1 Introduction

Quality seeds, irrigation and fertilizers are prerequisite materials for harvesting higher productivity from a crop. Though farmer’s supply quality seeds, fertilizers and irrigation in time and grow rice in well managed way, they found difficulty to get its potential yield in countries like Nepal. Agricultural scientists and policy makers have also reported the yield reduction in farmer’s field which might be due to farmer’s poor field management, less use of fertilizers, lack of high yielding fertilizer responsive variety, unavailability of irrigation facility in time and lack of trained farmers (NARC, 1997). Earlier scientists have reported that late transplanting cause yield reduction and reduce total biomass of the crop (Santhi et al, 1998).

Yield is the end result of interaction between genetic constitutions of a plant and environment under which it grows. Among environmental factors, climate plays an important role in getting high yield. The highest yield can be harvested with earliest planting (Kumar, 2001). Nielsen and Thomison (2003) also reported that delayed planting of corns shortens the available growing seasons. The reason could be that too early and too late transplanting could not fulfill the required temperature and photoperiod for rice crop. Late transplant are severe to cold and effect plant growth and yield (Bashir et al, 2010). Akram et al. (2007) reported that yield and yield parameters like number of tillers, grains per panicle, plant height, 1000 grain weight and sterility of different rice varieties were significantly affected by transplanting dates. Similarly, Gangwar and Sharma (1997) also observed more number of panicles in early transplanting than in late transplanting. This was due to the fact that rice genotypes planted earlier had longer period for their vegetative growth compared to those sown later. But Nazir (1994) reported that earlier transplanting in rice causes lower number of grains per panicle due to grain sterility because of high temperature at the time of grain maturation. Transplanting at its optimum time reduces grain sterility. The overall results of the present investigations lead us to the conclusion that there is a significant effect of transplanting dates on the yield, yield components and days taken to 100% flowering of rice genotypes even though all input materials are supplied in time (Safdar et al., 2008). Thus transplantation of high yielding varieties of rice at the appropriate time is the most important factor for obtaining high yield of rice.

Due to lack of irrigation facility, quality seeds, fertilizers and labour in time; most Nepalese farmer’s cannot transplant rice seedlings in appropriate time and get delayed. Hence the main objective of this experiment was to find out the reasons behind the yield reduction in farmer’s field though farmers supply all inputs materials in time for rice production.

2 Material and Methods

2.1 Experimental sites

This experiment was conducted in Agriculture Botany Division, Khumaltar, Lalitpur, Nepal at an altitude of 1368 m from mean sea level and latitude of 27⁰ 40^’ N 85⁰ 20^’ E. Two sites with irrigated low land and rainfed upland were chosen for both early and delayed transplanting respectively. Rice growing seasons monthly average maximum and minimum temperature with average rainfall was also recorded from 2011 to 2014 (Table 1).

2.2 Genotypes used, design and procedure

Randomised complete block design with three replications were used to perform this experiment. Twelve rice genotypes were selected for coordinated varietal trial (CVT) from initial evaluation trial (IET) along with Khumal-4 as a popular standard check. Six rice genotypes viz. NR10769-4-2-2, NR 10553-B1-25-2, NR 10676-B-5-3, NR 11082-B-B-16, Khumal-11 and Khumal-4 were common in 2011 and 2012 whereas seven genotypes IR 84899-B, NR 10676-B-5-3, NR 11050-B-B-B-B-17, YR25696-B-196-3-3, NR 11011-B-B-B-B-29, 08FAN10 and Khumal-4 were common in 2013 and 2014. Soil of the experimental plot was silty-clay loam with pH 6.5 to 6.7 tested before transplanting. Recommended dose of fertilizers @80:30:30 kg/ha NPK were applied. Full dose of phosphorus and potassium and half dose of nitrogen were applied as basal. 1/4^th part of nitrogen was  applied at 30 days i.e. at tillering stage after 1^st weeding and the remaining 1/4^th part at booting stage after 2^nd manual weeding. A total of 4m x 3m net plot area with a plant spacing of 20cm x 15cm was used for transplanting. One seedling per hill was transplanted in both early and delayed transplanting. Rice early transplanting was done in last week of June when seedlings were 25-28 days old but delayed transplanting was done at 1^st week of July when seedlings became 38-40 days old in all years of 2011, 2012, 2013 and 2014.

2.3 Data collection and analysis

Observations and data records of all the traits were made based on Standard Evaluation System for Rice (IRRI, 2002). Rice different parameters such as days to heading, days to maturity, panicle length, plant height, fertile grain number per panicle and grain yield per hectare were taken. Days to heading and days to maturity were taken when each plot was 80% flowered and matured respectively. Average plant height and panicle length were taken from five plant of each plot before grain full physiological maturity. Grain yield per hectare were taken at 12% moisture content. Statistical analysis was done by using MSTAT and GenStat program.

