Introduction

Globally, sugarcane cultivation is mainly concentrated in tropical and subtropical regions. Brazil and India are the world’s largest sugarcane producers. Brazil has a sugarcane planting area of over 8 million hectares, mainly used for sugar and ethanol production1. Its consumption of phosphate fertilizer is huge, and it mainly relies on imported phosphate rock. And ultimately produce major phosphate fertilizer products such as superphosphate (SSP, Ca(H2PO4)2 H2O), triple superphosphate (TSP, Ca2(HPO4)2 H20 ), monoammonium phosphate (MAP, NH4H2PO4), and diammonium phosphate (DAP)2. Brazil has diverse soil types, with a relatively high proportion of acidic soil. Therefore, the selection and use of phosphate fertilizer have a significant impact on soil acidification. As the second-largest sugarcane producer, India has a sugarcane planting area of about 5 million hectares, and its phosphate fertilizer consumption has also been increasing year by year. Moreover, the compound fertilizer DAP holds a dominant position in India. In the 2022–2023 fiscal year, DAP accounted for 60.5% of the total P2O5 fertilizer usage3. The problem of soil acidification in India is equally serious, especially in areas where chemical fertilizers have been applied for a long time. To address the issue of soil acidification, Brazil and India have also been actively exploring the application of new types of phosphate fertilizers in recent years, such as slow-release phosphate fertilizers and organic phosphate fertilizers, to reduce the negative impact on the soil.

China is the world’s third-largest sugarcane producer, following Brazil and India4. The country has a sugarcane planting area of approximately 1.5 million hectares5, mainly concentrated in southern provinces such as Guangxi, Yunnan, and Guangdong. And most of the soil in these regions is classified as Oxisol, with acidic soil (pH < 5.5) accounting for as high as 84.3%6, making soil acidification a particularly serious issue. Fertilization is one of the main driving factors of soil acidification7, especially the excessive application of nitrogen and phosphorus fertilizers. In recent years, with the development of intensive agriculture, replacing FCMP with DAP has gradually made DAP the main phosphorus fertilizer in sugarcane fields. The main reason for the mainstream use of DAP in intensive sugarcane cultivation is that its high concentration, rapid action and mechanization compatibility are highly compatible with the efficient needs of intensive production. However, the widespread use of DAP may exacerbate soil acidification8, thereby affecting the yield and quality of sugarcane9. Although DAP and FCMP have similar effects in providing phosphorus nutrients, their mechanisms of action in the soil acidification process have not been fully studied. Therefore, exploring the impact of DAP replacing FCMP on soil acidification is of great significance for optimizing fertilization management in sugarcane fields and reducing environmental risks.

In recent years, with the development of global climate change and agricultural intensification, the problem of soil acidification has become increasingly serious, especially in tropical and subtropical regions. Acidic soil not only affects the growth and yield of crops but also leads to the activation of toxic elements such as aluminum and manganese in the soil, further exacerbating soil degradation. Sugarcane, as an important economic crop in southern China, has high requirements for soil conditions, especially for soil pH and nutrient content. Therefore, studying the impact of different phosphorus fertilizers on soil acidification in sugarcane fields is of great significance for increasing sugarcane yield and improving soil quality.

Nitrogenous fertilizer (urea) input is the main cause of soil acidification7,10,11. Soil acidification caused by nitrogenous fertilizers has been extensively studied12. After urea is added to the soil, nitrification occurs and H+ and NO3- are released. When NO3− is removed by crops or leached by water, it causes a loss of base cations (K+, Ca2+, and Mg2+) and H+ remains in the soil, causing acidification13. However, phosphorus fertilizers impact soil acidification in complex manners14. When water-soluble phosphate fertilizers (e.g., DAP) are applied to soil, the phosphate ions (e.g., H2PO4−) released through dissolution increase the negative charge in the soil solution. To maintain charge balance, soil colloids release hydrogen ions (H+) or exchange other cations (e.g., Ca2+, Mg2+), ultimately leading to soil acidification15. The associated cations (e.g., NH4+ in DAP or Ca2+ in calcium phosphate) introduced via the input of phosphate ions also affect soil acidification. If the associated cations are base cations (e.g., Ca2+, Mg2+, K+), they mitigate soil acidification16,17. In soils with pH less than 5.0, Al2O3 is the main material that buffers the decline in pH18,19,20,21, and an excess of exchangeable aluminum in soil negatively affects crop production22,23,24. Phosphate ions are prone to precipitation into aluminum phosphate with Al3+, which may reduce the content of exchangeable aluminum in the soil and alleviate its toxicity25,26,27,28. Therefore, replacing FCMP with DAP may alter the process of soil acidification and exchangeable aluminum accumulation in sugarcane fields.

