Effect of Spacing and Fertigation on Growth and Yield Parameters of French Bean (Phaseolus vulgaris L.) under Protected Cultivation

French bean (Phaseolus vulgaris L.) is an important vegetable crop belonging to the family leguminaceae. In North India it is known as “Rajmah”. French bean provides direct economic returns in the form of pod, which is used as vegetable and dried seeds for human beings, fodder for animals after harvest and it adds nitrogen to the soil. Among different vegetables, leguminous crops are the only source of vegetable protein which is required for human health, particularly for the vegetarians.
       
Optimum plant population is the main criterion for attaining maximum growth, quality and yield of a crop. It also ensures judicious use of natural resources and makes the intercultural operations easier. Densely planted crop obstructs the proper growth and development. On the other hand, wider spacing ensures the basic nutritional requirements but decreases the total number of plants as well as total yield. In recent years, some of the farmers started growing pole beans on raised beds with black polyethylene mulch under drip irrigation. There is scanty of information on spacing and nutritional requirement for pole bean under protected condition. Hence this study was planned to generate information on suitable spacing, mulching and fertigation to realize higher yield, better quality and reduce cost of production.

The experiment was carried out under naturally ventilated polyhouse during Kharif 2018 at Zonal Agricultural and Horticultural Research Station, Shivamogga, Karnataka. The experiment was laid out in split plot design with three replications. There were 18 treatment combinations comprised of three different spacing treatments (S₁: 60 × 75 cm; S₂: 60 × 60cm; S₃: 60 × 45 cm) and six fertigation treatments [T₁ - 44:70:53 kg ha^-1 (Control); T₂ - 55:87.5:66.25 kg ha^-1 (125 % control); T₃ - 33:52.5:39.75 kg ha^-1 (75 % control); T₄ - 44:70:53 kg ha^-1 (control) + mulching + micronutrient spray; T₅ - 55:87.5:66.25 kg ha^-1 (125% control) + mulching+ micronutrient spray; T₆ - 33:52.5:39.75 kg ha^-1 (75 % control) + mulching + micronutrient spray. The variety used for the investigation was NZ. The selected experimental land was sandy loamy in nature. Prior to sowing, it was brought to fine tilth and the plot was laid out as per the plan. During final land preparation, the FYM @ 20 t ha^-1 (50 kg 25 m^-2) was applied 10 to 15 days prior to sowing. In the experimental plot, the drip irrigation system was installed after the preparation of beds. The black LDPE sheet of 40 micron thickness was covered on the beds which required for the mulching treatment. After covering the beds with mulching sheet, 10 cm diameter holes are made on the sheet as per the treatment details. The sowing of the crop was taken up during Kharif in the first week of September. Basal dose of fertilizer (25 %) of the individual treatment was given 2 to 3 days prior to sowing and remaining 75 per cent of fertilizer was applied in seven splits after sowing through fertigation. Fertigation and micronutrient sprays (0.5 % IIHR Vegetable special) were applied at fortnight intervals up to grand growth period. The growth and yield parameters were recorded and the data obtained were statistically analysed by adopting the Fisher’s method of analysis of variance as outlined by Gomez and Gomez (1984). The critical differences were calculated at five per cent level of significance wherever ‘F’ test was significant.

Maximum plant height (480.50 cm) was recorded in the treatment S₃T₄ (60 × 45 cm spacing with 44:70:53 kg of N:P:K kg ha^-1 + mulching + micronutrient spray) and least plant height (378.67 cm) was recorded in S₁T₃ (60 × 75 cm spacing with 33: 52.5: 39.75 kg of N:P:K kg ha^-1) which is presented in Table 1. This was due to the greater inter plant competition for space and light, thereby forcing the plants to grow taller. Higher plant height at narrow spacing could be explained by the fact that, when the plants are sown closely, their stems are shaded from light resulting in accumulation of auxin (growth hormone) that stimulates cell division and elongation of internodes, thereby increases height. Whereas in widely spaced plants, auxin destruction by light occurs resulting in plants being shorter. This was evident by Satodiya et al., (2015) and Asaye et al., (2018). The application of optimum nutrients required for the plants along with mulching, facilitates the optimum moisture content, promotes not only microbial activity in the soil, but also avoid the leaching of soil whereas, the foliar application of micronutrient spray increases the metabolic activity in the plant. The above all factors are responsible for the maximum plant height. These findings were in conformity with Kalanjiya and Manickam (2015), Prabu et al., (2016), Sahana et al., (2018).
       
