Influence of transplanting techniques and age of wash root type seedlings on planting attributes of paddy rice

Abstract

Globally, Rice (Oryza sativa) is one of the most important crops. In India cultivars majorly use wash root type seedlings for rice production. The objective of the study was to assess the influence of transplanting techniques for transplanting wash root paddy seedlings. Two types of mechanical transplanting techniques (two-row hand cranked rice transplanter and tractor operated rice transplanter) were evaluated for three different age of nursery and compared with manual transplanting. The performances for each technique were evaluated in terms of average hill spacing, missing index, multiple index, damage seedlings, floating/buried hills, number of hills/m², planting efficiency, actual field capacity, field efficiency, energy required and cost of transplanting. Acquired results revealed that the best combination observed was tractor operated rice transplanter and 25 days of seedlings (desirability—0.764). The tractor operated rice transplanter increases the labor productivity by 32.22 times and saved about 66.69% average transplanting cost compared to manual transplanting, whereas it increases the labor productivity by 2.57 times and saved average 35.68% transplanting cost compared to hand crank rice transplanter. Manual transplanting causes non-uniform transplanting, higher missing index and cost of transplanting. Tractor operated rice transplanter at 25 days of seedlings was the best combination for transplanting due its superior techno-economics results.

Keywords:

• field capacity
• mechanical transplanting
• paddy
• rice
• planting efficiency

Public Interest statement

Rice is one of the main staple foods specially in Asian countries. Therefore, it is predominantly produced and consumed in these countries. In India farmers generally use wash root/conventional rice seedlings for transplanting which is mainly transplanted manually. Whereas comparing to other advanced Asian countries like China, Japan and South Korea, transplanting of rice seedlings was done by using mechanical transplanters. These machines use mat type rice seedlings instead of wash root rice seedlings, which is the main reason behind farmers were not adopting these machines. Growing mat type nursery requires skill labor as well as agro-climatic conditions (arid/semi-arid) is very different in India as compared to other Asian nations. This study was conducted to find the best mechanical transplanting technique for transplanting wash root seedlings. The tractor operated transplanter was found to be the best suited transplanting technique and significantly better than manual transplanting.

1. Introduction

Rice (Oryza sativa) is one of the most important crops and a staple food for the majority of the world’s population. In the year 2019, world rice production was about 755.47 million tons from the total planted area of 162.06 million hectare (Mha), with an average yield of 4.662 tons per hectare (t/ha; Anonymous, 2021a). Rice production, consumption and the market are mainly concentrated in Asia. Asian farmers produced about 90% of the world’s total rice production, out of which China and India jointly contribute nearly 51% of the total rice crop production (Anonymous, 2021a; Muthayya et al., 2014). Rice is a primary cereal crop of India which occupies about 35.1% of the total area under food grains contributing more than 40.8% of food grains production in the country during 2017–18 (Anonymous, 2018). In Punjab during the year 2016–17, area under rice was 3.142 Mha with a total production of 19.13 million tons. The average yield of paddy rice in Punjab was 6.088 t/ha, out of which the yield of the rice grain comes out to be 4.59 t/ha (Anonymous, 2021b).

The most common method of paddy rice transplanting requires rice seedlings of approximately 20–30 days. The transplanting can be done either manually or with the help of mechanical transplanter (Asenso et al., 2019; Baek & Chung, 2012; Dixit et al., 2007). Transplanting is done in the interest of achieving higher yield and reduced weeds problem (Chauhan & Johnson, 2011; Jehangir et al., 2021; Rao et al., 2007; Tuong et al., 2005). Traditional rice cultivation is laborious, expensive and time-consuming. The investment for preparing the field with a transplanting nursery receives 50% of the total production cost of paddy rice. The labor required to transplant the nursery ranges from 40- to 50-man days/ha (Chaudhary et al., 2005). To overcome such problems, adoption of appropriate technological advancement over existing agricultural practice is needed (Ishfaq et al., 2020, 2022; Manian et al., 2002; Zilpilwar et al., 2020).

Transplanting was found to be the most tedious operation in the rice production (Dixit et al., 2007). There were very frequent complaints by laborers that they suffer from back problems during transplanting. Also, it was very difficult to keep optimum spacing and uniform plant density during manual transplanting which results in either low or excessive plant density and low yields (Alipour & Mobasser, 2021; Anonymous, 2019). Timely transplanting of rice seedlings is essential to achieve optimal yield (Li et al., 2021), and this can be achieved by eliminating or minimizing the labor (Pandey et al., 2001). Hence, mechanical transplanting has been observed to be a very promising technique as it conserves labor, minimizes stress and drudgery, ensures timely transplanting, optimum plant density and contributing to higher productivity (Asenso et al., 2019; Yogeswari & Porpavai, 2018).

A rice transplanting machine is a specially designed tool to transplant paddy rice seedlings in the puddled field. Transplanters are notably beneficial because it can reduce peak labor requirement during rice transplanting operation (Dholay & Matekar, 2015). Also, transplanting has benefits of good levelling of land, reduced weed problem, uniform plant population and better supply of plant nutrients to the crop (Jehangir et al., 2021; Rao et al., 2007; Tuong et al., 2005).

