INTRODUCTION

The response of fruit tree to externally applied mineral nutrients needs to be quantified to provide technology innovations to fruit growers as ready to use package of practices. This process might lead to nutrient richness in the end product i.e. fruit pup. This is very significant in case of sand, loamy sand, sandy loam soils having low water holding capacity, soil organic matter, nutrient reserve and microbial activity. Significant response of the tree to nutrient application depends on several attributes like tree physiology, soil response, weather interactions and varietal ability etc. Adak et al. (2021) scientifically explained that there is an urgent need for revisiting policy issues in terms of soil nutrition vis-à-vis productivity and profitability for subtropical zone. Soil nutrients play significant role in responding to the signal transduction to roots and from roots to sink. The source-sink continuum often either hastens or restricted by the pools of nutrients. Lower the nutrient pool, response to end product may be low. However, foliar application may improve the positive response through xylem-phloem pathways through leaf stomata. Adak et al. (2019) indicated that lower soil nutrient index is responsible for lower productivity of Dashehari mango in farmers’ field in Maal area of Uttar Pradesh. This certainly had contributed to yield variations within the orchards. Similarly in apple orchards Aggelopoulou et al. (2010) described the spatial yield and quality variability within the apple orchards. Nutrient deficiency in the foliar part is one of the top most priority for any commercial or non-commercial orchards to indentify and its possible solutions for correction of nutrient limitations. Several nutrients were recorded to be deficient on long-term basis in orchards. Raja et al. (2005) inferred boron deficiency in mango and also suggested for possible remediation. Tehranifar and Tabar (2009) observed that foliar application of K and B (1.5 and 3.0 g L-1) leads to nutrient richness in pomegranate. Liu et al. (2021) emphasized potassium fertilization during fruit development for improving quality and potassium use efficiency of tomato in deficit irrigation regime. The quality of the produce is to be authenticated for which low cost near-infra- red spectroscopy technology could be employed (Yang et al., 2021). Similarly, Davarynejad et al. (2009) recorded positiveness of foliar nutrition technology in enhancing the yield, quality and alternate bearing as well in pistachio fruit tree. The statistical significance of such response is to be recorded and multivariate interpretation should be done in order to understand the foliar chemical composition of essential nutrients (Raghupathi and Shilpashree, 2018) for development of technologies for corrections. On the present field study, trails were laid out to record the response of Zn levels on nutrient richness and productivity level on sandy loam soil at Lucknow, Uttar Pradesh.

MATERIAL AND METHODS

The field study was conducted on 9th and 10th year old mango cv Dashehari trees spaced at 10×10 m on sandy loam soil at Rehmankhera Farm, Lucknow, Uttar Pradesh during 2015-18. Seven treatments were replicated thrice in a randomized block design. Initial nutrient status of the experimental field was poor. The treatments applied were as T : control, T : 0.25% digestion and soil digestion was completed following laboratory protocol and micronutrients were analysed using AAS. Statistical analysis viz., significance, standard error of mean, standard error of difference and coefficient of variations were computed in OPSTAT (Sheoran et al., 1998).

RESULTS AND DISCUSSION

The study reveals the effectiveness of different Znlevels on the Dashehari mango grown on sandy loamsoils in Indo-Gangetic plains under subtropicalclimate. The results showed significant responseamong mango trees treated with different foliar Znlevels (Table 1). Lowest ZnSO4 application yield of33.17±2.25 kg tree-1 was noted. In general, yieldimproved up to 1%. Beyond that T5, the response wasnot significant. Highest yield of 43.50±2.00 and50.72±2.40 kg tree-1 was noted. TSS of 19.90±0.31(T1) to 19.63±0.25 (T5) and 19.67±0.21 (T1) to20.03±0.21°Brix (T5) was estimated. Similarly, acidityof 0.158±0.03, 0.200±0.02 (T5) to 0.175±0.03 to0.158±0.01% (T1) was recorded. Ascorbic acid contentwas ranging from 35.17±1.32 (T5) to 30.58±3.50 mgper 100 g (T1). Variable content of quality attributessuggested possible nutrient interaction in the mangotrees. The enhanced nutrient concentration in fruit pulpwas also recorded (Table 2). Lowest Zn concentrationof 1.17±0.10 (T1) to 1.73±0.10 (T4), 1.60±0.06 mgkg-1 (T5) wa s r ecor ded. Cu concentr a tion of3.50±0.015 mg kg-1 (T1) to 3.93±0.015 mg kg-1 (T5),B concentration of 2.01± 0.09 mg kg-1 (T1) to 3.13±0.18 mg kg-1 (T5) followed by 2.56±0.12 mg kg-1 (T4)were recorded. Non-significant response was observedin some mineral composition like Fe that variedbetween 16.20±0.15 to 20.10 ±0.15 mg kg-1. A narrowrange of 0.021 to 0.026% P and 0.26 to 0.28% K wasobserved. The observed results suggested strongresponse of Zn levels on fruit pulp Zn content.The mineral contentions of leaf tissue showed Znvariations between 29.7±5.51 (T1) to 52.0± 5.29 mgkg-1 (T5), Cu content of 13.7±0.58 (T1) to 19.7±1.53mg kg-1 (T4), B content of 32.367±3.11 (T1) to35.93±1.79 mg kg-1 (T5) (Table 3). However, Fe andMn contents were non-significant with a narrow rangeof 170.3±11.59 mg kg-1 to 206.7±10.26 mg kg-1 and137.7±5.13 mg kg-1 to 158.0±8.72 mg kg-1 wa sobserved. Similarly, P and K content were recordedas 0.147 to 0.159% and 0.936 to 1.022% respectively.Soil organic matter in general was low i.e. 0.316 to

