Foliar application of nanoboron fertilizer at different growth stages enhanced the nutrient use efficiency of cauliflower, leading to improve productivity, quality, and profitability

Abstract

Background

Boron (B) is an essential element for the production of cauliflower (Brassica oleracea var. botrytis); nevertheless, conventional soil or foliar applications frequently suffer from inadequate nutrient uptake and leaching. Nano-boron fertilizers offer a highly efficient alternative due to their small particle size and superior surface-to-volume ratio, which enhances cellular penetration. This study aimed to determine the optimal dose of a foliar application of boron nanoparticles (B-NPs) and to compare the effects of conventional boron (B) and boron nanoparticles on the growth, yield, quality, nutrient dynamics, and profitability of cauliflower.

Methods

A field experiment was conducted using a randomized complete block design with 5 treatments involving four concentrations of boron nanoparticles (0, 100, 200 and 300 ppm) and conventional boric acid@1 gL^− 1. Foliar sprays were applied at 30 and 45 days after transplanting.

Results

Foliar application of 200 ppm boron nanoparticles resulted in the highest fresh curd yield (50.2 t ha^− 1), which was 69.6% greater than that of the control and 23.3% greater than that of the conventional boron treatments. This improvement was driven by the superior curd size and an individual curd weight of 1761 g. The same treatment significantly enhanced the quality parameters, yielding the highest vitamin C content (46.9 mg/100 g), protein content (25.1%), and curd firmness (1.23 kgf). This dose also resulted in the highest total B uptake (0.299 kg ha^− 1), maximum agronomic efficiency (45.9 kg g^− 1), and apparent recovery efficiency of B (356%). Economically, the 200 ppm nanoboron application proved most viable, achieving the highest benefit‒cost ratio of 4.14.

Conclusion

The results suggest that the foliar application of 200 ppm B nanoparticles can be used for sustainable cauliflower cultivation. However, this method is a highly effective and suitable approach for optimizing cauliflower productivity and quality in B-deficient environments.

Introduction

Global agriculture is adopting smart nanotechnology to generate high-efficiency nutrient delivery systems that maintain rapidity with increasing food and nutritional demands [1]. In particular, precision nutrient management significantly enhances the yield and quality of high-value horticultural crops such as cauliflower (Brassica oleracea var. botrytis L.) [2]. Cauliflower is a key high-value vegetable crop belonging to the family Brassicaceae [3, 4]. The edible portion is the curd, which is generally white and enclosed by inner leaves until it is exposed [5]. The curd is a rich source of essential dietary nutrients, mostly vitamins C, K, A, and B, and contains a fair amount of protein and minerals such as calcium, magnesium, potassium, and iron [1, 6, 7]. It also contains antioxidant compounds, including glucosinolates and phenolic acids such as caffeic acid, ferulic acid, and sinapic acid [8, 9]. These nutrients support a range of therapeutic health benefits, including improved digestion, a reduced risk of diabetes, inhibited cardiovascular disease development, and enhanced immune function [1, 10, 11].

Although cauliflower is highly prized for its nutritional profile and economic value, it is very sensitive to micronutrient deficiencies, particularly those associated with boron. Boron is recognized as a vital component of plant nutrition and vigour [6] because it facilitates key physiological processes, including cell wall formation and the maintenance of structural integrity in plant membranes [12–13]. Moreover, boron is crucial for sugar and carbohydrate translocation and plays a pivotal role in reproductive development, specifically flowering, pollen germination, and curd initiation [14–16]. Boron deficiency is associated with severe quality and yield losses in cauliflower [3]. Boron deficiency causes characteristic physiological disorders like browning of the curd which reduce the market value of crops [17]. The availability of boron to plants is frequently restricted in agricultural soils, particularly those that are sandy, alkaline, or low in organic matter, because of its low mobility and vulnerability to leaching and fixation. Traditional soil-based management practices face significant challenges, such as nutrient runoff and slow nutrient uptake, resulting in poor nutrient use efficiency [15]. Additionally, conventional foliar fertilizers, such as boric acid, often suffer from inefficient absorption, nonuniform distribution, and limited translocation to critical sink organs such as developing cauliflower curd [18]. To overcome these limitations, foliar application has emerged as a superior delivery method for correcting B deficiency, allowing direct absorption through the leaf stomata and immediate metabolic integration to rapidly ensure improved plant growth, yield, and quality and to increase nutrient content [19–21]. The introduction of foliar nanoboron fertilizers represents a transformative progression in modern agriculture [22]. Characterized by an ultrafine particle size (1–100 nm) and a high surface-area-to-volume ratio, these nano-formulations offer superior membrane permeability and a more targeted delivery system than conventional boric acid does [19, 22]. Although their efficacy is highly dependent on concentration levels and specific plant growth stages under physiological pH conditions [23], foliar application optimizes nutrient availability at the leaf surface, thereby increasing total nutritional uptake efficiency [18–19]. Nanotechnology represents a paradigm shift in nutrient delivery to plants through the utilization of nanoparticles (NPs). Recent studies demonstrate that reducing particle and droplet size significantly increases nutrient absorption efficiency while preventing excessive material accumulation during application. This precision technology successfully mitigates environmental hazards and minimizes plant toxicity [19, 24]. This emerging technology has the potential to revolutionize agricultural research, enhancing productivity as well as food and nutritional security [25]. However, because nanoparticles are relatively labile within soil–water–plant systems, it is crucial to balance their use with soil quality preservation, water use efficiency, and economic profitability [26–27]. In particular, boron nanoparticles (B-NPs) exhibit unique physicochemical properties, such as extremely high surface-area-to-volume ratios. These characteristics are hypothesized to optimize fertilizer performance by improving adhesion to the leaf cuticle and facilitating rapid penetration into metabolic sites. Consequently, compared with conventional bulk materials, B-NPs may increase nutrient use efficiency (NUE) because they require significantly lower application rates [28].

Several studies have documented the positive influence of conventional B on cauliflower growth and yield [4, 16], but a significant knowledge gap remains regarding the comparative efficacy of boron nano formulations. Specifically, the ability of nanoboron fertilizers to increase cauliflower productivity and quality has not been fully explored. Using nanoboron fertilizers represents an innovative method for precise nutrient management, potentially offering a more sustainable and environmentally friendly solution than traditional methods do. Therefore, the goal of this study was to determine the optimal dose for the foliar application of boron nanoparticles (B-NPs) and compare the effects of conventional boron (B) and boron nanoparticles on the growth, yield, quality, nutrient dynamics, and profitability of cauliflower to maximize productivity and profitability by enhancing curd quality and resource sustainability. These findings provide scientific evidence for the integration of nanofertilizers into modern agricultural practices to ensure sustainable crop production.

Materials and methods

Brief description of the location

This study was conducted at the Soil and Water Management Section, Horticulture Research Centre, Bangladesh Agricultural Research Institute (BARI), during the winter seasons of 2023-24 and 2024-25. The study site was in the Gazipur district of the Dhaka Division. Geologically, it is situated at 23–59´N latitude and 90–24´ E longitude. The site is elevated at 8.4 m above sea level. The land at this site is typically high and medium-high. The experimental soil is a gray terrace with a clay loam texture. This soil belongs to the Chhiata soil series of the central Madhupur Tract (Agro-ecological Zone-28) [29]. The site has a subtropical climate that is shaped by the southwestern monsoon. Throughout the crop season, the mean temperature fluctuated between 13.5 °C and 32.5 °C, with the average relative humidity between 76.5% and 86.6% (Fig. 1). The total rainfall during the study period fluctuated from 0 to 259 mm. According to Fig. 1, the temperature values were generally uniform across both years of cultivation.

Fig. 1.

Monthly average minimum and maximum temperatures, monthly average humidity and rainfall during the experimental period

Before beginning the experiment, the initial soil samples at a depth of 0 to 15 cm were methodically collected in accordance with the procedure detailed by [30]. These samples were then subjected to analysis through standard methods. The results of the physicochemical properties are presented in Table 1.

