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Article

Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality

by
Yifei Du
1,2,
Xiao Ge
1,2,
Yimei Du
1,2,
Hongrui Ding
1,2,* and
Anhuai Lu
1,2,*
1
Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, China
2
Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China
*
Authors to whom correspondence should be addressed.
Minerals 2025, 15(8), 825; https://doi.org/10.3390/min15080825
Submission received: 3 July 2025 / Revised: 29 July 2025 / Accepted: 31 July 2025 / Published: 2 August 2025
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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Abstract

In the rock–soil–biology–water ecosystem, rock weathering provides essential plant nutrients. However, its supply is insufficient for rising crop demands under population growth and climate change, while excessive fertilizer causes soil degradation and pollution. This study innovatively irrigated with carbonate rock leachates to enhance soil nutrient availability. A pot experiment with lettuce showed that irrigation significantly increased soil NO3−-N (+102.20%), available K (+16.45%), available P (+17.95%), Ca (+6.04%), Mg (+11.65%), and Fe (+11.60%), and elevated the relative abundance of Firmicutes. Lettuce biomass per plant rose by 23.78%, with higher leaf minerals (P, K, Ca, and Mg) and antioxidants (carotenoids and ascorbic acid). A field experiment further confirmed improvement of soil nutrient availability and peanut yield. This carbonate rock leachate irrigation technique effectively enhances soil quality and crop productivity/quality, offering a sustainable approach for green agriculture.

1. Introduction

Within Earth’s ecosystem, complex interactions exist among “surface rock–soil–biology–water”. During the weathering of rock into soil, mineral elements essential for plant growth are released. Water, serving as both the solvent for rock weathering and the transport medium for nutrients, constitutes a critical nexus connecting rock, soil, and plants. Plants absorb water and nutrients from the soil through their root systems, while plant growth, in turn, influences changes in soil structure and composition, as well as the weathering of carbonate minerals. However, against the backdrop of continuously increasing global population and complex, variable climate change [1,2], enhancing crop yields can no longer rely solely on the nutrients provided by natural rock weathering processes. While the Green Revolution of the 1960s achieved substantial increases in crop production through the breeding of high-yielding varieties and the application of pesticides and chemical fertilizers [3,4,5], it has also resulted in global nitrogen [6] and phosphorus [7] cycles exceeding their safe operating space, causing severe negative impacts on global biodiversity [8], human health [9], the atmospheric environment [10], and groundwater security [11].
The excessive application of chemical fertilizers not only impacts the nutritional quality of crops but, with prolonged use, can also lead to soil nutrient imbalances [12,13], structural degradation [14], heavy metal contamination [15], and degradation of microbial communities [16,17]. Minerals, as essential components of soil, serve as its skeleton and the source of mineral elements, playing a crucial role in improving soil physicochemical properties and supporting the growth and metabolism of microorganisms. Previous research primarily focused on the direct addition of carbonate rocks and silicate rocks [18,19] to agricultural soils. This approach offers synergistic benefits by restoring soil health [20] and increasing crop yields [18,19], while also effectively sequestering atmospheric CO2 and mitigating the greenhouse effect [21]. For instance, the application of the silicate mineral basalt releases additional Si, Ca, and K into the soil. While improving soil nutrient availability and boosting sorghum yields [22], it can also enhance plant stress resistance.
However, it should be noted that numerous factors requiring in-depth research and careful consideration remain for the practical promotion and application of this technology. Regarding its long-term ecological effects on climate and soil [23,24], although short-term experiments have preliminarily confirmed its positive outcomes in carbon sequestration and soil improvement, whether this technology may trigger negative ecological impacts over extended timescales remains incompletely understood. For instance, the long-term, large-scale addition of carbonate and silicate rocks to soil leads to significantly increased bioavailable concentrations of certain elements [25]. Key uncertainties include whether this will induce inhibition of plant uptake of other ions [26], introduce harmful metal elements into the soil [27] facilitating their accumulation through the food chain, or cause irreversible alterations to the structure and function of soil microbial communities, thereby affecting the stability of the soil ecosystem. Furthermore, the significant amount of dust generated during the processing and production of mineral materials raises concerns regarding potential environmental pollution. These potential issues necessitate long-term systematic research and monitoring in practical applications. Additionally, the economic viability of directly applying mineral materials for soil amendment and their compatibility with agricultural irrigation systems (e.g., drip and sprinkler irrigation) constitute essential considerations for practical implementation.
Therefore, in this study, we propose a technical strategy involving irrigation with carbonate rock leachate, shifting away from the conventional approach of direct mineral material application. Leveraging the pivotal role of water within the “mineral–soil–plant” system, we investigate the effects of carbonate rock leachate on soil physicochemical properties, soil microbial community structure, and plant growth. Through a pot experiment with lettuce conducted under controlled conditions, we examined the impact of carbonate rock leachate on soil physicochemical properties, soil microbial community structure, plant growth, and nutritional quality. Concurrently, a field experiment was conducted to preliminarily assess the soil amendment efficacy of carbonate rock leachate under local conditions. These combined experiments allow for an evaluation of carbonate rock leachate irrigation as a valuable alternative practice to the direct application of carbonate minerals, characterized by its strong practical application potential and low-input requirements. Our preliminary findings from both the controlled and field experiments demonstrate the environmental compatibility of this technique for soil improvement and its significant efficacy in promoting plant growth, thereby providing a novel approach for sustainable and green agricultural development.

2. Materials and Methods

2.1. Source and Characterization Methods of Samples

The rock samples were collected from the carbonate rock strata of the Mantou Formation (Middle Cambrian) exposed in the western Shandong Province, China (35°24′ N, 116°34′ E).
X-ray diffraction (XRD) analysis utilized a PANalytical X’Pert Pro diffractometer, manufactured by Malvern Panalytical (Almelo, Gelderland, The Netherlands) with Cu Kα radiation (λ = 0.15418 nm). Scans were collected across a 2θ range spanning 10° to 80°, employing a scan rate of 5°/min. The operating conditions were maintained at 40 kV and 40 mA. Subsequent data fitting and structural analysis were performed using Highscore Plus software (Malvern Panalytical Inc., Malvern, UK; Version 5.1.0).
Mineralogical identification was conducted via Raman spectroscopy utilizing a confocal microspectrometer (Renishaw inVia Reflex, Renishaw plc, Wotton-under-Edge, UK) employing a 532 nm excitation source. Measurements were performed under the following conditions: laser power set at 50 mW, a slit width of 65 µm, and a 50× magnification objective lens. The acquisition time per spectrum was 10 s, and each spectrum was the accumulation of 3 scans; the measurement error was ±1 cm−1, and the wavenumber range of the spectrum was 100–1350 cm−1.
Sample micromorphology was examined using a field emission scanning electron microscope (FEI-Quanta FEG 650) (Thermo Fisher Scientific, Waltham, MA, USA) operating in back-scattered electron (BSE) imaging mode. Thin sections underwent chromium coating prior to analysis. Elemental composition and spatial distribution were subsequently characterized via energy-dispersive X-ray spectroscopy (EDS) integrated with the SEM. This involved single-point quantification and multi-elemental mapping. Analyses were executed under high vacuum using whole-spectrum acquisition, with operational parameters set to an accelerating voltage of 20 kV, a resolution of 2.5 nm, and a working distance of approximately 10 mm.
Analysis of major elements was performed using an ARL ADVANT XP+ X-ray fluorescence spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). Measurements were conducted via the wavelength-dispersive pressed-pellet method, employing a supersharp end-window ceramic rhodium target (4 kW). The operating current and voltage during analysis were maintained at 50.0 mA and 50.0 kV, respectively. Trace element concentrations in the powdered rock samples were determined using a NexION 350X inductively coupled plasma mass spectrometer (ICP-MS, PerkinElmer, Waltham, MA, USA). Prior to ICP-MS analysis, samples were pretreated using a CEM Mars6 high-throughput closed-vessel microwave digestion system (CEM Corporation, Matthews, NC, USA). During ICP-MS operation, the radio frequency (RF) power was set to 1600 W, and the plasma gas flow rate was controlled at 18 L min−1.