3 Result

3.1 Days to heading

Statistically significant difference in days to heading were found for both early and delayed transplanting in 2011 to 2013 and non significant in 2014 (p<0.05)(Figure 1). The average days to 80% rice heading was 84 and 111 days for early and delayed transplanting in 2011, 107 and 121 days in 2012, 113 and 121 days in 2013, and 106 and 127 days in 2014 (Table 2; Table 3; Table 4; Table 5). Longest days to heading were obtained from NR 11050-B-B-B-B-17 (122 days) in 2013 and shortest from Khumal 4 (78 days) in 2011 in early transplanting. Similarly, longest days to heading were obtained from NR 11011-B-B-B-B-29 and 08FAN2 (132 days) in 2014 and shortest from NR 11082-B-B-16 and Khumal 11 (106 days) in 2011 in delayed transplanting.

3.2 Days to maturity

Statistically significant difference in days to maturity were found for both early and delayed transplanting in 2011, 2012, 2013 and non significant in 2014 (p<0.05). The average days to 80% rice maturity were 120 and 152 days in 2011, 144 and 158 days in 2012, 151 and 159 days in 2013, and 143 and 166 days in 2014 for early and delayed transplanting (Table 2; Table 3; Table 4; Table 5). Longest days to maturity were recorded from NR 11050-B-B-B-B-17 (159 days) in 2013 and shortest from Khumal 4 (111 days) in 2011 in early transplanting. Similarly, longest days to maturity were obtained from NR 11011-B-B-B-B-29 (178 days) in 2014 and shortest from Khumal-4 (144 days) in 2011 in delayed transplanting (Table 2; Table 3; Table 4; Table 5).

3.3 Plant height

Significant difference in plant heights were found for both early and delayed transplanting in 2011 to 2013 and non significant difference in 2014 respectively (Table 2; Table 3; Table 4; Table 5) (p<0.05). Mean plant height were 149.5 cm in 2011, 127.8 cm in 2012, 134 cm in 2013 and 137 cm in 2014 for early transplanting and 136.6 cm in 2011, 105 cm in 2012, 115.14 cm in 2013 and 101 cm in 2014 for delayed transplanting. Similarly, tallest plant height was obtained from NR10591-B-B-3-3-3-3 (171.8 cm) in 2011 and shortest from 08 FAN10 (100 cm) in 2014 for early transplanting and tallest plant found was NR10591-B-B-3-3-3-3 (156 cm) and shortest was Sugandha-3 (80 cm) in 2012 for delayed transplanting.

3.4 Panicle length

Significant difference in panicle length was obtained from both early and delayed transplanting in 2011 to 2013 and non significant difference in 2014 for arly and delayed transplanting (Table 2; Table 3; Table 4; Table 5). Average panicle length for early transplanting were 29 cm in 2011, 25.8 cm in 2012, 26.33 cm in 2013 and 26.8 cm in 2014 and for delayed transplanting average panicle length were 26.5 cm in 2011, 24.1 cm in 2012, 25.6 cm in 2013 and 25.3 cm in 2014 respectively. Longest panicle length was found for NR10676-B-3-4-1 (34.5 cm) in 2011 and shortest for Khumal-11 (22.3 cm) in 2012 for early transplanting and NR10851-B-B1-4 (30.4 cm) in 2011 and Khumal-11 (20.7 cm) in 2012 for delayed transplanting respectively.

3.5 Number of fertile grain per plant

Fertile grain number per plant is a direct attributes of yield. Significant difference were found in number of kernel per panicle of early and delayed transplanting in 2011, 2012, 2013 and non significant difference in 2014 (p<0.05) (Table 2; Table 3; Table 4; Table 5). Average number of fertile grain per plant was 145 in 2011, 145 in 2012, 120 in 2013 and 144 in 2014 in early transplanting whereas 131 in 2011, 78 in 2012, 128 in 2013 and 91 in 2014 in delayed transplanting. Maximum grain number was obtained from NR 10553-B1-25-2 (199) and minimum from IR 55419-04 (78) in early transplanting in 2012. Similarly, maximum grains per plant were from YR25696-B-196-3-3 (192) and minimum from Khumal-11 (51) in delayed transplanting in 2012 .

3.6 Grain yield

Grain yield is the main component of a crop. Highly significant difference among yield were found in 2011, 2012, 2013 and non significant difference in 2014 for both early and delayed transplanting. Mean grain yield (kg/ha) obtained from different years were 5862 kg in 2011, 5026 kg in 2012, 6872 kg in 2013 and 6689 kg in 2014 in early transplanting and 4487 kg in 2011, 1877 kg in 2012, 6086 kg in 2013 and 2447 kg in 2014 in delayed transplanting(Figure 2). Maximum grain yield was recorded from NR10769-4-2-2 (8103 kg/ha) in 2013 and minimum from NR 10546-B2-8-3-2-1 (3872 kg/ha) in 2012 in early transplanting. In the same way, highest grain yield were found in IR 80937-B-166-4 (6743 kg/ha) in 2013 and lowest in Khumal-4 (965 kg/ha) in 2012 in delayed transplanting (Figure 3).

