
==== Front
Heliyon
Heliyon
Heliyon
2405-8440
Elsevier

S2405-8440(24)12167-6
10.1016/j.heliyon.2024.e36136
e36136
Research Article
Optimizing leaf nutrient status, growth, and yield parameters in high-density apple orchards (cv. Super chief) via integrated drip irrigation and fertigation techniques
Sharma Kapil kapiluhf123@gmail.com
a⁎⁎1
Sharma J.C. a1
Sharma Sunny Sunny.29533@lpu.co.in
bd1⁎
Sharma Nitin c
Sharma Rohit d
S Ananthakrishnan a
Hashem Abeer habeer@ksu.edu.sa
e
Almutairi Khalid F. almutairik@ksu.edu.sa
f
Abd_Allah Elsayed Fathi eabdallah@ksu.edu.sa
f
a Department of Soil Science and Water Management, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, 173230, India
b Department of Horticulture, School of Agriculture, Lovely Professional University, Phagwara, Punjab, 144411, India
c Department of Basic Science, College of Forestry, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Solan, H.P, 173230, India
d Department of Fruit Science, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, 173230, India
e Botany and Microbiology Department, College of Science, King Saud University, P.O. Box. 2460, Riyadh, 11451, Saudi Arabia
f Plant Production Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box. 2460, Riyadh, 11451, Saudi Arabia
⁎ Corresponding author. Sunny.29533@lpu.co.in
⁎⁎ Corresponding author. kapiluhf123@gmail.com
1 Contributed equally.

10 8 2024
30 8 2024
10 8 2024
10 16 e3613613 3 2024
4 8 2024
9 8 2024
© 2024 The Authors
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
Nutrients and water are important ecophysiological components for apples' development and productivity. The combination of high-density plantation, drip irrigation, and weekly fertigation not only conserves irrigation water, but also reduces cultivation costs compared to conventional methods. Leaf nutrient analysis provides insight into nutrient levels and assists in determining irrigation and fertigation schedules. We conducted the current research over two years (2021–22 and 2022–23) to evaluate different drip-fertigation effects on leaf nutrient status, vegetative growth, and yield of high-density apples. The experimental study employed a factorial randomised block design, replicating 16 different treatment combinations three times each. Each replication consisted of three plants, and the treatments included four irrigation levels (100 %, 80 %, 60 %, and control) and four fertigation levels (absolute control, 100 %, 75 %, and 50 % of the recommended NPK dosage). Analysis of the leaves indicated that IR1 (Drip irrigation at 100 % ETc) showed notably higher levels of nitrogen at (3.06 %), phosphorus at (0.48 %) and potassium at (2.07 %) compared to other treatments. Regarding fertigation levels, FN1 [100 % (AD) NPK] showed the highest nitrogen (3.12 %), phosphorus (0.50 %), and potassium (2.09 %) content. Parameters related to vegetative growth, including tree height, plant spread in both east-west (EW) and north-south (NS) directions, trunk girth, annual extension growth, and leaf area showed significant increases with higher irrigation and fertigation levels, surpassing conventional irrigation (IR4) by 6.17 percent, 7.78 percent (EW), 8.62 percent (NS), 10.49 percent, 4.53 percent and 1.96 percent, respectively. Among fertigation, FN1- 100 % AD (NPK) registered a maximum increase in growth parameters. Our analysis demonstrated that combining irrigation and fertigation improved leaf nutrient status and vegetative growth characteristics, which are critical determinants of fruit yield.

Keywords

Conventional irrigation
Evapotranspiration
Productivity
Recommended dose of fertilizers
Trunk girth
Water soluble fertilizers
==== Body
pmc1 Introduction

Environmental protection, saving water resources, and responsibly managing land resources are essential factors necessitating the more efficient and balanced utilization of available resources. This is crucial in achieving increased productivity per unit area to fulfill the demands for food, fiber, and other necessities crucial for our survival and development [1,2]. However, the indiscriminate application of fertilizers and certain agricultural methods has frequently led to environmental degradation, soil depletion, and other ecological challenges [3,4]. Therefore, the study aims to achieve this goal by ensuring an appropriate and balanced provision of water and nutrients. High-density planting is a modern tactic that has gained substantial traction in current years as a means to boost productivity within confined spaces. It demonstrates increased efficacy, and enhanced manageability, and offers substantial potential for yielding superior-quality fruits and greater returns per unit area [5]. High-density planting embodies a more intensive system, necessitating increased initial capital for establishment but promises enhanced productivity and profitability when executed with a scientific approach [2,5].

Apple is an essential temperate fruit crop that is grown in Jammu and Kashmir, Himachal Pradesh, and Uttarakhand. The area and production of apples in India have increased notably, but low productivity remains a concern. In Himachal Pradesh, many orchards have low density and are established using seedlings, resulting in poor yields. The farmers combat climate change's impact on their orchards by adopting the state-promoted high-density apple plantation method [5]. Therefore, apple growers in the state are increasingly transitioning to high-density orchards using clonal rootstock on a larger portion of their land. Orchards utilizing clonal rootstock require reliable access to irrigation and nutrients. To achieve maximum productivity, it is crucial to implement an optimal irrigation and fertigation schedule for high-density apple plantations [6,7].

Drip irrigation proves highly efficient in delivering water directly to plant roots, conserving water while ensuring optimal yield and superior product quality. Additionally, it facilitates precise fertigation by delivering fertilizers directly into the active root zone, thereby meeting crop needs with precision [8,9]. Drip irrigation outperforms flood methods in water conservation, yield, and produce quality due to its capability for frequent irrigation [5,10]. This strategy mitigates leaching losses and increases growth parameters, yield of produce, and Nutrient use efficiency (NUE) [11].

Fertigation, the method of applying water-soluble fertilizers alongside irrigation water, has proven particularly effective in apple orchards. This success stems from the synchronization of nutrient application with the plant's demand, influenced by factors such as plant age, growth stages, weather conditions, and the promotion of both the juvenile phase and reproductive phase, ultimately enhancing the quality of apple fruits [[12], [13], [14], [15]]. Fertigation via drip irrigation holds promise for augmenting farmers' income, not only by conserving resources but also by enhancing output through improved yield quality, increased growth parameters, and improved leaf nutrient status of apples. Additionally, it offers time and labor savings of approximately 50–60 percent, water conservation ranging from 50 to 60 percent, while simultaneously increasing yields by 12–76 percent and water use efficiency (WUE) by 70–95 percent [[11], [16], [17], [18], [19]]. In essence, the research aims to fine-tune and optimize irrigation and fertilization techniques to support the unique requirements of high-density apple orchards, aiming for increased apple yield, vegetative growth parameters, improved leaf nutrient status, resource conservation, and economic viability. Super Chief is an important cultivar for the midhills of the western Himalayan region. Although previous studies have proved the benefits of integrated drip irrigation and fertigation on many crop species, only very few were conducted with the Super Chief apple cultivar under high-density conditions. Thus, it has yet to be delineated how such advanced irrigation and nutrient management techniques might affect leaf nutrient status, growth parameters, and yield in an orchard with Super Chief apples.

The three objectives of this research are to establish the optimum irrigation and fertigation schedules for high-density apple orchards, their effects on the leaf nutrient concentration, and the changes during growth and yield. It is hoped that the results of this study will give the farmers who aim to grow quality apples sustainably some insights into the relationships between water and nutrient resource management.

