INTRODUCTION

Mustard (Brassica spp.) is an important oilseed crops and cultivated almost all place in India next to cereals crops. The area under rapeseed-mustard in India was 6.23 Million hectares, produced about 9.34 million tonnes with 1499 kg ha^-1 productivity during the year 2018-19(Anonymous, 2019). The low yield is due to lack of high yielding varieties and improper agronomic practices (Rathour et al., 2021). There is a great scope of increasing yield of mustard by improving management practices. Therefore, modified crop production technologies, which support sustainable crop intensification can be developed and spread among the farmers. One growing concept of sustainable intensification is presently focusing on increasing input use efficiency, adoption of high-tech precision agriculture technologies for field crops, AWD (alternative wetting-and-drying) for irrigated rice production, and integrated pest and nutrient management to reduce and optimize the use of agrochemical inputs in different crops  (Anonymous, 2015, Heaton et al., 2013, Anonymous, 2013).System of crop intensification is one of those practices which improve the crop productivity and sustainability by proper management of natural resources. System of crop intensification principles can be applied in wide range of crops like System of Rice Intensification (SRI), System of Wheat Intensification (SWI), System of Sugarcane Intensification (SSI) and System of Mustard Intensification (SMI). Crop intensification provides better root growth by modification of management practices with their better functioning in soil. This makes the soil system better for living and also provides support against biotic and abiotic stress by making the crop healthier (Adhikari et al., 2018). It was found that presence of extensive root system, the interactions between plants and the soil microorganisms was comparatively higher with respect to water and nutrient uptake(Anas et al., 2011, Barison and Uphoff, 2011, Rupela et al., 2006, Thakur et al, 2013). System of Mustard Intensification was a new initiative for increasing mustard yield by some modification of soil, plant, moisture and nutrient management pattern. System of mustard intensification has been successfully done in Bihar and Gujrat  Verma, 2013).

Row spacing is one of the very important practices for mustard production (Mondal et al., 1999). Chaudhary et al. (2016) from Pantnagar, reported that transplanting of Brassica carinata at 60×60 cm² spacing improved its yield potential through root intensification in tarai region of Uttarakhand. SMI is the system of transplanting mustard of 8−10 days old seedling at wide spacing provides advantage of proper plant density and allows sufficient aeration, moisture, sunlight and nutrient availability leading to proper root system development from the early stage of crop growth. Spacing between rows of plants is another factor that affects the growth and yield of the crop. Improved varieties of mustard are capable of higher yields when grown under optimum row spacing and good method of planting. The seed yield and maturity of mustard plants are greatly influenced by environmental conditions regardless of proper row spacing. The improper row spacing of mustard decreased seed yield through synchronization of silique filling period with high temperatures, the decrease in assimilates production, drought stress occurrence, shortened silique filling period and acceleration of plant maturity (Mendham et al., 1981). Satapathy (2007) reported that with specific management practices, under system of mustard intensification local mustard varieties of Odisha yielded better than the conventional practice.  However, the System of Mustard Intensification along with row spacing information is still lacking. Therefore, the present study was undertaken to find out the suitable row to row spacing for mustard yield enhancement under SMI technology.

MATERIALS AND METHODS

2.1.  Experimental area

The experiment was conducted in Rabi seasons (November−February) of year 2018 and 2019 at Instructional farm, RRS (OAZ), UBKV, Majhian, Dakshin Dinajpur, W.B, India lying at 26°19’86’’N latitude and 89°23’53’’E longitude with an average altitude of 43 m above the mean sea level. It comes under Gangetic old alluvial plain of sandy loam soil with acidic in nature.  The experimental site is situated under sub-tropical humid region with an average temperature range of 25–37°C during summer to 12–25°C during winter months. Average annual rainfall is about 1535 mm.

2.2.  System of Mustard Intensification (SMI) Methodology

2.2.1.  Production of seedling in nursery under micropots

For SMI study many micropots (2×2.5 cm² size) were purchased from local market. All the micropots were filled up with 1:1 combination of compost and soil. Each variety of mustard was shown by placing of one seed in each micropot in the month of middle October and allows them for seedling growth under natural environment. After 15 days of age at three leaf stage all the seedling under micropots were considered for transplanting in the main field.

2.2.2.  Transplanting and yield parameter observation

Nursery raising requires about 200 g seed which may produce about 70,000 seedlings that enough for one hectare. Before transplanting, the main field was ploughed properly and used recommended dose of NPK fertilizers (60:40:40 kg ha^-1) and two tonnes of FYM ha^-1. Transplanting was done by planting of one seedling from the micropots in field by maintaining planting distance. Irrigation, weeding and all the plant protection measures undertaken whenever required. The soil type of the research plot was sandy loam and pH was 5.52. During entire growth period different yield attributing traits were monitored such as plant height, number of secondary branches, number of siliqua plant^-1, number of seeds siliqua^-1 and seed yield kg ha^-1. The leaf chlorophyll content also estimated as per protocol described by Davies (1976).

2.3. Treatment combination

The treatments consisted of three levels of intra spacing (25×25, 45×45, and 60×60 cm²) among the three different variety of Toria (cv. Agrani), Yellow sarson/ rapeseed (cv. Vinay) and Indian Mustard (cv. Bhagirathi) with plot size of 4×5 m². The 9-treatment combination spacing and variety under SMI techniqueswere arranged in following pattern (Table 1).

