Electronic Journal of Biology

Keywords

Growth; Rice; Transplanting date; Yield components.

Introduction

Nowadays,Rice (Oryza sativa L.) is gradually representing as the main food regime among the world countries [1]. In Asia,it is the main staple food of about 3.5 billion people [2]. Its daily demand is increasing and would reach 70 percent more due to increase in population by 2025 [3]. Among the constraints in rice production,the microclimate like time of transplanting has focused attention of many researchers. The transplanting dates have direct effect on length of growing season which may reduce yield by 20 to 50% by 2050 in rainfed area [4]. Among the rice production tools,the proper sowing time is prerequisites that allow the crop to fulfil its life span on a timely manner and successfully in a particular micro climate condition [5]. Accordingly,suitable planting date is known as the major components in efficient agricultural management playing a significant role in production control [6]. The variation in planting date might influence crop yield through affecting plant phonology in vegetative and the reproductive growth stages [7]. The appropriate planting dates ensure satisfactory vegetative growth,grain quality and quantity [8].The transplanting dates are associated with increase in temperatures which is main reason of spikelet sterility at flowering stage. Any type of increase in ambient temperature within the grain filling period improves the rate of metabolic actions and,as a consequence,expedites the grain filling rate [9]. Rice is normally transplanted in between May and July [2]. The effects of transplanting dates vary between regions,which can affect plant initial growth and grain yield [10]. Early transplanting produces more tillers,biomass,taller plants,bolder grains with higher 1000-grain weight and grain yield [11]. On the contrary,in late transplanting most of the panicles become immature and grain yield is reduced in long-duration varieties [12]. The late transplanting limited the growth period which further reduced the leaf surface,panicle length and the mean number of kernels per panicle [2]. Delayed transplanting of rice decreases the amount of productive tillers and spikelets,deters panicle heading [13] and ultimately reduces the weight of the grains,but however,promotes the grain's protein content [14]. Various authors also reported the benefits of optimum planting dates in rice [15,16]. In most of the offered reports,it has been affirmed that sowing in the range of neither too early nor too late gives better yield performance through lengthening the growth period while alleviating the possibility of exposure to heat stress during reproductive growth [17]. The local recommendation of a transplanting date should be considered looking the climate condition and rice cultivars [18]. Accordingly,this research was initiated to assess the best planting date for different rice cultivars to achieve maximum grain yield of rice. Hence,the study was undertaken to identify the best transplanting time among the select rice cultivars under moderate climate.

Methods

Location of the experimental site and climatic condition

This study was conducted in the research field of Rice Research Institute (RRI),Mazandaran,Iran (latitude 31° 20' N,longitude 48° 41' E,altitude 22 m above mean sea level) during the period of 2012 cropping season. This site has a temperate climate with mean annual rainfall varying between 718 to 1274 mm,while the yearly average temperature ranges from 12.5 to 20°C [19].

Soil status

The experimental soil was clay loam,total nitrogen of 2.2%,phosphorus and potassium content of 160 and 20 mg/kg,respectively,with a pH of 6.9.

Experimental design and treatments

The study was done as split plot designed according to completely randomized blocks with three replications. The seedling transplanting dates,i.e.,1^st May,21^st May and 10th June were set as main plots,and six rice cultivars,i.e.,‘Neda’,‘Hovaze’,‘Hashemi’,‘Domsiah’,‘Tarom’ and ‘Fajr’ were allotted to subplots. The selection of cultivars and transplanting dates was done according to the conventional crop patterns in the region.

Agronomic practices

The seedlings were grown at 25 x 25 cm distance (2-3 seedlings per hill) in the main plots. After seedling establishment,the water level was maintained constant (3-4 cm height) in the whole growth period. The N-P-K was applied at 125-60-45 kg/ha. The whole amount of P (ordinary superphosphate) and K (potassium chloride) were applied during the soil puddling. However,N fertilizer was used in three equal doses,i.e.,50% at the time of seedling transplanting,25% at the active tillering and the rest 25% in the panicle initiation stage.