Table 1.

Physicochemical properties of the initial soil at the trial location

Physicochemical properties	Soil test value	Critical value	Interpretation*
Sand (%)	30.4	-
Silt (%)	38.3	-
Clay (%)	31.3	-
Textural class	Clay loam	-
Field capacity (%)	25.8	-
Wilting point (%)	15.4	-
Particle density (g/cc)	2.47	-
Bulk density (g/cc)	1.40	-
Porosity (%)	43.3	-
Soil temperature (0C)	17.9	-
Soil EC (dS/m)	0.10	-	Non saline
Soil pH	6.2	5.5–6.5	Slightly acidic
OM (%)	1.18	2–3	Low
Total N (%)	0.064	0.12	Very low
K (meq/100 g)	0.11	0.12	Low
P (µg g− 1)	11.6	7	Medium
S (µg g− 1)	13.0	10	Low
Zn (µg g− 1)	0.86	0.60	Low
B (µg g− 1)	0.18	0.20	Low

*Interpretation source: Ahmmed et al. [31]

Brief description of the soil analysis technique

The physical properties were carefully measured. The textural class was determined using the hydrometer method [32]. The soil particle density and bulk density were assessed using volumetric flask and core sampler methods. Soil electrical conductivity (EC) and temperature were measured through a Groline direct soil meter (HI98331). A spot soil moisture tester (Model DM-15, Tokyo, Japan) was used to quantify the soil moisture. To determine the chemical properties of the soil, standard analytical techniques were utilized. Soil pH was measured with a 1:2.5 soil–water suspension by a glass electrode pH meter [33]. Organic carbon (OC) was estimated by the wet oxidation method [33]. Total organic matter was subsequently calculated by using the Van Bemmelen factor (1.73×%OC). The total nitrogen content was determined by the micro-Kjeldahl method [33]. Calcium and Mg were extracted using a 1 M NH₄OAc solution [34] and then analysed through atomic absorption spectrometry (AAS). The exchangeable K was measured by the 1 N NH₄OAc method [35]. Phosphorus was determined via the Bray and Kurtz [36] method, and sulfur was determined through BaCl₂ turbidimetry [37]. Zn is available through the DTPA extraction method [38], and B is available through the azomethine-H method [33].

Planting material source and seedling rising and land preparation

The Hybrid Shiragiku F1 cauliflower seeds were obtained from a local entrepreneur in the Gazipur district, Bangladesh. The seeds of cauliflower were sown on 26 October 2023 and 27 October 2024 in hand-prepared, elevated seed beds. Adequate irrigation was provided immediately following seeding. Postemergence (after 4 days), the seedlings were irrigated twice per week. Disease (damping off) and pest prevention were managed using the fungicide Autostin^® 50 WDG (a.i. Carbendazim) and the insecticide Sevin^® WP 85 (a.i. Carbaryl). The experimental mainland was properly prepared by ploughing three to four times with a tractor-driven disc plough and subsequently levelling it using a rotavator. The land was also meticulously cleaned to remove all debris.

Experimental treatments, design and field layout

Afterward, the experiment was structured with five distinct treatments, viz., T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L). Based on the predetermined nutrient composition of the initial soil, all treatments standardized the N-P-K-S-Zn-Mg application to 140–40–90–10–3–12 kg ha^{− 1} as per the Fertilizer Recommendation Guide-2018 [31]. Furthermore, a recommended rate of 5 t ha^{− 1} of decomposed cow dung was applied to all the treatments [31]. The investigational treatments were scheduled on the basis of a randomized complete block design (RCBD) with three replications. The unit plot dimensions were 4.0 m × 2.6 m, and a plant spacing of 60 cm × 50 cm was employed. Each plot was delineated at a 15 cm elevation and separated from its neighbour by a 50 cm inter-plot gap. A 1-meter-wide distance was used to ensure separation between the replicated blocks.

Nanoboron and other fertilizer sources and application procedures

The nano-boron fertilizer was sourced from distributors such as Nano Crops Ltd., Dhaka, a Bangladesh-based firm. This nano-boron fertilizer was developed by the Sodour Ahrar Shargh Knowledge-based Company (SASh Co.) in Tehran, Iran. This advanced fertilizer incorporates boron nanoparticles that are less than 100 nm in size. Its manufacturing process involves the preliminary conversion of borax to boric acid, which is then processed into nanoparticles to create the final chelated product. The sources of N, P, K, S, Mg, Zn and B were urea (46% N), triple superphosphate (20% P, 1.3% S, and 14% Ca), muriate of potash (50% K), gypsum (18% S, 20% P), magnesium sulfate (12.5% S, 9.5% Mg), zinc sulfate heptahydrate (10.5% S, 21% Zn), nano-boron fertilizer (9% B) and conventional boric acid (17% B), respectively. Fertilizers were applied manually as basal application and subsequent top dressings. The preliminary incorporation of fertilizers included 50% decomposed cow dung, 100% triple superphosphate, 50% muriate potash, and the full amounts of gypsum, zinc sulfate heptahydrate, and magnesium sulfate, which were thoroughly mixed into the soil. The remaining 50% of the decomposed cow dung was directly applied to the planting pits before the seedlings were transplanted. The urea and the remaining 50% of the muriate of potash were split into three equal portions, which were applied at 15, 30, and 45 days after transplanting (DAT). These split doses were applied by the ring method when the soil was sufficiently moist and then mixed for better utilization.

Seedling transplanting and agronomic practices

Twenty-five-day-old, homogenous and healthy seedlings were selected. The seedling beds were irrigated one day prior to transplanting to comfort uprooting and minimize root damage. To reduce transplanting stress, the plants were planted during the afternoon to take advantage of cooler temperatures. A single seedling was transplanted per pit at a spacing of 60 cm × 50 cm (row-to-row and plant-to-plant). Transplanting was carried out on 23 November 2023 and 24 November 2024. The seedlings were irrigated immediately upon transplanting, followed by two irrigations during the first week for establishment. Afterward, irrigation was applied using a plastic hose pipe according to field moisture conditions and crop needs. Hand weeding was performed at 15 and 30 days after transplanting. In accordance with the experimental treatment, both nanoboron fertilizer and conventional boric acid were applied through foliar spraying.

Treatment wise nano-boron fertilizer and conventional boric acid were applied twice as foliage at 30 and 45 days after transplanting (DAT). Plant protection measures were implemented to manage diseases and pests. Leaf spot was controlled through two foliar applications of Dithane M-45^® a.i. Mancozeb (2 g L^− 1) at 30 and 40 days after transplanting. Insects such as the diamondback moth (DBM) and aphids were controlled using Imitaf^® 20 SL a.i. Imidacloprid insecticide (0.5 ml L^− 1 water). The initial spraying of insecticide was performed at 30 DAT, followed by a second spray at 15-day intervals. The crop was harvested during the first and second weeks of February 2024 and 2025. At the harvest stage, the curds reached their full marketable potential, characterized by a dense structure and the absence of riceyness or discolouration.

Data curation procedure

Five representative plants were randomly selected from each plot for collection of growth and yield parameter data. Plant height (cm) was measured using a standard scale at 55 days after transplanting (DAT). Root length was recorded at the time of harvest. The total number of leaves per plant was noted. The leaf length and diameter were measured. The leaf chlorophyll content (SPAD value) was recorded at 55 DAT using a SPAD-502 Plus chlorophyll meter (Konica Minolta, Tokyo, Japan). At harvest, leaves from the preselected plants in each treatment plot were collected and subjected to a two-stage drying process. First, the samples were sun-dried for three days (5 h per day). The sun-dried leaves were transferred to the laboratory for oven drying, which was maintained at 70 °C for 72 h. The oven-dried leaf samples were weighed on the basis of treatment. The recorded dry leaf matter yield was converted to kg ha^− 1. A similar protocol was applied to the cauliflower curds. The separated curds were systematically sliced to increase the surface area for uniform sun drying following the same 3days. Afterward, it was transferred to the laboratory for oven drying for 72 h at 70 °C. The dry matter yield of the curds was measured and converted to kg ha^− 1. The yield parameter data were measured on the basis of treatments from the five preselected marketable curds. The curd length and diameter were measured by a standard graduated scale and then averaged according to the treatment. The unit curd weight (g) was determined using a digital balance. The marketable curd yield was calculated on a whole-plot basis. These values were then converted to tonnes per hectare (t ha^− 1).