In the present study, experiments were performed in acidic sugarcane field to study how the replacement of FCMP with DAP impacted soil acidification. We aimed to examine the following: (1) how soil acidification was affected when FCMP was replaced with DAP, and (2) how the replacement affected the accumulation of soil exchangeable aluminum.By comparing the changes of soil pH value, exchangeable cation content and sugarcane yield under different fertilization treatments, the action mechanism of DAP and FCMP in acidic soil was discussed, which provided scientific basis for sustainable fertilization management of sugarcane field.

Materials and methods

Site description

This study was conducted in a sugarcane field in Tuolu Town of Jiangzhou District (22° 37′ 56′′ N, 107° 39′ 49′′ E), Guangxi Zhuang Autonomous Region, China, which is characterized by a typical subtropical monsoon climate. Climatic data presented here represent long-term averages for the region, which show an average annual temperature of 22–23 °C and an average annual precipitation of 1200–1400 mm. Historically, more than 70% of the annual precipitation falls during the May-September period. The soil at the experimental site is classified as lateritic soils, derived from the weathering products of limestone and sandstone. According to the Chinese Soil Taxonomy, the field have lateritic soils derived from limestone and sand shale, which is equivalent to Rhodudult soil according to the American Soil Taxonomy. Prior to the experiment, the field had been continuously cultivated with sugarcane for over five years. The initial soil pH, SOC (soil organic carbon), and exchangeable Al3+ values are shown in Table 1, indicating significant soil acidification in the area.

Due to long-term sugarcane cultivation and excessive use of chemical fertilizers, soil acidification has become increasingly severe. The experimental site features a relatively flat terrain, facilitating mechanized operations and field management. Sugarcane was planted with a row spacing of 1.0 m and a plant spacing of 0.5 m, resulting in a moderate planting density that is conducive to sugarcane growth and field management. During the experiment, field management practices included regular weeding, fertilization, and pest control to ensure the normal growth of sugarcane. Table 1 lists the chemical properties of the selected soil.

Table 1 Chemical properties of the selected soil. (n = 45).
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Experimental design

Field experiments were designed based on the substitution ratio of P2O5:100% FCMP and 0% DAP (0%DAP), 75% FCMP and 25% DAP (25%DAP), 50% FCMP and 50% DAP (50%DAP), 25% FCMP and 75% DAP (75%DAP), and 0% FCMP and 100% DAP (100%DAP). The contents of CaO, MgO and P2O5 in FCMP were 37.5%, 10.5%, and 18.0%, respectively(Yunnan Jinda Phosphorus Chemical Co., Ltd., Yunnan, China). The contents of N and P2O5 in DAP were 15% and 42%, respectively(Nanning Hangjia Chemical Co., Ltd., Nanning, China). The amount of P2O5 applied to the various treatments was 270 kg ha–1 (total amount over three years, equivalent to 90 kg ha−1 yr–1), but Ca2+ and Mg2+ additions varied significantly due to fertilizer composition. All P fertilizers were supplied as basal fertilizers and applied to the soil surface before planting (N contained in the DAP was balanced with urea), and a rotary tiller was used to mix the fertilizer with the soil. The amounts of N and K2O were 300 and 240 kg ha–1 yr–1, respectively. Urea(Nanning Guangfei Agricultural Materials Co., Ltd., Nanning, China) and potassium chloride(Nanning Guangfei Agricultural Materials Co., Ltd., Nanning, China) were also used. The specific fertilization details for different treatments are shown in Table 2.

A 3-yr experiment was performed in 2022 to 2024. Sugarcane was planted in February, 2022. The second and third crops were ratoon sugarcane plants. Sugarcane was planted with a row spacing of 1.0 m. Sugarcane was manually harvested from each plot, and the canes and leaves were removed from the field after harvesting. The experimental fields were not irrigated. Each treatment consisted of three replicate plots arranged in completely randomized blocks. The designed area of each plot was 7 × 9 m2, and a 2 m belt between adjacent plots was used as a buffer zone, which was excluded from the sampling and yield calculation.