In Punjab, farmers are not adopting the existing mat type seedlings fed rice transplanter regardless of multiple attempts of popularization since the 1980s, due to multiple reasons associated with raising of mat type seedlings (Anonymous, 1986; Chaba, 2014). For existing mechanical transplanter pre-required land leveling operation for uniform water depth at time of transplanting, this adds one more operation during field preparation. Mat type seedlings raising requires skilled labor and continuous monitoring for nutrients supply since “mat type” seedlings generally are grown in trays and on poly-sheets, which restrict the uptake of nutrients from the ground. Agro-climatic conditions become worse during sowing period of rice seedlings as Punjab lies in Semi-arid climatic zone. The average temperature during seedling transplanting is usually high and dry in June (Anonymous, 2017). Due to this “mat type” of seedlings requires more attention and frequent irrigation as compared to the traditional/wash root seedlings. Therefore, the traditional/wash root seedlings could be the best solution for paddy rice cultivation in Punjab. To transplant the traditional/wash root seedlings a rice transplanter is needed. Therefore, this study has been carried out to evaluate the transplanting techniques for wash root paddy rice seedlings. The null hypothesis of the study is that planting attributes will not be affected by transplanting technique.

2. Material and methods

2.1. Description and specification of different transplanting techniques

Two types of mechanical rice transplanter, viz., two-row hand cranked rice transplanter and tractor operated rice transplanter, were evaluated during Kharif season 2021–22 and compared with farmer’s practice—manual transplanting. Technical specifications of selected transplanters are given in Table 1 and their stationary and operational views are shown in Fig. 1 and 2. The description of the two transplanters are as follows:

Figure 1. Stationary view and operational view of two-row hand cranked rice transplanter.

Figure 2. Stationary view and operational view of tractor operated rice transplanter.

Table 1. Technical specifications of transplanting mechanism selected for the study

Sr. No.	Specifications	Two-row hand cranked rice transplanter (T1)	Tractor operated rice transplanter (T2)
1	Power Source	Manual	Tractor operated (35 hp or more)
2	Name of supplier/ manufacturer	Raftaar Professional Engineering Company (Rpec), Ludhiana, India	M/s Kisan Agro, Ludhiana, India
3	Overall dimensions L x W x H (cm)	60 x 117 × 112	240 x 185 × 110
4	Number of rows	2	10
5	Finger type	A couple of Rotating fingers mounted on disk, opening is controlled by eccentric cam mechanism	Gripping arm mounted on Extended link controlled by slider cam mechanism
6	Plunger Type	Oscillating arm type	NA
7	Type of nursery	Wash root type	Wash root type
8	Hill to hill Distance (cm)	10	10–25

2.1.1. Two-row hand cranked rice transplanter (T1)

The two-row hand cranked rice transplanter is a hand operated device which requires one labour for functioning (Figure 1). The seedlings were kept horizontally on the two seedling trays keeping the roots at the centre of the transplanter. A cam mechanism was used to open the pair of rotating clips which picks seedlings, rotates it to vertical position and transfers it to the planting finger. Planting finger is a four-bar extended arm mechanism which then plants seedling in the soil. On single rotation of crank the extended arm makes two strokes. Therefore, hill-to-hill spacing was dependent on crank rotational speed and forward speed. Weight of the transplanter is 15 kg, and row-to-row spacing was 300 mm.

2.1.2. Tractor operated rice transplanter (T2)

It requires 25.74 kW (power) or above tractor and has an operational speed of 1.0–5.0 km/h. The machine consists of main frame, seedling trays, transplanting mechanism, gear box and belt pulley drives. The number of rows in the machine was ten and row-to-row spacing was fixed at 300 mm. A four-bar extended arm mechanism was used for transporting seedlings from seedlings tray to the ground. The opening and closing of planting finger jaws were led by a travelling cam in between curved rails. The power from power take-off (PTO) of the tractor is transmitted to transplanting mechanism and seedling tray through a gear box (10:18 gear ratio) and belt pulley drives. The seedling tray reciprocates in a fixed path for each strike of the planting mechanism so that there will be a new set of seedlings in front of it. A flat plate is attached in front of transplanting mechanism for reforming the firm transplanting bed which deforms due to tires of the operating tractor. The mechanism is operated at fixed PTO 540 RPM. Therefore, hill-to-hill spacing is dependent only on the forward speed of the tractor. The stationary view and operational view of tractor operated rice transplanter are shown in Figure 2.

2.1.3. Manual transplanting (T3)

In manual transplanting, paddy rice seedlings of 25, 35 and 45 days were manually transplanted by laborers in three different plots. Two to three wash root paddy seedlings per hill with the spacing of 300 mm x 100 mm at depth of 20–40 mm were transplanted in each plot (Anonymous, 2021c; Figure 3). The hill-to-hill spacing is maintained by labor by their own sense, and it differs from person to person.

Figure 3. A view of farmer’s practice of paddy rice transplanting.

2.2. Preparation of seedlings and its selection

A well-drained, tilled and levelled site was selected for rice nursery raising. During field preparation farmyard manure (FYM) is mixed with soil at a rate of 12,000 kg per acre (Anonymous, 2021c). Small irrigation basins were created for irrigation and fertilizer application. At a time of nursery sowing, urea (at rate of 26 kg per acre), zinc sulphate monohydrate (at a rate of 25.5 kg per acre) and single superphosphate (at a rate of 60 kg per acre) was also mixed with soil (Anonymous, 2021c). Sprouted paddy rice seeds of the variety PR-121 were broadcasted manually on three different plots having area of 10 m² for preparing wash root type seedlings at a regular interval of 10 days. After 15 days of sowing nursery a single dose of urea (at rate of 26 kg per acre) was applied. The ages of seedlings during transplanting were 25 days after sowing (DAS), 35 DAS and 45 DAS. The seed rate was kept at 20 kg/ha in all the three plots (Anonymous, 2021c). The seedlings of respective DAS were pulled out from the ground, then the roots were washed and placed in trays of hand cranked transplanter and tractor-operated paddy transplanter manually.

