Effect of integrated nutrient management on the growth and yield of onion (Allium cepa.) under chironji (Buchanania lanzan) based Agroforestry system

Introduction

Forests are one of the most vital natural resources, providing ecological stability, biodiversity conservation, and a wide range of ecosystem services such as air purification, soil and water conservation, and climate regulation (FAO, 2020) [6] . They are also a source of numerous products including timber, fruits, fodder, medicinal plants, gums, and resins, which support both rural livelihoods and national economies (Tewari, 1995; CSIR, 1986) [17,2] . In India, forests and trees have been deeply integrated into cultural, social, and spiritual life since ancient times. Traditional systems of land management often combined agriculture with trees and livestock, laying the foundation for what is today known as agroforestry (Nair, 1993) [13] . Agroforestry, a sustainable land-use practice that integrates trees and shrubs with crops and/or livestock, enhances soil fertility, reduces erosion, improves water use efficiency, and promotes biodiversity (Jose, 2009) [11] . By mimicking natural ecosystems, agroforestry systems not only sustain agricultural productivity but also provide resilience against climate change (Kumar & Nair, 2011) [12] . India, with its diverse agro-climatic regions and long history of tree-crop interactions, holds immense potential for agroforestry in addressing food security, livelihood enhancement, and environmental sustainability. However, in the process of agricultural intensification, monoculture practices have largely replaced traditional agroforestry systems, leading to reduced ecological balance and overexploitation of natural resources (Dhyani et al., 2013) [4] . Among the important species associated with agroforestry and forest ecosystems, Chironji (Buchanania lanzan Spreng.) is a multipurpose tree valued for its edible kernels, oil, fodder, fuelwood, tannin-rich bark, and gum. The kernels, often used as a substitute for almonds, hold significant nutritional and economic importance for rural and tribal communities in central India (Janick & Paull, 2006) [10] . Despite its socio-economic value, natural regeneration of Chironji is poor due to premature harvesting and site degradation, raising concerns about its sustainable utilization and conservation (Troup, 1986) [19] . Similarly, onion (Allium cepa L.) is one of the most widely cultivated vegetable crops, second only to tomato in global importance (FAO, 2012) [5] . Known as the "queen of the kitchen" (Selvaraj, 1976) [15] , onion is consumed worldwide in multiple forms fresh, dried, or processed and contributes significantly to the agricultural economy of India, which is the second largest onion producer globally (Dhaker et al., 2017) [3] . In addition to its culinary value, onion is recognized for its medicinal properties and high export potential through dehydrated products (Hazra et al., 2021) [8] . However, onion production is highly sensitive to climatic and photoperiodic conditions, and faces challenges such as postharvest losses, price fluctuations, and inadequate storage facilities (Brewster, 1990) [1] . Given the ecological and economic significance of multipurpose tree species like Chironji and horticultural crops like onion, it becomes essential to explore their integration within sustainable agroforestry systems. Such an approach can provide diversified products, improve rural livelihoods, conserve biodiversity, and strengthen resilience against environmental stresses. The present study is therefore aimed at evaluating the role and potential of these species in agroforestry and agricultural systems, with particular emphasis on their ecological, economic, and cultural importance in India.

Materials and Methods

The field experiment entitled "Effect of Integrated Nutrient Management on the Growth and Yield of Onion (Allium cepa L.) under Chironji (Buchanania lanzan Spreng.) Based Agroforestry System under Prayagraj Agro-climatic Conditions" was conducted during Rabi season 2024-25 at the Research and Nursery, College of Forestry, Sam Higginbottom University of Agriculture, Technology and Sciences (SHUATS), Prayagraj, Uttar Pradesh, India. The experimental site lies in a subtropical climate with extremely hot summers (46-48 °C) and cold winters (4-5 °C). Relative humidity ranges from 20-94%, and the average annual rainfall is 1013.4 mm. Meteorological data on temperature, rainfall, and relative humidity during the crop season (October 2024-March 2025) were recorded at the Meteorological Observatory, SHUATS. The soil of the experimental field was sandy loam in texture with pre-sowing properties under open and Chironji shade conditions, respectively, viz., pH 6.91 and 6.6 (Jackson, 1958), EC 0.11 and 0.17 dS m⁻¹ (Wilcox, 1950) [21] , organic carbon 0.23 and 0.31% (Walkley and Black, 1947) [20] , available N 234 and 231 kg ha⁻¹ (Subbiah and Asija, 1956) [16] , available P 30 and 19 kg ha⁻¹ (Olsen et al., 1954) [14] , and available K 164 and 187 kg ha⁻¹ (Tooth and Prince, 1949) [18] .

Post-harvest soil analysis was carried out using the same methods. The experiment was laid out in a Randomized Block Design (RBD) with 16 treatments and 3 replications under both open and Chironji-based agroforestry systems. Each plot measured 2 × 2 m with 0.25 m bunds and irrigation channels. Onion seedlings (45-50 days old, raised in nursery beds using soil, FYM, and vermicompost mixture) were transplanted at 10 cm × 15 cm spacing in open field and 10 cm × 30 cm spacing under Chironji (7 × 3 m spacing). The treatments included: T1 -100% RDF (NPK), T2 -100% FYM, T3 -100% Vermicompost, T4 -100% Bonemeal, T5 -100% Poultry manure, T6 -75% RDF + 25% FYM, T7 -75% RDF + 25% Vermicompost, T8 -75% RDF + 25% Bonemeal, T9 -75% RDF + 25% Poultry manure, T10 -50% RDF + 25% FYM + 25% Vermicompost, T11 -50% RDF + 25% FYM + 25% Bonemeal, T12 -50% RDF + 25% FYM + 25% Poultry manure, T13 -50% RDF + 25% Vermicompost + 25% Bonemeal, T14 -50% RDF + 25% Vermicompost + 25% Poultry manure, T15 -50% RDF + 25% Bonemeal + 25% Poultry manure, and T16 -20% RDF + 20% FYM + 20% Vermicompost + 20% Bonemeal + 20% Poultry manure. Fertilizers were applied through urea, single superphosphate, and muriate of potash as per treatment combinations. Organic manures were applied 5 days before transplanting. Cultural operations such as irrigation, weeding, and plant protection were carried out uniformly. A total of six irrigations were applied during the crop cycle at critical growth stages. Weeding was performed manually at 20, 40, 60, and 80 days after transplanting. Harvesting was done when 70-80% of the onion tops bent down and bulbs developed a papery outer skin. Observations on growth parameters included Chironji tree height, onion plant height (30, 60, and 90 DAS), number of leaves, leaf length, and survival percentage. Yield attributes recorded were bulb weight per plant, bulb weight per plot, and yield per hectare. Economic analysis was carried out to estimate cost of cultivation, gross return, net return, and benefit-cost ratio for each treatment. The recorded data were subjected to statistical analysis following the Analysis of Variance (ANOVA) technique for RBD as suggested by Fisher (1960). Treatment means were compared using critical difference (CD) at 5% probability level.

Results and Discussion

The pre harvest data on the plant height (PH), number of leaves (NL), leaf length (LL) are presented on table 3.1 under open and under Chironji based Agroforestry System which revealed that there were significant differences between integrated nutrient management on the growth parameters. At 90 DAS treatment T9 (75% RDF + 25% Poultry Manure) showed the best results in both the experimental sites where a maximum plant height of (61.97 cm under open and 59.20 cm under Chironji based Agroforestry System), maximum no. of leaves of (11.37

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