2 Material and methods

An experiment carried place between 2021-22 and 2022-23 at the research farm of the Division of Soil Sciences and Water Management, Dr. Yashwant Singh Parmar University of Horticulture and Forestry in Nauni, Solan (HP). The study included super chief apple trees, aged 6 and 7 years, which were grafted onto MM106 (Malling Marton) rootstock and planted at a spacing of 2.5 m × 2 m (equivalent to 2000 plants per hectare). The experimental design followed a factorial randomized block layout, encompassing 16 different treatment combinations. The combinations included four irrigation levels viz. IR1 (DI at 100 percent ETc), IR2 (DI at 80 percent ETc), IR3 (DI at 60 percent ETc), and IR4 (Conventional Irrigation, respectively) and four fertigation levels viz. FN0: absolute control), FN1: 100 percent (AD) NPK, FN2: 75 percent (AD) NPK, and FN3: 50 percent (AD) NPK, respectively). Each treatment combination was replicated three times, with three plants in each replication. The experimental farm is situated in the mid-hills of Himachal Pradesh. It resides at 30° 51′31 N latitude and 77° 10′23 E longitude boasting an elevation of 1175 m above MSL (Mean Sea Level), with a moderate slope averaging between seven to eight percent. The region experiences an average yearly precipitation of 110 cm, with about 75 percent occurring during the monsoon period, from mid-June to mid-September. Meteorological data on monthly rainfall distribution, evaporation, maximum and minimum temperatures, and relative humidity were gathered from the Meteorology Laboratory at the Department of Environment Science, Dr. Yashwant Singh Parmar University of Horticulture and Forestry in Nauni, Solan (HP). The records cover the period from March to November in both years (Fig. 1, Fig. 2). During the study, the second year had 36.68 cm. A 100 percent ad-hoc dose (AD) of 35:17.5:35 g tree−1 year−1 was applied for high-density plantation.Fig. 1 Meteorological data during the experimentation period in the first year (March–November 2021).

Fig. 1

Fig. 2 Meteorological data during the experimentation period in the first year (March–November 2022).

Fig. 2

2.1 Irrigation scheduling of drip irrigation

The quantity of water administered through drip irrigation was determined by calculating cumulative pan evaporation, pan factor, crop coefficient, and canopy area factor. This volume was refilled every week under the previous week's recorded evapotranspiration (Ep). The calculation of the water volume (V) for 100 percent crop evapotranspiration (ETc) followed a specific formula in Equation (1):(1) V=[(Ep×Kc×Kp×Sp×Sr×Wp×N)]−[(Sp×Sr)×Re]

Where,

V: The amount of water to be applied for each irrigation cycle; (L tree−1); Ep = cumulative pan evaporation (mm week−1); Kc: crop factor; Kp: pan factor; Sp: spacing between individual plants; Sr: spacing between rows of plants; Wp: Wetting area; N: No of days; Re: effective rainfall; Traditional surface irrigation involved 9 waterings, each providing 4 cm of water, occurring every 20 days in March and April, and every 10 days in May and June. 36 cm of water was applied in total. The determination of the water volume applied per tree in liters was performed as follows in Equation 2(2) V=πr2d/1000

where;

V = amount of water administered (l tree−1)

r = radius of tree basin (average radius 75 cm in the present study)

d = depth of water applied (cm)

1000 = Factor to convert cubic cm into liters.

Drip irrigation was carried out every two weeks, amounting to approximately 30 irrigation cycles. The seasonal water demand for 6 to 7-year-old Super Chief apple trees under drip irrigation was determined to be 20.69 cm and 23.68 cm, respectively. Considering effective rainfall of 19.40 cm and 13.00 cm, the irrigation requirement was determined to be 7.98 cm and 5.02 cm, respectively. Fertigation was conducted using a venturi system, dividing the process into 15 equal applications spread over weekly intervals. This schedule was initiated in March of each experimental year and persisted until July, spanning the periods of flowering and fruit maturation. Water-soluble fertilizer (WSF-19:19:19) was used in fertigation to provide phosphorus, while urea and muriate of potash (MOP) were used to supply nitrogen and potassium. A 25-L stock solution was carefully produced for each fertigation session to guarantee the dissolution and compliance of water-soluble fertilizer (WSF) i.e. 19:19:19, urea, and Muriate of potash (MOP). In 2021, the amounts of water-soluble fertilizer, urea, and muriate of potash calculated were 30.70 g, 12.68 g, and 9.72 g respectively per tree per split during the formation of plantations at 5 years of age. However, for 6 to 7-year-old plants, the amount of WSF remained consistent with that of 5-year-old plants, as the prescribed fertilizer dosage for high-density planting was standardized for trees aged 5 years or above. For traditional soil fertilization methods (conventional), nitrogen, phosphorus, and potassium were applied through urea, single superphosphate, and muriate of potash. Details regarding the analysis of physical and chemical parameters, the available macro-nutrient status of the soil before the experiment, the volume of water applied, and the quantity of fertilizers under different irrigation levels are given in Table 1, Table 2, Table 3.Table 1 Assessment of soil physical and chemical characteristics before experiment commencement.

Table 1Soil characteristics	Values	
	Depth of soil (cm)	
Physical Characteristics	0–15 cm	15–30 cm	
Soil Texture	Sandy clay loam	Sandy clay loam	
Sand (%)	53.4	50.56	
Silt (%)	25.1	24.72	
Clay (%)	21.6	22.48	
Bulk Density (g/cm)	1.30	1.33	
Particle Density (g/cm)	2.35	2.52	
Porosity (%)	45.0	47.00	
Field Capacity (%)	24.7	23.0	
Infiltration rate (cm/h)	2.31	
pH	6.7	6.5	
EC (dS/m)	0.2	0.1	
OC (g/kg)	15.2	11.0	
Available N (kg/ha)	333.0	314.1	
Available P (kg/ha)	132.6	122.2	
Available K (kg/ha)	598.4	562.1	

Table 2 Volume of water applied under drip irrigation.

Table 2Date		2021				2022	
	Volume of water (l tree−1)				Volume of water (l tree−1)	
DI-100 (IR1)	DI-80 (IR2)	DI-60 (IR3)	Date	CI-100 (IR4)	Date	DI-100 (IR1)	DI-80 (IR2)	DI-60 (IR3)	Date	CI-100 (IR4)	
18–03–21	14.56 (0.97)	11.65 (0.78)	8.74 (0.58)	19–03–21	14.56 (0.97)	15–03–22	14.56 (0.97)	11.65 (0.78)	8.74 (0.58)	20–03–22	14.56 (0.97)	
25–03–21	14.56 (0.97)	11.65 (0.78)	8.74 (0.58)	28–03–21	14.56 (0.97)	23–03–22	14.56 (0.97)	11.65 (0.78)	8.74 (0.58)	26–03–22	14.56 (0.97)	
02–04–21	19.27 (1.28)	15.42 (1.03)	11.56 (0.77)	05–04–21	22.09 (1.47)	05–04–22	25.72 (1.71)	20.58 (1.37)	15.43 (1.03)	05–04–22	25.72 (1.71)	
11–04–21	20.38(1.36)	16.30 (1.09)	12.23 (0.82)	14–04–21	20.38 (1.36)	11–04–22	25.72 (1.71)	20.58 (1.37)	15.43 (1.03)	09–04–22	25.72 (1.71)	
19–04–21	18.12 (1.21)	14.50 (0.97)	10.87 (0.72)	21–05–21	15.85 (1.06)	20–04–22	25.72 (1.71)	20.58 (1.37)	15.43 (1.03)	18–04–22	25.72 (1.71)	
28–04–21	11.32 (0.75)	9.06 (0.60)	6.79 (0.45)	30–05–21	11.32 (0.75)	27–04–22	25.72 (1.71)	20.58 (1.37)	15.43 (1.03)	28–04–22	25.72 (1.71)	
07–05–21	3.40 (0.23)	2.72 (0.18)	2.04 (0.14)	05–05–21	8.82 (0.59)	03–05–22	26.01 (1.73)	20.81 (1.39)	15.61 (1.04)	05–05–22	24.16 (1.61)	
13–05–21	7.06 (0.47)	5.65 (0.38)	4.24 (0.28)	10–05–21	10.21 (0.68)	09–05–22	20.88 (1.39)	16.70 (1.11)	12.53 (0.84)	15–05–22	34.29 (2.29)	
20–05–21	15.13 (1.01)	12.10 (0.81)	9.08 (0.61)	20–05–21	20.43 (1.36)	17–05–22	5.76 (0.38)	4.61 (0.31)	3.46 (0.23)	23–05–22	17.58 (1.17)	
27–05–21	23.83 (1.59)	19.06 (1.27)	14.30 (0.95)	29–05–21	30.64 (2.04)	25–05–22	6.96 (0.46)	5.59 (0.37)	4.18 (0.28)	31–05–22	20.88 (1.39)	
03–06–21	6.63 (0.44)	5.30 (0.35)	3.98 (0.27)	09–06–21	18.81 (1.25)	02–06–22	28.47 (1.90)	22.78 (1.52)	17.08 (1.14)	12–06–22	42.48 (2.83)	
10–06–21	7.69 (0.51)	6.15 (0.41)	4.61 (0.31)	15–06–21	3.04 (0.20)	08–06–22	21.24 (1.42)	16.99 (1.13)	12.74 (0.85)	16–06–22	14.16 (0.94)	
17–06–21	3.04 (0.20)	2.43 (0.16)	1.82 (0.12)	24–06–21	16.47 (1.10)	15–06–22	14.16 (0.94)	11.33 (0.76)	8.5 (0.57)	21–06–22	7.08 (0.47)	
22–06–21	13.42 (0.89)	10.74 (0.72)	8.05 (0.54)	30–06–21	12.18 (0.81)	21–04–22	7.08 (0.47)	5.66 (0.38)	4.25 (0.28)	29–06–22	28.32 (1.89)	
28–06–21	12.18 (0.81)	9.74 (0.65)	7.31 (0.49)			27–04–22	17.34 (1.16)	13.87 (0.92)	10.40 (0.69)			
Total	190.59 (12.71)	152.47 (10.16)	114.35 (7.62)	Total	219.36 (14.62)	Total	279.9 (18.66)	223.96 (14.93)	167.95 (11.20)	Total	320.95 (21.40)	

