Integrated Nutrient Management as a Low Cost and Eco-Friendly Strategy for Sustainable Fruit Production in Apricot (Prunus armeniaca L.)

ABSTRACT

Prolonged and excessive use of chemical fertilizers has resulted in serious harm to soil health and ecosystems. This study aimed to reduce the cultivation costs for apricot trees, nearly 1/3^rd of which are spent on fertilizers. The research was conducted on fully grown apricot trees of the cultivar “New Castle,” in the Solan district of Himachal Pradesh, India. The experiment consisted of fourteen treatment combinations evaluated in triplicate and statistically analyzed using a randomized block design (RBD). Results revealed that treatment T₁₂ [50% Nitrogen (Calcium Nitrate) + 50% Nitrogen (Urea) + Azotobacter + Phosphate Solubilizing Bacteria + Vermicompost] resulted in the highest percent increase in tree trunk girth (6.82%), highest leaf chlorophyll content (3.00 mg g⁻¹ fresh weight), leaf area (58.29 cm), fruit set (61.00%) and total yield (61.9 kg tree⁻¹). In terms of nutrient status, T₁₂ had the highest leaf N (2.95%), leaf K (2.60%), soil N (386.33 kg ha⁻¹), soil P (51.00 kg ha⁻¹) and soil organic carbon (1.81%). The highest net return and profit over recommended dose of fertilizers (RDF) was also recorded in treatment T₁₂. The results of this study show that judicious fertilizer use along with integrated organic manure and bio-fertilizers can reduce cultivation costs, improve soil health, and increase fruit production with minimum ecosystem damage.

KEYWORDS:

• Integrated nutrient management
• apricot
• low-cost
• Azotobacter
• phosphate solubilizing bacteria
• vermicompost
• eco-friendly

Introduction

Apricot (Prunus armeniaca L.), a diploid species originating in China (Ham, 2009), is among the most popular temperate stone fruits (Faust et al., 1998; Layne et al., 1996; Mohit Verma et al., 2022). The plant is a 2–10 m hardy tree which can withstand cold temperatures as low as −35°C (Kumar et al., 2009), while some cultivars can withstand warm temperatures up to 37°C (Kumar et al., 2009; Moustafa and Cross, 2019). Its fruits are extremely versatile (Erdogan-Orhan and Kartal, 2011), as they can be used fresh, dried, canned, and made into jam and juice, or for ornamental purposes (Ham, 2009). The fruits are high in sugars, vitamins, dietary fiber, minerals, phytochemicals and pantothenic acid (Khasawneh et al., 2022; Leccese et al., 2010; Roussos et al., 2023). Apricot is also used as medicinal plant, a status attributed to the prevalence of secondary metabolites like carotenoids, phenolics, flavonoids and o-diphenols (Ozsahin and Yilmaz, 2010; Roussos et al., 2023). Some cultivars’ seeds are edible and taste like almonds, while others’ seeds are used to extract oil (Faust et al., 1998). “New Castle”, a commercially accepted apricot cultivar, is an excellent source of income for orchardists in the mid-hill regions of Himachal Pradesh, India, since it commands high market prices for both table and processing purposes.

The application of plant mineral nutrients is a major factor influencing plant growth and development, fruit quality and production (Ahmad and Anjum, 2023). The availability of limited water resources and consistently rising fertilizer costs make nutrient-efficient plants crucial for increasing crop yield, and to address globally rising environmental concerns (Baligar et al., 2001; Srivastava et al., 2021). Fruit quality, productivity, soil and environmental health have become primary concern for research in recent years, necessitating a balance between enhanced production and environmental sustainability (Aulakh and Grant, 2008). Despite the fact that due to higher global market demand, apricot cultivation has grown rapidly during the last decade (Cricca, 2010; Pergola et al., 2017), productivity remains low (Cricca, 2010). Imbalanced nutrient implementation and poor soil health are the primary causes of low productivity in Indian fruit orchards (HebbaraI et al., 2011; Meena et al., 2019; Savita et al., 2013; Somasundaram et al., 2011). Maintaining equilibrium among crop nutritional needs and soil nutrient reserves is critical to ensuring sustainable fruit production and preventing environmental contamination (Mohit Verma et al., 2022). On the other hand, continuous and excessive application of chemical fertilizer has an adverse effect on beneficial microorganisms, soil fertility and nutrient use efficiency (Reddy and Reddy, 2016).