Data gathering and measurements

The soil pH was determined through pH meter (Mettler Toledo MP 120),soil texture by the Bouyoucos Hydrometer method [20],total nitrogen (%) by Kjedahl method [21],available phosphorus and potassium (mg/kg) by AB-DTPA method [22]. The flag leaf length and width was measured through measuring tape. The distance from base to the tip of the panicle was considered as plant hight. The plant height was measured using 20 primary tillers selected randomly from each experimental plot and then the recorded data were averaged. The selected plants were then kept for further measuring (number of tillers and panicles per plant). Panicle length and panicle exertion were counted from the lowest point of the panicle (panicle base) to highest point (panicle tip) employing a meter stick. Fertile and unfertile spikelets were counted from 20 randomly selected panicles taken from each plot. Thousandgrain weight was estimated by weighing on digital balance. Each plot was harvested and threshed manually to determine grain yield per square meter and computed on a hectare basis.

Statistical analysis

Data were exposed to the SAS statistical software [23] for analysis of variance (ANOVA). The treatment means were compared through employing least significant difference(LSD) test at 5% probability level (p<0. 05).

Results and Discussion

The rice crop transplanted on 21^st May recorded higher values of important yield components. The transplanting of 21^st May recorded higher number of effective tillers (21.80 numbers) and grain yield (6625 kg/ha) in cultivar ‘Neda’. However,1^st May transplanting showed non-significant differences between the mean values of 21^st May of other yield contributing traits by producing maximum fertile spikelets (124?130) per panicle in ‘Hovaze’ and ‘Fajr’,and 1000-grain weight (28.83?29.0 g) in ‘Neda’. The increase in yield could be predicted due to less number of sterile spikelets in both 1^st and 21^st transplanting dates. Regarding morphological characters,only total number of tillers per hill (25.0; ‘Neda’) and panicle exertion (9.1 cm; ‘Domsiah’) were greater in 21^st May sowing date,indicating that the environmental condition like temperature was most favourable for grain development. Irrespective of the studied cultivars,the morphological traits of plant height and flag leaf length declined in the early (1^st May) and mid (21^st May) transplanting dates,however,the flag leaf width in all the studied transplanting dates was amongst the highest mean values in the studied cultivar of “Hovaze”. The allocation of the highest flag leaf width to ‘Hovaze’,suggests its specific genetic feature in comparison with other cultivars (Tables 1 and 2). The sooner transplanting of the usual plantation time in a given region,the more time intervals within the following cropping will provides. Inversely,delayed planting will reduce the grain yield as a result of immaturity of most of the panicles [12]. Achieving the proper ranges in plant height,1000-grain weight,grain yield and maximum tillering is highly dependent on the early sowing date [11]. Bashir et al. [2] demonstrated that number of kernels per panicle was better with early sowing,but,however,late sowing restricted the growth period,decreased the length of panicle,leaf area,and number of kernels per panicle. In their study,Soleymani and Shahrajabian [24] came to a result that sowing on 25^th May is an adequate time for attaining the greatest number of grains,1000-grain weight,and grain yield. It can be mentioned that the crop grown on optimum dates,is usually taken a more suitable number of days from the seeding to maturity time,so as to be capable of exploiting a more efficient sink development or its formation,more potent and wide-spreading root system,greater carbohydrate and sink size,and durable leaf area index; indicating better translocation of assimilates from vegetative parts (second sources) into the spikelets during the grain filling phase [8]. Hence,the above-mentioned trend might be the possible reason for yield stability in optimum transplanting dates [25]. In addition,optimal sowing date largely ensures the grain filling,even when the process concomitants with the potential,milder temperatures in autumn [8]. In addition,optimal sowing date largely ensures the grain filling,even when the process concomitants with the potential,milder temperatures in autumn [8].