Table 3 Quantity of fertilizer used during both years.

Table 3Fertilizers	Quantity in kg (for 1plant)	Quantity in kg (for 36 plants)	
Absolute control	FN1 100 % (AD) NPK	FN2 75 % (AD) NPK	FN3 50 % (AD) NPK	Absolute control	FN1 100 % (AD) NPK	FN2 75 % (AD) NPK	FN3 50 % (AD) NPK	
19:19:19	–	0.460	0.345	0.230	–	16.57	12.42	8.28	
Urea	–	0.190	0.142	0.095	–	6.84	5.11	3.42	
SSP	–	–	–	–	–	–	–	–	
MOP	–	0.145	0.109	0.072	–	5.22	3.92	2.59	
*The experiment was carried out with three replications, each consisting of three plants. Thus, each replication included nine plants, resulting in a total of 36 plants across the three replications.

2.2 Leaf analysis

2.2.1 Collection of leaf samples

Annually, leaf samples were collected in late June from the mid-terminal shoots of the current year's growth for the research. The samples were obtained from the same trees in the basin area as soil samples had been taken before. The leaf samples were cleaned, air-dried, and subjected to hot air oven drying at 60 ± 5 °C for 72 h. Following the drying process, the samples were finely pulverized with a stainless steel blender and stored in butter paper bags. Conventional methods were used to examine the nitrogen (N), phosphorus (P), and potassium (K) levels in the leaf samples [20].

2.2.2 Digestion of plant samples

Leaf samples of predetermined weight were finely powdered and digested using a di-acid mixture (combining concentrated HNO3: Nitric acid and HClO4: Perchloric acid in a 4:1 ratio). All essential precautions, as described by Piper [21] for determining phosphorus (P) and potassium (K), were carefully followed throughout the digestion procedure. To estimate nitrogen (N) levels, a separate digestion method was employed involving concentrated sulfuric acid and a digestion mixture consisting of K2SO4: Potassium sulphate (400 parts), CuSO4: Copper Sulphate (20 parts), HgO: Mercuric oxide (3 parts) and Se: Selenium powder (1 part) as suggested by Ref. [22].

2.3 Vegetative plant growth parameters

2.3.1 The height of the trees was evaluated using a graded staff, measuring from the base to the apex before and after the trial. The percent increase in height was determined by percent.

2.3.2 The measurement of tree spread was conducted in two directions: EW & NS, utilizing a tape measure upon completion of the experiment. Subsequently, the tree spread was calculated and reported in centimeters.

2.3.3 Before the commencement of the trial, the tree trunk was identified by marking it with a red plus sign. The girth of the trunk at the marked location was then measured annually, both before and after the experiment's conclusion, using a measuring tape. The results were presented as the percentage increase in trunk girth.

2.3.4 The annual shoot growth data were gathered following the harvest of each year's crop. Five shoots were randomly selected from different positions around the circumference of the tree, and their lengths were measured using a tape measure. The average length was then calculated and reported in centimeters.

2.3.5 The leaf area of each leaf was assessed using a leaf area meter equipped with a sensor and a read-out unit.

2.4 Fruit yield

Data on fruit yield (t ha−1) was gathered by assessing the cumulative weight of fruits harvested from trees subjected to each treatment.

2.4.1 Statistical analysis

The variance assessment was conducted following the model proposed by Ref. [23]. The data acquired in this study was statistically analyzed using MS Excel, OPSTAT, and the SPSS 16.0 software. The experiment was conducted using a factorial randomized block design. Correlation is a measure of a monotonic association between 2 variables. The covariance of two variables divided by the product of their standard deviation gives Pearson's correlation coefficient [24]. It is usually represented by Equation 3(3) Correlationcoefficient:ρ(X,Y)=cov(X,Y)σX.σY

3 Results

3.1 Influence of drip-fertigation on leaf nitrogen

The data collected over two years revealed that different irrigation and fertigation levels had a considerable influence on the NPK levels found in apple leaves. The data in Table 4 demonstrated that IR1 (DI at 100 % ETc) recorded significantly higher nitrogen content in the leaves i.e. 3.06 percent which was statistically comparable to IR2 i.e. 2.98 percent, while the lowest nitrogen content was observed under IR3 i.e. 2.74 percent. The fertigation level FN1 {100 % (AD) NPK} recorded significantly higher leaf N content (3.12 %) and showed statistical similarity with FN2 {75 % (AD) NPK}i.e. 3.06 percent, whereas the lowest nitrogen content was noted under FN0 (absolute control) i.e. 2.55 percent. The combined influence of irrigation and fertigation (IR × FN) did not have a significant impact on the N content in leaves.Table 4 Influence of drip-fertigation on leaf NPK levels.

Table 4Treatments	Leaf NPK content (%)	
Year	Nitrogen	Phosphorus	Potassium	
	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	
IR1	2.68	3.30	3.26	3.01	3.06	0.38	0.56	0.54	0.44	0.48	1.91	2.20	2.16	2.00	2.07	
IR2	2.61	3.21	3.15	2.95	2.98	0.37	0.52	0.50	0.42	0.45	1.88	2.12	2.07	1.97	2.01	
IR3	2.50	2.86	2.81	2.77	2.74	0.35	0.45	0.43	0.39	0.40	1.86	1.97	1.93	1.88	1.91	
IR4	2.43	3.09	3.01	2.73	2.82	0.35	0.48	0.46	0.42	0.43	1.81	2.08	2.03	1.92	1.96	
Mean	2.55	3.12	3.06	2.87	2.90	0.36	0.50	0.48	0.42	0.44	1.87	2.09	2.05	1.94	1.99	
LSD		
IR	0.09	0.01	0.04	
FN	0.09	0.01	0.04	
IR × FN	NS	0.02	NS	
IR1- DI at 100 percent ETc, FN0- absolute control; IR2- DI at 80 percent ETc, FN1- 100 percent of AD (NPK); IR3- DI at 60 percent ETc, FN2- 80 percent of AD (NPK); IR4- Conventional irrigation, FN3- 60 percent of AD (NPK).

*The data showed a pooled mean of two years (2021–22 & 2022-23)LSD: Least significant difference.

