and plant density has been observed. It was shown that panicle density significantly increased with increase of seeding densities, while filled spikelets per panicle were reduced significantly (Wells and Faw, 1978; Gravois and Helms, 1992). Tiller per plant and spikelets per panicle increased with decreases of plant density in direct-seeded rice (Wu et al., 1998). A number of workers have reported that maintenance of a critical level of rice plant population in field was necessary to maximize grain yield. The effect of plant density on kernel dimension were also identified during different panicle development stages. The reason for such low yield mainly associated with cultural technologies. Among cultural technology application of best planting space is the important ones (Barari, 2007).

Almost all yield contributing characters were influenced significantly by planting density (Islam and Hossain, 2002). They also showed that total tiller and fertile tiller number in 25x15 cm planting space were more than 15x10 cm planting space. Wider spacing had linearly increasing effect on the performance of individual plants. The plants grown with wider spacing had more solar radiation to absorb for better photosynthetic process and hence performed better as individual (Baloch et al., 2002). Appointing the best planting space related to rice variety. Determine best planting density for native and modern rice varieties in north of Iran were purposes of this experiment.

MATERIALS AND METHODS

The experiment was conducted at field of Gaemshahr Islamic Azad university in North of Iran. This experiment was laid out in split plot in basis of Randomized Completely Block Design (RCBD) with three replications. The plot size was 15 m². Main factor was rice variety in three levels (Hashemi Tarom, Fajr, Neda) and minor factor was planting density (Including 10x8.3, 10x10, 12.5x10, 16.6x10, 16.6x15, 25x20 cm or 120, 100, 80, 60, 40 and 20 plant m^-2, respectively). All plots received 100 kg P₂O₅ ha^-1 and 100 kg k₂O ha^-1 before transplanting. The nitrogen fertilizer in the form of urea was applied at the rate of 132 Kg N ha^-1 in two split doeses. Half of nitrogen fertilizer was applied as top dressing in the maximum tillering stage. Standards cultural practices were carried out until the plant was matured. Five hills (excluding border hills) were randomly selected from each plot for measuring total tiller number. Six hills (excluding border hills) were randomly selected from each plot prior to harvest for measure yield components. Days numbers after transplanting till to 50% flowering stage and vegetative growth period length were measured in this experiment. Grain yield was determined from harvest area of 5 m² adjusting to 14% moisture content. All statistical tests were done using the statistically analysis system (SAS Institute, 1996) and mean values were compared by Duncan Multiple Range Test (DMRT).

RESULTS

Days numbers till to 50% flowering stage: Results showed that variety had significant effect on days numbers till to 50% flowering stage in this experiment (Table 1). In a way that the highest and the least days numbers till to 50% flowering stage were obtained in Neda variety (68.1 days) and Hashemi Tarom Variety (54.4 days), respectively (Table 2). This duration was 59.4 days for Fajr variety (Table 2). According to results planting density had not significant effect on days number till 50% flowering stage (Table 1). But maximum and minimum of this characteristic were obtained in density of 20 and 60 plant m^-2, respectively (Table 2).

Vegetative period length: Variety had significant effect on vegetative period length (Table 1). The least vegetative period length was obtained in Hashemi Tarom (48.3 days) and maximum vegetative period length was produced in Neda (54.6 days) variety (Table 2). Vegetative period length for Fajr variety was 52.7 days (Table 2). According to results planting density had not significant effect on vegetative period length (Table 1).

Plant height: Planting density and variety had significant effect on plant height at 0.01 and 0.05 probability levels, respectively (Table 1). Highest plant height was obtained in Hashemi Tarom variety (157.8) while minimum plant height was produced in Neda variety (90.3 cm). Plant height for Fajr variety was 106.7 cm. The highest (124.5 cm) and the least (113.5 cm) plant height were obtained in planting density of 20 and 120 hills m^-2, respectively (Table 2).

Panicle length: Results showed that variety had significant effect on panicle length at 0.01 probability level (Table 1). The highest panicle length was obtained in Hashemi Tarom variety (30.9 cm) and the least panicle length was produced in Neda variety (23.4 cm) while panicle length for Fajr variety was 28.5 cm (Table 2). Plant density had not significant effect on panicle length in this experiment (Table 1).

Total spikelets per panicle: Planting density and variety had a significant effect on total spikelets per panicle at 0.01 probability level (Table 1). The highest and the least total spikelets per panicle were obtained in Fajr variety and Hashemi Tarom variety, respectively. Total spikelets per panicle were 96 and 101.9 for Hashemi Tarom and Neda variety respectively (Table 2). Total spikelets per panicle for 20 plant m^-2 planting density were 130.8 while for 120 plant m^-2 planting density were 101.4 (Table 2). Intraction effects mean showed that highest spikelets per panicle (132.8) were obtained in Fajr variety in case of 20 per m^-2 planting density (Table 3).

Filled spikelet percentage: Results showed that variety had significant effect on filled spikelets percentage at 0.01 probability level (Table 1). Highest and the least filled spikelets percentage were obtained in Hashemi Tarom variety (94.06%) and Neda variety (86.9%), respectively (Table 2).