To obtain quality attribute data, fresh curd samples of cauliflower were transported to the laboratory and preserved at -30 °C. The samples were defrosted to determine the total soluble solids (TSS), vitamin C content, and titratable acidity. Curd firmness was assessed at an ambient temperature of 25 ± 1 °C using a fruit texture analyser (GUSS, model GS-25, South Africa). In each treatment, each cauliflower curd was bisected longitudinally from the stem to the calyx end. The resulting slices were mechanically pressed to extract the juice. The TSS were determined using a digital handheld refractometer (Atago Ltd., PAL-1, Tokyo, Japan); values were recorded in °Brix following established protocols [39]. Titratable acidity was quantified by diluting a 2 mL juice aliquot with 8 mL of distilled water. Following the addition of phenolphthalein as an indicator, the solution was titrated against 0.1 N NaOH until a stable pH of 8.2 was reached, as described by Shukla et al. [40]. The vitamin C content was estimated with standardized procedures outlined by Shukla et al. [39]. Protein levels in dry curd of cauliflower were determined by multiplying the total nitrogen content by a constant factor of 6.25 [41].

Plant sample analysis

On the basis of treatment, the oven-dried samples of the cauliflower curd and leaves were crushed by a Cyclotec™ 1093 sample mill (Made in Sweden). One hundred grams of ground powder from each curd and leaves was stored in small polybags (15 cm × 10 cm) for laboratory analysis. Dry curd and dry leaf samples were wet digested using a 5:1 diacid mixture (HNO₃-HClO₄) following the procedure documented by Piper [42]. Total nitrogen was assessed by the micro-Kjeldahl technique [33]. P was estimated spectrophotometrically using the sodium bicarbonate extraction method [43]. Potassium and Zn concentrations were determined using an atomic absorption spectrophotometer (AAS; Varian, SpectrAA 55B, Sydney, Australia) following the techniques of Gupta [34]. Sulfur was estimated by the BaCl₂ turbidity method [37], and B was determined spectrophotometrically utilizing the azomethine-H procedure [33].Nutrient uptake by dry biomass such as curds and leaves of cauliflower was calculated on the basis of the following formula of Quddus et al. [44].

1

2

Boron use efficiency calculation

The agronomic efficiency of boron (AEB) was computed on the basis of the method outlined by Quddus et al. [45], measuring the kg of curd yield produced per gram (g^{− 1}) of B applied.

3

where, Yb is the dry curd yield with boron, Y0 is the dry curd yield without boron (control), and Ba is the amount of boron applied.

The physiological efficiency of boron (PEB) was calculated following the formula outlined by Godebo et al. [46].This physiological efficiency indicated the amount of biological yield (kg) per gram (g^{− 1}) of boron absorbed by the plant.

4

where, BYb signifies the biological yield (dry curd + dry leaf) in the B fertilized plot and BY₀ indicates the biological yield in the B unfertilized (control) plot. Ub indicates the total B uptake in the B-fertilized plot, and U0 indicates the total B uptake in the B-unfertilized (control) plot.

The apparent boron recovery efficiency (ABR) was calculated by the dry weight-based formula outlined by Quddus et al. [47]. This metric reflects a clear understanding of how effectively the plant utilizes applied boron.

5

Profitability analysis

The total variable cost (TVC) for the cauliflower cultivation in each experimental treatment was calculated on a per-hectare basis. The land rent was omitted from this economic analysis. The gross return was calculated by multiplying the fresh curd yield of cauliflower (kg ha^{− 1}) by the current local market price. The gross margin was consequently calculated by deducting the TVC from the gross return. The benefit‒cost ratio (BCR) was determined by the following formula, outlined by Quddus et al. [47]:

6

Statistical analysis

Statistical analysis was performed using open-source R software (version 3.5.2). Data concerning cauliflower growth, yield attributes, quality traits, profitability and nutrient dynamics were subjected to two-way analysis of variance (ANOVA). Treatment means were compared by using the least significant difference (LSD) test at p ≤ 0.05, p ≤ 0.01, or p ≤ 0.001. To ensure the precision and reliability of the experimental data, the standard error of the mean (SEm) and the coefficient of variation (CV %) were also determined. Spearman rank correlation analysis was performed to examine the relationships among the variables, and the resulting correlation matrix was illustrated as a heatmap using the “corrplot” package in R. To construct the PCA biplot, the R packages Factoextra, FactoMineR, and ggplot2 were used [48].

Results

Growth of cauliflower as influenced by the foliar application of boron and boron nanoparticles

The data in Table 2 indicate that the year of cultivation had no significant effect on the growth traits of cauliflower, including plant height, root length, leaf number per plant, leaf length, leaf width, or SPAD value. Foliar application of boron and boron nanoparticles significantly enhanced the growth traits of cauliflower (Table 2).

Table 2.

Effects of cultivation year and boron nanoparticles on the growth traits of cauliflower

Cultivation year (Y)	Plant height (cm)	Root length (cm)	No. of leaves plant− 1	Leaf length (cm)	Leaf breadth (cm)	SPAD value
2023-24	66.7 ± 1.65a	28.7 ± 0.85a	19.0 ± 0.75a	54.1 ± 1.38a	24.8 ± 0.75a	54.6 ± 0.95a
2024-25	67.6 ± 1.65a	29.2 ± 0.85a	19.5 ± 0.76a	54.6 ± 1.38a	25.5 ± 0.75a	54.7 ± 0.95a
F test	ns	ns	ns	ns	ns	ns
CV (%)	5.07	10.4	10.1	4.96	8.04	2.84
LSD0.05	2.61	2.31	1.50	2.07	1.55	1.19
Treatment (T)
T1	56.3 ± 0.43b	25.7 ± 1.06c	15.0 ± 0.63c	45.5 ± 0.74c	21.3 ± 0.75c	48.7 ± 0.73c
T2	69.7 ± 1.94a	29.5 ± 1.72ab	19.6 ± 1.10b	56.0 ± 1.50ab	24.6 ± 0.74b	55.6 ± 0.55b
T3	72.0 ± 0.56a	32.1 ± 0.38a	21.9 ± 0.38a	58.6 ± 1.10a	27.4 ± 1.07a	58.4 ± 0.37a
T4	69.0 ± 1.30a	29.2 ± 0.74a-c	19.8 ± 0.56ab	57.2 ± 0.70ab	26.9 ± 0.57ab	56.0 ± 1.06b
T5	68.9 ± 1.29a	28.3 ± 1.10bc	20.3 ± 0.74ab	54.8 ± 0.74b	25.8 ± 0.75ab	54.7 ± 0.37b
F test	***	*	***	***	***	***
CV (%)	5.07	10.4	10.1	4.96	8.04	2.84
LSD0.05	4.13	3.66	2.36	3.28	2.45	1.88
Interaction (Y*T)	ns	ns	ns	ns	ns	ns

T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L). Means within the same column followed by dissimilar letters are significantly different according to the least significant difference (LSD) test at a 5% (p ≤ 0.05) level of probability. CV (%) = coefficient of variation. Note: ns designates not significant, *designates significance at p ≤ 0.05, **designates significance at p ≤ 0.01 and ***designates significance at p ≤ 0.001 according to ANOVA

The maximum plant height (72.0 cm) and root length (32.1 cm) were recorded under the foliar application of 200 ppm (T₃). These results were statistically comparable to those of treatments T₄ and T₂, whereas the control (T₁) treatment yielded the minimum values for both traits. The greatest number of leaves per plant (21.9) occurred in the T₃ treatment, which was comparable to that in the T₄ and T₅ treatments. The lowest number of leaves was observed in the control (T₁) treatment. The application of 200 ppm B nanoparticles (T₃) resulted in maximum values for leaf length (58.6 cm) and leaf width (27.4 cm). These results were comparable to those of treatments T₄ and T₅, while the minimum values for both parameters were recorded in the control treatment. The T₃ treatment resulted in a significantly increased SPAD value (58.4), whereas the control treatment resulted in the lowest value (Table 2).