2.3. Evaluation procedure

Field studies for evaluating the rice transplanting techniques for wash root type seedlings were conducted on the research farms at Dept. of Farm Machinery and Power Engineering, Punjab Agricultural University, Ludhiana, Punjab, India (Latitude: 30°54ʹ37.3” N and Longitude: 75°48ʹ43.2” E). The selected field had dimensions of 90 m X 33.5 m (0.3 ha) and sandy clay loam (sand 55.2% and clay 24.6%) soil. The climate of research location falls under hot and semi-arid category. The time of nursery sowing varied between 20 May and 9 June which is the optimum time of sowing (Anonymous, 2021c) for the location. The performance of each technique was evaluated in terms of average hill spacing, missing index, multiple index, damage seedlings, floating/buried hills, number of hills/m², planting efficiency, actual field capacity, field efficiency, energy required and cost of transplanting. Transplanters were operated length wise in the field on the puddled soil with approximately 10–20 mm water level in the field. The experiment was laid out with a factorial Randomized Complete Block Design (RCBD) with three replications for each method. Transplanting technique (3 level) and age of seedlings (3 level) were selected as factors of factorial design (Table 2). Each replication had dimensions of 33.5 m × 3 m. A random number generator was used for the allotment of field position; each replication was assigned with a serial number which was used in the allotment procedure. The layout of experiment is shown in Figure 4.

Figure 4. Field layout of the experiment.

Table 2. Independent and dependent parameters selected for experiment

S. No.	Independent variable		Level			Value
1.	Transplanting Techniques		3 levels
			Two-row hand cranked rice transplanter			T1
			Tractor operated rice transplanter			T2
			Manual Transplanting			T3
2.	Age of Seedlings		3 levels
			25-day-old seedlings			A1
			35-day-old seedlings			A2
			45-day-old seedlings			A3
Dependent variables
Average plant spacing, mm	Missing Index (%)		Multiple Index (%)			Damage Percentage (%)
Floating/buried percentage (%)	Planting Efficiency		Numbers of hills per sq. meter			Actual field capacity, ha/h
Field efficiency, %	Energy required, MJ/ha		Cost of transplanting, INR/ha

The transplanting techniques were evaluated as per the Asian and Pacific Network for Testing of Agricultural Machinery (ANTAM) and Regional Network for Agricultural Machinery (RNAM) standard testing code for rice transplanters (ANTAM-003-2017, 2017; RNAM, 1983). Average hill spacing was the indicator of uniformity in seedling placement during transplanting. It is the mean of hill spacing values recorded for a square meter sample area and calculated using equation as mentioned in Table 3. The missing index signifies the frequency of missing of the desired spacing during transplantation. It represents the percentage of spacing instances that were greater than 1.5-fold of the theoretical spacing and was calculated based on the equation in Table 3. The multiple index (M_u) indicated the frequency of more than one hill planted within the desired spacing of 100 mm. It is represented by the percentage of spacing instances which are less than or equal to 0.5 times of the theoretical spacing. The damage to seedlings was divided into two categories. Internal damage to the developing tissues and the damage caused by cutting or bending of seedlings due to physical crushing/force during transplanting by finger/plunger. The number of damaged seedlings due to cutting/bending was counted and recorded for a square meter sample area (D_cb) and the seedling were observed for the next 40 days for internal damage and counted for same sq. meter sample area (D_i). During transplantation, the roots of seedlings get into soil, but sometimes due to higher water level and disturbance by transplanter movement, seedlings get uprooted and float on the water, such seedlings are called floating hills. Whereas hills which buried under the soil after transplanting either due to inadequate depth of transplanting or movement of soil by machine travel are called buried hills. Therefore, the number of hills floating/buried in square meter area was counted and recorded. Floating/buried percentage was calculated by using equation in Table 3. Missing index, multiple index, damage percentage and floating/buried percentage are the major parameters which play a vital role in the determination of quality of transplanting. The transplanting efficiency was determined by subtracting cent percent with the percentage non-existence of seedlings in any planting point due to floating, buried and inability to pick the seedlings by the finger (missing index and multiple index). Theoretical field capacity of the implement is defined as the field capacity at the ideal conditions, i.e., no time is wasted in turning, no overlapping, no missing area, no time wasted in setting up of the machine and loading/unloading of machine. Whereas the actual field capacity was computed under real condition. It includes the time taken for turning, loading/unloading, setting up of machine, overlapping and missing area with working time. It is the ratio of actual field capacity to theoretical field capacity in percentage. It includes the effect of time lost in the field and failure to utilize the full width of the machine.