Fertilizers are a major input in the twenty-first century, accounting for nearly one-third of cultivation costs. Inorganic fertilizers are among the most expensive inputs (Reddy and Reddy, 2016), however plants use only 30–50% of total applied nitrogen fertilizers and 10–45% of total applied phosphorus fertilizers, while 60–90% of applied fertilizer is lost to the environment (Adesemoye and Kloepper, 2009; Adesemoye et al., 2008). These losses have a significant impact on fertilizer use efficiency and pollution, particularly in emerging and developing countries (Shah and Wu, 2019; Zhang et al., 2013). Excessive use of chemical fertilizers is not only concerning economically, but it also has ecological and fruit quality consequences (Aspel et al., 2022). Excessive use of chemical fertilizers causes pollution in soil, ground waters and surface water via leaching and water runoff, affecting both biotic and abiotic function of soil, crop quality, and the health of humans as well as animals (Keesstra et al., 2018). Furthermore, leaching or volatilization in dry conditions increases carbon emissions which harm the environment and ecosystems (Khasawneh et al., 2022).

Organic manures and bio-fertilizers are plant nutrients which are environmentally safe and renewable in nature, and improve soil fertility, structure, water retention capacity and the population of microbes in the soil (Mohit Verma et al., 2022). Hence, they improve crop yield and quality (Mohit Verma et al., 2022; Zink and Allen, 1998). By benefiting both plants as well as environment, biofertilizers play a vital role in the Integrated Nutrient Management (INM) system, maintain agricultural productivity, and reduce environmental damage (Adesemoye and Kloepper, 2009; Adesemoye et al., 2009; Malusa and Sas, 2009; Malusà et al., 2016). The use of beneficial microbes (Nitrogen-fixing, P-solubilizing and P-mobilizing etc.) that are highly compatible with mineral inputs has positive influence on both crops and the environment (Bargaz et al., 2018). Vermicompost, as a rich supply of nutritional components, improves soil physicochemical qualities, microbial activity, and plant growth regulatory compounds (Anitha and Prema, 2003). Integrated nutrient management determines long-term sustainable productivity levels as well as immediate nutrient availability in the soil.

According to the United Nations Climate Technology Centre and Network (UNCTCN) “Integrated Nutrient Management refers to the maintenance of soil fertility and of plant nutrient supply at an optimum level for sustaining the desired productivity through optimization of the benefits from all possible sources of organic, inorganic and biological components in an integrated manner” (United Nations Climate Technology Centre and Network, 2023). The judicious use of manures and fertilizers in plants is the key to mineral nutrition. The price of chemical fertilizers is increasing day by day and farmers have limited purchasing capacity (Kumar et al., 2019). By providing macro and micro nutrients utilizing inorganic, organic manures, and bio-fertilizers in an integrated manner to maximize crop yield and economic return to the farmer, INM is the most effective and affordable method of fertilization (Ghosh, 2000; Kumar et al., 2019). Calcium Nitrate (CN) is substantially more expensive than Calcium Ammonium Nitrate (CAN) (Kumar et al., 2019), and due to the scarcity of CAN in some areas, the majority of the farmers are relying on CN as a source of nitrogenous fertilizer (Kumar et al., 2019). During the current study, efforts were made to combine cheaper sources of N with CN to maximize crop productivity as well as economic returns. The objectives of the current research were to study the costs and effects of integrated nutrient sources on vegetative, fruiting traits and nutritional status of soils and trees in an established apricot orchard.

Materials and Methods

Experimental Site, Design and Treatments

The current research was done in a 20-year old Orchard of “New Castle” apricot trees raised on wild apricot (Chulli) root stock (Kumar et al., 2019; Mohit Verma et al., 2022), spaced 5 m between rows and 5 m within rows at the Horticultural Research and Training Station and Krishi Vigyan Kendra (HRTS & KVK), Kandaghat, Solan, Himachal Pradesh, India. The research farm was located at latitude 30.9541408 °N and longitude 77.122449 °E (Figure 1), with yearly rainfall of 125–135 cm and altitude of 1325 m (Kumar et al., 2019). This location represents the agro-climatic zone III of Himachal Pradesh. Table 1 lists the physicochemical parameters of the soil, recorded prior to the start of the research. The trial included fourteen treatment combinations, with each treatment replicated thrice in randomized block design (RBD) including one tree per experimental unit (42 trees total). Table 2 provides details on the treatment combinations employed in the current research.

Figure 1. The experimental apricot orchard under the INM system and its geographical location.

Table 1. Physico-chemical traits of research orchard soil in the Solan district of Himachal Pradesh, India prior to the start of study during 2015.

Particulars	Content
pH	6.98
EC	0.19 dSm^−1
Organic carbon	1.43%
Available Nitrogen	372.55 kg/ha
Available Phosphorus	38.25 kg/ha
Available Potash	426.40 kg/ha

Table 2. Details of treatment combinations used in the present study.