2.2. Preparation and Analysis of Carbonate Rock Leachates

The preparation and analysis of carbonate rock leachates were conducted as follows: Carbonate rock materials were sorted, crushed, and processed into powder with a particle size of 100–200 mesh. Carbonate rock leachates were prepared at a 0.5% (w/v) ratio (mineral powder to water), followed by stirring and soaking for 3 h. After the mineral material settled to the bottom of the container, the supernatant was collected for irrigation in both the pot and field experiments. For the pot experiment, mineral leachates were prepared by mixing mineral material with ultrapure water. For the field experiment, mineral leachates were prepared using local well water mixed with mineral material, then applied via existing irrigation channels or drip systems.
Leachates derived from carbonate rocks were analyzed for pH and major cation content. pH measurements employed a Mettler Toledo FE28-Standard meter (Mettler Toledo, Greifensee, Switzerland), with triplicate readings performed and their mean value documented. Cation quantification involved filtering samples through 0.45 µm membranes, followed by acidification with 2% HNO3 and five-fold dilution. These prepared leachates were subsequently analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES) on an EXPEC 6500 instrument (Focused Photonics, Hangzhou, China).

2.3. Lettuce Pot Experiment

2.3.1. Design and Management of the Lettuce Pot Experiment

The plant material selected for the pot experiment was the Italian semi-heading lettuce (Lactuca sativa L.), a semi-heading variety characterized by strong adaptability, tolerance to both heat and cold, and suitability for year-round cultivation. Lettuce seeds were purchased from Zhongshu Seed Technology Co., Ltd. (Beijing, China). The experiment was conducted from 30 April to 30 July 2022, in the laboratory of the School of Earth and Space Sciences at Peking University. During the experiment, the temperature and relative humidity in the growth chamber were maintained at 25 °C and 70%, respectively, with a light/dark photoperiod ratio of 2:1. An LED plant supplementary light served as the primary light source for plant growth, with its main emission bands in the red and blue–violet spectrum.
The potting substrate was prepared by mixing a base soil (sandy loam (Chinese Soil Taxonomy), bulk density 1.20 kg L−1) with coconut coir (bulk density 0.35 kg L−1) at a 1:1 (v/v) ratio to ensure physicochemical homogeneity between CK and MW treatments. The base soil was collected from the 0–20 cm layer of an agricultural field in Beijing City (40°15′ N, 117°12′ E). Prior to mixing, the coconut coir was soaked and rinsed with deionized water (1:5 w/v, 30 min per rinse, three rinses) to remove residual salts and soluble acids. Subsequently, it was buffered with CaCO3 (1% w/w, 25 °C, 7 days) to ensure that it would not induce acidification or alkalinization effects during the pot experiment period. Soil physicochemical properties were determined before the pot experiment (Table 1).
Two treatments were established: the MW treatment, where lettuce plants were irrigated throughout their entire growth cycle with carbonate rock leachates, and the CK (control) treatment, where plants were irrigated with ultrapure water. Each treatment comprised 40 lettuce plants (one lettuce plant per pot). Irrigation volume and timing were determined based on soil moisture status. Plant nutrition was supplied via a formulated nutrient solution. Apart from the irrigation water source, all other management practices were identical between the two treatments.

2.3.2. Measurement of Growth Data, Root Activity, and Nutritional Quality in the Lettuce Pot Experiment

During the lettuce growth period, plant height and leaf number of all plants were measured every 5 days for each treatment. Leaf SPAD values (indicative of relative chlorophyll content) were measured on day 60, day 75, and day 90 after sowing using a portable chlorophyll meter (SPAD-502, Konica Minolta, Tokyo, Japan).
After harvest, lettuce plants were sequentially washed 1–2 times with tap water and deionized water. Surface moisture was blotted dry before weighing, and the fresh weights of both the aboveground and underground parts were recorded separately. Leaves from each treatment were collected, rapidly frozen in liquid nitrogen, lyophilized, and ground to homogeneous powder prior to storage at −80 °C. Fresh root tips were collected at harvest for root activity determination.
The extraction of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) elements from lettuce leaf samples was performed using microwave digestion (TOPEX versatile microwave digestion system, Shanghai Yiyao Instruments, Shanghai, China) for sample pretreatment. The specific experimental procedure was as follows: An appropriate amount of sample was weighed into a polytetrafluoroethylene (PTFE) digestion vessel, followed by the addition of 5 mL nitric acid (HNO3). After standing to allow initial reactions to subside, the vessel was sealed and placed into the microwave digestion system. The digestion program consisted of the following temperature and hold times: 100 °C (3 min) → 140 °C (3 min) → 160 °C (3 min) → 180 °C (3 min) → 190 °C (15 min). Once cooled to below 50 °C, the digestion vessel was removed and transferred to a fume hood. The vessel was then opened, and the contents were rinsed and brought to volume 50 mL using ultrapure water. Lettuce leaf concentrations of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were quantified via inductively coupled plasma optical emission spectrometry (ICP-OES; PerkinElmer Optima 8000, PerkinElmer Inc., Waltham, MA, USA). For phytochemical analysis, ultraviolet–visible (UV–Vis) spectrophotometry was employed to determine soluble sugar, soluble protein, total polyphenol, and total flavonoid levels. Ascorbic acid and carotenoid contents were measured using high-performance liquid chromatography (HPLC). Root activity was determined based on the triphenyltetrazolium chloride (TTC) reduction assay. Three composite biological replicates per treatment were generated by homogenizing tissues from forty pooled plants.

2.4. Peanut Field Experiment

A field experiment with peanut (Arachis hypogaea L.) was conducted in Jining City, Shandong Province, China (35°24′ N, 116°34′ E). The research site exhibits a semi-humid temperate climate. Mean annual climatic parameters are 14.3 °C and 633 mm for temperature and precipitation, respectively. Approximately 70% of the yearly rainfall is concentrated during the period from June to September. Soil at the experimental site was classified as sandy loam, possessing a pH value of 6.48. The physicochemical properties of the field soils were determined before the field experiment (Table 2).
The study utilized a randomized complete block design (RCBD) with three replicates per treatment, encompassing a total experimental area of 648 m2. All field management protocols, excluding irrigation, adhered to conventional local practices and remained uniform across treatments. To prevent mixing of irrigation water between plots, isolation ridges were established between plots receiving different irrigation treatments.
Peanuts (cultivar ‘Jinguan No. 1’) were sown on 21 April 2023, and harvested on 21 September 2023. Planting was performed via open-field direct seeding using a ridge tillage system characterized by wide row spacing and narrow plant spacing. Plant spacing was 20 cm, and row spacing was 60 cm. Base fertilizer was applied before sowing.
Two irrigation treatments were established: the MW treatment, where peanuts were irrigated throughout their entire growth cycle with carbonate rock leachates, and the CK (control) treatment, where plants were irrigated with conventional well water. Both treatments received irrigation during three critical growth stages: the seedling stage, the flowering and pegging stage, and the pod formation stage, resulting in a total of three irrigation events during the growth cycle.