Table 3. Descriptions of various dependent parameters and equations used in its calculations

Sr. No.	Dependent Parameter	Descriptions	Abbreviations	References
1	Average plant spacing (Hs)	${\mathrm{H}}_s=\frac{{\sum }_{i=1}^n{H}_{si}}{n}$	Hs = Average plant spacing I = Plant spacing at ith term n = total number of spacing recorded	Patil et al., 2017 Pal et al., 2018
2	Missing index (Mi)	$M_i=\frac{N_1}{n}\times 100$	N1 = number of times spacing in the region is greater than 1.5 times of the theoretical spacing recorded in sq. meter n = total number of hills in sq. meter sample area	Nare et al., 2014 Kumar et al., 2018 Singh et al., 2018 Mishra et al., 2021
3	Multiple index (Mu)	$M_u=\frac{N_2}{n}\times 100$	N2 = number of times hill spacing in the sq. meter area was less than or equal to 0.5 times of the theoretical spacing (100 mm) n = total number of observations	Nare et al., 2014 Badgujar et al., 2017 D Kumar et al., 2017
4	Damage seedlings	$D_s,\mathrm{\%}=\frac{\left(D_{cb}+D_i\right)}{n_t}\times 100$	Ds = damaged Seedlings Dcb = damage seedlings due to cutting/bending Di = damage seedlings due to internal damage nt = number of seedlings transplanted in sq. meter area	G. Singh et al., 1985 Patil et al., 2017 Mishra et al., 2021
5	Floating/buried percentage	$F{B}_h=\frac{(F_h+B_h)}{n}\times 100$	FBh = percentage of floating/buried hills Fh = Numbers of floating hills per Sq. meter Bh = Numbers of buried hills per Sq. meter n = Total numbers of hills per Sq. meter	Patil et al., 2017 Pal et al., 2018
6	Planting efficiency	$Pe,\mathrm{\%}=100-M_i+M_u+FB{ }_h$	Mi = missing index Mu = multiple index FBh = floating/buried hill percentage	Pal et al., 2018
7	Theoretical field capacity	$TFC,\frac{ha}{h}=\frac{speedofoperation\left(\frac{km}{h}\right)\times widthofimplement\left(m\right)}{10}$		Patil et al., 2017 Condra, 2017 Pal et al., 2018 Mishra et al., 2021
8	Actual field capacity	$AFC,ha/h=\frac{Areaofoperation\left(m^2\right)\times 0.36}{Timetakenforoperation\left(s\right)}$		Taylor et al., 2001 Patil et al., 2017 Mishra et al., 2021
9	Field efficiency	$FE=\frac{AFC}{TFC}\times 100$		Patil et al., 2017 Pal et al., 2018 Mishra et al., 2021

The energy requirement for transplanting paddy rice was mainly dependent on human labor, machinery and fuel consumption (diesel). The sources of mechanical energy used in the study include tractor, tractor operated rice transplanter, hand crank rice transplanter and diesel. The mechanical energy was computed based on total fuel consumption (l/ha) and energy of machinery in different replicated trials. Therefore, the energy consumed was calculated using conversion factors (human = 1.96 MJ/man-hour; diesel = 56.31 MJ/l; machinery = 62.7 MJ/kg) and expressed in MJ/ha (Jat et al., 2020; M. K. Singh et al., 1997; Mittal & Dhawan, 1988). The energy input occurred was calculated and recorded for each replicated trial.

The overall cost incurred in paddy rice transplanting using the three methods was comparatively evaluated. The cost of nursery raising and roots washing for the uprooted seedlings was considered constant between each transplanting technique, whereas the cost of transplantation was separately calculated. The life of tractor was assumed to be 10 years, and that of the tractor-operated rice transplanter and hand cranked rice transplanter was considered as eight years. Average annual usage was represented by the number of hours for hand cranked rice transplanter (T1) operation (50 hours) and tractor-operated rice transplanter (T2) operation (140 h). The cost of transplanting was determined as per BIS code IS 9164 (Zachariah,1979). The cost of transplanting was estimated after incorporating fixed (depreciation cost, interest cost, taxes, insurance, and shelter cost) and variable costs (labor cost, fuel cost, repair and maintenance cost and cost of lubricants) of individual steps. Cost analyses were carried out using the straight-line method of depreciation (Donnell, 2001). The cost of transplanting was calculated based on the initial cost of tractor, hand cranked rice transplanter (T1) and tractor operated rice transplanter (T2) and was INR 4,50,000/- ($ 5684.29), 25,000/- ($ 315.79) and 1,20,000/- ($ 1515.81) respectively. Rate of interest was kept at 12%, and skilled human labor was INR 50.3/h ($ 0.64/h). The calculated actual field capacity for T1 (≈0.045 ha/h), T2 (≈0.232 ha/h) and T3 (≈0.0036 ha/h) transplanting techniques was considered for analysis.

2.4. Statistical analysis

The numerical data recorded during rice transplantation were evaluated using a freely available statistical analysis software (SAS on demand software for Academics). The software was used to determine the influence of seedlings age and transplantation technique on plant characteristics. ANOVA with randomized Complete Block Design (RCBD) was used for analyzing the recorded data (Table 5). The probability (p-value) was assumed for its significance at P < 0.05. At P ≤ 0.05, the variation was considered significant. Tukey’s post hoc test was used to determine the relationship within and in between groups. The “Design Expert 13” analysis software was used for selecting the best solution and prediction of planting attributes.