3.2 Influence of drip-fertigation on leaf phosphorus

The analysis of pooled data in Table 4 revealed the data regarding leaf phosphorus levels influenced by various irrigation and fertigation levels. The combined data revealed that irrigation level IR1 (DI at 100 % ETc) resulted in significantly higher leaf phosphorus content i.e. 0.48 percent, while the lowest was observed under IR3 (DI at 60 % ETc) i.e. 0.40 percent. Similarly, among fertigation levels, significantly higher leaf phosphorus content was noted under FN1 {100 % (AD) NPK} i.e. 0.50 percent, whereas the lowest was recorded in FN0 (absolute control) i.e. 0.36 percent. The interaction (IR × FN) recorded significant influence on leaf P. Interaction IR1 × FN1 was recorded the highest leaf P (0.56 %) and showed statistical similarity with IR1 × FN2 (0.54 %) and the lowest leaf P found in interaction IR3 × FN0 and IR4 × FN0 (0.35 %).

3.3 Influence of drip-fertigation on leaf potassium

A comprehensive examination of the data depicted in Table 4 showed significant effects of varying irrigation and fertigation levels on leaf potassium (K) content. The average data indicated that irrigation level IR1 (DI at 100 % ETc) resulted in significantly higher leaf K content (2.07 %), while the lowest level was observed under IR3 (DI at 60 % ETc) i.e. 1.91 percent. Among fertigation, significantly higher leaf K was found under fertigation level FN1 {100 % (AD) NPK} i.e. 2.09 percent, statistically comparable to FN2 {75 % (AD) NPK} i.e. 2.05 percent, whereas the lowest leaf K was recorded under FN0 (absolute control) i.e.1.87 percent.

3.4 Influence of drip-fertigation on percentage increment in height of apple tree

The analysis of pooled data in Table 5 demonstrates that varying irrigation and fertigation levels significantly influence the increase in tree height, indicating a correlation between increased water volume and NPK doses with tree height. Analysis of combined data shows that tree height was significantly higher (28.20 %) under irrigation level IR1 (DI at 100 % ETc) and lowest under IR3 (DI at 60 % ETc) i.e. 25.04 percent. Similarly, among fertigation treatments, significantly greater tree height was observed in FN1 {100 % (AD) NPK} 31.68 percent, while the lowest was found under FN0 (absolute control) 21.60 percent. Regarding interactions, significantly higher tree height was noted in IR1 × FN1 (34.32 %), whereas the lowest was recorded in IR4 × FN0 (20.43 %).Table 5 Influence of varied irrigation and fertigation levels on vegetative parameters.

Table 5Treatments	Pooled data	
Year	Percent increase in tree height	Plant Spread in cm (EW)	Plant Spread in cm (NS)	
	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	
IR1	23.36	34.32	29.90	25.21	28.20	211.70	280.00	263.30	248.30	250.83	225.00	276.67	265.00	241.67	252.09	
IR2	21.66	32.25	27.05	26.07	26.76	221.70	271.70	255.80	233.70	245.73	233.33	268.33	256.67	228.33	246.67	
IR3	20.95	28.89	25.81	24.52	25.04	206.70	249.50	221.50	214.20	222.98	200.02	236.67	218.33	213.33	217.09	
IR4	20.43	31.24	27.70	26.88	26.56	216.70	254.20	235.00	225.00	232.73	210.00	253.33	236.67	228.33	232.08	
Mean	21.60	31.68	27.62	25.67	26.64	214.20	263.80	243.90	230.30	238.05	217.08	258.75	244.17	227.92	236.98	
LSD		
IR	0.63	8.46	11.18	
FN	0.63	8.46	11.18	
IR × FN	1.27	NS	NS	
*The data showed a pooled mean of two years (2021–22 & 2022-23)LSD: Least significant difference.

IR1- DI at 100 percent ETc, FN0- absolute control; IR2- DI at 80 percent ETc, FN1- 100 percent of AD (NPK); IR3- DI at 60 percent ETc, FN2- 80 percent of AD (NPK); IR4- Conventional irrigation, FN3- 60 percent of AD (NPK).

3.5 Influence of drip-fertigation on plant spread (NS &EW)

The analysis of pooled data in Table 5 depicted that various levels of irrigation and fertigation significantly influenced the tree spread in EW and NS directions. The average data demonstrated that irrigation level IR1 (DI at 100 % ETc) recorded significantly higher plant spread in both EW and NS directions (250.83 cm and 252.09 cm, respectively), statistically comparable to IR2 (DI at 80 % ETc) i.e. 245.73 cm and 246.67 cm, respectively, while the lowest spread was observed in IR3 (DI at 60 % ETc) i.e. 222.98 cm and 217.09 cm, respectively. Among the various fertigation levels, significantly higher plant spread was observed in fertigation level FN1 {100 % (AD) NPK} i.e. 263.80 cm and 258.75 cm, respectively, while the lowest spread was recorded under FN0 (absolute control) i.e. 214.20 cm and 217.08 cm, respectively. The interaction between irrigation and fertigation (IR × FN) did not have a significant effect on tree spread in both EW and NS directions.

3.6 Influence of drip-fertigation on the percent increase in trunk girth

Pooled data analysis in Table 6 revealed that various drip irrigation and fertigation levels significantly influence the trunk girth. Trunk girth was significantly higher under IR1 (DI at 100 % ETc) i.e. 9.90 percent and the lowest was recorded in IR3 (DI at 60 % ETc) at 8.38 percent. However, IR1 is statistically similar to IR2 i.e. (DI at 80 % ETc) i.e.9.49 percent, and IR4 (conventional irrigation at 100 % ETc) 8.96 percent. Among fertigation, it was evident that a significantly greater trunk girth was observed in fertigation level FN1 {100 % (AD) NPK} i.e.10.59 percent, which was statistically comparable to FN2 {75 % (AD) NPK} i.e.9.67 percent, while the lowest trunk girth was noted under FN0 (absolute control) 7.79 percent. The interaction (IR × FN) had non-significant effects on trunk girth.Table 6 Influence of varied irrigation and fertigation levels on vegetative parameters.

Table 6Treatments	Pooled data	
Year	Percent increase in trunk girth	Annual extension growth (cm)	Leaf area (cm2)	
	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	
IR1	8.15	11.56	10.51	9.36	9.90	69.13	112.63	109.93	102.32	98.50	22.67	31.45	29.85	26.56	27.63	
IR2	7.92	11.13	10.16	8.74	9.49	66.03	100.85	96.25	88.98	88.03	21.99	29.38	27.81	26.29	26.37	
IR3	7.36	9.35	8.78	8.02	8.38	63.75	94.97	90.37	80.15	82.31	20.49	25.48	24.30	23.22	23.37	
IR4	7.74	10.32	9.22	8.58	8.96	67.50	107.42	103.42	98.60	94.23	22.32	30.64	29.17	26.29	27.10	
Mean	7.79	10.59	9.67	8.68	9.25	66.60	103.97	99.99	92.51	90.77	21.87	29.24	27.78	25.59	26.12	
LSD		
IR	1.06	2.49	1.87	
NU	1.06	2.49	1.87	
IR × FN	NS	4.98	NS	
*The data showed a pooled mean of two years (2021–22 & 2022-23)LSD: Least significant difference.

IR1- DI at 100 percent ETc, FN0- absolute control; IR2- DI at 80 percent ETc, FN1- 100 percent of AD (NPK); IR3- DI at 60 percent ETc, FN2- 80 percent of AD (NPK); IR4- Conventional irrigation, FN3- 60 percent of AD (NPK).

3.7 Influence of drip-fertigation on annual extension growth

The pooled data depicted in Table 6 revealed that significantly higher extension growth was recorded under IR1 (DI at 100 % ETc) i.e. 98.50 cm and minimum extension growth was observed in IR3 (DI at 60 % ETc) i.e. 82.31 cm. Among the fertigation treatments, FN1 {100 % (AD) NPK} exhibited significantly greater (103.97 cm) annual extension growth compared to the lowest observed under FN0 (absolute control) i.e.66.60 cm. The interaction (IR × FN) recorded a significant effect on annual extension growth. The interaction IR1 × FN1 exhibited significantly higher growth (112.63 cm), which was statistically similar to IR1 × FN2 (109.93 cm) and the minimum was in IR3 × FN0 (63.75 cm).