Yield traits and yields of cauliflower as influenced by the foliar application of boron and boron nanoparticles

As shown in Table 3, the year of cultivation had a significant effect on individual curd weight, fresh curd yield, and curd dry yield. However, no significant effect of cultivation year was observed for curd length, curd diameter, or dry leaf yield. In particular, better yield and yield attribute performance were recorded in the second year than in the first year. Foliar application of boron and boron nano-fertilizer significantly enhanced curd growth and yield in cauliflower (Table 3). The highest curd length (19.9 cm), curd diameter (25.6 cm), individual curd weight (1761 g), fresh curd yield (50.2 t ha^− 1), dry curd yield (5019 kg ha^− 1), and dry leaf yield (3884 kg ha^− 1) were recorded with 200 ppm B nano-fertilizer (T₃), while the control (T₁) showed the lowest values. However, increasing the concentration to 300 ppm (T₄) resulted in a decline in yield.

Table 3.

Effect of cultivation year and boron nanoparticles on yield traits and yields of cauliflower

Cultivation year (Y)	Curd length (cm)	Curd diameter (cm)	Individual curd wt. (g)	Fresh curd yield (t ha− 1)	Curd dry yield (kg ha− 1)	Dry leaf yield (kg ha− 1)
2023-24	17.1 ± 0.52a	23.4 ± 0.55a	1435 ± 57.3b	39.6 ± 1.92b	3960 ± 191b	3112 ± 129a
2024-25	17.8 ± 0.51a	24.0 ± 0.55a	1510 ± 57.4a	42.1 ± 1.92a	4208 ± 192a	3115 ± 129a
F test	ns	ns	*	*	*	ns
CV (%)	8.10	6.90	5.64	6.52	6.49	4.99
LSD0.05	1.08	1.25	63.7	2.04	203	119
Treatment (T)
T1	15.1 ± 0.73c	20.8 ± 0.78b	1134 ± 39.1c	29.6 ± 1.46d	2956 ± 146d	2423 ± 65.4c
T2	17.0 ± 0.40b	23.9 ± 0.78a	1458 ± 41.2b	39.1 ± 1.23c	3905 ± 122c	3103 ± 48.9b
T3	19.9 ± 0.57a	25.6 ± 0.40a	1761 ± 40.2a	50.2 ± 1.27a	5019 ± 126a	3884 ± 66.5a
T4	18.3 ± 0.40ab	24.1 ± 0.17a	1548 ± 40.2b	44.8 ± 0.78b	4475 ± 78.3b	3156 ± 48.6b
T5	17.2 ± 0.40b	24.3 ± 0.71a	1463 ± 19.1b	40.7 ± 0.67c	4066 ± 66.0c	3002 ± 36.5b
F test	***	**	***	***	***	***
CV (%)	8.10	6.90	5.64	6.52	6.49	4.99
LSD0.05	1.71	1.98	101	3.23	322	189
Interaction (Y*T)	ns	ns	ns	ns	ns	ns

T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L). Means within the same column followed by dissimilar letters are significantly different according to the least significant difference (LSD) test at a 5% (p ≤ 0.05) level of probability. CV (%) = coefficient of variation. Note: ns designates not significant, *designates significance at p ≤ 0.05, **designates significance at p ≤ 0.01 and ***designates significance at p ≤ 0.001 according to ANOVA

Postharvest qualities of cauliflower as influenced by the foliar application of boron and boron nanoparticles

The year of cultivation influenced the total soluble solids (TSS) and titratable acidity. However, other crucial quality indicators of cauliflower, such as curd firmness, vitamin C concentration, and protein content, remained unaffected by the specific growing season. Overall, the quality attributes showed marginally superior performance during the second year of cultivation compared with the first year (data not presented). Foliar spraying with boron and boron-based nano-fertilizers significantly affected cauliflower curd firmness, vitamin C concentration, titratable acidity, and protein content. Conversely, TSS remained unaffected by these treatments (Figs. 2a–e).

Fig. 2.

Effects of boron and boron nanoparticles on (a) total soluble solids (TSS), (b) curd firmness, (c) vitamin C content, (d) titratable acidity and (e) protein content of cauliflower. Vertical bars represent the standard error of the mean (n = 3); the mean values indicated by the common letters are not significantly different at the 5% level according to the least significant difference test. T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L)

In this study, the highest total soluble solids (TSS) concentration in cauliflower was recorded in Treatment T₃ (5.61 °Brix). These results were achieved by the foliar application of 200 ppm boron nanofertilizer. The TSS values obtained from the other treatments were not significantly different (Fig. 2a). Treatments T₃ and T₅ produced a peak curd firmness of 1.23 kgf, with T₄ yielding nearly identical results (Fig. 2b). Furthermore, the greatest accumulation of vitamin C (47.1 mg/100 g) resulted from the T₃ treatment (200 ppm boron nanoparticles), and the results did not significantly differ from those of T₂ and T₅ (Fig. 2c). Both of these quality metrics were lowest in the control (T₁) treatment. The results for the titratable acidity were inconsistent, although it increased significantly (0.321%) with the foliar application of 300 ppm boron nanofertilizer (T₄); the lowest value was observed in the T₃ treatment (Fig. 2d). The protein content of the cauliflower reached its maximum (25.1%) in T₃, which was statistically similar to that in most other treatments, while the minimum was recorded in the control (T₁) (Fig. 2e).

Nutrient content in dry curd as influenced by the foliar application of boron and boron nanoparticles

According to the data in Table 4, the year of cultivation did not significantly influence the concentrations of N, K, S, Zn, or B in dry curd, except for the concentration of P, which significantly varied across years. Compared with the first year, the second year of cultivation yielded higher concentrations of all the measured elements (N, P, K, S, Zn, and B). Foliar supplementation with conventional and nanoboron fertilizers significantly modulated the nutrient content of the dry curd of cauliflower, particularly affecting the N, P, K, S, Zn, and B concentrations (Table 4). While the T₃ treatment yielded the highest numerical values for N (4.02%), P (0.825%), K (2.92%), and S (0.913%), they remained statistically identical to those of the T₂, T₄, and T₅ groups. The T₁ control yielded the most depleted nutrient levels. The maximum Zn concentration (50.6 ppm) occurred in the T₃ treatment, which was statistically equivalent to that in the majority of the other treatments. Furthermore, T₃ elicited peak B content in dry curd (36.2 ppm), following the T₄ and T₅ treatments. The control (T₁) treatment manifested the poorest levels of both Zn and B (Table 4).

Table 4.

