Abstract: In order to investigating the effects of second crop cultivation on growth, yield and yield components of rice, a field experiment was conducted at the Rice Research Institute of Iran-Deputy of Mazandaran (Amol) during 2004 and 2005. Tarom as a traditional variety and Fajr as a improved variety were used in this research. Faba, pea, Lettuce and garlic were used as a second crop in rotation with rice. Second crop cultivation, variety and interaction between them had a significant effect on tiller number at 0.01 probability level. Results showed that rice yield after lettuce and garlic rotation was lower than with Faba bean, pea and fallow rotation. These results indicated that rice varieties had different reaction to second crop cultivation. For example, Tarom variety in rotation with lettuce and garlic had higher yield deficiency than Fajr variety. These results suggested that Lettuce and garlic can not be a permanent second crop in paddy field. According to results, pea and faba bean in rotation with rice for the best performance of yield attributes of rice varieties were recommended.
INTRODUCTION
More than one-third of the human population rely on rice for their daily sustenance, making it the most important of the world’s food crops (Brennane et al., 1994). The rice industry, world wide, is facing the challenge of a dramatic rise in demand due to population pressure where almost 100 million additional people must be fed each year. Thus, the global rice production needs to be increased by 75% by 2020 to feed the world rice consumers (Donald, 1994). Since arable land is becoming limited, improving productivity and increasing cropping intensity by adopting rice cultivation with second crops in potentially irrigated areas will be required to meet the food demand of the region’s increasing population (Regmi, 1994). There are many reports about rice-second crop-rice rotation systems in many tropical Asian countries. The analyses of some of these experiments have shown declining rice and second crop yields (Cassman et al., 1995; Yadave et al., 2000; Duxbury et al., 2000). Whereas in others, yield either increased or were maintained (Dawe et al., 2000). Where a yield decline is reported, the major causes suggested are a gradual decline in the supply of soil nutrients because of inappropriate fertilizer application, decline in soil organic matter content, atmospheric pollution, pest and disease infestations and negative changes in the biochemical and physical composition of soil organic matter (Nambiar, 1994; Yadav et al., 2000). Also second crop cultivation maybe had positive effect in rice rotation. For first time second crop cultivation has been used at Iran’s paddy field in 1965 (Fallah, 2000). In the first years, foliage crops and oil seed crops were used as a second crop. Different experiments had been showed that Berseem Clover (Trifolium alexandrinum) could be a good crop as a second crop in rice rotation also had a positive effect on soil texture (Ying, 1993). Rice yield with wheat rotation is lower than with potato rotation (Sidhu and Rakotonaivo, 1988). Handand and Dhillon (1993) showed the positive effects of Vigna unguicuta as a green manure on rice yield, they reported that rice yield in the plots with green manure was more than in fallow plots. Sing et al. (1988) studied the effects of Phaseolus vulgaris and cluster bean as green manures on rice growth. They showed that Phaseolus vulgaris make the most quantity of nitrogen for rice growth. Know about the positive or negative effect of different plants on rice growth is very important. The farmer’s should be aware about the plants that can be as a second crop in paddy field. They should know which plant have a positive effects on rice growth indices. A purpose of this research is investigating the effect of some plants as a second crops on rice varieties in North of Iran’s paddy field and indicate the best plant as second crop in rice rotation.
MATERIALS AND METHODS
The experiment was conducted at the Rice Research Institute of Iran-Deputy
of Mazandaran (Amol) located in North of Iran ( 52° 22´ N, 36° 28´ E,
altitude 28 m ) during 2004 and 2005. After rice harvesting, the field was prepared
for second crops cultivation. Lettuce (Lactuca sativa), Faba bean (Faba
vulgaris), Pea (Pisum sativum) and Garlic (Allium sativum)
and fallow were choosed as a second crop. The soil total N and organic carbon
contents were low, the available P and exchangeable K contents are medium (Table
1). Cultivation of second crop was done as a experiment in Randomized Completely
Block Design with three replications. Standards cultural practices were carried
out until each second crop was mature. After harvesting the all of second crops
the field was prepared for rice varieties cultivation. The plots related to
second crop were divided in two sections and rice cultivation was done as a
experiment in Split plot in basis of Randomized Completely Block Design with
three replications. Tarom variety as a traditional variety with yield average
of 4 t ha-1 and Fajr variety as a improved variety with yield average
of 6 ton per hectare were choosed for this research. Standard cultural practices
were carried out until the rice was mature. Six hills (excluding border hills)
were randomly selected from each plot prior to harvest for measure rice components.
Grain yield was determined from harvest area of 5 m2 adjusting to
14% moisture content. All statistical tests (simple and combined analysis) were
done using the statistically analysis system (SAS, Institute, 1996) and mean
value were compared by Duncan Multiple Rang Test (DMRT).
| Table 1: | Physical and chemical properties of the top soil in the experimental field at Iran Rice Research Institute |
RESULTS
Plant height: Results showed that second crop cultivation had significant effect on rice height at 0.01 probability levels (Table 2, 5 and 8). This results showed that rice height affected by genetically and environmental factors such as second crop cultivation in rotation. Mean comparison of data showed that the least rice height was obtained after lettuce cultivation and the most rice plant height was obtained after garlic cultivation in each two years. There was a significant difference between varieties height at 0.05 probability levels. In this research maximum Tarom height (160.2 cm) and maximum Fajr height (156.4 cm) were obtained after garlic cultivation in paddy field (Table 10).
