Influence of different plant spacing on growth and yield attributes of okra (Abelmoschus esculentus L). A reviews

Keywords: Okra, Plant population, Crop geometry, Plant spacing, Growth characteristics, Fruit yield, Fruit quality

Introduction

The Malvaceae family includes the major warm-season vegetable crop okra (Abelmoschus esculentus L. Moench), which is widely grown in tropical and subtropical climates. It is prized for its delicate green fruits, which are eaten both raw and cooked. In addition to providing vitamins, minerals, and dietary fiber, the crop gives vegetable growers a significant source of revenue. Genetic potential, soil fertility, fertilizer management, irrigation, climate, and agronomic techniques are some of the elements that affect its productivity.

Plant spacing is one of the many crop management techniques that affects okra growth and yield. It controls the number of plants per unit area and affects each plant's access to vital resources. Adequate space for root growth, canopy expansion, branching, flowering, and fruit formation is provided by appropriate spacing. On the other hand, overly wide spacing may lead to underutilization of available area and production resources, while extremely close spacing may create competition for sunshine, water, and nutrients.

Inter-row and intra-row distances are commonly used to describe plant spacing. The space between plants within a row is known as intra-row spacing, whilst the gap between neighboring rows is known as inter-row spacing. The number and spatial distribution of plants in the field are determined by the combined effect of these distances. Canopy structure, light interception, photosynthetic activity, evapotranspiration, nutrient intake, weed growth, and reproductive organ development are all impacted by crop geometry.

Okra may react differently to spacing depending on its growth and yield characteristics. Because plants fight for light, closer spacing can encourage vertical development and, in certain cases, enhance plant height. However, lateral branching and the growth of individual fruits may be limited by competition for resources. In addition to offering more growing room per plant, wider spacing may promote branching, fruit development, and individual fruit weight. However, these reactions are not universal and rely on crop management, plant population, soil and climate conditions, and cultivar traits.

The impact of spacing on okra and other vegetable crops has been studied by a number of researchers. In okra cv. Pusa Sawani, Ashtaputre (1987) ^[1] found that plants were taller at 30 × 15 cm than at 30 × 30 cm. In okra, higher plant height under closer intra-row spacing was also documented by Singh et al. (1996) ^[2] and Randhawa et al. (2000) ^[3]. On the other hand, Saha et al. (1989) ^[4] found that a plant had more branches at an intra-row spacing of 40 cm than at 20 cm. Additionally, Soni et al. (2006) ^[5] found that the okra cv. Akola Bahar had maximum branching at 45 × 45 cm.

Fruit length, diameter, weight, and quantity per plant have all been found to be impacted by spacing. Greater green fruit weight and length were found at broader spacing than at closer spacing, according to Ashtaputre (1987) ^[1]. Similarly, under specific wider-spacing treatments, Talukder et al. (2003) ^[6] and Moniruzzaman et al. (2007) ^[7] found better fruit-related qualities or more fruit per plant. These results suggest that okra's reaction is contingent upon the equilibrium between the number of plants and the resources available to individual plants.

The impact of spacing on okra has been the subject of several studies, however the results vary according on the cultivars, experimental settings, and spacing treatments assessed. Understanding how spacing affects vegetative growth, blooming, fruit development, and yield-related traits hence requires a methodical synthesis of the material.

1. The impact of spacing on okra growth characteristics

1.1 Height of the plant

Plant population, light availability, competition, and genetic traits all have an impact on plant height, a crucial vegetative development. Plant height's reaction to spacing is frequently linked to competing for sunlight. Wider spacing can lessen competition for light and promote lateral growth, while closer spacing may cause plants to grow taller.

According to Singh et al. (1996) ^[2], plants grow taller when the intra-row spacing was closer 30 cm than when it was wider 40 cm. According to Ashtaputre (1987) ^[1], the okra cv. Pusa Sawani plant height ranged from 30 × 15 cm to 30 × 30 cm. In okra, Randhawa et al. (2000) ^[3] likewise found that plants grow taller when intra-row spacing was closer than when it was broader.