3.8 Influence of drip-fertigation on leaf area

The pooled data in Table 6 illustrates the significant impact of different irrigation and fertigation levels on leaf area. Significantly higher leaf area was observed in irrigation level IR1 i.e. (DI at 100 % ETc) 27.63 cm2, statistically comparable to IR4 i.e. (Conventional Irrigation at 100 % ETc) 27.10 cm2 and IR2 (DI at 80 % ETc) i.e. 26.37 cm2, while the lowest leaf area was recorded under IR3 (DI at 60 % ETc) i.e. 23.37 cm2. Among fertigation treatments, a significantly higher leaf area was found under FN1 {100 % (AD) NPK}i.e. 29.24 cm2, statistically similar to FN2 {75 % (AD) NPK}i.e. 27.78 cm2, whereas the lowest leaf area was observed under FN0 (absolute control) 21.87 cm2. The interaction (IR × FN) showed no significant effect across both years.

3.9 Influence of drip-fertigation on fruit yield

A comprehensive examination of data depicted in Table 7 illustrates that different levels of irrigation and fertigation significantly influence the fruit yield. The findings revealed that higher fruit yield was observed with higher levels of irrigation and fertigation. A significantly higher yield was recorded in full irrigation (DI) at 100 percent of the crop evapotranspiration (ETc) rate with 100 percent (AD) NPK fertilization, followed by DI at 80 percent ETc with 75 percent (AD) NPK, while the lowest fruit yield was observed under DI at 60 percent ETc with 50 percent (AD) NPK.Table 7 Influence of irrigation and nutrient levels on fruit yield.

Table 7Treatments	Fruit yield (t ha−1)	
Year	2021	2022	Pooled	
	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	FN0	FN1	FN2	FN3	Mean	
IR1	17.87	28.73	25.87	23.03	23.88	42.51	62.23	56.93	52.00	53.42	30.19	45.48	41.40	37.52	38.65	
IR2	17.07	24.07	22.07	20.30	20.88	37.67	55.12	50.61	45.93	47.33	27.37	39.60	36.34	33.12	34.11	
IR3	15.73	22.40	20.70	18.90	19.43	29.73	48.99	43.67	38.73	40.28	22.73	35.70	32.19	28.82	29.86	
IR4	17.27	25.24	22.80	20.90	21.55	39.29	58.12	52.70	48.07	49.55	28.28	41.68	37.75	34.49	35.55	
Mean	16.98	25.11	22.86	20.78	21.43	37.30	56.11	50.98	46.18	47.64	27.14	40.61	36.92	33.48	34.54	
LSD		
IR	2.54	3.03	1.79	
FN	2.54	3.03	1.79	
IR × FN	NS	NS	NS	
*The data showed a pooled mean of two years (2021–22 & 2022-23)LSD: Least significant difference.

IR1- DI at 100 percent ETc, FN0- absolute control; IR2- DI at 80 percent ETc, FN1- 100 percent of AD (NPK); IR3- DI at 60 percent ETc, FN2- 80 percent of AD (NPK); IR4- Conventional irrigation, FN3- 60 percent of AD (NPK).

The combined data revealed that significantly greater fruit yield was achieved under irrigation level IR1 (DI at 100 % ETc) i.e. 38.65 t ha−1, while the lowest yield was observed under IR3 (DI at 60 % ETc) i.e. 29.86 t ha−1. Similarly, significantly higher fruit yield was recorded under fertigation level FN1 {100 % (AD) NPK} i.e. 40.61 t ha−1, whereas the lowest yield was observed under FN0 {absolute control} i.e. 27.14 t ha−1. However, the interaction between irrigation and fertigation did not have a significant effect on fruit yield.

3.10 Influence of drip irrigation and fertigation on water use efficiency (WUE)

The pooled data depicted in Table 8 revealed that the highest water requirement was observed at irrigation level IR4 (conventional irrigation at 100 % ETc) i.e. 36.00 cm, while the lowest was at IR3 (DI at 60 % ETc) i.e. 13.31 cm. The data showed that conventional irrigation required significantly more water compared to drip irrigation. The combined data indicated that the highest Water Use Efficiency (WUE) was seen under the IR3 (DI at 60 % ETc) irrigation level i.e. 3.07 t ha−1 cm−1 and the lowest was recorded under IR4 (conventional irrigation at 100 % ETc) i.e. 1.00 t ha−1 cm−1. Comparing various irrigation levels, it was found that deficit irrigation (DI) at 60 percent ETc achieved the highest Water Use Efficiency at 207 percent. This was followed by DI at 80 and 100 percent ETc, with WUEs of 162 percent and 136 percent, respectively, compared to the surface irrigation method and fertilizer application.Table 8 Influence of irrigation and nutrient levels on water use efficiency.

Table 8Treatments	Yield t ha−1	Water applied(cm)	Effective rainfall (cm)	WR= I + ER (cm)	Water Use Efficiency t ha−1 cm−1	
2021	2022	2021	2022	2021	2022	2021	2022	Mean	2021	2022	Mean	
IR1	23.88	53.42	12.71	18.66	7.98	5.02	20.69	23.68	22.19	1.87	2.86	2.36	
IR2	20.88	47.33	10.16	14.93	6.38	4.02	16.54	18.95	17.75	2.06	3.17	2.62	
IR3	19.43	40.28	7.62	11.20	4.79	3.01	12.41	14.21	13.31	2.54	3.59	3.07	
IR4	21.55	49.55	36.00	36.00	–	–	36.00	36.00	36.00	0.60	1.38	1.00	

3.11 Influence of drip irrigation and fertigation on nutrient use efficiency (NUE)

The data in Table 9 clearly showed that nutrient use efficiency was affected by different irrigation and fertigation levels over both years of the study. The pooled data depicted that the maximum NPK use efficiency (43.70, 87.39, and 43.70 kg kg−1, respectively) was recorded under treatment T2 [DI at 100 % ETc with 100 % NPK (AD)], while the lowest (32.65, 65.30 and 32.65 kg kg−1, respectively) was found in treatment T12 [DI at 60 % ETc with 50 % NPK (AD)]. Treatment T2 [DI at 100 % ETc with 100 % NPK (AD)] showed a 12.34 percent increase in NUE (NPK) compared to treatment T14 [CI with 100 % NPK (AD)] using the surface method of irrigation and fertilization.Table 9 Influence of irrigation and nutrient levels on Nutrient Use Efficiency.

Table 9Treatments	Nutrient Use Efficiency (kg kg−1)	
N	P	K	
2021	2022	Mean	2021	2022	Mean	2021	2022	Mean	
T1	–	–	-	–	–	-	–	–	-	
T2	31.05	56.34	43.70	62.10	112.69	87.39	31.05	56.34	43.70	
T3	30.48	54.96	42.72	60.96	109.93	85.44	30.48	54.96	42.72	
T4	29.52	54.25	41.89	59.05	108.50	83.77	36.19	54.25	41.89	
T5	–	–	-	–	–	-	–	–	-	
T6	20.00	53.79	36.90	40.00	107.58	73.79	20.00	53.79	36.90	
T7	19.05	51.07	35.06	38.10	102.15	70.13	22.86	51.07	35.06	
T8	18.48	50.13	34.30	36.95	100.27	68.61	22.48	50.13	34.30	
T9	–	–	-	–	–	-	–	–	-	
T10	19.05	49.87	34.46	38.10	99.73	68.91	19.05	49.87	34.46	
T11	18.92	49.32	34.12	37.84	98.65	68.25	23.62	49.32	34.12	
T12	18.10	47.20	32.65	36.19	94.40	65.30	26.29	47.20	32.65	
T13	–	–	-	–	–	-	–	–	-	
T14	22.78	55.01	38.90	45.56	110.02	77.79	22.78	55.01	38.90	
T15	21.08	53.08	37.08	42.16	106.17	74.16	23.11	53.08	37.08	
T16	20.76	51.43	36.10	41.52	102.86	72.19	28.57	51.43	36.10	

Fig. 1 showed that all the parameters positively correlated with each other. Pearson's correlation matrix between leaf nutrient content, vegetative parameters, and fruit yield. The asterisks denote the significance levels of the Pearson correlation coefficient (*, **, *** represent p-values of ≤0.05, 0.01, and 0.001, respectively). Percent increase in tree height was highly correlated with leaf N i.e. 0.89 at p ≤ 0.001, leaf area and fruit yield i.e. 0.93 at p ≤ 0.001, and annual extension growth and fruit yield i.e. 0.95 at p ≤ 0.001. Pearson's correlation shows a significant positive correlation between leaf NPK and fruit yield at P < 0.001 (Fig. 1).