2.5. Soil Sampling and Physicochemical Property Analysis

For the pot experiment, soil samples were acquired both prior to planting and post-harvest. Following harvest, rhizosphere soil adhering to lettuce roots was isolated using a root-shaking technique. After manually removing impurities, samples were homogenized and refrigerated at 4 °C for later analysis. For the field experiment, soil samples (0–20 cm depth) were collected from each treatment plot employing a soil auger and a five-point sampling strategy. Each composite sample was subdivided: one subset was air-dried, with visible impurities (debris, roots, and residues) manually extracted. This material was subsequently pulverized and sieved through a 150 μm (100-mesh) sieve for physicochemical characterization. The remaining portion was preserved at −80 °C for subsequent high-throughput microbial community analysis.
Soil pH assessment employed a potentiometric methodology with a 1:2.5 solid-to-water ratio. Precisely 10.00 g of air-dried soil (<2 mm particle size, 10-mesh sieved) was combined with 25 mL of CO2-free water in 50 mL centrifuge tubes. Following 30 min of oscillation and subsequent settling, pH values were recorded in triplicate using a Mettler Toledo FE28-Standard instrument (Mettler Toledo, Greifensee, Switzerland), with mean values documented. Organic matter content was quantified through potassium dichromate oxidation involving external heating. For available phosphorus, extraction utilized 0.5 mol L−1 NaHCO3 solution followed by molybdenum–antimony colorimetric determination. Potassium availability was evaluated by extracting with 1 mol L−1 NH4OAc and subsequent flame photometric measurement. Inorganic nitrogen fractions (nitrate nitrogen and ammonium nitrogen) were extracted with 2 mol L−1 KCl (soil: solution = 1:5 w/v, 30 min, 25 °C) and quantified via UV–Vis spectrophotometry (NO3−-N at 220 nm; NH4+-N at 540 nm after indophenol-blue reaction). Total elemental analysis required microwave digestion (200 °C, 45 min) of 0.25 g soil with 9 mL 69% HNO3 and 3 mL 40% HF, followed by dilution to 50 mL with 2% HNO3 and 0.45 μm membrane filtration. Extractable calcium (Ca) and magnesium (Mg) were obtained using 1.0 M ammonium acetate (pH 7.0, 1:5 ratio, 30 min), while available iron (Fe) was extracted with DTPA-TEA buffer (pH 7.3, 1:2 ratio, 2 h). After centrifugation and 0.45 μm filtration of these extracts, elemental quantification of total and available Ca, Mg, and Fe fractions was performed via ICP-OES (Thermo Fisher Scientific, Waltham, MA, USA).

2.6. Determination of Soil Microbial Communities

Rhizosphere soil was collected from lettuce plants subjected to two distinct experimental treatments in the pot trial, with each treatment group comprising three biological replicates. Microbial community analysis targeted the 16S rRNA gene within these six soil samples. Total genomic DNA was isolated employing the TGuide S96 Magnetic Soil/Stool DNA Kit (Tiangen Biotech, Beijing, China), following the manufacturer’s protocol. Assessment of DNA integrity was performed via electrophoresis on 1.8% agarose gels, while concentration and purity were measured using a NanoDrop 2000 UV–Vis spectrophotometer (Thermo Scientific, Wilmington, DE, USA). Amplification of the bacterial 16S rRNA V3–V4 hypervariable regions utilized the primer pair 338F (5′-ACTCCTACGGGAGGCAGCA-3′) and 806R (5′-GGACTACHVGGGTWTCTAAT-3′). Sample-specific Illumina index sequences were appended to both forward and reverse primers to enable multiplexed high-throughput sequencing. Polymerase chain reactions (10 μL total volume) contained 5–50 ng DNA template, 0.3 μL each of forward and reverse primers (10 μM), 5 μL KOD FX Neo Buffer, 2 μL dNTPs (2 mM each), 0.2 μL KOD FX Neo polymerase, and ddH2O to volume. Thermal cycling parameters comprised initial denaturation (95 °C, 5 min); 20 cycles of denaturation (95 °C, 30 s), annealing (50 °C, 30 s), and extension (72 °C, 40 s); and final extension (72 °C, 7 min). Amplified products underwent purification with an Omega DNA kit (Omega Inc., Norcross, GA, USA) and quantification on a Qsep-400 system (BiOptic Inc., New Taipei City, Taiwan). The resulting amplicon library was subjected to paired-end sequencing (2 × 250 bp) on an Illumina NovaSeq 6000 platform (Tsingke Biotechnology Co., Ltd., Beijing, China).

2.7. Statistical Analysis

Statistical analyses were performed using IBM SPSS Statistics 27. Between-group comparisons employed the two-tailed Student’s t-test. Results are presented as means ± standard deviation (SD). Data processing and graphical figure generation were conducted using OriginPro 2021b.