Kumar et al. (2011) ^[8] in okra cv. Nirmal-20, recorded maximum plant height of 121 cm and lowest plant height of 85.33 cm at intra-row spacing levels of 30 cm and 5 cm, respectively. In okra cv. Sabz Pari, Amjad et al. (2002) ^[9] found a maximum plant height of 37.58 cm at 15 cm spacing and a minimum plant height of 32.8 cm at 45 cm spacing.

In okra cv. NH47-4, Ijoyah et al. (2010) ^[10] found a maximum plant height of 93.3 cm at an intra-row spacing of 25 cm and a minimum height of 85.2 cm at 30 cm. Okra cv. Hisar Unnat had a maximum plant height of 105.63 cm at 60 × 30 cm and a minimum height of 84.76 cm at 45 × 20 cm, according to Sharma et al. (2012) ^[11]. Okra cv. Clemson Spineless had a maximum plant height of 147.2 cm at 30 × 45 cm and a minimum height of 111.7 cm at 60 × 45 cm, according to Maurya et al. (2013) ^[12].

1.2 Number of branches per plant

Since branches offer more locations for flowering and fruit development, the number of branches per plant is a crucial growth characteristic. The availability of growing area, light penetration, nutrition availability and competition between nearby plants all affect branching.

In okra, Saha et al. (1989) ^[4] found that there were more branches per plant at an intra-row spacing of 40 cm as opposed to 20 cm. According to Bilekudari et al. (2005) ^[13], radish cv. Pusa Chetki had maximum and minimum branch numbers of 9.25 and 8.04, respectively, at 60 × 45 cm and 60 × 30 cm. The latter result shows how plant density may affect branching in vegetable crops even though it only applies to radish.

In okra cv. V35, Ibeawuchi et al. (2005) ^[14] found maximum branching of 8.0 and lowest branching of 3.0 at 75 × 50 cm and 30 × 50 cm, respectively. In okra cv. Akola Bahar, Soni et al. (2006) ^[5] reported that the largest number of branches with a wider spacing of 45 × 45 cm.

Ekwu et al. (2012) ^[15] in okra cv. Clemenson Spineless, found that the maximum and minimum branch numbers were 13.98 and 12.21 at 50 × 25 cm and 50 × 75 cm, respectively. In okra cv. Clemson Spineless, Maurya et al. (2013) ^[12] found maximum branching of 1.72 at 60 × 40 cm and minimum branching of 1.25 at 30 × 45 cm.

The results that are now available indicate that the number of branches per plant can be significantly influenced by spacing. Although cultivar and environmental factors can result in varied reactions, wider spacing may promote lateral branch development by lowering competition. Branching' relationship to fruit number and overall output should also be taken into account because it can increase fruit-bearing capacity.

1.3 Number of nodes per plants

Because leaves, branches, and reproductive structures develop at or in conjunction with nodal regions, nodes are crucial structural elements of plants. Potential locations for flowering and fruit production may depend on the number of nodes per plant.

Kumar et al. (2011) ^[8] in okra cv. Nirmal-20, found maximum and minimum node numbers of 16.40 and 7.70 at intra-row spacing values of 30 cm and 5 cm, respectively. In okra cv. Akola Bahar, Soni et al. (2006) ^[5] reported the largest number of internodes under closer spacing of 45 × 15 cm.

These results suggest that the growth of the main stem and its nodal configuration can be influenced by plant spacing. However, fruit production also depends on blooming, fruit set, nutrient availability, and the plant's capacity to hold on to growing fruits, therefore the number of nodes by itself does not influence yield.

1.4 Internode length

Plant architecture, total height, and the arrangement of leaves and reproductive organs along the stem are all influenced by internodal length. Growing circumstances, plant density, light environment, and genotype all have an impact.

Kumar et al. (2011) ^[8] in okra cv. Nirmal-20 found that a maximum internodal length of 10.03 cm at an intra-row spacing of 30 cm and a minimum length of 7.20 cm at 5 cm. This finding suggests that stem development was impacted by the spacing treatments assessed in that investigation.

2. Spacing affects flowering

2.1 Days before the first bloom

One significant phenological factor that affects crop earliness and harvest timing is days to first flowering. Genetics, temperature, light availability, nutrient status, and plant competition can all affect flowering.