4 Discussion

Interpretation of four year's data from 2011 to 2014 show that day to heading and maturity in delayed transplanting was longer than early transplanting. On an average, 18.82% and 14.43% more days were taken by delayed transplanted crop to head and mature than early transplanted crop from 2011 to 2014 respectively. More days for maturity (26.66%) were taken in 2011 and less days (5.29%) in 2013. Mean difference in days to flowering were 27, 14, 8 and 22; and mean days to maturity were 32, 14, 7 and 23 in 2011 to 2014 respectively (Figure 1). This result is similar to the findings of Nahar et al (2009) and Shah (2001) who reported delayed transplanting cause delay heading and maturity which might be due to low solar radiation during crop vegetative stage.

On an average, 16.78% decrease in plant height was obtained from early to delayed transplanting from 2011 to 2014. Highest reduction in plant height (26.27%) were achieved in 2014 and lowest (8.96%) in 2011. The mean difference in plant height were 13.4 cm, 23 cm, 18.8 cm and 36 cm from 2011 to 2014 respectively (Figure 4). The decrease of plant height in all years of delayed transplanting might be due to improper development of roots and short photoperiod duration. This result is similar to the findings of Vandana et al. (1994) who reported that dry matter accumulation in leaves decreased with test cultivar with later transplanting dates.

This result is similar to the findings of Vandana et al. (1994) who reported that dry matter accumulation in leaves decreased with test cultivar with later transplanting dates.

The average reduction in panicle length was found from early to delayed transplanted crop was 5.92% from 2011 to 2014. Highest reduction (8.79%) was obtained in 2011 and lowest (2.73%) in 2013. Similarly, mean difference in panicle length were 2.5 cm, 1.7 cm, 0.7 cm and 1.5 cm from 2011 to 2014 respectively (Figure 4). Reduction in panicle length in delayed transplanting from the early one may be due to lack of full photosynthesis during its growing period, inability of roots to absorb minerals from soil. This result reveals the findings of Hussain et al (2005) and Shah (2001) who reported that maximum number of panicle was produced by line transplanted method in early transplanting. This might be due to adaptation with climate, well adopted root system and well adopted leaf structure and canopy having optimum light absorption, nutrients uptake and synthesis of more carbohydrates.

Average increase in fertile grain number per plant was 21.51% from delayed to early transplanting from 2011 to 2014. Maximum increase was 46.2% in 2012 but there was decrease in fertile grain number by 6.6% from early to delayed transplanting in 2013. The difference in fertile grain number was 14, 67, -8 and 53 from 2011 to 2014 respectively (Figure 4). These results resembles to the findings of Akram et al. (2007) and Kameswara and Jackson (1997) who reported that number of kernels per panicle were significantly affected as sowing date is delayed. Awan et al. (2011) also reported that reasons for low yield and less grain number are use of imbalance inputs at improper time, transplanting of aged rice nursery and imbalanced use of fertilizer etc. However these results are contrary to that of Habibullah et al. (2007) who reported that sowing date had no significant effect on number of grains per panicle.

There was 2452.45 kg (38.44%) decrease in mean grain yield from early to delayed transplanting from 2011 to 2014. Maximum decrease in yield was 63.41% in 2014 and minimum was 4.22 in 2013. The mean grain yield difference were 1375.2 kg (23.45%), 3149.6 kg (62.65%), 1043.11 kg (4.2%) and 4241.9 kg (63.45) from 2011 to 2014 respectively (Figure 3). These results supports the findings of Hwang et al (1998) who reported that paddy yields deteriorated as planting date was delayed. Shah (2005) also reported that June 15 seeding recorded significantly the highest paddy yield and decreased with the delay in planting time. In the same way, Iqbal et al (2008) reported that the highest yield was obtained when the rice crop was sown earlier in the season. Similarly, according to Baloch et al. (2006) among planting dates, June 20^th planted crop gave highest paddy yield. Somato et al. (1961) concluded that early transplanting of seedlings resulted in higher yield of grain than late transplanting. This concept is further supported by Khan and Baloch (1970) and Pirzada et al. (1962) who revealed that sowing of nursery in the month of April and transplanting in June produced the highest yields which reveals the results of Bali and Uppal (1995) who concluded that rice crop transplanted on 10^th July gave 9.4 to 17.9 % higher grain yield than 30^th July transplanting due to higher root density, NPK uptake and head rice recovery. Khakwani et al. (2006) also suggested that highest paddy yields are obtained in early transplanting. The reason could be that this might be due genotype genetic superiority, appropriate temperature for growth and development, nutrients absorption, proper root system of the genotype and proper time of transplanting which leads to provide optimum duration for seed filling.

5 Conclusion

On an average 38.44% decrease in yield was found from early to delayed transplanted rice from 2011 to 2014. Comparison of different parameters of rice from 2011 to 2014 showed that late transplanted aged rice seedlings had always lower yield than early transplanted rice which might be due to aged seedlings, improper root growth and development causing less absorption of nutrients from soil, shorter duration of photosynthesis during grain filling period and cold during grain maturation time. So this might be the possible reason to have high yields in earlier transplanting. Climate change and irratic rainfall pattern has pushed away the planting time of rice. Labor scarcity and delay in monsoon also causes delay in transplanting. Thus farmer’s field have lower yield because of delayed transplanting of aged rice seedlings. The yield reduction of farmer’s field can be minimised by transplanting rice in appropriate time with recommended package of practices.

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