Effect of cultivation year and boron nanoparticles on nutrient content in dry curd of cauliflower

Cultivation year (Y)	N content (%)	P content (%)	K content (%)	S content (%)	Zn content(ppm)	B content (ppm)
2023-24	3.93 ± 0.03a	0.766 ± 0.02b	2.85 ± 0.03a	0.864 ± 0.018a	49.5 ± 0.46a	34.1 ± 0.65a
2024-25	3.98 ± 0.03a	0.816 ± 0.02a	2.88 ± 0.03a	0.893 ± 0.018a	50.4 ± 0.46a	34.7 ± 0.65a
F test	ns	*	ns	ns	ns	ns
CV (%)	2.00	7.07	3.21	6.78	2.91	4.13
LSD0.05	0.06	0.04	0.07	0.05	1.11	1.09
Treatment (T)
T1	3.88 ± 0.02b	0.745 ± 0.04b	2.71 ± 0.041b	0.833 ± 0.037b	48.7 ± 1.12b	30.4 ± 0.74c
T2	3.97 ± 0.03ab	0.795 ± 0.02ab	2.89 ± 0.04a	0.863 ± 0.02ab	49.9 ± 0.43ab	34.1 ± 0.74b
T3	4.02 ± 0.05a	0.825 ± 0.03a	2.92 ± 0.04a	0.913 ± 0.037a	50.6 ± 0.75a	36.2 ± 0.34a
T4	3.96 ± 0.049ab	0.805 ± 0.01ab	2.91 ± 0.02a	0.895 ± 0.009ab	50.5 ± 0.76a	36.1 ± 0.39a
T5	3.97 ± 0.02ab	0.785 ± 0.03ab	2.90 ± 0.04a	0.887 ± 0.023ab	50.3 ± 0.36ab	35.2 ± 0.37ab
F test	*	*	**	*	*	***
CV (%)	2.00	7.07	3.21	6.78	2.91	4.13
LSD0.05	0.09	0.07	0.11	0.07	1.76	1.72
Interaction (Y*T)	ns	ns	ns	ns	ns	ns

T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L). Means within the same column followed by dissimilar letters are significantly different according to the least significant difference (LSD) test at a 5% (P ≤ 0.05) level of probability; CV (%) = coefficient of variation. Note: ns designates not significant, *designates significance at p ≤ 0.05, **designates significance at p ≤ 0.01 and ***designates significance at p ≤ 0.001 according to ANOVA

Nutrient content in dry leaves of cauliflower as influenced by the foliar application of boron and boron nanoparticles

The cultivation year had a pronounced influence on the N, P, and K contents of dry cauliflower leaves, whereas its impact on the S, Zn, and B levels remained statistically negligible (Table 5). The second year surpassed the first year in terms of the yield of higher concentrations of all measured nutrients. Foliar management with both conventional and nanoboron fertilizers substantially influenced the contents of N, P, K, S, Zn, and B in dried cauliflower leaves (Table 5). The highest concentrations of N (3.97%), P (0.817%), and S (0.875%) were observed in treatment T₃. While these values were statistically comparable to those of the majority of the other treatments, they significantly increased over those of the control treatment (T₁), which presented the lowest nutrient levels. With respect to K accumulation, treatment T₃ yielded the greatest concentration (3.39%), a result that was statistically equivalent to that of treatment T₄. Furthermore, T₃ triggered a pronounced increase in micronutrient levels, with the highest values recorded for Zn (49.9 ppm) and B (30.3 ppm). Minimal concentrations of both Zn and B were detected in the control group (T₁) (Table 5).

Table 5.

Effect of cultivation year and boron nanoparticles on nutrient content in dry leaves of cauliflower

Cultivation year (Y)	N content (%)	P content (%)	K content (%)	S content (%)	Zn content (ppm)	B content (ppm)
2023-24	3.82 ± 0.04b	0.738 ± 0.02b	3.16 ± 0.04b	0.812 ± 0.02a	47.8 ± 0.33a	26.4 ± 0.94a
2024-25	3.97 ± 0.03a	0.788 ± 0.02a	3.31 ± 0.04a	0.861 ± 0.02a	48.2 ± 0.33a	26.8 ± 0.94a
F test	***	*	**	ns	ns	ns
CV (%)	2.71	8.34	3.80	8.47	1.22	2.66
LSD0.05	0.08	0.05	0.09	0.05	0.45	0.54
Treatment (T)
T1	3.79 ± 0.07b	0.703 ± 0.02b	3.06 ± 0.05d	0.773 ± 0.021b	46.9 ± 0.33d	20.3 ± 0.34d
T2	3.88 ± 0.04ab	0.755 ± 0.04ab	3.18 ± 0.08 cd	0.835 ± 0.02ab	47.7 ± 0.20bc	26.1 ± 0.31c
T3	3.97 ± 0.09a	0.817 ± 0.022a	3.39 ± 0.05a	0.875 ± 0.04a	49.9 ± 0.41a	30.3 ± 0.41a
T4	3.93 ± 0.04a	0.775 ± 0.021ab	3.33 ± 0.05ab	0.855 ± 0.02ab	48.1 ± 0.31b	28.6 ± 0.18b
T5	3.93 ± 0.04a	0.765 ± 0.03ab	3.23 ± 0.04bc	0.845 ± 0.04ab	47.1 ± 0.24 cd	28.0 ± 0.27b
F test	*	*	***	*	***	***
CV (%)	2.71	8.34	3.80	8.47	1.22	2.66
LSD0.05	0.13	0.08	0.15	0.09	0.71	0.86
Interaction (Y*T)	ns	ns	ns	ns	ns	ns

T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L). Means within the same column followed by dissimilar letters are significantly different according to the least significant difference (LSD) test at a 5% (p ≤ 0.05) level of probability. CV (%)=coefficient of variation. Note: ns designates not significant, *designates significance at p ≤ 0.05, **designates significance at p ≤ 0.01, and ***designates significance at p ≤ 0.001 according to ANOVA

Total nutrient uptake by cauliflower as influenced by the foliar application of boron and boron nanoparticles

As illustrated in (Fig. 3a–d), the cumulative nutrient uptake (N, P, K, S, Zn, and B) of the cauliflower plants substantially increased during the 2024–25 season (Fig. 3a–b). This pronounced upwards trend highlights a significant improvement in nutrient uptake compared with that in the previous year. Foliar management with conventional and nanoboron fertilizers profoundly influenced cumulative nutrient uptake by cauliflower (Figs. 3c–d). The T₃ treatment resulted in the greatest total uptake of all the nutrients, including nitrogen (356 kg ha^− 1), P (73.4 kg ha^− 1), K (278 kg ha^− 1), S (79.9 kg ha^− 1), Zn (0.448 kg ha^− 1) and B (0.299 kg ha^− 1). The control treatment (T₁) resulted in the minimum uptake values for all six nutrients investigated (Figs. 3a–d).

Fig. 3.

Total uptake of N, P, K, S, Zn and B by cauliflower as influenced by cultivation year (a, b) and foliar application of boron nanoparticles (c, d). The error bars represent the ± standard error of the mean (n = 3). The mean values indicated by the different letters in the bars are significantly different at the 5% level according to the LSD test. T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L)

Boron use efficiency in cauliflower

The year of cultivation had no significant effect on the boron use efficiency of the cauliflower. Specifically, the agronomic efficiency, physiological efficiency, and apparent recovery efficiency remained consistent across both seasons (data not presented). As demonstrated in Fig. 3a–c, the foliar management of both conventional and nano-boron fertilizers markedly increased the boron use efficiency (BUE) of the cauliflower crop. Treatment T₃ resulted in the greatest values for agronomic efficiency (45.9 kg g^− 1) and apparent boron recovery efficiency (356%). The highest physiological efficiency of B (23.4 kg g^− 1) was achieved in T₂, followed by the T₃ treatment. Across all efficiency indices, the lowest values were observed in the T₅ treatment (Figs. 3a–c). (Fig. 4).

Fig. 4.

Effects of foliar-applied boron and boron nanofertilizer on (a) the agronomic efficiency of boron (AE), (b) the physiological efficiency (PE) of boron, and (c) the apparent boron recovery efficiency in cauliflower. Vertical bars represent the standard error of the mean (n = 3); the mean values indicated by the common letters are not significantly different at the 5% level according to the least significant difference test. T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L)

Principal component analysis (PCA)

The PCA biplot summarized the multivariate response of cauliflower to nano-boron treatments across both years. Principal Component 1 (PC1) accounted for the majority of the total variance (81.0%), indicating that most traits shifted together along a single major gradient reflecting overall plant performance (Fig. 5).