Treatment Code	Treatment Combinations
T1	RDF (Recommended dose of fertilizers)
T2	Jeevamrut (3 applications at one month interval)
T3	FYM + Azotobacter + PSB
T4	Vermicompost + Azotobacter + PSB
T5	100% N (CN) + Azotobacter + PSB + FYM
T6	75% N (CN) + 25% N (Urea) + Azotobacter + PSB + FYM
T7	50% N (CN) + 50% N (Urea) + Azotobacter + PSB + FYM
T8	25% N (CN) + 75% N (Urea) + Azotobacter + PSB + FYM
T9	100% N (Urea) + Azotobacter + PSB + FYM
T10	100% N (CN) + Azotobacter + PSB + Vermicompost
T11	75% N (CN) + 25% N (Urea) + Azotobacter + PSB + Vermicompost
T12	50% N (CN) + 50% N (Urea) + Azotobacter + PSB + Vermicompost
T13	25% N (CN) + 75% N (Urea) + Azotobacter + PSB + Vermicompost
T14	100% N (Urea) + Azotobacter + PSB + Vermicompost

*RDF for apricots is nitrogen (0.50 kg per tree), P₂O₅ (0.25 kg per tree), K₂O (0.70 kg per tree) and FYM (40 Kg per tree); 3 applications (1 L per plant) of Jeevamrut; Azotobacter (0.025 kg per tree); PSB (0.02 kg per tree); Vermicompost (15 Kg per tree); SSP (1.56 Kg per tree); MOP (1.17 Kg per tree); Two split doses of Nitrogen Based on treatments through urea and calcium nitrate (CN); 800 g lime per 1kg of urea used.

**Recommended Dose of Fertilizers: RDF; Farm Yard Manure: FYM; Calcium nitrate: CN; Single Super Phosphate: SSP; Muriate of Potash: MoP and Phosphate Solubilizing Bacteria: PSB.

Procurement and Application of Nutrient Sources

Urea, Calcium nitrate (CN), Single Super Phosphate (SSP), Muriate of Potash (MoP), Azotobacter and Phosphate Solubilizing Bacteria (PSB), Farm Yard Manure (FYM) and Vermicompost were acquired from the market of Solan, Himachal Pradesh in the month of November. For the preparation of Jeevamrut at the research farm, 10 kg cow dung and 10 liters of cow urine were mixed in a plastic drum, then 2 kg old jaggery, 2 kg gram flour and 1 kg live soil was added and mixed. The mixture in the drum was then allowed to ferment while stirred regularly for 7 days. Prepared Jeevamrut was diluted ten times with water before drenching the basin soil. A total of 3 applications (1 L per plant) of Jeevamrut were done, 1^st at full bloom and after that 2 more at one month intervals. The manures and fertilizers were widely broadcasted and thoroughly mixed with the soil of the tree basin, 30 cm outward from the plant trunk (Figure 1). The recommendation of fertilizers for apricots is nitrogen [500 g per tree (200 kg ha⁻¹)], P₂O₅ [250 g per tree (100 kg ha⁻¹)], K₂O [700 g per tree (280 kg ha⁻¹)] and FYM [40 Kg per tree (16000 kg ha⁻¹)]. However, Azotobacter [25 g per tree (10 kg ha⁻¹)] and PSB [20 g per tree (8 kg ha⁻¹)] were combined with FYM [40 kg per tree (16000 kg ha⁻¹)] and Vermicompost [15 kg per tree (6000 kg ha⁻¹)]. The required amount of SSP (1.56 kg per tree) and MOP (1.17 kg per tree) was applied at the end of December, along with farm yard manure (40 kg per tree) or vermicompost (15 kg per tree). Based on treatments, two split doses of Nitrogen were applied, through urea and calcium nitrate (CN) (Table 2). The half dose was applied around two weeks prior to flowering, and one month after that, the remaining dose was given. However, for every 1 kg of urea, 800 g of lime was applied to the soil.

Vegetative and Fruiting Parameters

The vegetative growth traits such as tree height, spread, girth and volume were observed twice: first before the start of the growth period (December, 2015) and again at the end (December, 2016), and the results were presented in terms of percent (%) increase. Height of the tree was assessed from the bottom to the top using a graduated flag staff, and the spread of the tree was assessed in 2 directions, East to West and North to South. With the aid of a measuring tape, tree trunk girth was measured 15 cm above the graft union. In the month of December the length of ten shoots were randomly selected from current season growth and assessed with measuring tape, and average value was presented in centimeters (cm). Tree canopy volume was calculated through the formula suggested by Westwood (1978) and presented in m³. The leaf area was assessed by using a leaf area meter (LI-COR 3100; Biosciences, USA), and the average leaf area was presented in square centimeters. At 645 and 663 nm, the absorbance of leaf extract was examined on a Spectronic-20 D (NUKES, Canada) against a dimethyl sulfoxide (DMSO) blank, and the total chlorophyll content was determined using the formula:

$\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{C}\mathrm{h}\mathrm{l}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{l}\left(\mathrm{m}\mathrm{g}{\mathrm{g}}^{-1}\right)=\frac{20.2\mathrm{A}645+8.02\mathrm{A}663\times \mathrm{V}}{\mathrm{A}\times 1000\times \mathrm{W}}$

In terms of fruiting parameters, fruit set was computed in accordance with the process recommended by Westwood (1978), whereas at harvest, total retained fruits on the marked branches were counted and the percentage fruit drop was calculated. After harvesting, the fruits, total yield was calculated and expressed in kg tree⁻¹.