3. Results and discussion

3.1. Effect of transplanting technique and age of seedlings on average hill spacing

The age of seedlings and transplanting technique did not show any significant effect on the average hill spacing. Twenty-five and thirty-five days of seedlings were observed as the best ages for all transplanting techniques. Also, no significant (p > 0.05) effect was observed on average hill spacing due to interaction between transplanting technique and age of seedlings. The mean values of observed hill spacing at different Combination of age of seedlings and transplanting technique is represented in Table 4 and 5 and Figure 5 (a). The maximum average hill spacing (150 mm) was observed for T2 transplanting technique at seedlings age of 45 days, whereas minimum average hill spacing (105 mm) was observed for T1 transplanting technique at the same age of seedlings. A hill-to-hill spacing of 120 mm is recommended for mechanical transplanting of paddy rice in Punjab region of India (Anonymous, 2021c). This may be due to the reason that the hill spacing in transplanting mechanism of T1 and T2 has already been fixed mechanically (Described in section 2.1), whereas in transplanting technique T3, the manual labor while doing transplanting regularly becomes habitual of maintaining a certain fixed distance in between the hills.

Figure 5. Effect of transplanting techniques and age of seedlings on (a) Average hill spacing, (b) Missing Index, (c) Multiple Index and (d) Damage seedlings.

Table 4. Mean values and p-values of planting attributes at different combinations of age of seedlings and transplanting technique

Sr. No.	Independent parameter	Age of seedlings (D), days	Transplanting technique (T)			Significance (p-value) (p ≤ 0.05)
			T1	T2	T3	T	D	T*D	CV
1	Average plant spacing, mm	25	130.0^a ± 26.45	143.3^a ± 20.18	126.7^a ± 20.81	0.3160 (NS)	0.8270 (NS)	0.7825 (NS)	21.7
		35	136.7^a ± 30.55	140.0^a ± 10.00	130.0^a ± 62.44
		45	105.0^a ± 18.02	150.0^a ± 10.00	126.7^a ± 30.55
2	Missing index, %	25	8.58^e ± 0.460	28.28^c ± 1.131	19.66^cd ± 0.165	<0.001 (S)	0.0324 (S)	0.0059 (S)	7.8
		35	7.53^e ± 0.318	28.06^c ± 1.207	23.67^bd ± 0.760
		45	8.14^e ± 0.679	28.37^c ± 1.033	26.00^bc ± 0.245
3	Multiple Index, %	25	12.08^f ± 0.46	0^j	5.00^i ± 0.04	<0.001 (S)	0.0459 (S)	0.0005 (S)	15.9
		35	14.97^h ± 1.36	0^j	4.00^gi ± 0.07
		45	13.92^fh ± 1.33	0^j	2.00^gj ± 0.07
4	Damage Seedling, %	25	24.04^k ± 1.54	2.73^l ± 0.26	0.33^l ± 0.47	<0.001 (S)	0.3355 (NS)	0.5568 (NS)	10.9
		35	23.54^k ± 0.72	2.07^l ± 0.17	0.33^l ± 0.47
		45	23.73^k ± 1.25	1.05^l ± 0.01	0.33^l ± 0.47
5	Floating/buried percentage, %	25	1.95° ± 0.149	6.20^m ± 0.201	1.00° ± 1.00	<0.001 (S)	0.0119 (S)	0.0285 (S)	26.9
		35	2.11° ± 0.193	7.50^mn ± 0.060	2.33° ± 2.08
		45	1.96° ± 0.163	9.21^n ± 0.135	1.67° ± 0.57
6	Numbers of hills per sq. meter	25	23.00^q ± 2.64	22.33^pq ± 1.527	20.00^pq ± 2.00	0.0006 (S)	0.4266 (NS)	0.3525 (NS)	7.02
		35	21.67^pq ± 2.51	23.33^b ± 1.154	17.00^p ± 1.00
		45	23.00^q ± 1.73	22.00^pq ± 2.000	19.67^pq ± 1.05
7	Planting efficiency, %	25	53.35^t ± 1.91	62.79^s ± 1.22	74.00^r ± 2.79	<0.001 (S)	0.0278 (S)	0.3541 (NS)	2.9
		35	51.85^t ± 2.31	62.38^s ± 1.39	69.67^r ± 2.20
		45	52.25^t ± 0.57	61.37^s ± 1.13	70.00^r ± 1.00
8	Actual field capacity, ha/h	25	0.0481^w ± 0.004	0.234^u ± 0.002	0.0035^x ± 0.00	<0.001 (S)	0.0021 (S)	0.001 (S)	4.2
		35	0.0450^w ± 0.003	0.224^v ± 0.003	0.0036^x ± 0.00
		45	0.0425^w ± 0.002	0.237^u ± 0.005	0.0037^x ± 0.00
9	Field efficiency, %	25	80.18^A ± 0.75	78.09^A ± 0.77	88.17^z ± 0.77	<0.001 (S)	0.0010 (S)	0.001 (S)	1.7
		35	75.06^B ± 0.51	74.84^B ± 1.17	90.36^z ± 0.186
		45	70.97^C ± 0.46	79.32^A ± 1.83	94.68y ± 1.38
10	Energy required, MJ/ha	25	407.32^D ± 3.82	1513.45^F ± 15.44	1111.54^G ± 9.78	<0.001 (S)	0.0005 (S)	<0.001 (S)	2.4
		35	435.08^DI ± 2.99	1579.11^E ± 24.78	1084.46^G ± 2.24
		45	460.12^I ± 2.99	1490.47^F ± 34.58	1035.13^H ± 15.05
11	Cost of transplanting, INR/ha	25	13,956.04^P ± 33.26	10,420.09^J ± 39.55	17,783.67^K ± 99.80	<0.001 (S)	0.003 (S)	<0.001 (S)	0.61
		35	14,194.58^O ± 26.08	10,592.70^Q ± 65.15	17,507.38^L ± 22.89
		45	14,415.44^N ± 26.08	10,359.68^JQ ± 90.92	17,004.04^M ± 153.66

^aThe same superscripts represent no-significant difference.