3. Results

3.1. Characterization of Carbonate Rocks

Figure 1 displays the X-ray diffraction (XRD) analysis results for three representative rock samples. All samples contain a high content of dolomite, followed by calcite and quartz. The three strongest peaks at 30.9°, 41.1°, and 51.0° correspond to the (104), (11-3), and (11-6) planes of trigonal dolomite (JCPDS 84-1208), respectively. The three strongest diffraction peaks at 29.4°, 48.5°, and 47.5° correspond to the (104), (116), and (018) planes, indicating the presence of trigonal calcite (JCPDS 81-2027). The three strongest diffraction peaks at 26.7°, 20.9°, and 50.2° correspond to the (011), (100), and (11-2) planes of trigonal quartz (JCPDS 85-0795), respectively. Furthermore, semi-quantitative analysis of the representative samples (Table 3) reveals that the dolomite content is significantly higher than that of calcite and quartz, which is consistent with the observations under the microscope.
The Raman spectroscopic results of the sample thin sections further confirm that the primary constituents are dolomite (Figure 2a), calcite (Figure 2b), and quartz (Figure 2c). Figure 2a presents the Raman spectrum of dolomite. The peaks at 177 cm−1, 298 cm−1, and 1097 cm−1 correspond to the characteristic bands of dolomite [28]. The strongest peak at 1097 cm−1 corresponds to the symmetric stretching vibration mode of the CO32− ion. The two broader, secondary intensity peaks at the low-frequency end, 177 cm−1 and 298 cm−1, both represent lattice vibrations within the dolomite crystal [29]. Similarly, the Raman vibrational modes of calcite (Figure 2b) exhibit a peak at 1085 cm−1, representing the symmetric stretching vibration of CO32−. Peaks at 151 cm−1 and 278 cm−1 are attributed to lattice vibrations involving Ca2+ and CO32−, while the peak at 712 cm−1 corresponds to the in-plane bending symmetric vibration mode of CO32− [30]. Additionally, a peak observed at 465 cm−1 (Figure 2c) is consistent with the characteristic stretching vibration mode of the Si−O bond in quartz [31]. Peaks at 205 cm−1 are associated with the low-frequency vibrations of silica tetrahedra, and the peak at 1090 cm−1 corresponds to the symmetric stretching vibration of silica tetrahedra.
Furthermore, scanning electron microscopy (SEM) was employed to characterize the micromorphology of the carbonate samples (Figure 3). Numerous crystals exhibiting regular geometric shapes, predominantly rhombohedral, are visible within the mineral aggregates. Some crystals display a relatively high degree of euhedrality, showcasing characteristic growth features typical of carbonate minerals. Crystal surfaces exhibit certain irregularities, including concavities, convexities, and fractures. Distinct pores are observed in some areas; these pores are irregular in shape and are likely intergranular pores or secondary pores formed by dissolution. The pores in the bright white regions are more concentrated, possibly indicating zones of more intense dissolution. These features suggest the minerals may have undergone diagenetic alteration processes such as dissolution. Coupled with energy-dispersive X-ray spectroscopy (EDS) point analysis (Figure 3), the sample was found to contain major concentrations of O, C, Ca, and Mg. Where the Ca/Mg atomic ratio approaches 1:1, the phase composition corresponds to dolomite (① dark gray regions). Where the Ca content significantly exceeds the Mg content within mineral grains, the phase is calcite (② light gray regions). Elements such as Al, Fe (③ bright white regions), Zn, and Si (④ dark gray regions) detected within the grains, combined with mineral typomorphic characteristics and elemental associations, suggest the presence of non-carbonate minerals such as quartz, limonite, and goethite as characteristic elements of their composition.
Further integrating the results from EDS mapping (Figure 4), the Ca element (Figure 4c) exhibits a widespread distribution, corresponding to the distribution of carbonate minerals (calcite and dolomite). The Mg-enriched regions (Figure 4d) show a high degree of overlap with the Ca distribution, confirming that dolomite regions exhibit co-enrichment of Ca and Mg elements, while calcite regions are dominated by Ca with minimal Mg presence. This strongly corroborates that dolomite and calcite constitute the primary mineral phases of the carbonate rock. The O element (Figure 4e) is distributed throughout the entire area. The distribution of the C element (Figure 4g) exhibits a high degree of coincidence with Ca- and Mg-enriched regions, matching the characteristic elemental composition of carbonate minerals. Additionally, the Fe element (Figure 4f) is concentrated in bright white regions within the image. Considering the elemental composition and genesis of iron oxides, it is comprehensively determined that these likely represent iron oxides or oxyhydroxides (such as hematite, goethite, etc.). The Si element (Figure 4h) displays a discrete, punctate distribution pattern with weak overlap with Ca- and Mg-rich regions, indicating the possible presence of siliceous minerals like quartz.
In summary, the sample is predominantly composed of carbonate minerals, with minor amounts of quartz and iron-bearing minerals. The primary mineral constituents are dolomite, calcite, and quartz, with dolomite significantly predominating over calcite and quartz. Additionally, the rock sample displays a laminated structure and exhibits poor crystallinity. Intergranular pores and secondary dissolution pores are also partially developed within the sample.
Furthermore, this study determined the concentrations of major elements (Table 4) and trace elements (Table 5) in the samples. The XRF data (Table 4) indicate that CaO ranges from 29.19 to 30.83 wt% (mean 29.91 wt%), while MgO ranges from 18.31 to 22.28 wt% (mean 20.19%). Minor constituents include ZnO (1.40 wt%), SiO2 (1.70 wt%), TiO2 (0.10 wt%), Al2O3 (0.37 wt%), Fe2O3 (4.14 wt%), MnO (0.12 wt%), and K2O (0.45 wt%). Trace-element ICP-MS data reveal low levels of potentially toxic metals (Table 5): Cr 4.40 μg g−1, Ni 5.01 μg g−1, Pb 7.9 μg g−1, As 6.36 μg g−1, and Cd 0.05 μg g−1, all well below the threshold limits for agricultural amendments set by GB 38400-2019.

3.2. Determination and Analysis of Carbonate Rock Leachates

Building upon the aforementioned mineralogical characterization of carbonate rock samples, this study focuses on preparing carbonate rock leachates. Consequently, characterizing the physicochemical properties of the leachates forms the basis for evaluating their potential application as irrigation water for soil amendment. It also provides a reference framework for analyzing subsequent results from the pot and field experiments. The pH and elemental content of irrigation water used in the pot and field experiments were measured, with the results presented in Table 6.
For the pot experiment, compared to the untreated pure water sample (Pot—CK), the concentrations of Ca and Mg in the carbonate rock leachates sample (Pot—MW) increased extremely significantly (p < 0.01), reaching 5.355 mg L−1 for Ca and 0.049 mg L−1 for Mg. In contrast, the concentrations of Na and K showed minimal fluctuation; analysis suggests these measured values represent background levels inherent to the pure water, rather than elements dissolved from the carbonate rock samples during soaking. Overall, within the carbonate rock leachate system, using ultrapure water as the background, the hydrolysis–dissolution coupling reaction of CaCO3 (CaCO3 + H2O → Ca2+ + OH− + HCO3−) predominates. The accumulation of OH− resulted in a slight pH increase in the Pot—MW sample compared to Pot—CK (+0.33, p < 0.01), while both Ca and Mg contents were significantly elevated.
For the field experiment, the pH of well water used for irrigation in western Shandong (Field—CK) was slightly alkaline relative to neutral (pH = 7.89). Within the carbonate rock leachate system using well water as the background, the initially high concentrations of Ca2+ and Mg2+ in the well water itself led to the precipitation of CaCO3 upon addition of carbonate rock [32]. This shifted the equilibrium of CaCO3 + H2O ⇌ CO2 + Ca2+ to the left. Consequently, the Ca and Mg contents decreased significantly to 19.098 mg L−1 and 3.825 mg L−1, respectively (p < 0.01), resulting in a corresponding pH decrease of 0.30 units (p < 0.01).
Therefore, based on the opposing trends in elemental ion concentrations and pH observed between these two leachate systems, the properties of carbonate rock leachates are not solely determined by the rock itself, but are also influenced by the initial chemical characteristics of the water used.

3.3. Effect of Carbonate Rock Leachates on Lettuce Growth and Nutritional Quality in the Pot Experiment

The primary objective of this study is to investigate the application efficacy of carbonate rock leachates in practical soil amendment and agricultural production. For this purpose, and to evaluate their impact on crop growth and nutritional quality, we initially conducted the lettuce pot experiment under strictly controlled indoor conditions. The following section focuses on analyzing the effects of irrigation with carbonate rock leachates on individual lettuce plant biomass and key nutritional quality indicators, including mineral elements and antioxidant compounds. This analysis aims to reveal the effects of carbonate rock leachate irrigation on plants.

