The crystalline phases were identified by X-ray diffraction (XRD) using a D8 Advance X-ray diffractometer. X-ray diffraction analysis (XRD) of the materials was performed using a D8 Advance diffractometer (Bruker AXS) operating at a tube voltage of 40 kV and a tube current of 40 mA. The X-ray beam was filtered with a Ni 0.02-mm filter to select a CuKα wavelength. The specimens were scanned over a 2θ range from 3° to 70° at a scanning speed of 5° min⁻¹ using a coupled two theta/theta scan type (Harrington and Santiso, 2021). The identification of zeolite sample was confirmed by matching the powder XRD patterns of the samples with the diffractograms of single-phase patterns from Powder Data File (PDF), compiled by the International Centre for Diffraction Data (ICDD).

The scanning electron microscopy (SEM) images of the zeolite sample were studied where the samples were fixed in 2.5% gluteraldehyde in 0.1 M phosphate buffer (pH 7.2) for 24 h at 4°C and post-fixed 2% in aqueous osmium tetroxide for 4 h (Sandoval-Molina et al., 2017). The samples were dehydrated in series of graded alcohols and dried to critical point drying with CPD (EMS-850) unit by using liquid carbon dioxide. The processed samples were mounted over the stubs with a double-sided carbon conductivity tape, and a thin layer of gold coat over the samples were done by using an automated sputter coater (Model JEOL JFC-1600, Peabody, Massachusetts, USA) for 3 min and scanned under a scanning electron microscope (SEM, Model JOEL-JSM 5600) at required magnifications as per the standard procedures at RUSKA Lab’s College of Veterinary Science, PVNRTVU, Rajendranagar, Hyderabad, India.

Batch experiments were conducted to evaluate the adsorption capacity of zeolite for ammonical-N, phosphorus, and potassium. Batch experiments were conducted in an array of conical flasks, where 100 mL of graded concentrations of ammonium solutions were added to 250-mL Erlenmeyer flasks with 1 g zeolite, sealed and shaken at a speed of 180 rpm for 2 h in a mechanical shaker at 25°C. The influence factors of ammonium and potassium adsorption were studied with the initial ammonium concentration (25–400 mg L⁻¹) and initial potassium concentration (25–300 mg L⁻¹). An ammonium chloride (NH₄Cl) salt was used to make the NH₄ ⁺ solutions, and potassium chloride (KCl) used to make the K⁺ solutions. The equilibrium ammonium concentration was measured using Nessler’s reagent and phosphorus through blue colour method in spectrophotometry, measured by a UV-VIS spectrophotometer (UV-1800, Shimadzu, Kyoto, Japan) and three replicates were performed in parallel for each set of experiments, while the equilibrium potassium concentration was measured using flame photometer. Differences in the concentration between the initial and residual solution were used to calculate the equilibrated adsorption capacity. The data were fit in the Langmuir and Freundlich isotherm equations as given below:

where qe is the adsorbed amount at equilibrium (mg g⁻¹) and C_e represents the equilibrium concentration (mg L⁻¹). K_F and n are equilibrium constants indicative of adsorption capacity and adsorption intensity, respectively. If n is greater than 2 and less than 10 (2 < n < 10), the adsorption process is favourable.

where qe and Ce are the adsorption capacity at equilibrium and the equilibrium concentration respectively, q_max represents the maximum adsorption capacity (mg g⁻¹), K_s is the adsorption equilibrium constant, and n is the dissociation parameter.

The removal efficiency (R %) and the adsorption capacities of adsorbents at time (qt, mg/g) and at equilibrium (qe, mg/g) were calculated using the following equations:

where C₀ and C_e are the initial and equilibrium concentration of the cation (mg L⁻¹), V is the volume (L) of solution, and m is the mineral mass (g).