Plant spacing did not significantly affect the number of days until okra flowered, according to Birbal et al. (1995) ^[16]. However, in okra cv. Nirmal-20, Kumar et al. (2011) ^[8] found maximum and minimum values of 65.30 and 47.82 days to first flowering at intra-row spacing levels of 30 cm and 15 cm, respectively.

In okra cv. BARI Dherosh-1, Moniruzzaman et al. (2007) ^[7] recorded 39.00 and 38.00 days to first flowering at spacing arrangements of 60 × 30 cm and 60 × 40 cm, respectively. Shrikanth (2007) ^[17] found that the lablab bean cv. Konkan Bhushan took 42.97 and 42.54 days to first blossom at 60 × 15 cm and 45 × 15 cm, respectively.

The findings suggest that how spacing influences blooming time may depend on cultivar growing conditions. While some studies revealed more noticeable reactions, others discovered that the variations across spacing treatments were negligible and not statistically significant. Fruit development and total yield should therefore be evaluated concurrently with flowering time.

3. Spacing's impact on green fruit characteristics

3.1 Green fruit length

Okra's green fruit length is a crucial quality feature that could affect consumer approval. Genotype, fruit ripeness, environmental factors, and resource availability during fruit development all have an impact.

In okra cv. Pusa Sawani, Ashtaputre (1987) ^[1] reported maximum green fruit length of 10.47 cm at wider spacing of 30 × 30 cm and minimum length of 8.60 cm at 30 × 15 cm. In okra cv. Nirmal-20, Kumar et al. (2011) ^[8] reported maximum and minimum green fruit lengths of 19.53 cm and 12.45 cm at intra-row spacing levels of 25 cm and 15 cm, respectively.

According to Talukder et al. (2003) ^[6] the okra cv. had a maximum fruit length of 18 cm at 60 × 50 cm and a minimum length of 14.9 cm at 60 × 30 cm. BARI Dherosh. Hossain et al. (2003) found that okra cv. had maximum and minimum fruit lengths of 13.00 cm and 12.00 cm at 35 × 40 cm and 45 × 45 cm, respectively cv. Pusa Sawani.

Philip et al. (2010) ^[18] observed that okra's maximum and minimum green fruit lengths were 9.10 cm and 8.50 cm at 75 × 45 cm and 60 × 60 cm, respectively. In okra cv. Clemson Spineless, Maurya et al. (2013) ^[12] found a maximum fruit length of 14.63 cm at 60 × 45 cm and a minimum length of 10.95 cm at 30 × 45 cm.

In general, the results show that in certain cultivars, greater spacing can promote fruit elongation. Fruit length, however, varies on more than just spacing, as evidenced by the varying responses among trials. The maturation stage at which fruits are measured, environmental factors, and cultivar traits must all be taken into account.

3.2 Green fruit diameter

Another crucial quality factor that affects fruit size and marketability is fruit diameter. It may react to the degree of plant competition and represents the fruit's growth throughout development.

In okra cv. Nirmal-20, Kumar et al. (2011) ^[8] found maximum and lowest green fruit diameters of 2.13 cm and 1.73 cm at intra-row spacing values of 30 cm and 5 cm, respectively.

According to Talukder et al. (2003) ^[6], the okra cv. BARI Dherosh-1 had a maximum fruit diameter of 1.72 cm at 60 × 30 cm and a minimum diameter of 1.71 cm at 60 × 40 cm. Moniruzzaman et al. (2007) ^[7] found that the okra cv. BARI Dherosh had maximum and minimum fruit diameters of 1.98 cm and 1.80 cm at 60 × 60 cm and 60 × 20 cm, respectively. According to Maurya et al. (2013) ^[12], okra cv. Clemson Spineless had a maximum green fruit diameter of 2.05 cm at 60 × 45 cm and a minimum diameter of 1.59 cm at 30 × 45 cm.

These results find that fruit expansion may be favored by less competition under appropriate wider-spacing arrangements. The requirement to assess fruit diameter under locally appropriate production conditions is highlighted by the fact that different research find different changes between spacing treatments.

3.3 Green fruit weight

Because it directly affects the total fruit production per plant, each green fruit weight is an important yield component. Genetic traits, fruit ripeness, plant nutrition, moisture availability and plant competition all affect fruit weight.