Nutritional Status of Leaf and Soil

Samples of leaves were obtained for digestion during the 1^st week of July to evaluate the plant’s leaf nutrient status, as in Kenworthy (1964). Total nitrogen was determined using the micro-kjeldhal’s procedure as in A. O. A. C (1975). Total P was estimated in accordance with the process given Jackson (1973). In contrast, potassium was estimated using an Atomic Absorption Spectrophotometer (NUKES, Canada) and presented as a % of dry weight. Samples of soil were drawn from 0–30 cm soil depth both before (December, 2015) and after (July, 2016) the trial to investigate the physico-chemical characteristics of the research orchard soil. The procedure described by Jackson (2005) was used to assess the pH and EC of soil in a 1:2 suspension of soil: water. The percentage of organic carbon was calculated using the process proposed by Walkley and Black (1934). The alkaline potassium permanganate method described by Subbiah and Asija (1956) was employed to compute the available nitrogen (N), presented in kg ha⁻¹. Using the method outlined by Olsen et al. (1954), the quantity of available phosphorus in soil was calculated and quantified at wavelength of 660 nm on a UV-Spectrophotometer (NUKES, Canada) and presented in kg ha⁻¹. In accordance with the instructions provided by Merwin and Peech (1951), available potassium was retrieved employing neutral normal ammonium acetate on a flame photometer (NUKES, Canada) and presented in kg ha⁻¹.

Statistical Analysis

All the research findings were presented as mean ± standard error. The statistical procedures implemented in R (R Studio, 2022.07.1) included a one way analysis of variance (ANOVA) at the 5% level of significance (Package used: stats). Furthermore, the Duncan Multiple Range Test (DMRT) i.e., Post Hoc analysis was applied to compare the means of various treatment combinations (Package used: agricolae). A box plot analysis was performed to assess traits, exhibiting the 25^th to 75^th percentile; center line, median; whiskers, comprehensive data range, i.e., lower limit, 1^st quartile (Q1), median, 3^rd quartile (Q3), upper limit, and interquartile range (IQR = Q3 - Q1, this contains the central 50% of the data). The coefficient of variation (CV) was computed to examine the differences within or between attributes. A Shapiro-Wilk normality test was also performed to evaluate the R², P and W values among different traits.

Economic Analysis

The economics on a per hectare basis was calculated for each treatment and total cultivation cost (fixed cost + variable cost + risk factor) for each treatment was calculated in Indian currency i.e. Rupees (Rs.) (Supplementary Table S1). The total yield was calculated for one hectare and then gross income was calculated by multiplying the total yield by 25, using Rs. 25 as the market price for one kg fruit. The net return was computed by subtracting the total cultivation costs from gross income. Profit over recommended dose of fertilizers (RDF) was calculated by subtracting the net income of RDF from the net income of a particular treatment. The benefit cost ratio was computed by dividing the net return by the total cultivation cost (Supplementary Table S1).

Results

Vegetative and Fruiting Parameters

The highest increase in tree height (31.73%), spread (34.22%), volume (38.84%) and maximum annual shoot extension growth (93.91 cm) were documented in treatment T₁₁, all of which were statistically comparable to the T₆, T₇, T₁₀, T₁₂ and T₁₃ treatments (Table 3). However, the treatment T₂ had minimal increases in tree height (20.03%), spread (20.04%), volume (21.51%) and minimal annual shoot extension growth (57.91 cm). In the cases of other traits, the highest increase in tree trunk girth (6.82%), maximum leaf area (58.29 cm²) and leaf chlorophyll content (3.00 mg g⁻¹ fresh weight) were documented in treatment T_12, which was statistically equivalent to T₈ and T₁₁ treatments and substantially higher than the rest (Figure 2). In contrast, the lowest increase in tree trunk trunk (4.10%), minimum leaf area (42.28 cm²) and chlorophyll content (2.61 mg g⁻¹ fresh weight) were recorded in treatment T_2, which was statistically equivalent with T₃ and T₄. In the contexts of fruiting traits, T₁₂ resulted in the highest fruit set (61%), lowest fruit drop (29.33%) and maximum yield (62.9 kg tree⁻¹; 25160 kg ha⁻¹) all of which were statistically equivalent to T₁₁ (Table 4). However, the lowest fruit set (45%), highest fruit drop (42.00%) and lowest yield (45.5 kg tree⁻¹ or 16,912 kg ha⁻¹) were observed with T₂, which were statistically equivalent with T₃ and T₄ (Figure 2).