Maximum number of primary and secondary branches were recorded in treatment 60 × 75 cm spacing with 44:70:53 kg of N:P:K kg ha^-1 (8.70 and 8.50) whereas, the least were recorded in 60 × 45 cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1 + mulching + micronutrient spray (4.27 and 4.50) respectively. The treatment combination (60 × 75 cm spacing with 44:70:53 kg of N:P:K kg ha^-1), mulching and foliar application of micronutrient spray has recorded the maximum number of branches which is presented in Table 1. The maximum number of branches recorded in the wider spacing due to the less plant density and more horizontal space among the plant which facilitates the lateral spread of the plant. As the plant density decreases, there will be more interception of sunlight for photosynthesis, which results in the accumulation of photosynthates  for partitioning towards the development of more branches. This was observed by Manjesh et al., (2019) and Melak (2018). The continuous supply of irrigation water and fertigation directly to the root zone which increases the fertilizer use efficiency with optimum maintenance of moisture content and less weed incidence. The spray of micronutrients to the plants at different stages of plant growth increases the rate of photosynthesis and photosynthates, which in turn increased the number of branches. These results were in line with the findings of Mostafa et al., (2014) and Sahana et al., (2018).
 

       
Highest number of pods plant^-1 (220.20), pod length (20.66 cm) and pod girth (2.95 cm) were recorded in the treatment 60 × 75 cm spacing with 44:70:53 kg of N:P:K kg ha^-1 + mulching + micronutrient spray whereas, the least (160.33, 15.61 cm and 1.75 cm) was recorded in 60 × 45 cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1 + mulching + micronutrient spray respectively (Table 2). The reason for enhanced yield attributes might be due to availability of favourable conditions, i.e., moisture, light, nutrients and less inter-plant competition, in wider spacing resulting in increased uptake of more nutrients and build-up of sufficient photosynthates which enabled the increased size of pods (length and girth). Similar findings were recorded by, Manjesh et al., (2019) and Melak (2018). The nutrient supplied through fertigation throughout the growth period with split doses might ave increased nutrient uptake, ultimately leading to greater photosynthetic rate and metabolic activities. Mulching helped in weed control, less weed competition for nutrient uptake and optimum soil temperature which could have enhanced the accumulation of the metabolites. The above all reasons are responsible for the increased yield attributing characters of the crop. This was evident by Wondimu and Tana (2017) and Sahana et al., (2018).
 

       
Maximum pod yield plant^-1(4.65 kg) was recorded in the treatment 60 × 75 cm spacing with 44:70:53 kg of N:P:K kg ha^-1 + mulching + micronutrient spray whereas, the least (3.04 kg) was recorded in 60 × 45 cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1 + mulching + micronutrient spray respectively (Table 3). This could be due to congenial environment required for the plants with wider spacing and optimum fertilizer dosage required for the plant along with mulching and micronutrient spray in the split dose throughout the crop duration which facilitates less competition for nutrients, moistures, fertilizer use efficiency and the light interception will be good in the plant canopy. These results are in conformity with Hussein et al., (2018).  The maximum pod yield 1000 m^-2 13.06 t) was recorded in the treatment 60 × 45 cm spacing with 44:70:53 kg of N:P:K kg ha-1+ mulching + micronutrient spray whereas, the least (9.28 t) was recorded in 60 × 75 cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1. As the plant population is high at wider spacing and the area is supplied with water soluble fertilizers, along with mulching and micronutrient spray in split dose throughout the crop duration the water and fertilizer use efficiency was high, which is the reason for high yield. The similar result findings reported by Assinapol et al., (2017), Jeevitha et al., (2017), Manjesh et al., (2019), Muhammad et al., (2017) and Hussein et al., (2018).
 

       
An appraisal of data presented in (Fig 1.) revealed that treatment combination 60 × 45cm spacing with 44:70:53 kg of N:P:K kg ha^-1 + mulching + micronutrient spray accrued maximum net realization (Rs. 1,28,661.1) whereas the lowest net realization (Rs.72,516.74) was recorded in the treatment 60 × 75cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1. The (Fig 2.) revealed that treatment combination 60 × 45cm spacing with 44:70:53 kg of N:P:K kg ha^-1 + mulching + micronutrient spray resulted highest B:C value of Rs. 2.48 and lowest B:C value of Rs. 1.89 was recorded in the treatment 60 × 75 cm spacing with 33:52.5:39.75 kg of N:P:K kg ha^-1. The higher B:C value might be due to higher total green pod yield and the gross return of French bean recorded in treatment combination with closer spacing, fertigation, mulching and micronutrients spray. This was in close conformity with the findings of Deka et al., (2015) and Manjesh et al., (2019).
 

 

The results obtained in the present study concluded that the cultivation of French bean under the naturally ventilated polyhouse by maintaining the closer spacing of 60 × 45 cm and by applying 44:70:53 kg of N:P:K ha^-1 through fertigation along with mulching and micronutrient spray (IIHR Vegetable Special 0.5%) in split dose was found best in increasing the productivity and profitability.

Thanks to the Director of Research, University of Agricultural and Horticultural Sciences, Shivamogga, India for providing the financial assistance under the staff research project No.5.19.