4 Discussion

4.1 Influence of drip irrigation and fertigation on leaf NPK levels

The findings indicated that there was an 11.68, 20.00, and 8.38 percent rise in leaf NPK content compared to conventional irrigation. Conversely, with fertigation, this increase reached 22.35, 38.88, and 11.76 percent over the control. This elevation in leaf NPK content was due to the fertilizer application being divided into 15 equal portions distributed at seven-day intervals, effectively meeting the nutrient demands of apples at various growth stages such as flowering and fruit development. Splitting fertilizer applications through drip irrigation helps decrease nitrogen and potassium leaching losses and prevents phosphorus fixation in the soil. Fertigation ensures a consistently higher level of nutrient availability in the soil compared to traditional fertilizer application methods. The improved uptake of nutrients, combined with the high mobility of NPK through the phloem, facilitates their efficient translocation in conditions of abundant availability, ultimately resulting in increased nutrient content in leaves [[25], [26], [27]].

4.2 Influence of drip irrigation and fertigation on percentage increase in tree height

The enhanced growth of plants resulting from consistent watering and nutrient distribution in the root area through drip irrigation and fertigation leads to an increase in plant height. Regular application of these techniques ensures a steady soil moisture level and nutrient supply, contributing to continuous plant development. Hence, the prolonged activity of roots facilitates greater nutrient availability and enhanced transportation of food materials, consequently fostering increased vegetative growth of plant components compared to traditional methods [28,29]. The results are in line with [26] reported that a significant rise in plant height is likely attributed to the ideal balance of soil moisture and nutrient availability, leading to improved growth of root biomass and enhanced nutrient absorption from the soil. Similar results were also supported by the finding of [30], which reported that the greatest plant height was observed when employing drip irrigation at 100 percent ETc along with fertigation at 100 percent AD (NPK).

4.3 Influence of drip irrigation and fertigation on plant spread (NS & EW)

The extent of plant spread is a vital factor influencing fruiting areas, directly influencing plant vigor and productivity. Plants subjected to fertigation exhibited accelerated growth compared to those under conventional fertilizer application methods. The distribution of trees benefited positively from the quantity of fertilizer applied [13]. The rise in plant spread could be attributed to the use of higher fertilizer doses, leading to an improved nutritional setting in both the root zone and the plant system. This, in turn, enhances tree spread, resulting in increased light interception and photosynthetic activity [31,32]. The results of this experiment were comparable to those obtained by [33] in kiwifruit, who revealed that the amount of nitrogen applied had a positive correlation with plant spread. The results were also supported by the findings of [30], who revealed that the greatest plant spread was observed with drip irrigation at 100 percent ETc and fertigation at 100 percent AD (NPK) in apple cultivation. Similarly observed comparable findings in Nagpur mandarin [34], in custard apple, and [26] in apple cultivation.

4.4 Influence of drip irrigation and fertigation on the percent increase in trunk girth

The trunk girth shows a positive correlation with the levels of nutrients and irrigation. The greater trunk girth observed in the second year is linked to the addition of nutrients in the first year, leading to enhanced assimilation of storage reserves [35]. The growth enhancement observed in various plant parameters (such as trunk girth, annual extension growth, plant height, and tree spread) could be attributed to improved NPK uptake by plants. NPK directly aids in the production of carbohydrates in leaves, resulting in the development of various bio-compounds such as protein, amino acids, chlorophyll, and other amides. This enhances the plant's ability to photosynthesize, resulting in the production of freshly formed tissues and stimulating total plant development [36]. The fertigation treatments ensured a consistent nutrient supply by dividing fertilizers into 15 equal portions during the plant's growth stages, potentially meeting nutrient needs crucial for crop growth phases like flowering and fruit development. The elevated vegetative growth parameters observed under 100 percent followed by 75 percent NPK fertigation at 7-day intervals may result from enhanced nutrient utilization efficiency, reducing leaching losses. This efficiency is achieved through the segmented application of NPK fertilizers via drip irrigation, contrasting with a single application as a soil treatment. The findings are reinforced by studies conducted [37] in apple [38], in pomegranate [39], in Nagpur mandarin [40], in peach [26], in apple, and [41] in apple, they found that increasing fertigation levels enhanced vegetative growth. Furthermore [30,35], supported these findings by noting that the highest trunk girth was observed with drip irrigation at 100 percent ETc and fertigation at 100 percent AD (NPK).

4.5 Influence of drip irrigation and fertigation on annual extension growth

The enhanced vegetative growth observed with increasing fertigation levels may be attributed to improved replenishment and efficient utilization of nutrients and moisture, particularly in plants receiving higher NPK levels through fertigation. Additionally, potassium (K) plays a vital role in regulating key plant functions including water absorption, stomatal opening, photosynthesis, as well as the synthesis of starch and proteins, and the modulation of enzymatic activities [42]. Plant growth was boosted with higher levels of fertilizer application, whereas it declined with lower fertilizer levels. The increased nutrient (NPK) content in the tree foliage might contribute partially to the elevated growth parameters observed at higher fertilizer levels. These findings are corroborated by Ref. [41] in apples [30], in apples [40], in peaches, and [26] in apples, revealing that the highest annual extension growth occurred with drip irrigation set at 100 percent ETc and fertigation at 100 percent AD (NPK).

4.6 Influence of drip irrigation and fertigation on leaf area

The findings indicated that various levels of irrigation and fertigation had a notable impact on leaf area. The expansion of leaf area could be attributed to the consistent supply of nitrogen and water through drip fertigation. Nitrogen application promoted chlorophyll content, meristematic cell activity, and overall growth, facilitating both branch formation and leaf expansion. These results align with the discoveries of [43,44] in potato cultivation.

4.7 Influence of drip irrigation and fertigation on fruit yield

The results of this study demonstrate the significant impact of drip irrigation (DI) at 100 percent crop evapotranspiration (ETc) on enhancing apple yield compared to lower irrigation levels (IR1 and IR3) and conventional irrigation methods (IR4). Specifically, DI at 100 percent ETc led to yield increases of 13.31, 29.43, and 8.72 percent over IR1, IR3 and IR4, respectively. Furthermore, among the fertigation levels tested, the application of 100 percent NPK (AD) resulted in substantial yield improvements compared to lower fertigation levels and absolute control. Specifically, 100 percent NPK (AD) led to yield increases of 49.63, 10.00, and 21.30 percent over absolute control, 75 percent NPK (AD), and 50 percent NPK (AD), respectively. These findings underscore the importance of optimal irrigation and fertigation management in maximizing apple yield. The results suggest that providing sufficient water and nutrients through drip irrigation at 100 percent ETc and 100 percent NPK (AD) fertigation can significantly enhance apple production, highlighting the potential for improved agricultural practices to increase crop productivity and profitability.

Optimizing soil moisture levels in plants supports photosynthesis and boosts nutrient uptake, fostering faster growth and increased yields. The drip irrigation system outperformed conventional methods, leading to higher crop yields. This improvement can be attributed to the equilibrium in soil-water-air interactions, coupled with enhanced oxygen levels in the root zone and improved nutrient absorption, which are believed to have contributed to the heightened productivity seen with drip irrigation [45]. The addition of nitrogen (N) enhances vegetative growth, while phosphorus (P) application promotes root development. Enhanced vegetative growth due to N fertigation led to an increase in stomatal conductance and chlorophyll content, consequently boosting photosynthesis [46,47]. Furthermore, the adequate amount of potassium (K) availability may have facilitated the transportation of photosynthates to the sink, thereby contributing to increased yields [48]. These findings align with those of [26] in apples [49], in strawberries [50], in apples [51], in onion and [52] in guava.