Table 5. ANOVA table of the effect of transplanting technique and age of seedling on different planting attributes

Source	df	Significance (p-value) (p ≤ 0.05)
		Average plant spacing, mm	Missing index, %	Multiple Index, %	Damage Seedling, %	Floating/ buried percentage, %	Numbers of hills per sq. meter	Planting efficiency, %	Actual field capacity, ha/h	Field efficiency, %	Energy required, MJ/ha	Cost of transplanting, INR/ha
Transplanting technique (T)	2	0.3160 (NS)	<0.001 (S)	<0.001 (S)	<0.001 (S)	<0.001 (S)	0.0006 (S)	<0.001 (S)	<0.001 (S)	<0.001 (S)	<0.001 (S)	<0.001 (S)
DAS (D)	2	0.8270 (NS)	0.0324 (S)	0.0459 (S)	0.3355 (NS)	0.0119 (S)	0.4266 (NS)	0.0278 (S)	0.0021 (S)	0.0010 (S)	0.0005 (S)	0.003 (S)
T*D	4	0.7825 (NS)	0.0059 (S)	0.0005 (S)	0.5568 (NS)	0.0285 (S)	0.3525 (NS)	0.3541 (NS)	0.001 (S)	0.001 (S)	<0.001 (S)	<0.001 (S)
Error	18
Total	27

3.2. Effect of transplanting technique and age of seedlings on missing index

Transplanting technique and age of seedlings had a significant (p ≤ 0.05) effect on missing index, whereas it shows no significant effect due to (p > 0.02) with increase in age of seedlings. The interaction of transplanting technique and age of seedlings was also found to have significant effect on missing index. Table 4 and Figure 5 (b) represent the mean values of observed missing index at different combination of age of seedlings and transplanting technique. The experiments showed that the missing index was observed minimum (7.53 %) in T1 transplanting technique at 35 days of nursery, and it was observed maximum (28.37 %) in T2 transplanting technique at 45 days of nursery. Higher missing index obstructs the higher crop yield (Islam & Salam, 2017; M. Kumar et al., 2021; Mishra & Salokhe, 2008). The best age of seedlings for T1 and T2 for operations was 35 DAS, whereas 25 DAS seedlings was best for manual transplanting (T3). The desired missing index needs to be as low as possible, therefore at above-mentioned DAS of seedlings, the transplanting technique reflects the minimum missing index. Tractor operated paddy transplanter (T2) has maximum missing index due to improper picking of seedlings by the picking mechanism, while in T3 transplanting technique multiple manual labor performs the transplanting operation simultaneously.

3.3. Effect of transplanting technique and age of seedlings on multiple index

The effect of transplanting technique and age of nursery along with their interaction was significant (p ≤ 0.05) on multiple index. The mean values of multiple index obtained from field evaluation of three different transplanting technique for three different ages of seedlings are shown in Table 4 and Figure 5 (c). It is clear from Table 4 that zero multiple index was observed for T2 transplanting technique for all ages of seedlings. Different studies showed that high level of multiple index leads to misuse of seedlings (Islam & Salam, 2017; M. Kumar et al., 2021; Mishra et al., 2021; Mishra & Salokhe, 2008). The maximum multiple index (14.97 %) was observed for T1 transplanting technique at seedlings age of 35 days. The reason for zero multiple index in T2 transplanting technique was continuous missing of seedlings by the picking mechanism as stated in effect of transplanting technique on missing index. Moreover, in T1 transplanting technique the labor operating the transplanter simultaneously performed the cranking and pulling operation which results in slowing of transplanter speed and undesired multiple index.

3.4. Effect of transplanting technique and age of seedlings on damage seedlings

The effect of transplanting technique and age of seedling on seedlings damages was observed and calculated for different combinations of independent parameters. There is significant (p ≤ 0.05) effect on damage seedlings due to transplanting technique, whereas no significant effect was observed due to (p > 0.05) increase in age of seedlings. The mean values of damage seedlings obtained during three replications of all experiments were calculated (Table 4) and compared (Figure 5 (d)). The percentage damage of seedlings was observed minimum (0.33 %) for T3 transplanting technique at all age of seedling, whereas maximum damage to seedlings (24.04 %) was observed for T1 transplanting technique at 25 days of seedlings. High rate of damage increases the requirement of seedlings per hill (Hossen et al., 2018). This may be due to the reason that with increase in seedlings age, there was increase in the resilience of seedling which results in reduction of damage due to transplanter’s mechanism. Also, T1 transplanting technique has higher damage seedlings (≈24 %) as compared to other two transplanting technique. The reason for the higher damage seedlings was that in hand crank transplanter seedlings were kept in horizontal position in seedling tray (Figure 2) which further rotated to vertical position by the help of picking mechanism and flat plate for transplanting.