Fig. 5.

PCA biplot (PC1 vs. PC2) for selected cauliflower traits across both years under foliar boron treatments, with variable vectors labelled as follows: 1–8: 1 = SPAD value (SPAD, unitless), 2 = fresh curd yield (FCY, t ha⁻¹), 3 = individual curd weight (ICW, g), 4 = curd diameter (CD, cm), 5 = total soluble solids (TSS, °Brix), 6 = vitamin C (VC, mg 100 g⁻¹), 7 = curd firmness (CF, kgf), and 8 = total B uptake (TBU, kg ha⁻¹) (n = 3; * p < 0.05, ** p < 0.01, *** p < 0.001)

Treatments were primarily separated along the PC1 axis; the control (T₁) clustered on the negative side, whereas the 200-ppm nano-boron treatment (T₃) clustered on the positive side. This separation demonstrates that T₃ is strongly associated with higher combined values of the yield and quality traits represented by the vectors. Furthermore, the confidence ellipses for Year 1 and Year 2 overlapped considerably, indicating that the multivariate pattern was stable across seasons and that treatment effects outweighed year-to-year variation. On the other hand, PC2 explained a smaller proportion of the variance (8.23%) and primarily captured secondary differences among quality attributes, as evidenced by the vertical orientation of vectors such as TSS, curd diameter, and curd firmness (Fig. 5).

Correlation coefficient analysis

Strong positive correlations among vegetative growth traits (such as plant height, root length, leaf number, leaf length, and SPAD) are shown in Fig. 6(A & B), indicating that enhanced vegetative growth traits tend to occur together. Yield formation is closely linked to curd size and mass, with individual curd weight strongly positively correlated with both fresh curd yield and curd dry matter yield, supporting the interpretation that higher yield is driven primarily by heavier curds.

Fig. 6.

Spearman rank correlation heatmaps (A= Year 1 & B= Year 2) showing relationships among plant height (PH, cm), root length (RL, cm), leaf number (LN, no. plant⁻¹), leaf length (LL, cm), leaf width (LB, cm), SPAD value (SPAD, unitless), curd length (CL, cm), curd diameter (CD, cm), individual curd weight (ICW, g), fresh curd yield (FCY, t ha⁻¹), curd dry matter yield (CDMY, kg ha⁻¹), leaf dry matter yield (LDMY kg ha⁻¹), ( total soluble solids (TSS, °Brix), vitamin C (VC, mg 100 g⁻¹), curd firmness (CF, kgf), titratable acidity (TC, %), total N uptake (TNU, kg ha⁻¹), total P uptake (TPU, kg ha⁻¹), total K uptake (TKU, kg ha⁻¹), total S uptake (TSU, kg ha⁻¹), total Zn uptake (TZU, kg ha⁻¹), and total B uptake (TBU, kg ha⁻¹)

The uptake levels of N, P, K, S, Zn, and B were strongly inter-correlated, suggesting that treatments considered to increase nutrient acquisition tend to promote the simultaneous uptake of multiple elements. Moreover, fresh curd yield and curd dry matter yield were strongly positively correlated with nutrient uptake traits, including total B uptake, supporting the mechanistic link between improved nutrient acquisition and productivity. Conversely, titratable acidity was negatively associated with several growth, yield, and uptake traits, as well as vitamin C content, indicating that higher acidity is characteristic of lower-performing trait profiles. Overall, this correlation structure aligns with the PCA results, which demonstrated that growth, yield, and nutrient uptake traits converge in the same direction across treatments (Fig. 6).

Profitability analysis

As shown in Fig. 7(a–b), foliar supplementation with both conventional boron (B) and B nanofertilizers markedly increased the gross returns, gross margins, and benefit‒cost ratios (BCRs) of cauliflower production. Among the evaluated treatments, T₃ (200 ppm B nanofertilizer) resulted in the most substantial economic gains, with a gross return of US$ 9124 ha⁻¹ and a gross margin of US$ 6919 ha⁻¹. Furthermore, T₃ achieved a peak BCR of 4.14, establishing it as the optimal treatment for maximizing the economic viability of cauliflower cultivation (Figs. 7 (a-b)).

Fig. 7.

Effects of boron and nanoboron fertilizer on the (a) total variable cost (TVC), gross return, gross margin and (b) benefit cost ratio (BCR) of cauliflower. The error bars represent the ± standard error of the mean (n = 3). The mean values indicated by the different letters in the bars are significantly different at the 5% level according to the LSD test. T₁: (control or B₀), T₂: (nanoboron fertilizer at 100 ppm), T₃: (nanoboron fertilizer at 200 ppm), T₄: (nanoboron fertilizer at 300 ppm) and T₅: (conventional boric acid @ 1 g/L)

Discussion

Cauliflower production is commonly hampered by macronutrient and micronutrient (especially B) deficiencies across many agricultural regions worldwide [14, 16, 49]. Among these, boron deficiency is highly prevalent and often co-occurs with bellow soil levels of N, P, and K [14]. While N, P, and K are critical for vegetative growth, photosynthesis, flowering, and overall plant defence capabilities, B is uniquely essential for maintaining cell wall structural integrity, crosslinking polysaccharides and regulating carbohydrate metabolism [14, 50]. Consequently, B deficiency severely disrupts curd formation and development, causing physiological disorders and yield reductions that compromise marketability [49–50]. Our experimental site exhibited deficiencies in organic matter, nitrogen, available potassium, zinc and boron. Hence, this study evaluates the comparative efficacy of traditional foliar B (applied as boric acid) and boron nanoparticles (BNPs), focusing on their respective physiological and biochemical mechanisms.

Effect of B and B nanofertilizer on the growth traits of cauliflower

Foliar application of nanoboron fertilizer, combined with standard N, P, and K fertilization, significantly enhances the growth parameters of cauliflower. This stimulation is likely driven by the critical role of boron in meristematic tissue activity and the regulation of carbohydrate metabolism [16, 51]. In this study, the maximum plant height and root length were achieved with the foliar application of 200 ppm boron nanofertilizer (T₃). This superior performance can be attributed to the specific role of nanoboron in cell wall biosynthesis, mitotic division and cellular elongation, which collectively establish the physiological framework necessary for healthy plant development [12, 14, 52]. Compared to both the control and traditional treatments, the T₃ group demonstrated a substantial boost in vegetative growth. Specifically, the leaf count per plant increased by 46% relative to the control and by 7.88% compared to the conventional foliar B treatment, aligning with the findings of Franco-Lagos et al. [52].

In our study, foliar application of BNPs significantly enhanced leaf size (length and width). The leaf length in the T₃ treatment was 28.8% and 6.93% greater than in the control and conventional treatments, respectively. A similar trend was observed for leaf width, which increased by 28.6% over the control and 6.20% over the conventional treatments. These improvements in leaf size suggest that nanoboron fertilizer facilitate more vigorous vegetative growth and development [53]. Several researchers were reported that among micronutrients, nanoboron fertilizer plays a key role in the physiological progress of plants [54]. It serves as a fundamental constituent of the cell wall matrix, confirming structural consistency through the cross-linking of pectins [55]. Beyond its structural effectiveness, boron is indirectly involved in carbohydrate splitting, increasing the photosynthetic rate, and stimulating the meristematic activity responsible for leaf spread [54]. Consequently, nanoboron application promotes significant foliar expansion, leading to increased leaf elongation and expanded laminar width [52, 55]. The application of Nano-B fertilizer at 200 ppm (T₃) significantly increased the SPAD value in cauliflower. This improvement in leaf chlorophyll content is likely associated with the stimulation of photosynthetic activity caused by the Nano-B fertilizer. Compared to the control and conventional boron applications, Nano-B increased the SPAD value by 19.9% and 6.76%, respectively. Acharya et al. [51] and Ahmed et al. [19] reported that nanoparticles hold a high surface-area-to-volume ratio and a tiny particle size (1–100 nm). Subsequently, these nanoparticles penetrate the leaf cuticle and stomatal openings more efficiently than bulk fertilizers. This enhanced penetration results in a higher internal concentration of available boron for plant metabolic processes [51]. Nano-B serves as a cofactor or activator for key enzymes within the Calvin cycle while simultaneously facilitating sugar transport and pectin synthesis [55]. Maintaining the structural integrity of the cell wall, often referred to as the cellular “skeleton” boron indirectly prevents chlorophyll degradation and safeguards the photosynthetic apparatus against oxidative stress [12].

