Yield, absorbed photosynthetically active radiation (PAR) and leaf area index (LAI) of mango varieties under ultra-high density planting system

Introduction

LAI is amount of leaf area per unit ground area which is important indicator of radiation, precipitation, interception, energy conversion and water balance. Since leaves are essential for photosynthesis and produce the bulk of biomass, the number of leaves also influence the yield. The relation between LAI and yield is however not simple, and will vary with the range of PAR is the amount of sunlight available for photosynthesis, which is light in 400 to 700 nanometers wavelength range. PAR changes seasonally and varies depending on the latitude and time of the day. The levels of PAR and LAI are most reliable to predict the tree yield which may vary with the canopy architecture of the tree.

Materials and methods

Varieties/ hybrids

Seventeen commercial/ popular mango varieties of Telangana viz., Alphonso, Amini, Amrapali, Baneshan, Dasheri, Dasheri-35, Himayat, Hydersahab, Jalal, Kesar, Mahamoodavikarabad, Ratna, Royal special, Sindhu, Suvarnarekha, Swarna sindhura and Totapuri were evaluated under ultra-high-density planting.

Leaf area index

Leaf area index was calculated by using an instrument called digital plant canopy imager (CID Bio Science). Leaf area index is the ratio of foliage area to ground area. Canopy imager is having optical sensor consists with fisheye lens and an optical system. The fish eye lens sees a hemispherical image, which the optical system focuses onto the photodiode optical sensor, which is made up of five concentric rings. Leaf area index was taken five random points of each plant at vegetative state, flowering stage (BBCH-615) and harvesting stage (BBCH-810).

Interception of Photosynthetically active radiation (PAR)

Photosynthetically active radiation (PAR) was calculated with using an instrument called digital plant canopy imager (CID Bio Science.). PAR is photosynthetically active radiation having the wavelength ranging from 400-700 nm and is the portion of light spectrum utilised by plants for photosynthesis. It varies with season and crop. PAR was taken at five random points of each plant at vegetative state, flowering stage (BBCH-615) and harvesting stage (BBCH-810). Results and discussion LAI, PAR and yield of seventeen mango varieties under ultra-high-density planting Canopy volume (cm 3 ) Canopy volume of tree was directly correlated with LAI and yield as the canopy volume represents leafiness and light interception of the tree. Pooled data revealed that, considerably maximum canopy volume was observed in Totapuri (30.33 cm 3 ) followed by Mahammoda vikarabad (26.13 cm 3 ) and Kesar (25.60 cm 3 ), while minimum canopy volume was observed in Amrapali (7.60 cm 3 ) followed by Royal special (10.34 cm 3 ) and Ratna (11.53 cm 3 ). Similar results were previously reported by Samant et al. (2020) [1] in mango Cv. Alphonso. They stated that canopy volume of tree was directly correlated with LAI and yield as the canopy volume represents leafiness and light interception of the tree. Our findings are in agreement with Bakshi et al. (2012) [2] who evaluated eight mango varieties (viz., Amrapali, Baramasi, Langra, Dasheri, Mallika, Arun, Varun and Rajiv) under rainfed areas of Jammu and mentioned in their results that Langra variety recoded maximum tree volume (389.97 cm 3 ) followed by Dasheri (312.72 cm 3 ), while Rajiv recorded minimum tree volume (29.44 cm 3 ).

It was evident from the pooled results that considerably maximum leaf area was observed in Suvarna sindhura (164.80 cm 2 ) followed by Totapuri (153.50 cm 2 ) and Alphonso (151.53 cm 2 ), while minimum leaf area was observed in Jalal (81.17 cm 2 ) followed by Kesar (82.49 cm 2 ) and Baneshan (94.31 cm 2 ). These findings are in accordance with the results of Ahmed et al. (2016) [3] . They also evaluated five mango cultivars viz., Kent, Keitt, Tommy Atkins, Heidi and Naomi and reported that Cv. Tommy Atkins recorded maximum leaf area (89.67 cm 2 ) followed by Keitt (85.33 cm 2 ), while minimum leaf area was recorded in Heidi (68.63 cm 2 ).