3.5. Effect of transplanting technique and age of seedlings on floating/buried percentage

Transplanting technique has a significant (p ≤ 0.05) effect on floating/buried percentage. However, no significant difference was observed between transplanting technique T1 and T3. The minimum floating/buried percentage (1.0 %) was observed for T3 transplanting technique at 25 days of seedlings whereas maximum floating/buried percentage (9.21 %) was observed for T2 transplanting technique at nursery age of 45 days (Table 4 and Figure 6 (a)). Different studies showed that floating/buried seedling affects the crop yield due to unavoidable reduction of hill density (Dou et al., 2021; Goel et al., 2008; Hayashi et al., 2006). Also, age of nursery and interaction between transplanting technique and age of seedlings have a significant effect on floating/buried percentage. The reason behind this result was the absence of plunger in T2 transplanting mechanism, resulting in non-placement of seedlings at desired depth. T1 transplanting mechanism has been provided with the pusher unit which pushes seedling into the soil while in T3 manual labor hand thumb acts as pusher which results in lowering of floating/buried hills (Nag & Gite, 2020).

Figure 6. Effect of transplanting techniques and age of seedlings on (a) Floating/buried percentage, (b) Hills Density, (c) Planting Efficiency and (d) Actual Field Capacity.

3.6. Effect of transplanting technique and age of seedlings on number of hills/m²

Table 4 shows that the transplanting technique had a significant effect on numbers of hill per sq. meter. Moreover, no significant difference has been observed between transplanting technique T1 and T2. Also, it was observed that there is no significant effect of the age of seedlings on number of hills/m². The minimum hill count observed in T3 transplanting technique might be due to the inconsistency between labors. The observations of effect of transplanting technique and age of seedlings on number of hill per sq. meter were analyzed and results are presented in Table 4 and Figure 6 (b). It is evident from the Table 4 that the effect of T2 transplanting technique with 35 days of seedlings has maximum (23.33) numbers of hills/m² whereas for same age of seedlings, the T3 transplanting technique has minimum (17.0) number hills/m². Higher numbers of hills per sq. meter results in higher numbers of effective tillers and grain yield (Alipour & Mobasser, 2021; He et al., 2020).

3.7. Effect of transplanting technique and age of seedlings on planting efficiency

Transplanting technique and age of seedlings had a significant (p ≤ 0.05) effect on planting efficiency. The interaction of transplanting technique and age of seedlings was found to have no significant effect on planting efficiency. Table 4 and Figure 6 (c) represent the mean values of observed planting efficiency at different combination of age of seedlings and transplanting technique. The experiments showed that the planting efficiency was observed maximum (74.0 %) in T3 transplanting technique at 25 days of seedlings, and it was observed minimum (51.6 %) in T1 transplanting technique at 35 days of seedlings. Planting efficiency is the overall parameter which was used to estimate the quality of transplanting along with helps in optimizing hills density which is the key parameter for increasing crop yield (Dihingia et al., 2016; Dou et al., 2021; Goel et al., 2008; Hayashi et al., 2006). T1 transplanting technique has a higher rate of damage seedlings, while in T2 transplanting technique minimum planting efficiency was due to higher missing index and floating/buried percentage.

3.8. Effect of transplanting technique and age of seedlings on actual field capacity

There was a drastic reduction (≈ ten folds) in actual field capacity from T2 transplanting technique to T1 transplanting technique followed by T3. Table 4 shows that the transplanting technique and age of seedlings had significant effect on actual field capacity. Moreover, no significant difference has been observed between individual transplanting techniques. The observations of the effect of transplanting technique and age of seedlings on field capacity were analyzed and results are presented in Table 4 and Figure 6 (d). It is evident from the Table 4 that the effect of T2 transplanting technique with 45 days of seedlings has maximum (0.237 ha/h) actual field capacity, whereas for 25 days of seedlings, the T3 transplanting technique has minimum (0.0035 ha/h) actual field capacity. The results are in line with Taylor et al. (2001); Buschermohle et al. (2016) and Condra (2017) which states that with increase in width of planter, the field capacity also increases. The field capacity can be improved in T3 transplanting technique by increasing the number of labors. This was the common practice followed by the farmers, but manual transplanting increases non-uniformity in row transplanting due to difficulty to maintain the optimum numbers of hills in field.

3.9. Effect of transplanting technique and age of seedlings on field efficiency

The effect of transplanting technique and age of seedlings along with their interaction was significant (p ≤ 0.05) on field efficiency. The mean values of field efficiency obtained from field evaluation of three different transplanting technique for three different ages of seedlings are shown in Table 4 and Figure 7 (a). It is clear from results presented in Table 4 that maximum field efficiency (94.68 %) was observed for T3 transplanting technique at 45 days of seedlings while minimum field efficiency (70.97 %) was observed for T1 transplanting technique at same age of seedlings. In transplanting technique T1 and T2, the time consumed in refilling of seedling tray and turning time was the cause of lower field efficiency. The results are in affirmation with Condra (2017) and Buschermohle et al. (2016), which states that increase in planter width decreases the field efficiency.

Figure 7. Effect of transplanting techniques and age of seedlings on (a) Field efficiency, (b) Energy required and (c) Cost of operation.

