Growth and Correlation with Weather Parameters as Affected by Transplanting Time and Different Varieties of Paddy (Oryza sativa L.)

Paddy has been the staple food for more than 60 per cent of the world population, providing energy for about 40% of the world population where every third person on earth consumes rice every day in one form or other (Virdia and Mehta, 2009). Therefore, crop paddy (Oryza sativa L.) is an important crop that is extensively grown in tropical and subtropical regions of the world. Global demand for food is rising because of population growth, increasing affluence and changing dietary habits. The UN/FAO forecasts that global food production will need to increase by over 40% by 2030 and 70% by 2050. Yet globally, water is anticipated to become scarce and there increasing competition for land, putting added pressure on agricultural production. Besides, climate change will reduce the reliability of the food supply through altered weather patterns and increased pressure from pests and diseases.

Transplanting time and sowing date significantly influenced on growth and yield of rice crops, it has been studied by the number of research workers from various parts of India and abroad. The transplanting time and sowing time of the rice crop are important for three major reasons. Firstly, it ensures that vegetative growth occurs during a period of satisfactory temperatures and total sunshine hours. Secondly, the optimum transplanting time and sowing time for each cultivar ensure the cold-sensitive stage occurs when the minimum night temperatures are historically the warmest. Thirdly, transplanting and sowing on-time guarantees that grain filling occurs when milder autumn temperatures are more likely, hence good grain quality is achieved. Results from different studies revealed that the maximum yield potential of a rice crop is usually achieved when the crop is exposed to the most appropriate temperature range, which can be controlled by transplanting sowing at the proper time. Recently weather variability being considered one of the major factors of inter-annual variability of crop growth and yield in all environments besides rainfall, temperature and bright sunshine hours also have been bearing on crop growth and development as well as yield response of different species to different environments can be quite different. The shift in sowing dates directly influences both the thermo and photoperiod and consequently has great impact on the phasic development and partitioning of dry matter (Patel et al., 2019). Timely planting, using proper plant protection measures and providing irrigation at right time was the most desired practices at the farmers own level for yield improvement by rice growers (Grover, 2013).

The early-planted photoperiod-sensitive rice varieties go through a lag vegetative phase during which increases height, as well as biomass, making them prone to lodging during the grain-filling stage. Adjustment in the transplanting time, therefore, enables the plants to take advantage of natural conditions favourable for growth. Yoshida (1993) reported that rice plants require a particular temperature for phenological responses such as panicle initiation, flowering and panicle exsertion from flag leaf sheath and maturity and these responses are very much influenced by the planting dates in the transplanted paddy. Moreover, the genetic variability and the potentiality of the genotypes were expressed differently due to planting at different dates. The optimum planting time of transplanted Kharif paddy is in July but transplanting is sometimes delayed due to various physical and socio-economic factors. Late planting exposes the reproductive phase as well as phonological events of the crop to unfavourable temperature regimes, thereby causing high spikelet sterility and poor plant growth. However, optimum rice planting dates are regional and vary with location and genotypes (Bruns and Abbas, 2006). Chowdhury et al., (2000) reported that grain and straw yields gradually decreased when rice is planted after 10th of August transplanting. Islam (1986) concluded that the time between 15 July and 20 August was optimum for transplanting of Kharif rice, especially the photosensitive varieties. As the timing of planting influenced the growth and yield of transplanted Kharif rice genotypes, the present study was conducted to find optimum transplanting time of four selected high-yielding varieties for the Kharif season.

An experiment entitled, “Effect of transplanting time on different varieties of paddy concerning weather parameters” was carried out in a split-plot with sixteen treatment combinations and three replications. The treatment comprising four transplanting times viz., T₁: 26^th MW (24^th June to 30^th June), T₂:28^th MW (8^th July to 14^th July), T₃: 30^th MW (22^nd July to 28^th July), T₄: 32^nd MW (5^th August to 11^th August) as main plot treatment and four paddy varieties viz., V₁: VDN-3-51-18 (Indrayani), V₂: VDN-99-29 (Phule Samruddhi), V₃: IET 13549 (Bhogawati), V₄: RDN-99-1 (Phule Radha) as sub-plot treatment during Kharif, 2013 at ARS Farm, Vadgaon-Maval, Tal-Maval, Dist-Pune (M.S.), India.

Experimental field soil was clay loam, normal in reaction (pH 7.1), having EC 0.32 dS m^-1 and OC was medium (0.53%), low in available nitrogen (162.67 kg ha^-1), high in available phosphorus (29.56 kg ha^-1) and high in available potassium (467.00 kg ha^-1). Crop was transplanted according to different treatments of transplanting time along with different varieties. The required quantity of fertilizer was given in the form of Urea-DAP briquette and MOP as basal dose. Gross plot size was 2.95 m x 2.15 m and net plot size was 2.65 m x 1.35 m. Paddy seedlings were raised by line sowing of seeds on the nursery bed. First, second, third and fourth sowing on nursery bed was done on 10^th June, 25^th June, 9^th July and 22^nd July, respectively and seedlings were transplanted at 15-25 cm x 15-25 cm spacing. For recording observations, five plants were selected randomly from each net plot and marked by fixing pegs near them. All the observations on growth were recorded on these plants. The statistical analysis of split-plot design with 4 replications, 3 main plot treatments and 3 sub-plot treatments were done by standard procedures suggested by Panse and Sukhamate (1967).
 