Leaf area index (LAI)

The amount of leaf area per unit ground area is known as leaf area index. LAI is nothing but photosynthetic capacity of plant and it was positively correlated with tree yield of that plant. Optimized light distribution in canopy and its interaction with different parts is critical for enhancing photosynthesis, flower bud development, fruit development and color formation (Samant et al., 2020) [1] . The results can be explained by the fact that since the young seedlings possess high root activity and high photosynthetic activity that cause increase of leaf area and dry-matter yield more than older one and hence resulted in higher PAR interception (Aggarwal and Singh 2015) [4] . As per the pooled data related to leaf area index, Totapuri cultivar recorded significantly maximum leaf area index (2.20, 4.49 and 4.01) followed by Kesar (2.13, 4.38 and 3.90) and Sindhu (2.08, 4.27 and 3.79), while Royal special cultivar recorded minimum leaf area index (0.98, 3.01 and 2.42) followed by Ratna (1.07, 3.08 and 2.50) and Suvarnarekha (1.15, 3.19 and 2.59) at bud breaking phase (BBCH-513), flowering phase (BBCH-615) and at the time of harvesting (BBCH-810) respectively. Present investigation results regarding leaf are index (LAI) indicated that an increasing trend from bud breaking phase to flowering phase and then decreased from flowering phase (BBCH-615) to harvesting time (BBCH-810). Similar findings previously observed by Samant et al. (2020) [1] in mango Cv. Alphonso. They confirmed plant canopy volume, LAI and yield are interrelated with each other. Yield of mango trees showed an increasing trend with rise in both plant canopy volume and LAI. They reported that well pruned mango Cv. Alphonso recorded maximum canopy volume (155.02 cm 3 ), LAI (1.26) and yield (48.76 kg/tree) than control.

Interception of Photosynthetically Active Radiation (PAR)

Results related to the photosynthetically active radiation (PAR) of seventeen mango varieties under ultra-highdensity planting are highlighted in Table 1

The interpretation of data with respect to fruit yield revealed that, there was a significant variation among the mango varieties and fruit yield significantly varied among the seventeen mango varieties was ranged from 4.56 to 15.00 kg/tree given in table 1. As per the pooled data, Totapuri variety recorded highest fruit yield (15.00 kg/ tree) followed by Kesar (13.83 kg/ tree) which was found to be on par with Sindhu (13.36 kg/tree), while lowest fruit yield was recorded by Royal special (4.56 kg/ tree) which was on par with Ratna (5.00 kg/ tree) followed by Suvarnarekha (5.99 kg/tree).

Correlation

It was identified from the data that, among the all seventeen varieties yield has significantly strong positive correlation with LAI (0.993 ** ) and PAR (0.990 ** ). Similar results were previously reported by Aggarwal and Singh (2015) [4] .

Conclusion

The present investigation clearly demonstrated that mango productivity under the ultra-high density planting system (3 × 2 m) is strongly influenced by canopy architecture and light utilization parameters. Among the seventeen mango varieties evaluated, significant variation was observed in canopy volume, leaf area, leaf area index (LAI), interception of photosynthetically active radiation (PAR) and fruit yield. Varieties such as Totapuri, Kesar and Sindhu consistently recorded higher canopy volume, LAI and PAR interception, which resulted in superior fruit yield per tree. The study revealed a strong and significant positive correlation of yield with LAI and PAR, highlighting the crucial role of optimized canopy structure and efficient light interception in enhancing photosynthetic efficiency and yield under ultrahigh density systems. LAI and PAR showed an increasing trend from bud breaking to flowering, followed by a decline towards harvest, indicating their dynamic nature across growth stages. Overall, Totapuri emerged as the most promising variety, suggesting its suitability for ultra-high density planting in Telangana conditions.

References

1. Samant AP, Warang OS, Kulkarni MM, Bhuwad AV, Bhingarde RT, Salvi BR, Haldankar PM, Parulekar YR. Relationship between plant canopy volume, leaf area index and yield in mango (Mangifera indica L.) cv. Alphonso. International Journal of Current Microbiology and Applied Sciences. 2020;11:859-863.
2. Bakshi P, Kumar R, Jasrotia A, Wali VK. Growth and yield performance of mango varieties under rainfed areas of Jammu. Indian Journal of Agricultural Research. 2012;46(3):281-285.
3. Ahmed YM, Roshdy KA, Badran MA. Evaluation study of some imported mango cultivars grown under Aswan Governorate conditions. Alexandria Science Exchange Journal. 2016;37(2):254-258.
4. Aggarwal N, Singh A. Crop performance and nutrient uptake in relation to weed suppressive ability of mechanically transplanted rice (Oryza sativa) as influenced by seedling age and planting density. Indian Journal of Agronomy. 2015;60(2):255-260.
5. Keitt TH, Lewis MA, Holt RD. Allee effects, invasion pinning, and species' borders. The American Naturalist. 2001 Feb;157(2):203-16.