3.10. Effect of transplanting technique and age of seedlings on energy required

There was a significant (p ≤ 0.05) effect of transplanting technique, age of seedlings and interaction between transplanting technique and age of seedlings was observed on energy required. The mean values of observed energy required at different combination of age of seedlings and transplanting technique are represented in Table 4 and Figure 7 (b). The maximum energy required (1579.11 MJ/ha) was observed for T2 transplanting technique at seedlings age of 35 days, whereas minimum energy required (407.32 MJ/ha) was observed for T1 transplanting technique at 25 days of seedlings. The energy required was observed for T1 transplanting technique was minimum because it requires less man-hour as compared to T3 transplanting technique and equivalent energy of human power (1.96 MJ/man-hour) is also very small than that of diesel (56.31 MJ/l) in case of T2 transplanting technique (Zhang & Dornfeld, 2007). Despite the fact that the manual transplanting and hand crank rice transplanter consume lesser energy compared to tractor operated rice transplanter, the tractor operated rice transplanter increases the labor productivity by 32.22 and 2.57 times compared to manual transplanting and hand crank rice transplanter, respectively.

3.11. Effect of transplanting technique and age of seedlings on cost of transplanting

The minimum cost of transplanting (INR 10359.68/ha ($ 131.81/ha)) was observed in tractor operated rice transplanter (T2) at 45 days of seedlings and maximum (INR 17783.67/ha ($ 226.27/ha) was observed for manual transplanting (T3) at 25 days of seedlings. The cost savings by T2 transplanting technique were 66.69% over manual transplanting technique (T3) and 35.68% over hand crank rice transplanting technique (T1; Table 4 and Figure 7 (c)). Hence, it can be stated that the overall cost saving was observed in T2 transplanting technique over T1 transplanting technique with increased field capacity. Moreover, due to reason of requirement of 200–250 man-hour in T3 transplanting technique (Dixit et al., 2007), it has a significant impact on cost of transplanting.

3.12. Selection of best transplanting technique

The best combination of transplanting technique and age of nursery was determined by the degree of desirability on the basis of importance of different dependent parameters. Figure 8 displays the 3D surface chart for degree of desirability. The best combination observed was tractor operated rice transplanter (T2) and 25 days of seedlings (desirability—0.764), where the predicted values of average hill spacing, missing index, multiple index, damage seedlings, floating/buried percentage, hills density, planting efficiency, actual field capacity, field efficiency, energy required and cost of transplanting were 145.63 mm, 27.4%, 0%, 2.03%, 6.9%, 22.8, 63.82%, 0.233 ha/h, 78.36%, 1533.29 MJ/ha and INR 10,532.29/ha ($ 141.34)/ha respectively.

Figure 8. Three-dimensional surface chart for degree of desirability.

4. Conclusions

The null hypothesis is rejected; therefore, the planting attributes were affected by different transplanting techniques. The tractor operated rice transplanter increases the labor productivity by 32.22 times and saves 66.69% operational cost compared to manual transplanting on an average, whereas it increases the labor productivity by 2.57 times and saves average 35.68% operational cost compared to hand crank rice transplanter. The main objective of the study was to select the best transplanting technique. So, tractor operated rice transplanter at 25 days of seedlings was the best combination for transplanting due its superior techno-economics results. The current ineffectiveness of the planting mechanism of tractor operated rice transplanter could be solved by reducing the jerk load caused bigger linkages size which is essential for reduction of undesired missing index. Similarly, it was also observed that mat type nursery offers uniform seedling density and requires no time for washing roots; therefore, the recommended tractor transplanting mechanism can also be evaluated for this kind of nursery seedlings.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article.

Acknowledgement

Neeraj Kumar Singh reports financial support was provided by Council for Scientific and Industrial Research, New Delhi. We are very thankful to Punjab Agricultural University for providing financial support and space for research. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Council of Scientific and Industrial Research [09/272(0139)/19EMR-1];

Notes on contributors

Neeraj Kumar Singh

Neeraj Kumar Singh is currently serving as Subject Matter Specialist (Agricultural Engineering) at Krishi Vigyan Kendra, Bahraich – I, a district level setup for extension activities by Indian Council of Agriculture Research, New Delhi, India. He has been actively involved in development and technology transfer practices in the country for the past 10 years. He was the part of research for developing various agricultural mechanization practices in the region like Drum Planter for Maize, Tractor Operated Inter Row Rotary Cultivator for wide row crops, Mechanical Feeding System for Paddy Thresher, Refinement of Combine Harvester for Legume crops, Machineries for Crop Residue Management etc. He has also been awarded with Senior Research Fellowship for Development of Paddy Transplanter for wash root seedlings by Council of Scientific and Industrial Research, New Delhi.

Shashi Kumar Singh

Neeraj Kumar Singh is currently serving as Subject Matter Specialist (Agricultural Engineering) at Krishi Vigyan Kendra, Bahraich – I, a district level setup for extension activities by Indian Council of Agriculture Research, New Delhi, India. He has been actively involved in development and technology transfer practices in the country for the past 10 years. He was the part of research for developing various agricultural mechanization practices in the region like Drum Planter for Maize, Tractor Operated Inter Row Rotary Cultivator for wide row crops, Mechanical Feeding System for Paddy Thresher, Refinement of Combine Harvester for Legume crops, Machineries for Crop Residue Management etc. He has also been awarded with Senior Research Fellowship for Development of Paddy Transplanter for wash root seedlings by Council of Scientific and Industrial Research, New Delhi.