A soil leaching experiment was conducted to evaluate the inorganic nitrogen leaching for 45 days in the presence of mordenite zeolite in Alfisol of sandy loam texture. The surface soil (0–15 cm) was collected from Hayathnagar Research Farm, CRIDA for this study. Column study with glass columns of 5 cm internal diameter and 50 cm height was used to investigate the release pattern at field scale situation. Columns were organized with three replications. The treatments comprised of two levels of N (100 kg ha⁻¹ and 500 kg ha⁻¹) and four levels of zeolite (0.2 tonnes ha⁻¹, 0.5 tonnes ha⁻¹, 5 tonnes ha⁻¹, and 10 tonnes ha⁻¹). All treatment combinations were thoroughly mixed and scaled down to the amount of 900 g soil. The pore volume for these columns was found to be 981.25 cm³. The filled columns were saturated with distilled water and then irrigated homogeneously with known volume of distilled water, and the leachate was collected with an interval of 3 days and analysed for ammonical-N content using Nessler reagent for colour development (Krug et al., 1979).

The initial soil samples were analysed for mechanical composition, pH, electric conductivity (EC), organic carbon, and available nutrients (N, P, and K) following standard procedures. The physicochemical properties of the initial soil under study are presented in Table 2 . Soil water retention at permanent wilting point (PWP) and field capacity (FC) were measured in pressure plate apparatus at −1.5 MPa and −0.033 MPa (Cassel and Nielsen, 1986). The difference between PWP and FC was calculated as available water. A representative portion of each soil sample was air dried, powdered, and passed through a 0.2-mm sieve for the determination of organic carbon (OC) by Walkley and Black’s method (Jackson, 2005). Available soil nitrogen was determined by alkaline–KMnO₄ method given by Subbaiah and Asija (1956), which primarily measures easily oxidizable N using Kjeltec Auto 1030 Analyser made by Tecator in Sweden. Available P (Olsen P) was determined by sodium bicarbonate (NaHCO₃) extraction and subsequent colorimetric analysis (Olsen et al., 1954). Exchangeable K was measured using the method suggested by Hanway and Heidal, 1952.

Plant samples collected were dried in oven at 65°CC and powdered by using a plant sample grinder. The powdered samples were packed in polyethylene zip covers for further analysis. These samples were used for the estimation of nitrogen, phosphorus, and potassium according to the procedure.

X-ray diffraction (XRD) analysis was carried in order to identify the phases present in the zeolite sample as shown in Figure 2 . XRD revealed the presence of mixture of phases in the collected zeolite with peaks at 2 that match mordenite, tetracesium tetraaluminosilicate, leucite, octasodium tecto hexagallohexa silicate dibromide, Ga-sodalite, lithosite, and cerium nickel silicon. The lattice parameters (a, b, c) obtained from the XRD for zeolite sample are shown in Table 3 . Zeolites found in nature are rarely in their pure form but usually contain impurities such as other types of zeolite, other minerals, or amorphous materials. In this case, quartz impurities were found in mordenite as indicated by the XRD pattern. In our study, quantitative XRD analysis showed that the major component of the natural zeolite was mordenite with minor amounts of others. The diffraction pattern of the zeolite sample was matched with that of the literature, and identified phases are shown in Table 3 along with the chemical formulas and figure of merit of the crystalline phases of zeolite ( Table 4 ).

Scanning electron microscopy is a highly versatile technique that gives detailed surface information of samples and used to obtain high-resolution images. It is a type of electron microscopy that uses a focused beam of electrons to scan the surface of a specimen and generate images at a much greater resolution. The resolution of SEM instruments can range from up to several nanometres. With the help of scanning electron microscopy (SEM) imaging, the shape of zeolite was elucidated. In our study, the photographs at several thousands’ magnification have shown a needle-like structure ( Figure 3 ). According to the reports on natural zeolites, the morphology of natural mordenite with a small amount of impurities was needle- or fibre-like with c-axis elongation (Passaglia and Sheppard, 2001). The SEM results are consistent with the XRD results, suggesting that the sample is mordenite zeolite. The SEM images were matching the images presented by Sakizci and Kilinc (2015).