The late transplanting of 10^th June only increased the vegetative growth by recording taller plants (162.7 cm) and maximum flag leaf length (41.77 cm). However,late transplanting significantly decreased the yield due to higher number of sterile spikelets (Tables 1 and 2). It has been reported that delayed planting than to the optimum date reduces the yield potential exponentially raised in daily temperature,and plants pave all the growth phases earlier than normal condition [26]. In relation to yield components,the decrease in the number of fertile spikelets in late planted crop mainly resulted from factors such as improper temperature during the maturity and grain filling stages.

The formation of fertile spikelets in the panicle is substantially contingent upon the genetic potentiality of cultivars as well as the photosynthetic products supply during the maturity period. In the late planting,there is an increased risk of sterility for high temperatures at flowering stage. Thus,it seems that in the early and late planted crops,the panicle infertility is plausible,as if the thermal conditions intensify the competition for absorbing photosynthetic products [27]. Rakesh and Sharma [28],were in the opinion that any delay in planting significantly reduces the number of productive tillers per unit area,and ultimately attenuates the paddy yield. Akram et al. [29],found less number of grains per panicle in late sowing. Khakwani et al. [30] recorded a significant reduction in 1000-grain weight with delay in planting time. Reduction in the 1000-grain weight in the late transplanted crop was primarily due to unfavourable environmental temperatures since the grain formation and grain filling stages. In this regard,Iqbal et al. [31] reported that the highest yield was achieved once the rice crop was sown earlier in the season.

All the studied cultivars responded differently for yield components,so that the seedlings that have been transplanted on 21^st May showed the more improved yield components. The higher effective tillers and grain yield were found in ‘Neda’ transplanted on 21^st May. This transplanting date equally increased fertile spikelets in ‘Hovaze’ and ‘Fajr’ cultivars,respectively. However,seedlings of ‘Hovaze’ transplanted on 10th June increased the tallness of ‘Hashemi’. The highest productive tillers were found in 21^st May transplanting which reflects optimum planting time of ‘Neda’. The significant differences in terms of growth and yield traits were noted in ‘Neda’ compared to rest of cultivars across transplanting dates. Most of the cultivars were responsive for recording higher values of yield components in the first two transplanting dates (1^st May,21^st May). However,late planted crop due to high temperature caused disorder in grain formation and produced sterile spikelets which reduced the grain yield (Tables 1 and 2). The possible reason for decline in yield components and grain yield as a result of late transplanting (10^th June) might be because the temperature has gone increasing in late growing season which ultimately triggered more vegetative growth. The results are fully in alignment with the findings of Reddy and Reddy [32],that delayed planted crops undergo the development stages more rapidly,and each part of a development stage decreases exponentially as the delay in planting process increases. For obtaining a proper number of productive tillers,the relative importance of temperature at the time of panicle emergence for panicle fertility are considered important factors [33]. In this study,the number of productive tillers decreased due to temperature increase in the 10^th June planting date as well as genetic potentiality of the cultivar. The heat sensitive cultivar can easily be suppressed by late transplanting due to shortening in the growth cycle. Thus,in our study less panicle length has been recorded for the cultivars transplanted later on 10^th June.

The linear relationship between yield and yield components showed that a unit increase in effective tillers,total number of spikelets and 1000-grain weight correspondingly increased grain yield by 236.6,39.4 and 72.1 kg/ha,respectively (Figures 1-3). In compliance to our findings,Kariali and Mohapatra [34] were also supported the theory that the grain yield is highly dependent on the number of effective tillers. Grain yield is a function of interplay of various important yield components such as number of fertile spikelets per panicle,productive tillers and 1000-kernel weight [2]. The studies on the relationship between the yield and yield components in rice cultivars for grain yield had shown positive and significant correlation with the number of grains per panicle,the number of filled grains per panicle,and 1000-grain weight.

Figure 1: Linear regression between number of effective tillers per hill and grain yield.

Figure 2: Linear regression between total number of spikelets per panicle and grain yield.

Figure 3: Linear regression between 1000 grain weight and grain yield.