Tiller number: Results showed that second crop cultivation, variety and interaction between them had a significant effect on tiller number at 0.01 probability levels. In combined analysis of data the effect of second crop cultivation and interaction between year with second crop cultivation had significant effect on tiller number at 0.01 probability level (Table 8). Also interaction effect between year and variety on tiller number was significant at 0.05 probability levels (Table 4 and Table 7). In this research there was a significant difference between varieties tiller number In all of treatments the tiller number of Fajr variety is more than Tarom variety. The tiller number of Fajr and Tarom varieties were least after use of fallow treatment and Garlic in paddy field in each two years respectively (Table 3 and 6). This results showed that garlic had negative effect on Fajr tiller number more than Tarom tiller number. Results indicated that tiller number was not different in each two years when rice was cultivated after fallow treatments but tiller number was different significantly with use of second crop in rice rotation in each two years (Table 10).
Panicle length: Results showed that second crop cultivation in rice rotation had not significant effect on panicle length in each two years but the variety had significant effect on panicle length at 0.01 probability levels. The panicle length average were 24.8 and 30.3 cm in Tarom and Fajr variety, respectively. The effect of year was not significant on this character (Table 8).
Total spikelet per panicle: Results showed that second crop cultivation
treatments had not significant effect on total spikelet per panicle. Variety
had significant effect on total spikelet per panicle in each two year. Fajr
variety had more spikelet per panicle than Tarom variety in each two years.
| Table 2: | Mean squares of rice yield and yield components (Year, 2004) |
| ÊSCC: Second crop cultivation. ns: *, ** non significant, significant at 0.05 and 0.01 probability level, respectively | |
| Table 3: | Mean comparison of rice yield and yield component in different treatments (Year, 2004) |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
| Table 4: | Interaction effect of second crop cultivation and rice variety (year, 2004) |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
| Table 5: | Mean squares of rice yield and yield components (Year, 2005 ) |
| ÊSCC: second crop cultivation. ns, *, ** non significant, significant at 0.05 and 0.01 probability level, respectively | |
| Table 6: | Mean comparison of rice yield and yield components in different treatments (Year, 2005) |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
| Table 7: | Interaction effect of second crop cultivation and rice variety (Year, 2005) |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
| Table 8: | Combined Varianse Analysis of rice yield and yield components (Years 2004 and 2005) |
| ÊSCC: Second crop cultivation. ns, *, ** non significant, significant at 0.05 and 0.01 probability level, respectively | |
| Table 9: | Combined mean comparison of rice yield and yield components |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
Filled grain: Results showed that variety had significant effect on filled grain percentage at 0.01 probability level in annual data analysis and had a significant effect on filled grain percentage at 0.05 probability level in combined data analysis. Mean comparison of treatments in 2004 and 2005 showed that second crop cultivation had not significant effect on filled grain percentage. Combined mean comparison showed that Tarom variety with average 91% filled grain had more filled grain percentage than Fajr variety with average 81% filled grain (Table 9).
Grain yield: Variance Analysis of year 2004 did not show a significant
effect of second crop cultivation on rice yield. Also, variance analysis of
year 2005 didn’t show a significant effect of second crop cultivation on
rice yield (Table 2, 5 and 8).
But variety had significant effect on grain yield in each two years. Combined
Varians Analysis for two years showed a significant effect of year and interaction
of year with variety on rice yield (Table 8). The least rice
grain yield was obtained in rotation with garlic in each two years. Results
showed that rice yield with lettuce or garlic rotation was least than rice yield
with faba or pea rotation. Interaction of treatments in combined mean comparison
showed that all of treatments were in the same statistically group but Interaction
effect of year with variety indicate that yield of Fajr variety in 2005 is least
than 2004. Results of Table 10 showed that Tarom and Fajr
varieties had the least yield after rotation with garlic.
| Table 10: | Combined comparison mean of treatments interaction effects |
| Means with similar letter(s) in each column are not significantly different at the 5% probability level according to DMRT | |
DISCUSSION
Results showed that second crop cultivation in rice rotation had not significant effect on panicle length in each two years. Panicle length usually not affected by environmental conditions and it seemed be a genetically characteristic (Hatami, 2002). Tiller number is a important component in grain yield of rice varieties (Islam et al., 2002). Any factor that influenced this component can change rice yield (Hoseini, 2003). In this research, the tiller number of varieties were least after use of garlic in paddy field. In this experiment garlic had a negative effect on Fajr tiller number more than Tarom tiller number. Garlic can carry and transmit diseases. Some of these diseases and pests in garlic may contaminate the soil and make the field unusable for future crop production (Hannan, 2002). Fajr variety was seemed more sensitive to pests and diseases than Tarom variety. According to these results, Faba bean (Faba vulgaris) and Pea (Pisum sativum) can be a good second crops in rice rotation. Rodelas et al. (2004) got almost the similar results. They indicated that faba bean can be good crop in rotation with other crops because of its nitrogen fixation role. Yield of Fajr variety in 2005 is least than 2004 because in 2005 these varieties cultivated late. Tarom variety yield was not decreased, because this variety had a difference with Fajr variety in growth period. For these varieties, Rice-Faba bean-Rice and Rice-Pea-Rice rotation systems for the best performance of rice yield in north of Iran’s paddy field were recommended.
ACKNOWLEDGMENTS
Financial support by Rice Research Institute of Iran highly appreciated.