At the end of each experimental period, soil available N, P, and K was studied in post-harvest soil samples. The change in soil available nitrogen content of the post-harvest soil at different moisture levels, fertiliser levels, and zeolite levels is presented in Table 7 . There was a significant effect (p<0.05%) on the soil available N, P, and K due to the application of zeolite at both the moisture levels and fertiliser levels. The results revealed that fertiliser application along with zeolite application significantly improved soil available N, P, and K content ( Table 7 ). Under two moisture conditions, it was observed that soil available N, P, and K content increased significantly under 100% FC as compared to 50% FC, while under three fertiliser levels studied, 100% RDF could maintain higher soil available N, P, and K content as compared to 50% RDF and control. The soil available N increased with increasing dose of zeolite application. Highest was observed with zeolite application (Z200) of 89.28 mg kg⁻¹ (equivalent to 200 kg zeolite ha⁻¹). The treatment RDF100 + Z4 was most effective in maintaining higher soil available nutrient under both the moisture levels, and the increase in soil available N, P, and K was significantly (p < 0.05%) higher than the rest of the treatments. This suggests that zeolite application improves soil available nutrients if applied along with chemical fertilisers. Legese et al. (2024) impregnated zeolite (phillipsite) with 5% solutions of macro- (P, N, K, Ca, and Mg) and micro-nutrients (Fe, Zn, and Cu) in the form of their salts and evaluated the two samples (UNZC and SMNZC); it was found that total N increased in all amended plots as compared to amended plots. The content was higher where a higher dose was tested. Ravali et al. (2020) observed similar findings due to the application of zeolite @ 7.5 tonnes ha⁻¹ and N @ 200 kg ha⁻¹, which showed a significant effect on soil NPK content at different crop growth stages and at harvest in maize. Under 100% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 48.6%, 40.5%, and 25.1%, respectively, over Z0 (without zeolite application) ( Figure 9A ). With 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 62.1%, 44.7%, and 34.9%, respectively, over Z0. Under 50% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 37.5%, 27.8%, and 22.2%, respectively, over Z0 (without zeolite application). With 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 31.5%, 24.7%, and 4.7%, respectively, over Z0. Zeolite application @ 5 tonnes ha⁻¹ resulted in an increase of 35.13% in total N content in Alfisols (Triatmoko et al., 2019). The soil chemical properties that include soil cation exchange capacity, the soil total nitrogen concentration, and nitrogen use efficiency increased significantly due to the co-application of 150 kg N ha⁻¹ and 200 kg N ha⁻¹ with 10 and 15 tonnes ha⁻¹ of zeolite (Dastbaz et al., 2023).

Similarly, under 100% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil available P by 48.9%, 27.1%, and 23.7%, respectively, over Z0 (without zeolite application). With 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 37.8%, 28.4%, and 17.9% respectively, over Z0 ( Figure 9B ). Under 50% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 44.9%, 29.5%, and 11.6%, respectively, over Z0 (without zeolite application). With 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 43.9%, 42.1%, and 26.4%, respectively, over Z0. The capacity of zeolite to improve the P availability is found high under 100% FC as compared to 50% FC.

In case of soil available K, under 100% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil available K by 14.1%, 12.4%, and 6.92%, respectively, over Z0 (without zeolite application) ( Figure 9C ). While with 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 14.6%, 10.6%, and 6.97%, respectively, over Z0. Under 50% FC, with 100% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 21.1%, 15.8%, and 7.53%, respectively, over Z0 (without zeolite application). While with 50% RDF, the application of zeolite @ 200 kg ha⁻¹, 100 kg ha⁻¹, and 50 kg ha⁻¹ increased the soil N by 21.5%, 19.1%, and 7.01%, respectively, over Z0. The capacity of zeolite to improve the nutrient availability is found high under 100% FC as compared to 50% FC. There was significant difference in soil available nutrients in post-harvest soil due to zeolite and fertiliser use. The combined application of zeolite and fertiliser showed improved nutrient status than fertiliser application without zeolite. Some studies reported that N fertiliser requirement was reduced by 33% due to zeolite application in rice (Chen et al., 2017). The two- and three-way interaction effect among moisture, fertiliser rate, zeolite, and even year was significant for soil available N, P, and K contents. Averaged across the three zeolite amendments, topsoil available K increased from 13% (93 DAT, K₃₀) to 31% (55 DAT, K₆₀) in 2017, and from 16% (55 DAT, K₃₀) to 46% (34 DAT, K₆₀) in 2018 due to K₃₀ and K₆₀ applications application in rice (Li et al., 2022). In calcareous soils, it was reported that application of natural zeolite at 10 μg ha⁻¹ (Z10) significantly increased in N, P, and K in post-harvest soil samples with 42.72 mg N kg⁻¹ soil, 20.23 mg P kg⁻¹ soil, and 201.05 mg K kg⁻¹ soil, respectively (Saleh and Al Bahrani, 2023). Application of zeolite along with chemical fertilisers could improve soil N, P, and K content (Banik et al., 2023) and also with organic manures such as vermicompost and biofertilisers, and chemical fertilisers could improve soil N, P, and K content and also resulted in higher soil available N, P, and K in post-harvest soil samples (Rahmani et al., 2023; Idim et al., 2024).