Figure 2. Box plot analysis [mean (X) and 5% level of significance (α)] depicting the effect of integrated nutrient management on vegetative and fruiting characters of apricot cv. New castle illustrating the minimum, first quartile, median, third quartile and maximum values for comparison of different vegetative characters; A- increase in tree height (%); B- increase in tree trunk girth (%); C- annual shoot extension growth (cm); D- increase in tree spread (%); E- increase in tree volume (%); F- leaf area (cm²); G- leaf chlorophyll content (mg g⁻¹ fresh weight); H- fruit set (%), I- fruit drop (%), J- total yield (kg tree⁻¹). *Means with different letters are significantly different according to a Duncan’s multiple range test at p <.05.

Table 3. Effect of INM on vegetative characters of apricot.

Parameters	Increase in tree height (%)	Increase in tree trunk girth (%)	Annual shoot extension growth (cm)	Increase in tree spread (%)	Increase in tree volume (%)	Leaf area (cm^2)	Leaf chlorophyll content (mg g^−1 fresh weight)
Treatment	Mean (X)
T1	24.00^h	5.44^c	72.53^g	24.61^d	27.07^f	49.67^f	2.74^cd
T2	20.03^j	4.10^d	57.91^i	20.04^f	21.51^h	42.28^h	2.61^e
T3	21.36^i	4.28^d	59.35^hi	21.32^ef	22.69^gh	44.03^gh	2.64^de
T4	22.28^i	4.40^d	62.15^h	22.22^e	23.19^g	45.79^g	2.66^de
T5	24.48^gh	6.35^b	84.04^c	29.39^bc	29.76^e	52.35^de	2.78^c
T6	27.44^cd	6.49^b	77.61^ef	28.39^c	37.20^b	53.66^cde	2.81^c
T7	28.42^bc	6.29^b	88.33^b	33.41^a	35.27^c	55.38^bc	2.95^ab
T8	26.45^de	6.48^b	81.32^cde	30.53^b	30.38^e	54.70^bcd	2.80^c
T9	25.34^efg	6.40^b	78.18^def	28.18^c	31.05^e	53.34^cde	2.81^c
T10	25.98^ef	6.38^b	75.54^fg	25.34^d	34.63^c	51.71^ef	2.79^c
T11	31.73^a	6.57^ab	93.91^a	34.22^a	38.84^a	56.35^ab	2.98^a
T12	29.17^b	6.82^a	90.96^ab	30.51^b	36.95^b	58.29^a	3.00^a
T13	26.11^ef	6.41^b	76.31^fg	26.12^d	33.06^d	54.70^bcd	2.79^c
T14	25.08^fgh	6.38^b	82.10^cd	27.82^c	34.87^c	52.65^de	2.86^bc
CV	2.57	3.03	3.09	3.32	2.86	2.57	2.25

*Means with different letters are significantly different according to a Duncan’s multiple range test at p <.05.

**CV = Coefficient of variation.

Table 4. Effect of INM on fruiting characters and leaf nitrogen (N), phosphorus (P) and potash (K) content in apricot.

Parameters	Fruit set (%)	Fruit drop (%)	Total yield (kg tree^−1)	Leaf Nitrogen (%)	Leaf Phosphorus (%)	Leaf potassium (%)
Treatment	Mean (X)
T1	53.00^ef	33.67^e	52.10^f	2.38^e	0.27^e	2.45^bc
T2	45.00^g	42.00^a	45.50^h	2.22^f	0.20^h	2.28^d
T3	46.67^g	39.00^b	47.20^gh	2.25^ef	0.23^g	2.33^d
T4	47.33^g	38.67^b	48.10^g	2.29^ef	0.25^f	2.38^cd
T5	54.67^def	33.67^e	57.50^cde	2.53^d	0.29^c	2.48^abc
T6	55.00^de	34.33^de	57.80^cd	2.66^cd	0.30^d	2.53^ab
T7	59.67^ab	31.67^f	59.60^bc	2.93^a	0.31^a	2.57^ab
T8	58.67^abc	36.00^c	57.40^cd	2.94^a	0.28^d	2.49^abc
T9	57.00^cd	31.33^f	55.00^e	2.85^ab	0.29^c	2.46^bc
T10	52.33^f	35.00^cd	56.50^de	2.73^bc	0.29^c	2.51^ab
T11	57.00^cd	30.00^g	60.50^b	2.92^a	0.30^b	2.54^ab
T12	61.00^a	29.33^g	62.90^a	2.95^a	0.27^e	2.60^a
T13	54.33^ef	34.00^de	57.90^cd	2.59^d	0.28^d	2.48^abc
T14	57.67^bc	31.67^f	58.40^bcd	2.63^cd	0.28^d	2.49^abc
CV	2.52	1.92	2.32	2.84	1.68	2.87

*Means with different letters are significantly different according to a Duncan’s multiple range test at p <.05.