0.385%, much lower than critical level of 0.50%(Table 4). Lower SOC content thus recommends forhigher organic input remedies to sandy loam soil.Available K of 74.78±3.97 mg kg-1 (T1) to 84.48±3.81mg kg-1 (T4) to 81. 79±15. 87 mg kg-1 (T5) wa sestimated. Fe and Mn availability of 4.78 to 5.87 and8.21 to 9.31 mg kg-1 was observed. Significantdifference of Zn and Cu content of 0.52±0.08 mg kg-1 (T1) to 0.93±0.25 mg kg-1 (T5) and 0.43±0.15 (T1 to 1.29±0.30 mg kg-1 (T5) was evidenced (Table 4).Higher CV (%) of 20.78% (Zn) and 30.75% (Cu) wasalso noticed.T he ob ser ved yield diff er ences in the ma ngoorchards are accounted for different rate of Zna p p lic a t ion . Tr ee nu t r it ion wa s t hu s f ou ndresponsible for obtaining satisfactory yields. Zenget al. (2001) reported the possible soil and leaf K

concentration variations along with nut yield and quality in pistachio tree. Perry et al. (2010) exhibited the pear orchard tree characteristics and its variations with yield. The soil condition is always questionable for solute transport ability. Asghari et al. (2011) reported the effect of soil conditioners in a sandy loam soil in terms of physical quality and bromide transport while Yadav et al. (2011) recorded statistically significant improvement in Amrapali mango with nutrient transformation mechanisms. In fact, the fitness of soil for tree plantations with potential yield is always top most priority on long-term basis to sustain land productivity (Ganeshamurthy and Reddy, 2015). Recently, Vallentin et al. (2022) opined that the satellite remote sensing data coul potentially be used for yield estimation and infrared spectroscopy could also be scientifically applied for quality assurances in mango and apple (Li et al., 2021). The role of foliar spray of nutrients is beneficial in fruit trees as observed by Pal et al. (2018) in Arka Neelamani grape, Kumar et al. (2017) on guava, Hamze et al. (2018) on pistachio tree. Talang et al. (2017) found the effectiveness of calcium, boron and sorbitol on fruit-set, yield and quality in Himsagar mango. Adak et al. (2020) experimentally proved the beneficial effects of foliar nutrient technology on the yield performance, fruit quality and nutrient status of guava. In fact, the technological innovations should efficiently be disseminated to small and marginal growers for harnessing the benefits (Adak et al., 2022). Since, soil properties also influence the yield performances, particularly organic carbon recognized as effective indicator, soil organic carbon stock should be estimated (Hinge et al., 2018) and digital soil mapping of soil properties (Dharumarajan et al., 2020), should also emphasized for future precision orchard management. Thus, the response recorded within the current trial showed 1% ZnSO. should be applied to mango trees for better statistically higher yield, quality component and nutrient richness. Beyond 1% ZnSO , economical benefit may not be kindly acknowledged for smooth functioning of field trials and other staff for cooperation in laboratory and fields.

CONCLUSION

Harvesting of optimum fruit yield from orchard is thesole objective of mango farmers. Fruit yield and fruitquality increased significantly with application of1.0% ZnSO4 over control. In the current study yieldof 50.72 kg tree-1 indicated that there is enormousscope to increase the yield of mango in this regionthrough zinc application through foliar sprays. Thestudy recommends foliar spray of 1.0% ZnSO4 formango in Indo-Gangetic plain region for higher yieldsand improvement of fruit quality. Study further showsthe scope for improvement in soil management to geta desirable potential yield

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