The present study showed higher N, P, and K uptake due to zeolite addition along with chemical fertilisers ( Figure 10 ). Experimental treatments significantly affected N, P, and K uptake in tomato. Among the treatments, control treatment (RDF0Z0) had minimum N, P, and K uptake, whereas maximum N, P, and K uptake was obtained due to application of full recommended dose of fertilisers along with 200 kg zeolite ha⁻¹ (RDF100Z200). The zeolite addition improve,d N, P and K uptake by two times as compared to without zeolite addition under both the moisture conditions. The treatment RDF100+Z200 could maintain higher mean N, P, and K uptake with 560.63 mg pot⁻¹, 85.34 mg pot⁻¹, and 192.87 mg pot⁻¹, respectively, in 100% FC conditions, while least mean N, P, and K uptake with 289.39 mg pot⁻¹, 42.80 mg pot⁻¹, and 83.30 mg pot⁻¹, respectively, in 100% FC conditions in control treatment (RDF0Z0). However, the uptake reduced slightly under 50% FC conditions where the mean N, P, and K uptake was 436.53 mg pot⁻¹, 87.53 mg pot⁻¹, and 192.87 mg pot⁻¹, respectively, in F100+Z200 treatment and 224.90 mg pot⁻¹, 42.80 mg pot⁻¹, and 76.63 mg pot⁻¹, respectively, under RDF0Z0 treatment. Zeolite addition (5 tonnes ha⁻¹) along with manures improved potassium availability and uptake in soybean cultivated in Alfisols (Haniati et al., 2019) and also improved N availability and uptake in soybean (Triatmoko et al., 2019). In Iran, there was significant effect of combined application of zeolite and fertiliser on improved N uptake (Kavoosi, 2007) and K uptake in rice (Chen et al., 2017; Xia et al., 2019). Gholamhoseini et al. (2012) reported that the zeolite application @ 9 tonnes ha⁻¹ improved the N uptake by four times in canola.

In the first year of the experiment (2017), zeolite addition to the soil (along with chemical fertiliser) significantly increased the tomato biomass in respect to the control ( Table 8 ). The yield at the highest zeolite dose (Z200) was higher with 34.82 g pot⁻¹ than other doses. This observation was similar in second year of experimentation (2018) where it was 39.99 g pot⁻¹ due to application zeolite @ 200 kg ha⁻¹ (Z200). Result showed that the biomass of tomato was significantly influenced by the treatment applied ( Table 8 ). The greatest mean biomass yield was obtained by supplementing (RDF₁₀₀Z₂₀₀) under both moisture levels studied with 49.08 g pot⁻¹ in 100% FC and 38.31 g pot⁻¹ in 50% FC and the least with 26.93 g pot⁻¹ in 100% FC and 26.06 g pot⁻¹ in 50% FC in control (RDF₀Z₀). On other hand, with the increase in fertiliser rate from RDF0 to RdF100 (100% RDF-180: 100: 50 kg NPK ha⁻¹) and zeolite dose from Z0 to Z200 (0–200 kg ha⁻¹) led to an increase of 36.4% and 48.39% increase in biomass yield, respectively. Kotoulas et al. (2019) reported highest fresh weight of wheat due to zeolite application @ 40 mg kg⁻¹, which was fund to be 74% higher than the control. Another study revealed that combined application of 100 kg ha⁻¹ zeolite and 200 kg ha⁻¹ NPK provided optimal yields of dry shelled maize up to 5.44 tonnes ha⁻¹ grown in Inceptisol (Affendi et al., 2023).