**CV = Coefficient of variation.

Nutritional Status of Plant and Soil

Maximum leaf N (2.95%) and K (2.60%) contents were documented with treatment T₁₂, which were statistically comparable to treatments T₇, T₈ and T₁₁ (Table 4). However, the highest content of leaf P (0.31%) was recorded in T₇ which was statistically equivalent to treatments T₁, T₅, T₆, T₈, T₉, T₁₀, T₁₁, T₁₂, T₁₃ and T₁₄. On the other hand, treatment T₂ had the lowest leaf N (2.22%), P (0.20%) and K (2.28%) content, which was statistically comparable to T₃ (Supplementary Figure s1). The maximum soil nitrogen (386.33 kg ha⁻¹), available P (51 kg ha⁻¹) and soil OC (1.81%) content were detected in T_12, while the minimum soil available N (335.00 kg ha⁻¹), available P (27.67 kg ha⁻¹) and OC (1.36%) content were detected in treatment T₂. The maximum available K (479.33 kg ha⁻¹) and soil pH (7.08) were observed in treatment T₁₀, which was statistically equivalent to T₈. The minimum soil pH (6.73) was observed jointly in T₂ and T₁₃, whereas the lowest available K (380.67 kg ha⁻¹) was recorded in T₂. In the case of EC, the highest value of EC (0.22) was under T₉ treatment which was statistically equivalent with T₁₀, T₁₁, T₁₂ and T₁₄ treatments. However, the minimum value of EC (0.13) was recorded in T₂ which was statistically equivalent with T₃ and T₄ (Table 5, Supplementary Figure s2).

Table 5. Effect of INM on soil available nitrogen (N), available phosphorus (P), available potash (K), soil pH, EC and organic carbon content of apricot field after the harvesting of crop.

Parameters	Soil available N(kg ha^−1)	Soil available P(kg ha^−1)	Soil available K(kg ha^−1)	Soil pH	Soil EC (dS m^−1)	Soil OC (%)
Treatment	Mean (X)
T1	360.60^bc	29.00^hi	425.00^f	6.80^a	0.16^g	1.41^gh
T2	335.00^d	27.67^i	380.67^h	6.73^a	0.13^j	1.36^h
T3	340.33^d	29.67^h	395.00^gh	6.77^a	0.14^i	1.48^efg
T4	343.67^d	32.00^g	405.33^g	6.83^a	0.15^h	1.53^def
T5	367.67^bc	41.33^e	471.67^ab	7.05^a	0.19^d	1.63^c
T6	370.67^abc	48.33^bcd	457.33^bcd	7.00^a	0.19^d	1.49^def
T7	379.00^ab	48.67^bc	468.00^abc	6.87^a	0.17^f	1.73^b
T8	376.00^abc	46.67^d	473.00^ab	6.80^a	0.19^d	1.56^d
T9	379.33^ab	42.33^e	443.33^de	6.80^a	0.22^a	1.54^de
T10	375.00^abc	47.67^cd	479.33^a	7.08^a	0.20^c	1.48^efg
T11	378.00^ab	49.67^ab	437.67^ef	6.77^a	0.21^b	1.73^b
T12	386.33^a	51.00^a	448.33^de	6.88^a	0.20^c	1.81^a
T13	380.00^ab	39.00^f	451.00^cde	6.73^a	0.18^e	1.49^def
T14	381.00^ab	43.00^e	440.00^def	6.82^a	0.20^c	1.46^fg
CV	2.30	2.62	2.28	2.68	2.33	2.60

*Means with different letters are significantly different according to a Duncan’s multiple range test at p <.05.

**CV = Coefficient of variation.

Economics of Different Treatment Combinations

The statistics on the economics of different treatments showed that the treatment T₁₀ had the highest expenditure or cultivation cost (Rs. 1,93,035 ha⁻¹), and T₂ had the lowest (Rs. 99793 ha⁻¹) (Figure 3, Supplementary Table S1). On the other hand, the treatment T₁₂ resulted in the highest gross income (Rs. 7,54,800 ha⁻¹), net returns (Rs. 5,82,794 ha⁻¹) and maximum profit (Rs. 2,37,000 ha⁻¹) over RDF, while the treatment T₂ produced the lowest gross income (Rs. 4,22,800 ha⁻¹), net returns (Rs. 3,23,007 ha⁻¹) and profit (Rs. ˗22,787 ha⁻¹) over RDF. However, for the production of apricot, the maximum benefit cost ratio (B:C ratio) (3.9) and minimum (1.9) were recorded with treatments T₉ and T₁ respectively.

Figure 3. Economic evaluation of different INM treatments in apricot cv. New castle.