3.3.1. Effect of Carbonate Rock Leachates on Lettuce Biomass, Leaf SPAD Value, and Root Activity

This study investigated the impact of irrigation with carbonate rock leachates on lettuce growth and nutritional quality through pot experiments. Lettuce served as the model plant owing to its fast growth cycle and global prominence as a high-yield vegetable crop. The results demonstrate that irrigating lettuce throughout its entire growth period with carbonate rock leachates significantly increased plant height and biomass, while also enhancing root activity and leaf relative chlorophyll content (SPAD value) (Figure 5).
The lettuce pot experiment spanned 90 days. As illustrated in Figure 5a, lettuce plants subjected to the MW treatment demonstrated significantly greater height (p < 0.01) compared to the CK control throughout the period spanning 45 to 90 days after sowing (DASs). This height advantage was consistently observed and reached a magnitude of 25.68% by the 90 DASs measurement point. This indicates that irrigation with carbonate rock leachates significantly promoted the increase in plant height of pot-grown lettuce.
Figure 5b reveals that from 25 to 90 DASs, the average number of leaves per lettuce plant increased rapidly and continuously under both the MW and CK treatments, with no significant difference observed between them. This suggests that altering the irrigation water source did not affect the developmental rate of pot-grown lettuce, and irrigation with carbonate rock leachates did not markedly accelerate the lettuce growth process.
As illustrated in Figure 5c, at 60, 75, and 90 DASs, the average leaf SPAD value of lettuce under the MW treatment was significantly higher (p < 0.05) than that under the CK treatment. This indicates that irrigation with carbonate rock leachates significantly increased the relative chlorophyll content in lettuce leaves. Following harvest, root activity was measured. The results (Figure 5d) demonstrate that irrigation with carbonate rock leachates significantly enhanced lettuce root activity.
Following the conclusion of the lettuce pot experiment, the fresh weight of the aboveground and belowground parts of individual lettuce plants from each treatment was separately recorded. Following oven-drying, the dry-weight measurements were obtained. Table 7 demonstrates that plants receiving the MW treatment exhibited significantly greater (p < 0.01) mean fresh and dry biomass in their aboveground portions per plant compared to the CK group. These increases amounted to 23.78% and 29.41%, respectively. Conversely, neither the fresh nor dry weights of the root systems showed significant differences between treatments. Overall, irrigation with carbonate rock leachates significantly enhanced the accumulation of aboveground biomass in lettuce plants.

3.3.2. Effect of Carbonate Rock Leachates on Lettuce Nutritional Quality

Analysis of mineral element content (Figure 6a) revealed significantly elevated concentrations (p < 0.05) of P, K, Ca, and Mg in lettuce plants receiving the MW treatment relative to the CK group. These increases amounted to 16.00%, 24.06%, 12.77%, and 27.29%, respectively. Regarding antioxidant compounds and other nutrients, as shown in Figure 6b, the contents of carotenoids and ascorbic acid in lettuce leaves under the MW treatment were significantly higher than those under the CK treatment (p < 0.05), exceeding the CK treatment by 22.61% and 92.77%, respectively. Furthermore, the contents of total polyphenols, total flavonoids, soluble sugars, and soluble protein in the MW-treated lettuce leaves were higher than those in the CK treatment by 12.12%, 35.90%, 14.58%, and 21.43%, respectively. Overall, irrigation with carbonate rock leachates facilitated the synergistic enhancement of P, K, Ca, and Mg and nutrient contents in lettuce leaves, demonstrating a positive effect on both biomass accumulation and nutritional quality improvement.

3.4. Effects of Carbonate Rock Leachates on Soil Physicochemical Properties and Microbial Community Structure in the Pot Experiment

3.4.1. Effects of Carbonate Rock Leachates on Soil Physicochemical Properties

Following the conclusion of the pot experiment, composite soil samples were collected randomly from the rhizosphere of lettuce subjected to different irrigation treatments and analyzed for physicochemical properties. Measurements included soil pH, organic matter content, ammonium nitrogen, nitrate nitrogen, available potassium, available phosphorus, and the content of mineral elements (Ca, Mg, and Fe).
As shown in Table 8, soils from both the MW treatment and the CK treatment were slightly alkaline. Irrigation with carbonate rock leachates modulated soil pH to a certain extent, resulting in a significant decrease of 0.33 units (p < 0.05) in the pH of the MW treatment soil compared to CK. Simultaneously, irrigation with carbonate rock leachates substantially increased soil nutrient bioavailability. Relative to the CK group, concentrations of nitrate nitrogen (NO3−-N), available potassium, available phosphorus, Ca, Mg, and Fe were all significantly elevated (p < 0.05) in MW-irrigated soil. Specifically, they were higher by 102.20%, 16.45%, 17.95%, 6.04%, 11.65%, and 11.60%, respectively, compared to CK.

3.4.2. Effects of Carbonate Rock Leachates on Soil Microbial Communities

Soil microorganisms are pivotal in mediating energy flow and nutrient cycling, governing key processes including organic matter decomposition, xenobiotic degradation, soil carbon sequestration, and crop disease suppression [33,34,35].
Changes in soil microbial communities were characterized using 16S rRNA gene sequencing of soil microorganisms. This analysis was conducted to further examine the potential effects of variations in soil microbial communities under different irrigation treatments on soil physicochemical properties and plant growth. Alpha diversity assessment showed no distinct differences in microbial community composition between watering regimes, as measured by the Shannon (Figure 7a) and Simpson (Figure 7b) indices. These results demonstrate that the applied irrigation methods did not substantially alter taxonomic richness and evenness within the soil microbiota.
However, principal coordinate analysis (PCoA) of beta diversity (Figure 7c) demonstrated that microbial community structures were relatively consistent within the same treatment group, while the compositional profile of the MW treatment microbiota diverged significantly from that of the CK group.
Regarding microbial community composition (Figure 8), the soil microbial communities in both the MW treatment and the CK treatment were dominated by Proteobacteria, Bacteroidota, and Acidobacteriota. These three microbial groups constitute core drivers of microbial community function in soil [36,37,38]. Simultaneously, the significance analysis of inter-group differences in the microbiome (Figure 9) revealed distinct patterns at the phylum level. Chloroflexi exhibited significantly greater relative abundance in CK soil than in MW soil. Conversely, Firmicutes abundance was markedly elevated in the MW treatment compared to CK.

3.5. Effects on Soil Physicochemical Properties in the Field Experiment

The results from the preliminary pot experiment demonstrated significant potential for carbonate rock leachates in enhancing soil nutrient availability and promoting plant growth. To further validate the practical efficacy of this method under field conditions, this study, building upon the pot experiment, conducted a field experiment to investigate the soil improvement effects of carbonate rock leachates on field soils.
For the field experiment, peanut, as a subterranean-harvested crop, was selected. Yield measurement results demonstrated that the yield under the MW treatment was 21.92% higher than under CK. Upon experiment completion, physicochemical properties of soil samples from the MW treatment (irrigated with carbonate rock leachates) and the CK treatment (irrigated with local well water) were analyzed. As shown in Table 9, irrigation with carbonate rock leachates moderately regulated soil acidity. The CK treatment soil became slightly acidic after the peanut growing season, whereas the MW treatment soil remained nearly neutral. Concurrently, irrigation with carbonate rock leachates significantly enhanced the availability of nutrients in the field soil. The contents of ammonium nitrogen, nitrate nitrogen, and Fe were significantly higher in the MW treatment compared to the CK treatment (p < 0.05), showing increases of 219.86%, 88.15%, and 10.45%, respectively.