Table 2 Fertilizer application rates of different treatments.(n = 45).
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Soil sampling and measurement

Soil samples were collected annually from each experimental plot and averaged. Prior to sampling, the soil was tilled three times using a rotary tiller (25 cm tillage depth) to ensure uniformity and representativeness. In each plot, 30 sampling points were allocated according to the network format method29 and 1 kg of soil (0–25 cm) was preserved after pooling. The soil samples were air-dried, roots and plant residues removed, and the soil was sieved through a 2 mm mesh to ensure homogeneity and consistency of the soil samples.

In the process of measuring soil pH, we used a 0.01 M CaCl2 as the extractant, which effectively avoids the influence of CO2 in the soil and ensures the accuracy of the pH value30. At a 1:2.5 soil: water ratio using a pH meter (S220 Seven Compact pH/ion, Mettler Toledo, Greifensee, Switzerland). Soil NH4–N and NO3-N were extracted with 0.01 M CaCl2 and their concentrations were measured using a Smartchem 170 continuous-flow analyzer (AMS Srl Via E. Barsanti, Rome, Italy)31. Bray-P was extracted using 0.025 M HCl and 0.03 M NH4F32. Exchangeable K+ was extracted using 1 M NH4OAC33. K+ levels were measured using flame photometry. Soil exchangeable Ca2+, Mg2+, H+, and Al3+ concentrations were measured using 1 M KCl leaching34. Ca2+ and Mg2+ concentrations were measured using atomic absorption spectroscopy (SP-3880ZAA; Shanghai Spectrum Instrument Co., Ltd., Shanghai, China). The leachate was titrated with 0.02 M sodium hydroxide to a pH of 7.8 to determined the exchangeable acidity (H+ +Al3+)33. To obtain the exchangeable H+, 3.5% NaF was added to the leachate. Exchangeable Al3+ is derived as the difference between the exchangeable acidity and exchangeable H+35.

Plant sampling and measurement

At the mature stage, the total number of effective sugarcane (commercial) stalks in each plot was measured, and 20 effective sugarcane stalks were randomly selected from the middle three rows of each plot for yield measurements (60 plants per plot). The mean cane and leaf weights of a single stalk, plot area, cane yield, and leaf yield (kg ha–1) were calculated based on the number of effective sugarcane stalks in each plot. The cane and leaf samples were collected separately. The samples were dried in an oven at 70 °C to measure the water content of the canes and leaves. The samples were ground using a stainless-steel grinder to pass through a 40-mesh (0.425 mm) screen.

To ensure the accuracy and representativeness of plant sampling, we followed the principle of random sampling within each plot, selecting representative sugarcane plants for sampling. During the sampling process, we paid special attention to avoiding plants affected by pests, diseases, or other abnormalities to ensure the accuracy of the measurement results.

Plant samples were digested with H2SO4−H2O2 in a microwave-accelerated reaction system(ETHOS UP Microwave Digestion System - Milestone). Total N and P contents were determined using the Kjeldahl method36 and molybdenum blue spectrophotometry37, respectively. The K+ content was measured using flame photometry and the Ca2+ and Mg2+ contents were measured using atomic absorption spectroscopy.

Data analysis

The partial nutrient balance indices of N, P2O5, and K2O were calculated as:

$$\left( {{\text{PNB}}/{\text{PPB}}/{\text{PKB}}} \right)\left( \% \right) = {\text{Nutrient}}_{{{\text{upt}}}} \times 100/{\text{Nutrient}}_{{{\text{input}}}} ,$$
(1)

where Nutrientinput was the N, P2O5, or K2O input via fertilization during the three-year experimental period (all in kg ha− 1). Nutrientupt was the N, P2O5, or K2O removed from the sugarcane harvest (cane and leave) during the three-year experimental period (kg ha− 1).

The mean comparison of each index in the different treatments was performed using Duncan’s test with P < 0.05. The coefficients of determination (R2) for the regression equations were calculated to determine their relative importance. All statistical analyses were performed using SPSS (version 16.0; SPSS Inc., Chicago, IL, USA).