Discussion

The results of this study demonstrated that using Calcium Nitrate and Urea (chemical fertilizers), Azotobacter and PSB (biofertilizers), Vermicompost, FYM and Jeevamrut in various combinations and in an integrated way, had a significant effect on vegetative and fruiting traits. The observed influences may be due to the variety of nitrogen sources used in the study. Urea releases NH₄⁺ during hydrolysis, and calcium nitrate (CN) releases nitrogen in the form of nitrate, which is more easily available over an extended period of time and may resulted in increased plant vegetative growth (Kumar et al., 2019; Mohit Verma et al., 2022). This increase in plant vegetative growth and fruit yield may be due to the uptake of more N, perhaps due to efficient absorption of N and translocation of metabolites (Mohit Verma et al., 2022; Saini et al., 2013). Organic manures such as vermicompost and FYM produce favorable soil conditions with increased availability of plant nutrients, and may be responsible for this increased plant vegetative growth (Kamatyanatti et al., 2019). Chlorophyll is a primary pigment used in photosynthesis and phosphorus fertilizers have an important role in photosynthesis (Bargaz et al., 2018). In the case of chlorophyll content in apricots under different treatment conditions, the use of biofertilizers such as PSB which solubilize fixed soil phosphorus and Azotobacter which not only fix nitrogen but also solubilize fixed soil phosphorus by altering microbial balance may be the key factors for increased chlorophyll content in this study. This may be due to the availability of maximum nutrients in the rhizosphere, which may be helpful in the production of photosynthates (Kamatyanatti et al., 2019). Similarly Chtouki et al. (2022) also observed an increased chlorophyll content index in chickpea by applying different phosphorus fertilizers (Poly-P and Ortho-P fertilizers) under appropriate soil moisture conditions.

The combined applications of inorganic and organic nutrient sources in the field maintains the continuous supply of nitrogen, as organic manure reduces losses and helps in more efficient utilization of the applied nitrogen for long periods of time, and serve as and alternative source of nutrients; this may lead to retention of fruitlets, and ultimately to increased fruit set, reduced fruit drop and increased yield (Dwivedi et al., 2016). Similarly, applying combined applications of inorganic and organic nutrient sources, leads to increased grain and fruit yield in Rice-wheat systems (Dwivedi et al., 2016), apple (Jeet et al., 2016) and apricot (Mohit Verma et al., 2022). The combined use of organic as well as chemical fertilizers may also impact the synthesis and translocation of metabolites eventually gathered toward fruit tissues (Meena et al., 2019; Palaniappan and Annadurai, 2000), resulting in higher fruit yield and productivity. An estimated 60–90% of total fertilizers supplied in the soil are simply lost in to the environment, causing ecosystem damage (Adesemoye and Kloepper, 2009; Adesemoye et al., 2008). Azotobacter and PSB are the most common bio fertilizers used in the INM system (Meena et al., 2019) to maintain agricultural productivity and reduce environmental damage (Adesemoye and Kloepper, 2009; Adesemoye et al., 2009; Malusa and Sas, 2009; Malusà et al., 2016). By transforming unavailable ambient N and binding phosphates into usable forms, biofertilizers improve plant growth, soil fertility, and thus crop yields (Jayanta, 2013; Meena et al., 2019; Reddy and Reddy, 2016).

Organic manures are environmentally friendly, having positive effects on plants (Improves availability of nutrients for plants, increases plant growth and productivity) and environment. FYM improves the physical, chemical, and biological fertility of soil by releasing nutrients gradually over long periods, resulting in a healthier environment for root development (Ayuso et al., 1996; Belay et al., 2001; Meena et al., 2019; Reddy and Reddy, 2016). Likewise, vermicompost contains a high concentration of enzymes that aid in the organic matter breakdown of plant roots (Jayanta, 2013; Meena et al., 2019) and improve plant growth regulating substances (Anitha and Prema, 2003). Similar observations have been reported by Chaupoo and Kumar (2022), who reported increased plant growth, yield and nutrient uptake in marigold by combining organic, inorganic and bio fertilizers. They observed the highest plant height after applying a combination of Azotobacter, vermicompost and 50% RDF. However, Azospirillum + Azotobacter + vermicompost + 50% RDF were associated with increased leaf area, flowering duration, number of flowers per plant, yield of flower, and yield of seed (Chaupoo and Kumar, 2022). Similar results of increased plant growth, fruit yield and available nutrients in soils were reported in apricot (Chauhan, 2008; Shah Mahmood et al., 2006; Sharma et al., 2011; Singh et al., 2012), plum (Thakur and Thakur, 2014), guava (Goswami et al., 2015), and peach (Narayan et al., 2016) through the combined applications of inorganic and organic nutrient sources along with bio-fertilizers in an integrated manner.