4. Discussion

4.1. Mechanism of Carbonate Rock Leachates on Soil Nutrient Availability Enhancement

Through the lettuce pot experiment and peanut field experiment, we observed that irrigation with carbonate rock leachates significantly enhanced lettuce yield and nutritional quality, as well as peanut yield. This enhancement is intrinsically linked to alterations in the soil environment.
For the pot experiment, soil concentrations of nitrate nitrogen, available potassium, available phosphorus, Ca, Mg, and Fe under the MW treatment were significantly higher than under CK. This may be attributed to the carbonate rock leachate enhancing the content of mobile elements in the soil through ion exchange [39,40,41] and pH regulation. The leachate significantly increased available potassium and nitrate nitrogen levels by displacing ions such as K+ and NH4+ adsorbed onto soil colloids. Simultaneously, it slightly reduced the pH of the alkaline soil, promoting the dissolution of sparingly soluble Ca–P compounds [42,43], thereby increasing phosphate solubility and iron availability. Furthermore, the microbial community in MW-treated soil drove an enrichment of the Firmicutes. The phosphate-solubilizing and potassium-releasing functions of these microbes accelerated organic matter mineralization, which positively correlated with increases in soil organic matter and nitrate nitrogen content [44,45].
For the field experiment, soil concentrations of ammonium nitrogen, nitrate nitrogen, and Fe under the MW treatment were significantly higher than those under the CK treatment, while the pH increased from 6.84 to 7.12. Analysis suggests two primary reasons: Firstly, the leachate likely enhanced soil nutrient availability by neutralizing soil acidity. This suppressed the re-precipitation of Fe–P [42,46], thereby increasing Fe availability. Concurrently, the resulting near-neutral soil environment favored the nitrification of NH4+-N to NO3−-N. Secondly, iron, as an essential component of nitrogenase, promoted the development of nodules on iron-sensitive peanut roots. This synergized with the substantial increases in ammonium nitrogen (+219.86%) and nitrate nitrogen (+88.15%), driving enhanced biological nitrogen fixation and yield growth (+21.92%) [47,48,49,50].
Overall, the enhancement of soil availability by carbonate rock leachate is influenced not only by its direct effects but also closely associated with shifts in the dominant soil microbial community and crop–soil interactions. Specifically, the influence of the dominant microbial community manifests as the enrichment of the Firmicutes. The crop–soil interaction is characterized by enhanced physiological responses of plant roots, which activate nutrients in the rhizosphere. Furthermore, it should be noted that the opposing directions of soil pH regulation by carbonate rock leachate (decrease in the pot experiments vs. increase in the field experiments) primarily reflect its directional regulation effect on soils with different initial pH levels. Additionally, due to the superior water control in the pot experiments, which minimized nitrate nitrogen (NO3−-N) leaching, the increase in nitrate nitrogen was higher (+102.20%) compared to the field experiment (+88.15%). Conversely, the initially stronger phosphorus fixation in the acidic soil of the field experiment, coupled with pH neutralization, led to a more significant release of available phosphorus (+61.1%) than observed in the pot experiment.

4.2. Changes in Soil Microbial Community Structure and Their Functional Implications

Analysis of the microbial community composition in pot experiment soils revealed that the relative abundance of the Firmicutes phylum was significantly higher under the MW treatment than under the CK treatment, while the relative abundance of the Chloroflexi phylum was significantly lower (Figure 8 and Figure 9).
Firmicutes are broadly acknowledged as copiotrophic microorganisms in soil systems [51,52]. Their metabolic capabilities include decomposing labile organic matter and assimilating carbon from applied organic fertilizers for growth [53]. In contrast, some members of the Chloroflexi phylum have consistently been reported as oligotrophic bacteria [54,55], which possess a competitive advantage in nutrient-poor or carbon-limited soil environments [56,57]. When soil environmental conditions become eutrophic, the activity of some Chloroflexi microorganisms is suppressed, leading to a decrease in their abundance [58]. The relative abundance of Firmicutes shows a positive correlation with soil pH, nitrate, and available phosphorus, whereas the relative abundance of Chloroflexi shows a negative correlation with soil pH, soil nitrate, and available phosphorus [59,60]. Integrating these findings with the results of soil physicochemical property analysis from this experiment, the increased levels of soil-available nitrogen, soil-available phosphorus, and soil-available potassium in the MW treatment likely provided abundant carbon and energy sources supporting the growth of Firmicutes. Conversely, the significantly lower relative abundance of Chloroflexi in MW treatment soil compared to CK treatment indirectly indicates that the enhanced nutrient availability in MW soil inhibited the growth of Chloroflexi.
Synthesizing shifts in soil properties and microbiota, MW treatment did not significantly enhance overall microbial diversity. However, markedly increased bioavailability of nitrate nitrogen, available phosphorus, and available potassium corresponded with a substantial rise in soil Firmicutes abundance. This phylum contributes to nitrification within the nitrogen cycle [44,45] and liberate phosphorus and potassium from mineral lattices within the soil.

4.3. Crop Yield and Quality Responses to Carbonate Rock Leachate Irrigation

This study investigated the response of crop yield and quality to carbonate rock leachate through the lettuce pot experiment and peanut field experiment. The results demonstrated that the application of carbonate rock leachate significantly enhanced plant yield (by 23.78% in lettuce and 21.92% in peanuts) and concurrently increased the content of P, K, Ca, and Mg elements, as well as antioxidative compounds such as ascorbic acid and carotenoids, in plant tissues (Figure 6).
The lettuce pot experiment demonstrated that irrigation with carbonate rock leachate enhanced lettuce yield and quality by synergistically improving soil nutrient availability and plant physiological metabolism. Regarding mineral elements, phosphorus (P), as a key component of biological nucleic acids and ATP, directly participates in energy transfer and cell division, thereby accelerating leaf expansion and root growth in lettuce. Potassium (K) serves as an essential regulator of protein synthesis, enzyme activity, and osmotic balance. Given these critical physiological functions, plants demonstrate enhanced K uptake relative to other essential elements [61,62,63]. Calcium (Ca) serves as a vital structural component for the integrity of cell membranes and cell walls, while magnesium (Mg) occupies the central position in the chlorophyll molecule and is indispensable for photosynthesis [64]. Collectively, chlorophyll synthesis (dependent on Mg, evidenced by higher leaf SPAD values in the MW treatment) and K+-mediated osmotic regulation enhanced plant photosynthetic efficiency and carbon assimilation processes, promoting biomass accumulation and the synthesis of antioxidative compounds [65].
Specifically, for peanuts in the field trial, the yield increase under the MW treatment was also associated with enhanced availability of Fe in the soil. Peanut is an Fe-sensitive crop [49]. Iron (Fe) is a functional element for biological nitrogen fixation, influencing the development and nitrogen-fixing function of peanut root nodules [47,50]. Studies have demonstrated a significant positive correlation between nodule number, nodule biomass, and the concentration of available Fe in the growth medium [48]. Within a certain Fe concentration range, both the number and biomass of peanut root nodules increase with rising Fe concentration. Therefore, the enhanced availability of Fe in the soil likely promotes the growth and nitrogen fixation capacity of peanut root nodules. Moreover, the MW treatment increased the soil content of both ammonium nitrogen and nitrate nitrogen, providing additional nitrogen sources for biological nitrogen fixation. This creates a mutually reinforcing positive feedback loop.