Effect of B and B nanofertilizer on yield traits and yield of cauliflower

Foliar application of conventional B and nano-boron fertilizers, combined with standard doses of N, P, and K fertilizers, significantly enhanced the yield parameters of cauliflower, including curd length, diameter, and both fresh and dry weight. In this study, the application of 200 ppm nano-B fertilizer (T₃) achieved the highest curd lengths, which were 31.8% higher than the control and 15.7% greater than conventional B application. Similarly, the T₃ treatment produced the maximum curd diameter and weight, exceeding the control by 23.1% and 55.3%, respectively. Moreover, T₃ outperformed conventional B application by 5.35% in diameter and 20.4% in individual curd weight. These findings align with those of Behera et al. [4], who suggested that nano-B fertilizers increase curd dimensions by improving reproductive development particularly pollen tube elongation and stimulating the bio-metabolite functions that drive cellular enlargement [54, 56]. Nano-boron acts as a catalyst for numerous biometabolites, increasing the activity of enzymes involved in the antioxidant system and nitrogen metabolism. By reducing oxidative stress, plants can allocate more metabolic energy toward building curd biomass rather than stress defence mechanisms [54]. Consequently, the T₃ treatment produced the highest fresh curd yield, outperforming the control by 69.6% and conventional B applications by 23.3%. A similar positive trend was observed for dry curd and dry leaf yields, confirming that nano-boron fertilizers are more effective than traditional boron sources [57]. This increase in cauliflower yield is largely attributed to the vital role of boron in accelerating the translocation of carbohydrates, nutrients, and sugars from the leaves to the developing reproductive curd, as supported by Kumar et al. [8] and Poudel et al. [58].

Effect of B and B nanofertilizer on the quality attributes of cauliflower

Foliar application of boron and nanoboron fertilizer significantly changed the quality attributes of cauliflower, including curd firmness, amount of vitamin C (ascorbic acid), titratable acidity, and protein content. In our study, the 200 ppm nanoboron treatment (T₃) resulted in the highest curd firmness and maximum protein content. Additionally, the maximum accumulation of vitamin C occurred in the 200ppm boron nanoparticle treatment group. While the results for titratable acidity were slightly inconsistent across treatments, the maximum value (0.321%) was obtained with 300 ppm nanoboron application (T₄). The superiority of nanoboron over conventional B sources at lower doses is driven by its ability to enhance plant physiological and biochemical processes. A key mechanism involves strengthening the cell wall by cross-linking rhamnogalacturonan II (RG-II) molecules [59]. The high surface-area-to-volume ratio of the nanoboron allows superior penetration through the leaf cuticle and stomata. This ensures efficient delivery to the growing meristems of the cauliflower, resulting in denser cell packing and increased curd firmness [60]. Boron influences the pentose phosphate pathway and the flow of sugar metabolism. Moreover, vitamin C (ascorbic acid) is synthesized from glucose, and increased availability of boron facilitates the production of the necessary enzymatic precursors [18]. Moreover, boron is vital for uracil synthesis; by maintaining RNA integrity, it indirectly promotes protein production [61]. In our study, the 200 ppm dose (T₃) emerged as the optimal concentration. At higher levels, boron can become toxic, potentially inhibiting the enzymes responsible for nitrogen metabolism [15]. The increase in the titratable acidity observed with higher nanoboron concentrations (T₄) likely reflects an accumulation of organic acids such as citrate and malate. Boron plays a significant role in the translocation of sugars [17]; at relatively high B levels, plants may divert carbon skeletons toward organic acid pathways to maintain ionic homeostasis and, as a result, increase metabolic activity within the curd [15].

Effect of B and nanoboron fertilizer on nutrient accumulation and uptake by cauliflower

Foliar application of conventional and nano-boron (nB) fertilizers, combined with N, P, K and S fertilization, significantly modulates the uptake and accumulation of essential macro- and micronutrients in cauliflower. The 200ppm nano-boron treatment (T₃) resulted in the highest accumulation of N and P, outperforming both the control and conventional boron sources. Enhanced N uptake in T₃ treated plants is attributed to the synergistic role of nano-boron in chlorophyll biosynthesis and protein metabolism, which drives a stronger metabolic sink for nitrogen [62]. The superiority of nB at 200 ppm over conventional B fertilizers is driven by several physiological pathways. Nano-B fertilizers penetrate the leaf cuticle more efficiently than bulk fertilizers. Once absorbed, B activates plasma membrane H⁺-ATPase enzymes, creating an electrochemical gradient that drives the active transport of other ions, such as K⁺ and NO₃^- [63]. Furthermore, this study revealed a significant increase in P uptake. Boron directly influences phosphorylation, where an improved B status increases ATP synthesis and sugar translocation [64]. Plants with higher metabolic energy (ATP) can dedicate more resources to root exudation and active transport mechanisms, thereby enhancing the scavenging and uptake of P from the rhizosphere [65]. Foliar application of nB at 200 ppm (T₃) also maximized the accumulation and total uptake of K and S in cauliflower. Compared to conventional boron sources, this treatment facilitates a more efficient ionic balance, resulting in superior nutrient utilization efficiency. The increased K and S concentrations suggest that nano-boron at an optimal concentration of 200 ppm acts as a metabolic trigger, enhancing root-to-shoot translocation. This view is supported by the observations of Davarpanah et al. [66]. Moreover, nano-B treatment helps cells maintain turgor and structural integrity, which allows for continuous K⁺ accumulation [67]. Sulfur is vital for synthesizing S-containing amino acids like methionine and cysteine, which are essential for building the structural proteins of the cauliflower curd [68]. Boron facilitates the synthesis of uracil, a precursor to RNA; this upregulated RNA activity stimulates protein synthesis, increasing the plant physiological demand for sulfur [68]. Moreover, boron stabilizes cell walls by forming borate-ester cross-links [64]. These structural enhancements maintain xylem integrity, ensuring the efficient long-distance transport of sulfate ions (SO₄^2-). The T₃ treatment outperforms conventional fertilizers because nano-B particles avoid the leaf cuticle via stomatal pathways more effectively. This targeted cellular delivery regulates the transporters responsible for K and S uptake [64, 66]. Foliar application of 200 ppm nano-B significantly accelerates the absorptions and total uptake of Zn and B in cauliflower. This synergistic uptake is driven by the unique physicochemical properties of nanoparticles, which facilitate superior penetration through leaf stomata and cuticles compared to conventional bulk fertilizers [12, 62]. Furthermore, nano-B modulates plasma membrane permeability, creating a priming effect that facilitates the cotransport and influx of Zn²⁺ ions [62]. As smart delivery systems, nano-fertilizers release nutrients gradually, preventing the rapid fixation and leaching typical of bulk fertilizers [19]. Subsequently, nano-boron ensures a steady supply of both B and Zn during critical growth stages of the cauliflower curd. Because boron is essential for cell wall synthesis and pollen tube elongation, delivering it in a highly bioavailable form increases the plant metabolic sink strength [64]. This naturally draws additional micronutrients, such as Zn, into developing tissues to support rapid cellular expansion [69].