Growth characters of paddy
 
Plant height of paddy (cm)
 
Mean plant height was significantly influenced by different transplanting times presented in Table 1. The Kharif paddy transplanted during 28th MW has recorded significantly maximum plant height at harvest. This might be due to congenial climatic conditions for better seedling and further growth and development of the Kharif paddy crop. These results were in accordance with Saikia et al., (1989), Paraye and Kandalkar (1994), Rakesh and Sharma (2004) and Dileep et al., (2018).



Mean plant height was significantly influenced up to harvesting due to different varieties. The significantly maximum plant height was observed at harvest with the variety Phule Samruddhi (87.5 cm) over the rest of the varieties. This might be due to varietal characters, earlier same reported by Dileep et al., (2018), Suryavanshi (2015), Halimi et al., (2018) and Shende et al., (2020).

nteraction effect between transplanting times and different varieties of paddy was found significant in respect of the mean plant height of paddy shown in Table 2. Variety Phule Samruddhi when transplanted during 28th MW recorded significantly higher plant height at 15 DAT (32.3 cm), 30 DAT (51.6 cm), 45 DAT (67.8 cm), 60 DAT (84.7 cm), 75 DAT (97.4 cm), 90 DAT (99.4 cm), 105 DAT (100 cm) and at harvest (100.6 cm) however it was at par with Indrayani transplanted during 28th MW at all the growth stages except at 30 and 45 DAT as well as with same variety transplanted during 26^th MW at 15 and 30 DAT only.


 
Correlation between weather parameters and plant height
 
The correlation between parameters with growth characters shown in Table 4 and weekly weather meteorological data recorded during experiment period is presented in Table 3. Paddy variety Phule Samruddhi recorded maximum plant height due to varietal characters and weather conditions during that period.





The correlation between weather parameters and plant height revealed a significant negative correlation in case of maximum temperature from 30 DAT to harvesting, in bright sun hour from 15 DAT to harvesting and in case of GDD 30 DAT to 60 DAT. The Highly significant positive correlation found with T min 45 DAT, 60 DAT to at harvest, in RH-I 90 DAT and at harvest, in RH-II from 15 DAT to at harvest and in rainfall from 30 DAT to at harvest. The results found similar to Chandra et al., (2009).

Effect on number of tillers plant^-1
 
Number of tillers plant^-1 was significantly influenced due to different transplanting times at harvest presented in Table 1. The transplanting of paddy seedlings at 28^th MW recorded the significantly higher number of tillers (16) over the rest of the transplanting times. The transplanting of paddy at 26^th MW performed second-best treatment to produce the significantly higher number of tillers (14) plant^-1 than 30^th MW and 32^nd MW. The lowest number of tillers (8) were observed when transplanting was done 32^nd MW. These results were in accordance with Rakesh and Sharma (2004), Akram et al., (2007), Kabir et al., (2014) and Singh et al., (2019).

The maximum number of tillers plant^-1 (17) was found with the variety Phule Samruddhi which was significantly superior over the rest of the paddy varieties. The variety Phule Radha recorded the significantly lower number of tillers plant-1 (8) than the remaining varieties. These findings were collaborative with the earlier reported by Suryavanshi (2015), Halimi et al., (2018) and Shende et al., (2020).

Interaction effects of paddy transplanting times and varieties were significantly influenced number of tillers plant^-1 shown in Table 2. The transplanting of the variety Phule Samruddhi paddy in 28^th MW (2^nd week of July) was recorded the highest number of tillers plant^-1 (21) than the rest of treatment combinations while the lowest in variety Phule Radha in 32^nd MW (06).
 
Correlation between weather parameters and number of tillers plant^-1
 
Correlation between parameters with growth characters presented in Table 4 and weekly weather meteorological data recorded during experiment period is presented in Table 3. The variety Phule Samruddhi recorded the maximum number of tillers plant^-1 due to varietal characters and weather conditions during that period. The correlation between weather parameters and the number of tillers plant^-1 revealed the significant negative correlation in the case of maximum temperature (r=-0.630**) and bright sunshine hour (r=0.612**). Significant positive correlation with T min, RH-I, RH-II and rainfall founded r=0.586*, r=0.537*, r=0.643** and r=0.645**, respectively. The results found similar to Chandra et al., (2009).

Based on experiment findings it was concluded that transplanting time and different paddy varieties significantly influenced the growth attributing characters of paddy. Transplanting on 28^th MW (2^nd week of July) resulted significantly maximum in plant height, number of tillers plant^-1. The variety Phule Samruddhi recorded significantly higher plant height, number of tillers plant^-1, Phule Samruddhi was found suitable under Vadgaon-Maval conditions. Among the interactions, the VDN-99-29 (Phule Samruddhi) variety of paddy was transplanted during 28^th MW (2^nd week of July) favourably influenced growth attributing characters as compared to other interactions formed due to transplanting times and varieties. Transplanting of Phule Samruddhi on 28^th MW (2^nd Week of July) was found ideal and climatically suitable for Vadgaon-Maval conditions. Correlation indicated that tmax i.e., maximum temperature, bright sun hour and growing degree days (GDD) showed significant and negative co-relationship with growth attributing characters of paddy, whereas tmin i.e., minimum temperature, RH-I and RH-II during the crop growing period showed positive and significant correlation with growth attributing characters of paddy.

Authors sincerely thank the ARS, Vadgaon-Maval, Taluka- Maval, District-Pune, Maharashtra, India for ease and smooth conduct of laboratory and experimental work and also thank to the College of Agriculture, Pune and MPKV, Rahuri for providing all the facilities to conduct research. Thanks, Dr. N.V. Kashid for initial review of manuscript.