5. Conclusions

This study focuses on the pivotal role of water in the “mineral–soil–plant” system. Utilizing carbonate rock leachates as irrigation water, it systematically investigated the effects of this solution on soil physicochemical properties, soil microbial communities, and plants through an indoor lettuce pot experiment and peanut field experiment. The results demonstrate that irrigation with carbonate rock leachates can significantly enhance soil nutrient availability and promote improvements in plant yield and quality. Specifically, the indoor experiment confirmed its ability to increase soil nitrate nitrogen, available potassium, available phosphorus, Ca, Mg, and Fe contents, and elevate the relative abundance of the phylum Firmicutes in the soil. It also positively promoted increases in lettuce plant height, biomass, leaf mineral element content, and the levels of antioxidants such as ascorbic acid and carotenoids. The field experiment further validated the soil amelioration effects of carbonate rock leachates on local arable soils, providing practical evidence for soil improvement. The pot-to-field convergence in nutrient availability and yield response underscores the regional adaptability of carbonate rock leachate irrigation under contrasting edaphic conditions, while acknowledging that crop-, soil-, and climate-specific calibrations remain essential prior to large-scale deployment.
Overall, this study innovatively reveals a soil improvement pathway using carbonate rock leachates for irrigation. This technology breaks through the limitations of potential ecological risks associated with traditional soil amendments and offers a new approach for green and sustainable agricultural development. Future research could combine long-term fixed-site experiments with different geological regions to further refine the application framework and improve the application methodology of this mineral-based material.

Author Contributions

Conceptualization, H.D. and A.L.; methodology, Y.D. (Yifei Du) and H.D.; validation, Y.D. (Yifei Du) and X.G.; data analysis, Y.D. (Yifei Du) and Y.D. (Yimei Du); writing—original draft preparation, Y.D. (Yifei Du); writing—review and editing, H.D. and A.L.; visualization, Y.D. (Yifei Du); supervision, A.L.; funding acquisition, A.L. All authors have read and agreed to the published version of the manuscript.

Funding

Financial support has been provided by the National Natural Science Foundation of China (No. 42192502, 92251301).