Results

Sugarcane yield and nutrient use efficiency

The average sugarcane yields under different treatments are shown in Fig. 1. Replacing FCMP with DAP gradually led to decreased average sugarcane yields. A 9.50% reduction in average sugarcane yield was observed when replacing 100% FCMP with DAP. The results showed that replacing FCMP with DAP at increasing substitution ratios gradually imposed adverse effects on sugarcane growth.

Fig. 1
Fig. 1
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Effect of replacing FCMP with DAP on sugarcane yield(Mg ha−1 yr−1).(n = 45).The points in the figure represent the average yield of sugarcane over three years for the given treatment.The error bars represent the standard deviation (SD) of each data point.

NUE under the five treatments ranged from 55.8 to 61.0% (Fig. 2). The average NUE was 59.1%, indicating that approximately 40% of the nitrogen input from the fertilizer entered the water, atmosphere, or was retained in the soil. The PUE under the five treatments ranged from 32.5 to 35.9% (Fig. 2). The average PUE was 34.6%, and approximately two-thirds of the phosphorus input from the fertilizer remained in the soil. KUE under the five treatments varied from 88.3 to 96.2% (Fig. 2), with an average KUE of 94.0%. Completely replacing FCMP with DAP reduced NUE, PUE, and KUE by 8.5%, 9.3%, and 8.2%, respectively, corresponding to the observed sugarcane yield decline (Fig. 1). It indicates that the application of DAP not only affects the yield of sugarcane but also reduces the efficiency of nutrient utilization.

Fig. 2
Fig. 2
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Effect of replacing FCMP with DAP on nutrient use efficiency(%).(n = 45). Different lowercase letters indicate significant differences between the treatments at P < 0.05.The error bars represent the standard deviation (SD) of each data point.

Soil pH

Replacement of FCMP with DAP decreased soil pH, and the soil pH decreased with increasing DAP substitution ratio (Fig. 3). Specifically, compared to the 0% DAP treatment, the soil pH decreased by 0.05, 0.09, 0.16, and 0.22 under the 25%, 50%, 75%, and 100% DAP treatments, respectively. This trend suggests that the application of DAP exacerbates the soil acidification process. Furthermore, compared to the initial soil, the 0% DAP treatment resulted in a significant increase in soil pH, whereas the 75% and 100% DAP treatments caused significant decreases (Fig. 3).This indicates that the phosphate ions in DAP react with Al3+ in the soil, releasing H+, which in turn leads to a decrease in soil pH. In contrast, the Ca2+ and Mg2+ in FCMP can neutralize H+ in the soil, thereby mitigating or even reversing soil acidification.

Fig. 3
Fig. 3
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Effects of replacing FCMP with DAP on soil pH(n = 45). “Initial” indicates soil samples collected at the beginning of the experiment. Different lowercase letters indicate significant differences between the treatments at P < 0.05.The error bars represent the standard deviation (SD) of each data point.

Soil available N and P

In this study, replacing FCMP with DAP did not significantly affect the available soil N and P among the treatments (Fig. 4). Compared with the initial soil, the average NH4–N in the soil increased by 2.5 mg kg−1, and the average NO3–N decreased by 1.7 mg kg−1, all of which were not considered significant. Although more N was applied to the sugarcane field than the amount absorbed by the sugarcane, NO3–N and NH4-N in the soil did not increase notably. Although the average PUE was only 34.5%, Bray-P in the soil with increasing rate of DAP did not increase significantly compared with that in the initial soil, but could maintain Bray-P in the soil at a high level, and DAP had the same effect as FCMP.This stability could be attributed to processes such as microbial immobilization of nitrogen and potential leaching, which may have offset the direct input from fertilizers.

Fig. 4
Fig. 4
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Effect of replacing FCMP with DAP on soil available N and P(mg kg−1). (n = 45). “Initial” indicates soil samples collected at the beginning of the experiment. Same lowercase letters indicate no significant differences at P > 0.05.The error bars represent the standard deviation (SD) of each data point.