4.8 Influence of drip irrigation and fertigation on water use efficiency (WUE)

The maximum Water Use Efficiency (WUE) was observed with drip irrigation at 60 percent ETc, while the lowest was noted with conventional irrigation. The improvement in WUE at the lower irrigation level can likely be attributed to reduced water losses from evaporation, percolation, and leaching, which are less prevalent in lower-level drip irrigation compared to higher levels of drip irrigation and conventional irrigation methods. These findings are consistent with those reported by Refs. [30,51,[53], [54], [55]].

4.9 Influence of drip irrigation and fertigation on nutrient use efficiency (NUE)

Drip irrigation and fertigation enhanced nutrient use efficiency in all treatments compared to conventional fertilization methods. This improvement is likely due to increased nutrient availability, leading to higher uptake and reduced losses from leaching and mineralization. These results are supported by the findings of Similar outcomes observed by Refs. [17,30,54], who noted that the highest nutrient use efficiency (NUE) was achieved with drip irrigation at 100 percent ETc and full NPK application.

4.10 Pearson's correlation coefficient for vegetative parameters and fruit yield of apple

Fig. 3 showed that correlation between fruit yield and per cent increase in tree height, annual extension growth, leaf area, leaf potassium, leaf phosphorus, leaf nitrogen and per cent increase in tree height with values of 0.73, 0.95, 0.97, 0.74, 0.93, 0.92 and 0.93, respectively, which indicates that the fruit yield of apple closely related to all these parameters. The asterisks denote the significance levels of the Pearson correlation coefficient (*, **, *** represent p-values of ≤0.05, 0.01 and 0.001, respectively).Fig. 3 Pearson's correlation coefficient for vegetative parameters and fruit yield of apple.

Fig. 3

5 Conclusion

Installing a drip irrigation system at the full ETc rate combined with fertigation consistently results in significant water conservation and frequently enhances vegetative growth and foliar nutrient levels. The findings from a two-year study suggest that adopting the irrigation and fertigation module, specifically drip irrigation (DI) at 100 percent ETc and fertigation at 100 percent AD (NPK), significantly increases the nitrogen (N), phosphorus (P) and potassium (K) content in leaf tissues. The higher levels of both irrigation and fertigation significantly enhanced various vegetative growth parameters such as tree height, plant spread, trunk girth, annual extension growth, and leaf area. Based on the study findings, it can be inferred that employing DI set at 100 percent ETc and fertigation at 100 percent NPK (AD) is recommended for apple growers to enhance productivity and achieve better nutrient and moisture levels in the soil.

Funding

The authors would like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP2024R356 ), 10.13039/501100002383 King Saud University , Riyadh, Saudi Arabia.

Data availability statement

The raw date will be provided on the gentle request.

CRediT authorship contribution statement

Kapil Sharma: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. J.C. Sharma: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Sunny Sharma: Writing – review & editing, Writing – original draft, Visualization, Resources, Funding acquisition. Nitin Sharma: Writing – review & editing, Writing – original draft, Software, Resources, Conceptualization. Rohit Sharma: Writing – review & editing, Writing – original draft, Visualization, Data curation, Conceptualization. Ananthakrishnan S: Writing – review & editing, Writing – original draft, Visualization, Formal analysis, Conceptualization. Abeer Hashem: Writing – original draft, Visualization, Validation, Resources, Funding acquisition, Data curation. Khalid F. Almutairi: Writing – review & editing, Writing – original draft, Resources. Elsayed Fathi Abd_Allah: Writing – review & editing, Writing – original draft, Validation, Project administration, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

We would like to thank DR YSPUHF Nauni for providing the necessary facilities. The authors would like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP2024R356 ), 10.13039/501100002383 King Saud University , Riyadh, Saudi Arabia.
==== Refs
References