Data Availability Statement

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Minerals 15 00825 g001
Figure 1. XRD pattern of representative samples at room temperature.
Figure 1. XRD pattern of representative samples at room temperature.
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Figure 2. Micro-Raman spectra of dolomite (a), calcite (b), and quartz (c) identified in the natural carbonate thin section.
Figure 2. Micro-Raman spectra of dolomite (a), calcite (b), and quartz (c) identified in the natural carbonate thin section.
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Minerals 15 00825 g003
Figure 3. The SEM image and EDS spectra of the carbonate sample. The serial numbers in the SEM image correspond to the results of the EDS spectra.
Figure 3. The SEM image and EDS spectra of the carbonate sample. The serial numbers in the SEM image correspond to the results of the EDS spectra.
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Figure 4. Element distribution characteristics of the carbonate sample. (a) SEM image showing the micromorphology of the carbonate sample; (b) EDS element mapping overlay on the SEM image; (c–h) Distribution map of Ca (c), Mg (d), O (e), Fe (f), C (g), Si (h) element.
Figure 4. Element distribution characteristics of the carbonate sample. (a) SEM image showing the micromorphology of the carbonate sample; (b) EDS element mapping overlay on the SEM image; (c–h) Distribution map of Ca (c), Mg (d), O (e), Fe (f), C (g), Si (h) element.
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Minerals 15 00825 g005
Figure 5. (a) Plant height, (b) number of leaves, (c) SPAD value, and (d) root vitality of lettuce under different irrigation treatments. Dark and light shades of the same color respectively represent MW and CK treatment. The data are presented as mean values ± standard deviation (SD) of three replicates. The reported p-values are derived from two-sided statistical tests, where * indicates p < 0.05 and ** p < 0.01.
Figure 5. (a) Plant height, (b) number of leaves, (c) SPAD value, and (d) root vitality of lettuce under different irrigation treatments. Dark and light shades of the same color respectively represent MW and CK treatment. The data are presented as mean values ± standard deviation (SD) of three replicates. The reported p-values are derived from two-sided statistical tests, where * indicates p < 0.05 and ** p < 0.01.
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Figure 6. (a) Mineral element (P, K, Ca, Mg) content and (b) nutrient substance content of lettuce under different irrigation treatments. Shaded areas represent mean values of component contents (n = 3). Orange and blue colors represent MW and CK treatments, respectively. Percentages outside axes indicate the increase rate of substance content in MW treatment compared to CK treatment.
Figure 6. (a) Mineral element (P, K, Ca, Mg) content and (b) nutrient substance content of lettuce under different irrigation treatments. Shaded areas represent mean values of component contents (n = 3). Orange and blue colors represent MW and CK treatments, respectively. Percentages outside axes indicate the increase rate of substance content in MW treatment compared to CK treatment.
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Figure 7. Effects of different irrigation treatments on soil microbial community alpha and beta diversity. (a,b): box plots of differences between groups in the Shannon (a) and Simpson (b) indices. (c): PCoA analysis of microbial communities.
Figure 7. Effects of different irrigation treatments on soil microbial community alpha and beta diversity. (a,b): box plots of differences between groups in the Shannon (a) and Simpson (b) indices. (c): PCoA analysis of microbial communities.
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Figure 8. Bacterial community structure and distribution in soil samples under different irrigation treatments. (a) Stacked bar chart showing the relative abundance at the phylum level across different soil samples. Relative abundances are calculated from taxonomic assignments of DNA sequences at the phylum level. (b) Heatmap depicting the bacterial community composition at the phylum level.
Figure 8. Bacterial community structure and distribution in soil samples under different irrigation treatments. (a) Stacked bar chart showing the relative abundance at the phylum level across different soil samples. Relative abundances are calculated from taxonomic assignments of DNA sequences at the phylum level. (b) Heatmap depicting the bacterial community composition at the phylum level.
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Figure 9. Analysis of intergroup differences in relative abundance of soil microbial communities at the phylum level.
Figure 9. Analysis of intergroup differences in relative abundance of soil microbial communities at the phylum level.
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Table 1. The basic physicochemical properties of the soils in the pot experiment.
Table 1. The basic physicochemical properties of the soils in the pot experiment.
Pot—CKPot—MW
pH9.02 ± 0.049.11 ± 0.06
Organic matter
(g kg−1)		65.04 ± 4.5263.27 ± 3.73
Ammonium nitrogen
(mg kg−1)		0.71 ± 0.130.85 ± 0.18
Nitrate nitrogen
(mg kg−1)		1.41 ± 0.271.37 ± 0.16
Available potassium
(mg kg−1)		742.34 ± 37.68729.67 ± 45.29
Available phosphorus
(mg kg−1)		9.33 ± 0.399.63 ± 0.57
Ca (mg g−1)30.44 ± 3.5231.68 ± 4.29
Mg (mg g−1)10.95 ± 0.6310.07 ± 0.51
Fe (mg g−1)23.14 ± 2.7822.56 ± 2.13
Table 2. The basic physicochemical properties of the soils in the field experiment.
Table 2. The basic physicochemical properties of the soils in the field experiment.
Field—CKField—MW
pH6.51 ± 0.066.45 ± 0.05
Organic matter
(g kg−1)		5.27 ± 0.395.46 ± 0.53
Ammonium nitrogen
(mg kg−1)		0.45 ± 0.050.42 ± 0.04
Nitrate nitrogen
(mg kg−1)		4.75 ± 0.094.81 ± 0.14
Available potassium
(mg kg−1)		40.57 ± 2.4942.35 ± 3.18
Available phosphorus
(mg kg−1)		5.07 ± 0.085.13 ± 0.11
Ca (mg g−1)15.52 ± 3.36 13.89 ± 2.14
Mg (mg g−1)6.71 ± 1.147.13 ± 0.69
Fe (mg g−1)29.47 ± 5.38 29.08 ± 4.13
Table 3. XRD semi-quantitative analysis results of representative samples.
Table 3. XRD semi-quantitative analysis results of representative samples.
Dolomite (%)Calcite (%)Quartz (%)
S-174206
S-28794
S-3711514
S-476168
S-573198
S-684115
S-779147
S-881118
S-9721810
S-10771211
Table 4. Chemical analysis of representative samples from XRF measurement (values in wt%).
Table 4. Chemical analysis of representative samples from XRF measurement (values in wt%).
CaOZnOMgOSiO2TiO2Al2O3Fe2O3MnOK2OL.O.I.
S-130.561.3918.311.860.100.454.700.120.6341.84
S-229.221.3720.811.460.120.374.370.120.5441.53
S-329.741.3818.341.340.100.344.390.120.3943.79
S-429.191.4921.192.190.040.233.810.130.2141.43
S-530.831.3722.281.650.160.483.440.120.4839.08
AVE29.911.4020.191.700.100.374.140.120.4541.53
Table 5. Trace element (10−6) compositions of representative samples.
Table 5. Trace element (10−6) compositions of representative samples.
SS-1SS-2SS-3SS-4SS-5
Li9.079.024.994.149.22
Be0.180.210.170.110.24
Sc1.632.371.831.342.09
Ti155.94562.77234.47110.3309.84
V10.8816.9212.888.4926.86
Cr3.127.463.842.395.19
Mn525.52496.17505.61409.84459.74
Co1.822.872.382.313.17
Ni3.774.6844.657.96
Cu2.494.752.832.697.84
Zn99.1982.3547.3727.8134.2
Ga0.671.40.780.411.33
Ge0.20.190.140.10.17
Pb9.328.675.398.537.61
As2.233.352.031.865.94
Rb4.1910.786.062.118.65
Sr69.046437.9142.5926.49
Y3.143.192.122.023.3
Zr15.1919.419.36.3115.02
Nb0.692.381.050.451.59
Mo0.110.10.090.10.24
Cd0.070.110.030.020.02
Table 6. The Ca, Mg, Na, and K element content and pH value of irrigation water in the pot and field experiments.
Table 6. The Ca, Mg, Na, and K element content and pH value of irrigation water in the pot and field experiments.
Ca (mg L−1)Mg (mg L−1)Na (mg L−1)K (mg L−1)pH
Pot—CK0.843 ± 0.010/2.327 ± 0.0892.867 ± 0.0327.06 ± 0.04
Pot—MW5.355 ± 0.0870.049 ± 0.0132.313 ± 0.0242.860 ± 0.0357.39 ± 0.03
t-value−88.850−6.3840.2760.2300.031
p-value0.0000.0030.7960.8290.000
Field—CK38.305 ± 1.5076.688 ± 0.74813.033 ± 0.2103.527 ± 0.0837.89 ± 0.03
Field—MW19.098 ± 0.4983.825 ± 0.13311.165 ± 0.1113.303 ± 0.0217.59 ± 0.05
t-value20.961 6.52613.6134.5309.701
p-value0.0000.0030.0000.0110.001
Results display means ± standard deviation (SD) derived from three replicates. All p-values originate from independent samples t-tests, with statistically significant values (p < 0.05) highlighted in bold.
Table 7. Biomass (g) of individual lettuces under different irrigation treatment.
Table 7. Biomass (g) of individual lettuces under different irrigation treatment.
Growth IndexLeaf Fresh WeightLeaf Dry WeightRoot Fresh WeightRoot Dry Weight
CK20.14 ± 3.711.53 ± 0.212.33 ± 0.570.34 ± 0.09
MW24.93 ± 3.29 **1.98 ± 0.17 **2.56 ± 0.520.38 ± 0.11
Results display means ± standard deviation (SD) derived from 40 replicates. Independent samples t-tests yielded the p-values (p < 0.01, shown as **).
Table 8. Physicochemical properties of pot experiment soil under different irrigation treatments after harvest.
Table 8. Physicochemical properties of pot experiment soil under different irrigation treatments after harvest.
CKMW
pH 8.95 ± 0.038.62 ± 0.08 **
Organic matter (g kg−1)70.66 ± 4.0475.99 ± 4.91
Ammonium nitrogen (mg kg−1)1.66 ± 0.101.84 ± 0.57
Nitrate nitrogen (mg kg−1)7.31 ± 1.2514.78 ± 1.37 **
Available potassium (mg kg−1)1005.33 ± 29.481170.67 ± 50.96 **
Available phosphorus (mg kg−1)24.76 ± 2.1329.20 ± 1.62 *
Ca (mg g−1)36.71 ± 0.4438.93 ± 0.40 **
Mg (mg g−1)11.55 ± 0.1712.90 ± 0.07 **
Fe (mg g−1)26.68 ± 0.9429.77 ± 0.65 **
Results display means ± standard deviation (SD) of three replicates. Independent samples t-tests yielded the p-values (p < 0.05, shown as *; p < 0.01, shown as **).
Table 9. Physicochemical properties of field experiment soil under different irrigation treatments after harvest.
Table 9. Physicochemical properties of field experiment soil under different irrigation treatments after harvest.
CKMW
pH 6.84 ± 0.197.12 ± 0.32
Organic matter (g kg−1)6.32 ± 0.187.28 ± 1.60
Ammonium nitrogen (mg kg−1)0.49 ± 0.081.56 ± 0.41 *
Nitrate nitrogen (mg kg−1)6.95 ± 0.4113.08 ± 2.73 *
Available potassium (mg kg−1)55.67 ± 8.6256.00 ± 6.24
Available phosphorus (mg kg−1)6.09 ± 0.239.81 ± 3.55
Ca (mg g−1)18.72 ± 0.7519.58 ± 0.56
Mg (mg g−1)8.61 ± 0.488.91 ± 0.64
Fe (mg g−1)31.70 ± 0.5735.01 ± 1.56 *
Results display means ± standard deviation (SD) derived from three replicates. Independent samples t-tests yielded the p-values (p < 0.05, shown as *).
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Du, Y.; Ge, X.; Du, Y.; Ding, H.; Lu, A. Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality. Minerals 2025, 15, 825. https://doi.org/10.3390/min15080825

AMA Style

Du Y, Ge X, Du Y, Ding H, Lu A. Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality. Minerals. 2025; 15(8):825. https://doi.org/10.3390/min15080825

Chicago/Turabian Style

Du, Yifei, Xiao Ge, Yimei Du, Hongrui Ding, and Anhuai Lu. 2025. "Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality" Minerals 15, no. 8: 825. https://doi.org/10.3390/min15080825

APA Style

Du, Y., Ge, X., Du, Y., Ding, H., & Lu, A. (2025). Mineral–Soil–Plant–Nutrient Synergism: Carbonate Rock Leachate Irrigation Enhances Soil Nutrient Availability, Improving Crop Yield and Quality. Minerals, 15(8), 825. https://doi.org/10.3390/min15080825

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