Table 1: Treatment combination of variety and plant spacing of mustard

2.4. Statistical design and analysis

The experiment was laid out as a randomized complete block design with three replications of each treatment. The statistical analysis of experimental data utilized the ANOVA program was done on SPSS 20.0 software.

RESULTS AND DISCUSSION

3.1.  Effect of different spacing of SMI

Analysis of variance showed significant difference of yield traits except number of seeds siliqua^-1 among the treatments (different spacing and variety) studied under SMI practices. The interaction of plant spacing and varieties significantly influenced the plant height. Among the treatment combination maximum plant height was recorded in cv. Baghirathi with spacing of 60×60 cm² ie. S₃V₃ (165.32 cm) followed by S₂V₃ 161.25 and S₁V₃ (160.54) while minimum height in cv. Agraniwith 25×25 cm² S₁V₂ (92.25 cm). On the other hand, S₃V₃ produces maximum yield parameter such as number of primary (9.00), secondary branches (10.82), number of siliqua plant^-1 (297.45) and number of seeds siliqua^-1 (13.20), while crop spacing maintain with 25×25 cm significantly reduces these parameters among the varieties (Table 2). The number of seeds siliqua^-1 found no signification difference among the treatments. The test weight was maximum in S₂V₂ (3.49 g). The total chlorophyll content was recorded maximum in S₁V₃ (18.99 mg 100 g^-1) followed by S₃V₃ (17.61 mg 100 g^-1) and S₂V₃ (17.45 mg 100 g^-1) whereas, minimum in S₂V₂ (14.03 mg 100 g^-1) and S₁V₂(14.31 mg 100 g^-1). The interaction of plant spacing and varieties significantly influenced the yield. Establishment of an optimum spacing is one of the important factors for securing good yield of mustard. Maximum seed yield in SMI techniques among the varieties was recorded when plant spacing maintain by 60×60 cm² (Table 2). Satapathy (2007) reported that with specific management practices along with proper spacing under system of mustard intensification local mustard varieties of Odisha yielded better than the conventional practice.

Among the treatments studied highest seed yield was recorded in S₃V₃ (1348.08 kg ha^-1) followed byS₁V₃ (1331.42 kg ha^-1) S₂V₃ (1320.67 kg ha^-1) while lowest yield obtained from S₃V₁ (935.05kg ha^-1). The maximum seed yield under SMI with spacing of row at 60 cm could be due to significantly higher number of branches plant^-1, secondary branches, number of siliqua plant^-1 and number of seeds siliqua^-1. This result was in agreement with Singh et al. (2008) and Nautiyal et al. (2020).Maximum yield under wide spacing could be attributed to better growth of plants and maximum planting density and enhanced crop growth rate which might have resulted in efficient metabolism and also provide optimal growing conditions to individual mustard plants so that siliqua is maximized (Sondhiya et al., 2019). The yield enhancement effect of wider spacings between plants has also been reported Mevada et al. (2017) and Chhonkar et al. (2011). Gupta et al. (2018) reported that SMI techniques with sufficient irrigation facility improve oxygen supply to roots, thereby decreasing aerenchyma formation and causing a stronger, healthier root system with potential advantages for nutrient uptake. Previously a detail study on SMI in Bihar state found higher seed yield under transplanting system of mustard (ATMA, 2013). Additionally, the optimum plant spacing ensures proper growth of both aerial and underground parts of the plant through efficient utilization of solar radiation, nutrients and land as well as air spaces and water. The improper row spacing of mustard decreased seed yield through synchronization of silique filling period with high temperatures and decrease in assimilates production, (Alam et al., 2015).

Table 2: Effect of System of Mustard Intensification (SMI) on three different variety and spacing combination for yield attributing traits

3.2. Correlation and multiple regression analysis of yield and its attributing traits under SMI

The correlation coefficient analysis of mustard varieties with different planting density under SMI resulted the traits particularly number of secondary branches (r=0.841), number of siliqua plant^-1 (r=0.931) and total chlorophyll content (r=0.863) were significant and positive associated with seed yield among the varieties (Table 3).

Table 3: Estimation of correlation coefficient for yield attributing traits of System of Mustard Intensification (SMI)

On the other hand plant height also found significantly and positively correlated with number of secondary branches (r=0.970), number of siliqua plant^-1(r=0.904) and total chlorophyll content (r=0.944) but no significant relation observed with seed yield, this may due to plant height as an important yield traits but because of similar method of practices derived non-significant response to yield. In order to know the predictive abilities under SMI techniques, the multiple regression analysis was carried out by taking seed yield kg ha^-1 (Y) as dependent variable and yield attributing traits (X) as the independent variable. During the year 2018-19 of SMI studied, the coefficient of multiple determinants (R²) was 0.950 indicating 95.00% of the variation in yield improvement explained by the set of a variable in the study (Table 4).

The best fit of one model over the other has beenattained by comparison of the regression parameter Yintercept (Fried et al., 1979); R² (Berger, 1981,Waggoner, 1986).

Table 4: Multiple regression of SMI

CONCLUSION

Based on intra-raw spacing study under SMI system among the three different varieties we found wide spacing 60×60 cm² best for mustard yield. Among the three variety cv. Bhagirathi produces maximum yield and other traits response under wide spacing of System of Mustard Intensification. The character association under this study also revealed positive association of seed yield with number of secondary branches, number of siliqua plant^-1 and total chlorophyll content.

ACKNOWLEDGEMENT

This study was funded by the Project Director, ATMA, Dakshin Dinajpur, West Bengal.

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