1 Kalogiannidis S. Kalfas D. Giannarakis G. Paschalidou M. Integration of water resources management strategies in land use planning towards environmental conservation Sustainibility 15 2023 15242
2 Lauzike K. Nobertas U. Giedre S. The influence of rootstock and high-density Planting on Apple cv. Auksis fruit quality Plants 10 2021 1253 10.3390/plants10061253 34203040
3 Ashraf M.A. Maah M.J. Yusoff I. Soil contamination, risk assessment, and remediation Hernandez-Soriano M.C. Environmental Risk Assessment of Soil Contamination 2014 INTECH Rijeka 3 56 10.5772/57287
4 Chandini K. Ravendra Prakash Om Kumar R. The impact of chemical fertilizers on our environment and ecosystem Book: Research Trends in Environment Ecosystem 2019 69 86pp
5 Mir J.I. Sharma O.C. Raja W.H. Sammi-Ullah S. Raja R.H.S. High-density plantation in apple – a highly remunerative enterprise Indian Hortic. 66 2022 24 26
6 Banyal S.K. Sharma S.K. Effect of fertigation and rootstock on yield and quality of apple under high-density plantation Int. J. Hortic. 68 2011 419 424
7 Zhang S. Chen S. Hu T. Geng C. Liu J. Optimization of irrigation and nitrogen levels for a trade-off: yield, quality, water use efficiency, and environment effect in a drip-fertigated apple orchard based on TOPSIS method Sci. Hortic. 309 2023 111700 10.1016/j.scienta.2022.111700
8 Badr M.A. Abou Hussein S.D. El- Tohamy W.A. Gruda N. Nutrient uptake and yield of tomato under various methods of fertilizer application and levels of fertigation in arid lands Plant Health 62 2010 11 19
9 Li J. Zhang J. Lin G. Wang Y. Liu Y. Zhang M. Zhou J. Zhimin W. Zhang Y. Micro-irrigation improves grain yield and resource use efficiency by co-locating the roots and N-fertilizers distribution of winter wheat in North China Plain Sci. Total Enviorn. 67 2018 89-04
10 Yang P. Wu L. Cheng M. Fan J. Li S. Wang H. Qian L. Review on drip irrigation: impact on crop yield, quality, and water productivity in China Water 15 2023 1733
11 Kumawat K. Sarolia D. Kaushik R.A. Devra N. Effect of irrigation and fertigation scheduling on input use efficiency, yield, and quality of guava cv. Lalit under intensive orcharding system J. Soil Water Conserv. 74 2019 362 368 10.5958/2455-7145.2019.00019.5
12 Neilsen D. Neilsen G.H. Efficient use of nitrogen and water in high-density apple orchard Horti Tec 12 2002 19 25
13 Treder W. Influence of fertigation with nitrogen and a complete fertilizer on growth and yielding of ‘Gala’ apple trees. J. Fruit Ornam Plant Res. 144 2006 143 154
14 Rakicevic M. Miletic R. Pesakovic M. Effect of fertigation on productivity of apple trees Commun. Soil Sci. Plant Anal. 43 2012 589 594
15 Jeyabaskaran K.J. Shirgure P.S. Pandey V. Srivastava A.K. Uma S. Fertigation in horticulture: a guarantee to economized quality production Ind. J. Fert. 17 2021 364 383
16 Ranghaswami M.V. Arunadevi K. Selvaraj P.K. Kumar V. Optimal irrigation and fertigation scheduling on mulberry yield and water use efficiency 7th International Micro Irrigation Congress 2006 PWTC Kuala Lumpur 1 14 10-16 September, 2006
17 Sharma A. Kumar S. Lal S. Malik G. Sharma O.C. Mir J.I. Singh D.B. Raja W.H. Arora S. Nutrient saving and yield enhancement through fertigation in apple growing cold humid regions of North-west Himalayas J. Indian Soc. Soil Sci. 66 2018 10.5958/0974-0228.2018.00011.7 96-02
18 Hasan M. Sirohi N.P.S. Kumar V. Sharma M.K. Singh A.K. Performance evaluation of different irrigation scheduling methods for peach through efficient fertigation system network Acta Hortic. 662 2007 193 197 10.17660/ActaHortic.2004.662.26
19 Kenworthy A.L. Fruit nut and plantation crop, deciduous and evergreen: a guide for collecting foliar samples for nutrient element analysis Memorandum, Department of Horticulture 1964 Michigan State University 223 224
20 Jackson M.L. Soil Chemical Analysis 2005 Parallel Press, University of Wisconsin Madison, Wisconsin, USA 925p
21 Piper C.S. Soil and Plant Analysis 1966 Hans Publication Bombay, India 368p
22 Jackson M.L. Soil chemical analysis Prentice Hall of India Pvt 1973 Ltd New Delhi 111 126
23 Panse G.V. Sukhatme V.P. Statistical Methods for Agricultural Workers second ed. 1967 Indian Council of Agricultural Research New Delhi
24 Asuero A.G. Sayago A. Gonzalez G. The correlation coefficient: an overview Crit. Rev. Anal. Chem. 36 2006 41 59 10.1080/10408340500526766
25 Neilsen G.H. Neilsen D. Herbert L. Nitrogen fertigation concentration and timing of application affect nitrogen nutrition, yield, firmness, and color of Apples grown at high density Hortic. Sci. 44 2009 1425 1431
26 Thakur J. Sharma J.C. Mohit Verma P. Vegetative growth and foliage nutrient content of super chief apple under different irrigation and fertigation schedules in NW Himalayan region Commun. Soil Sci. Plant Anal. 51 2020 2174 2188 10.1080/00103624.2020.1820028
27 White P.J. Ding G. Long-distance transport in the xylem and phloem Marschner's Mineral Nutrition of Plants 2023 Academic Press 73 104 10.1016/B978-0-12-384905-2.00003-0
28 Ramnivas R.A. Kaushik Sarolia DK. Pareek S. Singh V. Effect of irrigation and fertigation scheduling on growth and yield of guava (Psidium guajava L.) under meadow orcharding Afr. J. Agric.e Res. 7 2012 6350 6356
29 Chandra A. Jindal P.C. Sustainable fruit production in arid regions for export Curr. Agric. 25 2001 13 16
30 Mankotia S. Response of NPK Fertilization and Irrigation on Growth and Productivity of High-Density Apple Plantation 2022 Dr. YS Parmar University of Horticulture and Forestry Nauni, Solan, India Ph D Thesis
31 Jung S.K. Choi H.S. Light penetration, growth, and fruit productivity in ‘Fuji’ apple trees trained to four growing systems Sci. Hortic. 125 2010 672 678 10.1016/j.scienta.2010.05.027
32 De Sousa M.L. Goncalves M. Effect of planting density on light interception and distribution, physiological and agronomic performance of ‘Gala’ apple orchards Acta Hortic. 1346 2022 337 346
33 Chauhan N. Chandel J.S. Growth, productivity, leaf nutrient contents and water use efficiency of kiwifruit (Actinidia deliciosa) under drip and basin irrigation system Indian J. Agric. Sci. 80 2010 584 587
34 Priya B. Kurubar A.R. Ashok H. Rames G. Udaykumar N. Umesh M.R. Rajkumar R.H. Effect of fertilizer sources and rate through drip fertigation on growth and yield of custard apple (Annona squamosal L.) cv. Balanagar Pharm. Innov. 11 2022 3050 3054
35 Bunea A. Stepanescu E. Water consumption by apple trees on sandy soils in North Western Romanian under natural and irrigated condition. LucrarileSliintific all instituted Carcelase Si Product Pentru Pomicultura Pitesti 11 1986 203 212
36 Zhang Y. Wang J. Gong S. Xu D. Sui J. Nitrogen fertigation effect on photosynthesis, grain yield and water use efficiency on winter wheat Agric. Water Manag. 179 2017 277 287 10.1016/j.agwat.2016.08.007
37 Kumar R. Haroon S. Water requirement and fertigation in high density planting of apples Indian J. Hortic. 78 2021 292 297 10.5958/0974-0112.2021.00042.6
38 Haneef M. Kaushik R.A. Sarolia D.K. Mordia A. Dhakar M. Irrigation scheduling and fertigation in pomegranate cv. Bhagwa under high density planting system Indian J. Hortic. 71 2014 45 48
39 Goud S. Pimpale A. Kharche V. Effect of fertigation on growth, yield and quality of Nagpur Mandarin Bulletin of Environment, Pharmacology and Life Sciences 1 2017 172 176
40 Verma P. Chandel J.S. Sharma N.C. Thakur Y. Effect of fertigation on growth, yield, fruit quality and fertilizer use efficiency of peach J. Hill Agric. 8 2017 181 186 10.5958/2230-7338.2017.00033.7
41 Majid I. Pandit A.H. Mir M.A. Nisar F. Lateef A. Ahad S. Din S. Wani J.A. Padder B.A. Effect of different doses and timings of fertigation on vegetative growth of high density cultivars Mitch Gala and Red Chief Campsur Biol. Forum Int. J. 14 2022 174 179
42 Wang Y. Wu W.H. Regulation of potassium transport and signaling in plants Curr. Opin. Plant Biol. 39 2017 123 128 10.1016/j.pbi.2017.06.006 28710919
43 Tabassum D. Akhtar A. Inam A. Effect of waste water irrigation on growth, physiology, and yield of mustard Int. J. Bot. Res. 3 2013 27 34
44 Badr M.A. Ali E. Salman S.R. Effect of nitrogen application and fertigation scheduling on potato yield performance under drip irrigation system Gesunde Pflanz. 2023 10.1007/s10343-023-00871-y
45 Nisha S.K. Sreelathakumary I. Vijeth S. Effect of fertigation and drip irrigation on yield and quality of watermelon [Citrullus lanatus (Thumb.) Matsum and Nakai] J. Appl. Hortic. 22 2020 67 70 10.37855/jah.2020.v22i01.13
46 Li Y. Song H. Zhou L. Xu Z. Zhou Z. Vertical distributions and chlorophyll and nitrogen and their association with photosynthesis under drought and rewaterring regimes in a maize field Agric. For. Meteorol. 272 2019 40 54 10.1016/j.agrformet.2019.03.026
47 Zhou H. Ma L. Zhang S. Zhao L. Niu X. Qin L. Wu Q. Effect of Water-Fertilizer coupling on the growth and physiological characterstics of young apple trees Agronomy 13 2023 2506 10.3390/agronomy13102506
48 Maluki M.J. Ogweno Gesimba RM. Evaluation of nitrogen effects on yield and quality of watermelon grown in coastal regions of Kenya Int. Jo. Plant Soil Sci. 9 2016 1 8 10.9734/IJPSS/2016/18821
49 Kachwaya D.S. Chandel J.S. Effect of fertigation on growth, yield, fruit quality and leaf nutrient content of strawberry (Fragaria × ananassa) cv. Chandler Indian J. Agric. Sci. 85 2015 1319 10.56093/ijas.v85i10.52276 23
50 Raina J.N. Suman S. Kumar P. Spehia R.S. Effect of drip fertigation with and without mulch on soil hydrothermal regimes, growth, yield and quality of apple (Malus × domestica Borkh.) Commun. Soil Sci. Plant Anal. 44 2013 2560 2570 10.1080/00103624.2013.811520
51 Piri H. Naserin Effect of different level of water, applied nitrogen and irrigation methods on yield, yield components and IWUE of onion Sci. Hortic. 268 2020 1 11 10.1016/j.scienta.2020.109361
52 Kulwant K.L. Sarolia D.K. Kaushik R.A.A. Jodha A.S. Effect of irrigation and fertigation scheduling on growth, flowering, yield and economics of guava cv. Lalit under ultra high density planting system Indian J. Hortic. 74 2017 362 368
53 Singh J. Sandal S.K. Yousuf A. Sandhu P.S. Drip irrigation and fertigation on soil water dynamics and productivity of greenhouse tomatoes Water 15 2023 2086 10.3390/w15112086
54 Thakur J. Standardization of Irrigation and Fertigation Schedules for Apple under High Density Plantation 2020 Dr. YS Parmar University of Horticulture and Forestry Nauni, Solan, India Ph D Thesis
55 Huang Y. Yang Y.R. Yu J.X. Huang J.X. Kang Y.F. Du Y.R. Tian G.Y. Interaction of the coupled effect of irrigation mode of nitrogen fertilizer format on tomato production Water 2023 15 1546pp 10.3390/w15081546