Results showed that filled spikelets percentage in 120 plant m^-2 was 88.33% and in 40 plant m^-2 was 89.56% (Table 2). Interaction effects mean showed that highest spikelets per panicle (91.37%) were produced in Hshemi Tarom variety in case of 20 plant m^-2 (Table 3).

1000 grains weight: Variety had a significant effect on 1000 grains weight at 0.01 probability level (Table 1). The most 1000 grains weight were obtained in Neda variety (27.55 g) and for Hashemi Tarom and Fajr variety were 24.03 and 23.23 g, respectively (Table 2). Planting density had not significant effect on 1000 grains weight (Table 1). Interaction effects mean showed that highest 1000 grains weight (26.5 g) were produced in Neda variety in case of 120 plant m^-2 (Table 3).

Total tiller: Results showed that planting density had significant effect on total tillers numbers at 0.01 probability level (Table 1). Highest tillers numbers (12.6) were obtained in 20 plant m^-2 planting density while minimum tillers number (2.9) were produced in 120 plant m^-2 planting density (Table 2). Variety and planting density had not significant effect on total tillers numbers (Table 1). In Intraction effect of variety and planting density, highest tillers numbers (9.48) was observed in Hashemi Tarom variety in case of 20 plant m^-2 planting density (Table 3).

Fertile tiller: Results showed that planting density had significant effect on total tillers number at 0.01 probability level (Table 1). Highest fertile tiller (12.51) and least fertile tiller (2.9) were produced in 20 and 120 plant m^-2, respectively. Variety had not significant effect on fertile tillers numbers (Table 1). Fertile tillers numbers for Hashemi Tarom, Fajr and Neda varieties were 7.33, 4.76 and 6.20, respectively (Table 2). Highest fertile tillers numbers (9.42) were produced in Hashemi Tarom variety in case of 20 plant m^-2 planting density in intraction effect of variety and planting density (Table 3).

Panicle per m²: Results showed that planting density had significant effect on panicle m^-2 at 0.01 probability level (Table 1). Highest panicles m^-2 (473.3) and the least panicles m^-2 (270.9) were produced in 120 plant m^-2 and 20 plant m^-2 planting densities, respectively (Table 2). Variety had not significant effect on panicle m^-2 (Table 1). Panicles numbers m^-2 for Hashemi Tarom, Fajr and Neda varieties were 430.3, 317.6 and 396.7 (Table 2). In intraction effect of variety and planting density, highest panicle m^-2 (451.8) were produced in Hashemi Tarom in case of 120 plant m^-2 (Table 3).

Grain yield: Results showed that variety and planting density had significant effect on grain yield at 0.01 probability level. Highest grain yield was obtained in Neda Variety (945 g m^-2) and the least grain yield was produced in Hashemi Tarom variety (566 g m^-2) while grain yield for fajr variety was 870.1 g m^-2 (Table 2). The least grain yield was obtained in 20 plant m^-2 plant density (719.4 g m^-2). Increase in plant density can improve grain yield in this experiment. Grain yield was increased in 120 plant m^-2 plant density for 20.6% compared to grain yield in 20 plant m^-2 (Table 2). Interaction effects mean showed that highest grain yield (925.7 g m^-2) were produced in Neda variety in case of 120 plant m^-2 (Table 3).

Harvest index: Result showed that plant density had significant effect on harvest index at 0.01 probability level (Table 1). Highest harvest index (44.86%) was obtained in 60 plant m^-2 plant density and the least harvest index (42.18%) were produced in 100 plant m^-2 plant density (Table 2). Highest and least harvest index were obtained in Hashemi Tarom and Fajr varieties, respectively while harvest index for Neda variety was 43.11% (Table 2).

DISCUSSION

Results of this experiment showed that vegetative period length was in maximum at low planting density (Table 2). Mobasser (2007) got almost similar result. In this experiment highest plant height was obtained in 20 plant m^-2 planting density (Table 2). Barari (2007) showed that panicle length can influenced significantly by agronomical treatments but Mobasser (2007) indicated that panicle length is genetical characteristics that is not influenced significantly by planting density. Increase in planting density can decrease spikeletes numbers per panicle (Baloch et al., 2002). Counce (1987) showed that panicle density significantly increased with increase of seeding densities, while filled spikelets per panicle were reduced significantly. In this experiment in highest plant density total spikelets per panicle were decreased significantly (Table 2). Tiller per plant and spikeletes per panicle increased with decrease of plant density in direct-seeded rice (Wu et al., 1998). Under nonstressed conditions, the responses of yield to the changes of plant densities were determined by a compensatory relationship between plant density and yield components. Increase of plant stand and panicle density were offset by the reduction in seed weight per plant and fertility with the increases of seeding densities. With increase in plant density grain yield was increased because of increase in panicle m^-2 (Table 2). Miller et al. (1991) showed that panicle density was the most important component of yield in rice. According to results panicle m^-2 had significant correlation with grain yield also fertile spikelets had significant correlation with 1000 grains weight (Table 4).

ACKNOWLEDGMENT

Financial support by Faculty of Agriculture, Gaemshahr Azad University was highly appreciated.

REFERENCES