Zeolite addition to the soil (along with chemical fertiliser) significantly increased the WUE as compared to the control ( Table 8 ). The WUE was found high with 50% FC as compared to 100% FC during both the years of experiment. The WUE was found high under 50% FC with 18.24 g L⁻¹ in 2017 and 20.19 g L⁻¹ in 2018 in F₁₀₀Z₂₀₀ treatment, while under 100% FC, the WUE was with 11.68 g L⁻¹ in 2017 and 14.01 g L⁻¹ in 2018 in F₁₀₀Z₂₀₀ treatment. Under 100% FC, the mean increase in WUE over 2 years with Z4 was 22.17% in control (without any fertiliser application), 38.11% in 50% RDF, and 67.34% in 100% RDF. Research states that zeolite holds water in its extraordinary porous structure and hence improves water availability to crops and enhances WUE (Xiubin and Zhanbin, 2001; Gholamhoseini et al., 2013). Zheng et al. (2018) reported that zeolite application @ 15 tonnes m⁻² along with energy-controlled irrigation improved grain yield with less water consumption. According to Kralova et al. (1994), soils enriched with natural zeolite were able to increase the water retention by 18%–19% and for sandy soils even up to 50% (Lancellotti et al., 2014). While Ravali et al. (2020) reported 48.5% increase in water retention capacity due to 7.5 tonnes ha⁻¹ zeolite application in sandy and loamy soils. Hazrati et al. (2022) reported an increase in WUE up to 22.10 g L⁻¹ with the use of 10 tonnes zeolite ha⁻¹ along with an application @ 150 kg ha⁻¹ even under 60% depletion of available soil water content in Salvia officinalis grown in loam sandy soils. The positive effect of zeolite application in increasing yield was observed in maize (Aboul-Magd et al., 2020); sugarcane (Cairo et al., 2017), and tomato (Méndez Argüello et al., 2018).

In most of the studies, clinoptilolite is widely used and tested for improving the soil availability. However, mordenite is also known to improve soil available nutrients and water use efficiency (Stamatakis et al., 2017). Mordenite is a high silicate zeolite and large-pore zeolite with high surface area (Gosselink et al., 2010). In our study, mordenite application could improve the soil available N, P, and K; their uptake; dry matter yield; and WUE in Alfisols. Overall performance for both the years is shown in Figure 11 . Uptake of nitrogen, phosphorus, and potassium by tomato is significantly affected by fertiliser levels and zeolite levels. An increase in fertiliser application leads to a decrease in nitrogen use efficiency and an increase in soil nitrate N accumulation and soil fertility. Combined supplementation of chemical fertilisers with zeolite had a notable effect on the chemical properties of the soil and also on yield. Zeolite prevents nutrients to be lost through leaching (Sun et al., 2019). Our study showed a strong correlation among N, P, and K availability in soil and their uptake in plant and dry matter yield and water use efficiency ( Figure 12 ).

Application of zeolites in soil has gained importance for reducing N leaching and increase N efficiency. Sepaskhah and Yousefi (2007) reported that application of 2–8 g zeolite kg⁻¹ prevented nutrient leaching in sandy loam soil. MesoLite zeolite has low surface area (9–12 m² g⁻¹) and very high cation exchange capacity [494 cmol(+)/kg]. The application of mesolite to sandy soil @ 0.4% resulted in reducing the NH₄ ⁺ to the extent of 90% as compared to unamended soil (Zwingmann et al., 2009). In canola, the application of 270 kg N ha⁻¹ without zeolite resulted in the greatest amount of N leaching loss to the tune of 144.23 kg ha⁻¹ in sandy soils (Gholamhoseini et al., 2012). Due to its multiple positive effects on the chemical soil properties, zeolite contributes to improved nutrient, crop productivity, and crop quality. Water scarcity is a major limiting factor of agricultural production in arid locations mainly due to low precipitation and high evaporation and is aggravated by global climate change through extreme events and prolonged dry seasons. However, studies proved that zeolite improves water and plant nutrients. Recently, it is reported that the positive impact of zeolite application on paddy yield could continue even in the fifth year after its initial application. Moreover, application of zeolite @ 10 tonnes ha⁻¹ (Z10) increased soil NH₄ ⁺–N by 27%–38% and NO₃–N by 14%–22% in 5 years compared to Z0 (control) (Zhao et al., 2023). Thus, zeolite application can last for 5 years. Thus, it can be used along with mineral fertilisers to earn more profits.