In okra cv. Pusa Sawani, Ashtaputre (1987) ^[1] observed maximum green fruit weight of 8.63 g at 30 × 30 cm and minimum weight of 7.76 g at 30 × 15 cm. Kumar et al. (2011) ^[8] found maximum and minimum fruit weights of 20.86 g and 13.99 g at intra-row spacing levels of 20 cm and 5 cm, respectively cv. Nirmal-20 in okra.

In okra cv. NH47-4, Ijoyah et al. (2010) ^[10] recorded the highest fruit weight of 15 g at an intra-row spacing of 30 cm. In okra, Hossain et al. (2003) found maximum and minimum fruit weights of 13.7 g and 11.5 g at 35 × 40 cm and 45 × 45 cm, respectively cv. pusa sawani in okra.

The findings show that in a number of scenarios, appropriate spacing can increase the weight of each individual fruit. Nevertheless, this response varies depending on the study. To ascertain its overall contribution to production per hectare, the impact of spacing on individual fruit weight should be evaluated in conjunction with fruit number per plant and plant population.

4. The number of green fruits harvested from each plant

An important yield that represents the combined effects of vegetative development, flowering, fruit set, and fruit retention is the quantity of green fruits gathered per plant. By changing the number of reproductive sites per plant and the availability of resources, spacing might affect this characteristic.

In okra cv. Pusa Sawani, Ashtaputre (1987) ^[1] found that the maximum and minimum numbers of green fruits per plant were 5.74 and 5.07 at 30 × 30 cm and 30 × 15 cm, respectively. A 45 cm row spacing produced 40.24 green pods per plant, according to Patel et al. (1994) ^[19].

Ijoyah et al. (2010) ^[10] in okra, found the highest number of pods per plant (6.50) at an intra-row spacing of 30 cm and the lowest number (5.00) at 20 cm. According to Philip et al. (2010) ^[18], at 90 × 30 cm and 60 × 60 cm, respectively, the highest and minimum fruit numbers were 7.40 and 6.50. In okra cv. Hisar Unnat, Sharma et al. (2012) ^[11] found that the maximum and minimum numbers of green fruits per plant were 16.73 and 12.69 at 60 × 30 cm and 45 × 20 cm, respectively.

Amjad et al. (2002) ^[9] found that at intra-row spacing values of 45 cm and 15 cm, respectively, the maximum and minimum numbers of green fruits per plant were 16.70 and 14.08 in okra. Talukder et al. (2003) ^[6] found maximum fruit numbers of 19.6 at 60 × 50 cm and minimum fruit numbers of 17.6 at 60 × 30 cm in okra cv. BARI Dherosh-1.

Moniruzzaman et al. (2007) ^[7] reported that a maximum of 26.70 green fruits per plant at 60 × 60 cm in okra cv. BARI Dherosh.

Ijoyah et al. (2010) ^[10] recorded the greatest number of pods per plant, 6.50, at an intra-row spacing of 30 cm and the lowest number, 5.00, at 20 cm in okra. Philip et al. (2010) ^[18] reported maximum and minimum fruit numbers of 7.40 and 6.50 at 90 × 30 cm and 60 × 60 cm, respectively. Sharma et al. (2012) ^[11] recorded maximum and minimum numbers of green fruits per plant of 16.73 and 12.69 at 60 × 30 cm and 45 × 20 cm, respectively, in okra cv. Hisar Unnat. These findings indicate that wider spacing may increase fruit number per plant in some cultivars.

Conclusion

One important agronomic aspect affecting okra's vegetative growth, flowering, fruit development, and yield characteristics is plant spacing. Plant height, branching, node growth, internodal length, flowering time, fruit length, fruit diameter, individual fruit weight, and the number of green fruits collected per plant can all be impacted by spacing, according to the evaluated studies.

While broader spacing frequently encourages branching and the growth of individual fruits, closer spacing may encourage higher plant height in competitive environments. However, the answers differ depending on the environment, cultivar, and spacing configurations assessed. It is important to assess overall productivity rather than just individual plant performance because wider spacing may boost yield per plant but decrease the total number of plants per unit area. Plant population, growth, fruit quality, total yield per hectare, and economic returns should all be balanced to determine the ideal spacing.

References

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