Conclusions

Since the rice cultivars are more sensitive to elevated temperatures,hence,sowing at proper time giving a favourable environmental condition facilitates growth and development and finally ensures yield stability. The crop sown on 1^st and 21^st May had better growth and yield components which resulted in higher grain yield of ‘Neda’ as compared to the rest of cultivars. Delay in transplanting inclusively increased the tallness of cultivars; while,the remaining plant characters,such as grain yield were showed decreasing trend in delayed planting beyond 21^st May. The correlation study revealed that a unit increase in effective tillers,total number of spikelets and 1000-grain weight correspondingly increased grain yield by 236.6,39.4 and 72.1 kg/ha,respectively.

Acknowledgements

The authors would like to express their sincere gratitude to the Universiti Putra Malaysia and the Ministry of Higher Education for Long term Research Grant Scheme (LRGS) Fund for Food Security of Malaysia as well as Rice Research Institute of Iran for undertaking an important role in continuing research activities.

References

1. Juraimi AS,Saiful AM,Uddin MK,Anuar A,Azmi M. (2011). Diversity of weed communities under different water regimes in Bertam irrigated direct seeded rice field. Australian Journal of Crop Science. 5: 595?604.
2. Bashir MU,Akbar N,Iqbal A,Zaman H. (2010). Effect of different sowing dates on yield and yield components of direct seeded coarse rice (Oryza sativa L.). Pakistan Journal of Agricultural Science. 47: 361?365.
3. Kim JK,Krishnan HB. (2002). Making rice a perfect food: Turning dreams into reality. Journal of crop production. 5: 93-130.
4. Kang Y,Khan S,Ma X. (2009). Climate change impacts on crop yield,crop water productivity and food security – A review. Progress in Natural Science. 19: 1665?1674.
5. Baloch MS,Awan IU,Hassan G. (2006). Growth and yield of rice as affected by transplanting dates and seedlings per hill under high temperature of Dera Ismail Khan,Pakistan. Journal of Zhejiang University SCIENCE-B. 7: 572–579.
6. Chandra D,Lodh SB,Sahoo KM,Nanda BB. (1997). Effect of date of planting and spacing on grain yield and quality of scented rice (Oryza sativa L.) varieties in wet season in coastal Orissa. The Indian Journal of Agricultural Science. 67: 93?97.
7. Dehghan A. (2007). The effect of delayed planting date on grain yield and yield components of three sorghum in Khouzestan. The Scientific Journal of Agriculture. 30: 123?132.
8. Farrell TC,Fox K,Williams RL,Fukai S,Lewin LG. (2003). Avoiding low temperature damage in Australia’s rice industry with photoperiod sensitive cultivars. In: Australian Society of Agronomy,Proceedings of the 11th Australian Agronomy Conference. Deakin University,Geelong (Feb. 2?6),Victoria,Australia.
9. Gornall J,Betts R,Burke E,et al. (2010). Implications of climate change for agricultural productivity in the early twenty-first century. Philosophical Transactions of the Royal Society B: Biological Science. 365: 2973?2989.
10. Vange T,Obi IU. (2006). Effect of planting date on some agronomic traits and grain yield of upland rice varieties at Makurdi,Benue state,Nigeria. Journal of Sustainable Development in Agriculture and Environment. 2:1?9.
11. Khalifa AABA. (2009). Physiological evaluation of some hybrid rice varieties under different sowing dates. Australian Journal of Crop Science. 3:178?183.
12. Slaton NA. (2001). Rice production hand book. University of Arkansas,Division of Agriculture,Research and Extension,Cooperative Extension Service,Little Rock,Arkansas,USA: Miscellaneous Publication. No. 192,p. 212.