Soil exchangeable cations

With an increase in the proportion of DAP replacing FCMP, exchangeable Ca2+ and Mg2+ showed a significant declining trend, and exchangeable K+ showed no obvious trend (Fig. 5). Compared with 0% DAP treatment, the exchangeable Ca2+ and Mg2+ in the soil with 100% DAP treatment decreased by 0.59 and 0.12 cmol kg−1 respectively. Among the exchangeable base cations, exchangeable Ca2+ accounting for 75.0-77.4%, and exchangeable Ca2+ were the dominant base cation.

With an increase in the proportion of DAP replacing FCMP, exchangeable Al3+ showed a significant increasing trend, and exchangeable H+ showed no obvious trend (Fig. 6). Compared with 0% DAP treatment, the exchangeable Al3+ under 100% DAP treatment increased by 0.70 cmol kg−1. Among the exchangeable acid cations, exchangeable Al3+ accounting for 89.8–91.7%, and exchangeable H+ accounting for 8.3–10.2%. It indicated that exchangeable Al3+ is the dominant exchangeable acidic cations.

Fig. 5
Fig. 5
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Effects of replacing FCMP with DAP on soil exchangeable base cations(cmol kg−1). (n = 45).

Fig. 6
Fig. 6
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Effects of replacing FCMP with DAP on soil exchangeable acid cations (cmol kg−1).(n = 45).

A significant positive linear correlation was found between soil pH and exchangeable Ca2+ and Mg2+ (Table 3). The result indicates that FCMP has a significant buffering effect in acidic soil, as it can release Ca2+ and Mg2+ to neutralize H+ in the soil, thereby slowing down the soil acidification process. In contrast, the application of DAP not only fails to provide sufficient Ca2+ and Mg2+, but also releases H⁺ through the reaction of phosphate ions with Al3+, further exacerbating soil acidification. Moreover, this study also found that the decrease in soil pH is significantly negatively correlated with the increase in exchangeable Al3+ in the soil (r = − 0.984**). This suggests that the application of DAP may exacerbate the toxic effects of soil acidification by increasing the content of exchangeable Al3+ in the soil.

Table 3 The correlation coefficient between soil pH and exchangeable cations.
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The soil exchangeable Al3+ is significantly correlated with the sum of exchangeable Ca2+ and Mg2+, and there is an approximate 1:1 negative correlation between them (Fig. 7).This shows that in acidic sugarcane soil, the increase of soil exchangeable aluminum is mainly caused by the loss of soil exchangeable calcium and magnesium.This stoichiometry suggests a direct cation exchange process on soil colloids, which is a fundamental response to soil acidification.

Fig. 7
Fig. 7
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The relationship between exchangeable Al3+ and exchangeable (Ca2+ +Mg2+)(cmol kg−1).(n = 45).

Discussion

Soil acidification is primarily manifested in the loss of base cations from the soil, which is driven by anion leaching and crop removal15,38. In the present study, the soil pH was less than 4.0 (Fig. 3), and the leaching of bicarbonate could be ignored39,40. The average NUE was only 59.3%, but there was no significant accumulation of active nitrogen in the soil (Fig. 3). Therefore, the nitrification of nitrogen applied by N-fertilizer and subsequent leaching of nitrate could be one of the main drivers of soil acidification41. In addition, the average removal of K2O, CaO and MgO from sugarcane harvest was 221, 78 and 31 kg ha−1 yr−1, which also lead to the secretion of H+ from the root42. Therefore, the removal of sugarcane biomass during harvesting constitutes a major driver of soil acidification43,44. Replacing FCMP with DAP reduces Ca2+ and Mg2+ input, and the loss of Ca2+ and Mg2+ from nitrate leaching and crop harvest will not be compensated, so the phenomenon of soil acidification will occur. Meng et al.16 and Du et al.17 reported that monocalcium phosphate consistently delayed the decline in soil pH in acid soil, which is consistent with our results.Therefore, in acidic sugarcane fields, the application of FCMP demonstrates significant soil amelioration effects.