Effect of B and B nanofertilizer on the boron use efficiency of cauliflower

Foliar application of both conventional and nano-boron (nB) fertilizers, in combination with N, P and K utilization, significantly increases boron use efficiency (BUE) in cauliflower. Particularly, application of 200 ppm nano-boron (T₃) results in the highest agronomic efficiency (AE) and apparent recovery efficiency (ARE), whereas physiological efficiency (PE) peaks at a lower concentration (T₂). Compared to nano-boron with conventional boron application, where conventional boron application results in drastically lower AE and ARE. These findings suggest that medium-low doses of nano-boron (200 ppm) optimize cell membrane integrity and root proliferation, thereby indirectly boosting nutrient uptake efficiency more effectively than conventional boron sources or higher nano-boron doses [70]. The higher efficiency of nB at 200 ppm over conventional boric acid is driven by several physiological and physicochemical mechanisms. Unlike conventional boric acid, nano-B fertilizer possesses a significantly higher surface area and a smaller particle size (generally < 100 nm), allowing them to avoid the size exclusion limits of the leaf cuticle and stomatal pores [71–72]. While conventional B fertilizers often suffer from high surface tension and crystallization on the leaf surface leading to poor absorption [73], nano-boron enters the plant via the hydrophilic pathway (cuticular pores) and endocytosis, ensuring a steady, controlled internal release of B ions [72]. On the other hand, the decline in BUE (AE and ARE) at higher nano-boron concentrations (T₄) highlights the narrow threshold between boron deficiency and toxicity, a phenomenon corroborated by Abou Seeda et al. [73]. At 200 ppm, Nano-B operates within the hormetic zone to stimulate growth, whereas higher doses (300 ppm) likely saturate metabolic pathways, diminishing nutrient utilization [70]. Mechanistically, boron acts synergistically with N, P and K to synthesize rhamnogalacturonan II (RG-II), a pectin component critical for cell wall cross-linking [73–59]. This metabolic shift promotes root elongation and lateral root development, enhancing the plant’s capacity to hunt for soil nutrients and ultimately improving its apparent recovery efficiency [72].

PCA, correlation and profitability of cauliflower

Principal component analysis (PCA) revealed a high degree of trait coordination, with the first principal axis (PC1) accounting for 81.0% of the total dataset variability. This dominance indicates that nanoboron application does not force a physiological trade-off between yield and quality; rather, it promotes holistic improvement across all measured parameters [74].The tight clustering and positive orientation of the vectors for SPAD (1), total B uptake (8) and fresh curd yield (2) suggest that nanoboron enhances chlorophyll density and photosynthetic efficiency. This relationship directly supports more effective biomass partitioning into the curd, thereby driving higher yields [70]. In particular, T₃ (200 ppm Nano B) occupied the most extreme positive position on PC1, significantly outperforming the traditional boric acid treatment (T₅). This physiological advantage is attributed to the high surface-area-to-volume ratio of nanoparticles, which facilitates superior cuticular penetration and stomatal uptake compared with those of bulk-scale fertilizers [66, 73]. The observation that T₄ (300 ppm) demonstrated overlapping confidence ellipses with T₃ and even a slight regression suggests a hormetic effect. In this context, 200 ppm serves as the biological optimum; beyond this threshold, metabolic saturation and developing toxicity occur, leading to a decline in efficiency [70]. Furthermore, the concentric overlap of Year 1 and Year 2 ellipses demonstrates that the effectiveness of the 200 ppm nanofertilizer is highly stable and strongly related to seasonal environmental fluctuations. This suggests that it is strongly recommended for sustainable cauliflower production [75].

On the other hand, PC2 accounted for only 8.23% of the total variation, primarily capturing secondary shifts in specific quality parameters. The vertical orientation of vectors such as total soluble solids (TSS), curd diameter, and curd firmness indicates that they vary independently of primary yield-contributing factors. This variation likely reflects differences in carbohydrate partitioning and cell wall lignification under diverse boron application rates. On the other hand, vegetative growth traits including plant height, root length and SPAD values show strong co-dependence, indicating concurrent improvement. Ultimately, yield development is directly driven by curd size, with individual curd weight serving as the primary determinant for both fresh and dry matter yields [76]. Nutrient uptake patterns were similarly intertwined, demonstrating that effective treatments comprehensively enhance the plant’s capacity for multi-nutrient acquisition. Specifically, the strong link between total nutrient uptakes particularly boron uptake and curd yield highlights the vital role of balanced nutrition in maximizing productivity. In contrast, titratable acidity was negatively correlated with both yield and vitamin C content, marking it as a reliable indicator of diminished performance.

From an economic point of view, the T₃ treatment (200 ppm B nanofertilizer) appeared to be the most viable intervention. The benefit‒cost ratio for this treatment was 61.7% higher than that for the control and represented a 21.1% increase over the conventional boron application. This enhanced profitability is likely attributable to the superior bioavailability and targeted delivery of nano-formulated nutrients, which significantly minimize nutrient waste compared to conventional bulk fertilizers. Our findings regarding improved nutrient use efficiency (NUE) align with results reported by Gayathri et al. [10] and Kumar et al. [77], who similarly demonstrated that nano-interventions optimize resource allocation and maximize crop returns.

Conclusions

The foliar application of 200 ppm nano-boron fertilizer significantly outperformed both the control and conventional boron treatments, leading to distinct improvements in cauliflower growth parameters, curd size, weight, yield, and quality attributes. This treatment also resulted in the highest boron content, maximum total boron uptake, a superior benefit-cost ratio, and the highest boron use efficiency. These results demonstrate that a foliar application of 200 ppm nano-boron is a highly effective and efficient alternative to traditional boron fertilizers. By improving crop productivity in boron-deficient soils, this technology enhances environmental sustainability through reduced nutrient waste and minimized chemical runoff. However, further multi-location trials are essential to standardize the optimum dosage and ensure cost-effectiveness across varied agroclimatic conditions.

Abbreviations

ABR

Apparent boron recovery efficiency

AEB

Agronomic efficiency of boron

ANOVA

Analysis of variance

B

Boron

BARI

Bangladesh Agricultural Research Institute

BCR

Benefit‒cost ratio

B-NPs

Boron nanoparticles

BUE

Boron use efficiency

CV(%)

Coefficient of variation

DAT

Days after transplanting

EC

Electrical conductivity

LSD

Least significant difference

OC

Organic carbon

PCA

Principal component analysis

PEB

Physiological efficiency of boron

TSS

Total soluble solids

TVC

Total variable cost

Authors’ contributions

M.A.Q., K.K.S., and A.H. conceived the study. Data analysis and software execution were carried out by M.A.Q., M.K., M.T.I., K.K.S., S.M., A.G., H.Z., A.H. and R.A. The methodology was designed by M.A.Q., M.S.A., M.T.I., N.A.S., and A.H. were responsible for visualization and validation. M.A.Q. and K.K.S. drafted the initial manuscript; M.A.Q., K.K.S., S.M., A.G., H.Z., A.H. and M.K. performed the subsequent revisions; Funding: A.G., H.Z., A.H. Experimental supervision was accomplished by M.A.Q., R.A., A.G., H.Z., A.H. and K.K.S. All the authors read and endorsed the submission.

Funding

All funding and arrangements were provided through institutional directives and internal allocations. This study was also funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2026R951), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study does not involve human participants or animal experiments. The plant material cauliflower (Hybrid Shiragiku F1) was used in this study which was obtained from obtained from a local entrepreneur in the Gazipur district, Bangladesh and at the Soil and Water Management Section, Horticulture Research Centre, Bangladesh Agricultural Research Institute (BARI), during the winter seasons of 2023-24 and 2024-25. No specific permissions or ethical approvals were required for the collection and use of this plant material, as it is not an endangered or protected species.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.