13. Hayat K.,Awan IU,Hassan G. (2003). Impact of seeding dates and varieties on weed infestation,yield and yield components of rice (Oryza sativa L.) under direct wet-seeded culture. Pakistan Journal of Weed Science Research. 9: 59?65.
14. Shahzad MA,Din W,Sahi ST,Khan MM,Ahmad M. (2007). Effect of sowing dates and seed treatment on grain yield and quality of wheat. Pakistan Journal of Agricultural Science. 44: 581?583.
15. Habibullah N,Shah H,Iqbal F. (2007).  Response of rice varieties to various transplanting dates. Pakistan Journal of Plant Science. 13:1?4.
16. Safdar ME,Ali A,Muhammad S,Sarwar G,Awan TH. (2008). Effect of transplanting dates on paddy yield of fine grain rice genotypes. Pakistan Journal of Botany. 40: 2403?2411.
17. Li Q,Wu X,  Ma J,Chen B,Xin C. (2015). Effects of Delaying Transplanting on Agronomic Traits and Grain Yield of Rice under Mechanical Transplantation Pattern. PLoS One. 10.
18. Ohta S,Kimura A. (2007). Impacts of climate changes on the temperature of paddy waters and suitable land for rice cultivation in Japan. Agricultural and Forest Meteorology. 147:186?198.
19. Tarzban S,Hadian AA. (2008). Geography of Mazandaran Province. Tehran,Iran: Ministery of Education Publication,pp. 3?7.
20. Gee GW,Bauder JW. (1986). Particle size analysis. In: Methods of Soil Analysis. Part 1: Physical and Mineralogical Methods,2nd edition (Klute A,ed). American Society of Agronomy,Madison,Wisconsin, USA,pp. 404?407.
21. Amin M,Flowers TH. (2004). Evaluation of Kjeldal digestion method. J. Res. Sci. 15: 159?179.
22. Soltanpour PN. (1991). Determination of nutrient availability and elemental toxicity by AB-DTPA soil test and ICPS. Adv. Soil Sci. 16: 165?190.
23. SAS institute. (2004). SAS/STAT users guide. Ver. 9.1. ,SAS Institute Inc.,Cary,NC,USA.
24. Soleymani A,Shahrajabian MH. (2011). The influence of different planting dates,plant densities on yield and yield components of rice on the basis of different nitrogen levels. International Journal of Agronomy and Plant Production. 2: 80?83.
25. Shah ML,Yadav R. (2001). Response of rice varieties to age of seedlings and transplanting dates. Nepal Agricultural Research Journal. 4: 14?17.
26. Hay RK,Walker AJ. (1989). Introduction to the physiology of crop yield. London,England: Longman Scientific & Technical,p. 465.
27. Shah L,Bhurer KP. (2005). Response of wet seeded rice varieties to sowing dates. Nepal Agricultural Research Journal. 6: 35?38.
28. Rakesh K,Sharma H. (2004). Effect of dates of transplanting and varieties on dry matter accumulation,yields attributes and yields of rice (Oryza sativa L.). Himachal Journal of Agricultural Research. 30: 1?7.
29. Akram H,Ali A,Nadeem MA,Iqbal MS. (2007). Yield and yield components of rice varieties as affected by transplanting dates. Journal of Agricultural Research. 45: 105?111.
30. Khakwani AA,Zubair M,Mansoor M,et al. (2006). Agronomic and Morphological Parameters of Rice Crop as Affected by date of Transplanting. Journal of Agronomy,5: 248?250.
31. Iqbal S,Ahmad A,Hussain A,et al. (2008). Influence of transplanting date and nitrogen management on productivity of paddy cultivars under variable environments. International Journal of Agriculture and Biology. 10: 288?292.
32. Reddy KS,Reddy BB. (1992). Effect of transplanting time,plant density and seedling age on growth and yield of rice. Indian Journal of Agronomy. 37: 18?21.
33. Kato T,Takeda K. (1996). Associations among characters related to yield sink capacity in space-planted rice. Crop science. 36: 1135?1139.
34. Kariali E,Mohapatra PK. (2007). Hormonal regulation of tiller dynamics in differentially-tillering rice cultivars. Plant Growth Regulation. 53: 215?223.