The present investigations revealed that the different INM treatments had a substantial influence on leaf and soil nutrient status. Exterior augmentation of different organic, inorganic as well as bio-fertilizers in various combinations, which greatly improved the buildup of accessible N, P, and K in the soil, could be responsible for the rise in available soil N, P, and K content. The increase in available soil N might be due to nitrification of NH₄⁺ions to NO₃⁻ ions and neutralization of the soil pH by lime application (Mohit Verma et al., 2022). Azotobacter fixes atmospheric nitrogen into the soil and similarly, PSB increases P solubilization in soil and make it available to the plants (Aseri et al., 2008; Meena et al., 2019). Neutral soils have a higher diversity of microbial populations (Fierer and Jackson, 2006; Malusà et al., 2016; Rousk et al., 2010). Organic amendments and biofertilizers lower soil pH while increasing soil organic carbon content (Berger et al., 2013; Liu et al., 2013; Srinivasarao et al., 2021) and reducing nutrient losses through leaching (Sreekala, 2015).

Favorable temperature and accumulation of organic matter through fertilizers (inorganic and organic) added in the soil may lead to increases in organic carbon (Mohit Verma et al., 2022; Thokchom et al., 2018). The present results are in accordance with previous findings of Blaise et al. (2007), who discovered that INM improved plant growth and yield in Asiatic cotton. Similarly, Chaupoo and Kumar (2022) found that applying Azotobacter + vermicompost + 50% RDF, increased phosphorus availability (42.56 kg ha⁻¹) in soil at harvest. However, Azospirillum + Azotobacter + vermicompost + 50% RDF were associated with increased N, P and K uptake. The current findings of increased nitrogen, phosphorus and potash uptake by the plants in this study also support previous observations by Verma and Rakesh (2010) in apple, Singh et al. (2010) in apricot, Sharma et al. (2011) in apricot, Marathe et al. (2012) in sweet orange and Singh et al. (2012) in apricot, who reported increased nutrient uptake through the combined applications of inorganic and organic nutrient sources along with bio-fertilizers in an integrated manner.

The current study revealed that different INM treatments had a significant impact on the cultivation costs of apricot. The key to lowering cultivation costs and increasing benefit-cost ratio is the integration of chemical fertilizers with cheaper sources of plant nutrition and the application of nitrogen fertilizers in split doses based on crop requirements (Reddy and Reddy, 2016). The present results are in accordance with the earlier findings of Dwivedi (2013), who observed a maximum net profit in guava by applying 500 g N: 200 g P: 500 g K + Zn (0.5%) + B (0.2%) + foliar spray of Mn (1%) in the month of August and October +10 cm thick organic mulch. However, INM reduced the use of chemical fertilizers by up to 50% while increasing yield and benefit-to-cost ratio (Chander et al., 2013). Similar outcomes were also found by Bajwa et al. (2003), Chatha and Chanana (2007), and Garai et al. (2014).

Conclusions

Prolonged and excessive application of chemical fertilizers has resulted in increased cultivation cost and serious harm to soil health as well as ecosystems. Therefore, the emphasis should be on more efficient, effective and sustainable utilization of inorganic, organic and biofertilizers for sustainable fruit production. This will not only reduce the cultivation or production costs, but will also improve soil health and lead to sustainable fruit production, thus improves economic status for farmers. The current study’s findings indicate that application of 50% Nitrogen (CN) + 50% Nitrogen (Urea) + Azotobacter + PSB + Vermicompost has more beneficial and economic effects compared to other INM treatments. Hence, this could be a low cost nutrient source combination for sustainable apricot production. Furthermore, Integrated Nutrient Management could be used as a low-cost and eco-friendly method for sustainable fruit production, providing the opportunity to minimize environmental concerns to a certain extent, if not entirely.

Author Contributions

AK and DDS conceived the research and planned the study; The research work was carried out by AK; DPS, BS, PV contributed to the morphological and biochemical work; US contributed to the plant and soil nutrition work; NSP, OAS and MM contributed to data and statistical analysis; AK and PV wrote the initial draft manuscript; DPS, RC, KFA, and HOE revised and edited the manuscript; all authors have read and approved the final manuscript.

Acknowledgments

The authors would like to express their gratitude to B S Thakur (Professor and Head, Department of Fruit Science) for providing all of the resources needed to carry out this research. The authors extend their appreciation to the Researchers Supporting Project number (RSP2024R118), King Saud University, Riyadh, Saudi Arabia.

Disclosure statement

The authors state that there are no known competing personal or financial interests that would appear to have influenced the work presented in this research.

Data availability statement

The data which supported the outcomes of this research are accessible from the corresponding author upon reasonable request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15538362.2023.2273356

Additional information

Funding

This work is supported by University funding of Dr YSP UHF Nauni, Solan, (H.P.) India and Researchers supporting project (RSP2024R118), King Saud University.