In acidic soil with pH less than 5.0, Al2O3 is the main buffer of soil pH, and H+ will react with Al2O3 to release Al3+, thus causing the accumulation of exchangeable aluminum in the soil19,20. The Al3+ in the soil solution of acidic soils is widely accepted as the main factor that impacts on plant growth, especially root growth, compared with H+ ions24,45. Accumulation of soil exchangeable aluminum lead to an increase in Al3+ concentrations in soil solution, so soil exchangeable aluminum is an important index to evaluate the toxicity of soil acidification. In this study, with the increase of the proportion of DAP replacing FCMP, soil exchangeable aluminum showed a significant increase trend. Therefore, replacing FCMP with DAP can increase the accumulation of exchangeable aluminum in soil, which is harmful to sugarcane production.When DAP is applied to the soil, the NH₄⁺ it contains is oxidized to NO2− by nitrifying microorganisms (such as Nitrosomonas and Nitrobacter). This process continuously releases a substantial amount of H⁺ ions, which directly cause a sharp decrease in soil solution pH, resulting in a highly acidic environment8. Under these conditions, previously fixed aluminum (e.g., Al(OH)2) that was stably bound in soil minerals is activated and dissolved, converting into toxic exchangeable Al3+ through subsequent reactions46.

The application of soil amendments is an effective approach for remediating acidified soils. Currently, quicklime and FCMP are widely adopted due to their relatively low operational costs47. As a strongly alkaline material, quicklime can rapidly raise soil pH and reduce exchangeable aluminum content. However, long-term and excessive application of lime may cause soil compaction, disrupt the balance of soil nutrients, and ultimately lead to reduced crop yields48. In contrast, FCMP, an alkaline mineral fertilizer, has a mild and prolonged effect with high phosphorus use efficiency. It can effectively increase soil pH and supplement nutrients such as calcium and magnesium, demonstrating promising application potential.When FCMP is applied to acidified soil, it enhances the content of exchangeable base ions in the soil. These ions participate in exchange reactions with soil exchangeable acids, thereby reducing the content of exchangeable acids49. On the other hand, alkaline components in FCMP (e.g., CaSiO2) dissolve in the soil and consume protons (H⁺), neutralizing acidity and raising soil pH. The increase in pH promotes the hydrolysis and polymerization of highly toxic monomeric aluminum (Al3+) into less toxic hydroxyl-aluminum polymers. Simultaneously, phosphate ions (PO₄³⁻) released during the dissolution of FCMP react with these aluminum polymers to form highly insoluble and stable aluminum phosphate minerals (e.g., AlPO4 2H2O), thereby permanently sequestering aluminum and fundamentally reducing its bioavailability and toxicity.

In acid soil, FCMP can release Ca2+ and Mg2+50, which can compensate for the loss of Ca2+ and Mg2+ by leaching of nitrate and crop removal, and reduce the loss of soil exchangeable Ca2+ and Mg2+. However, the application of DAP did not compensate for the loss of Ca2+ and Mg2+, and soil exchangeable Ca2+ and Mg2+ decreased. With the increase of the proportion of DAP replacing FCMP, exchangeable Ca2+ and Mg2+ showed a significant downward trend. FCMP can be produced using low-grade phosphate rock, reducing waste residues from tailings and phosphogypsum in the production of high-concentration phosphate compound fertilizers, and fully using phosphate rock resources51,52. For moderately acidic sugarcane soils, we recommend FCMP as a lime-alternative amendment due to its dual functionality in acid neutralization and phosphorus supply53. For soils receiving DAP, a 1:3 DAP: FCMP ratio effectively mitigates soil acidification while preventing sugarcane yield reduction.

It must be acknowledged that a limitation of this study is the absence of a phosphorus-free control treatment. Such a control would have been highly valuable for clearly distinguishing the observed soil acidification into components driven by natural background processes and those induced by the chemical properties of different phosphate fertilizers54. However, our analyses confirm fertilizer effects as the primary acidification driver. The observed pH reduction (0.05–0.22 pH units across treatments) showed significant dependence on DAP substitution ratios, while recorded values substantially exceeded typical natural acidification rates (0.01–0.03 pH units annually) for comparable agroecosystems55,56. Considering the practical production benefits in long-term field trials and the primary focus of this study on comparing the effects of different phosphate fertilizers rather than quantifying absolute phosphorus effects, no phosphorus-free control treatment was included. Future research should incorporate such a control to enable more precise quantification of net acidification effects.

Conclusions

The results indicate that replacing FCMP with DAP can lead to a decrease in soil pH and an increase in soil exchangeable aluminum in acidic sugarcane field. The application of FCMP can release Ca2+ and Mg2+, which can compensate for the loss of Ca2+ and Mg2+ via leaching nitrate and crop removal, and reduce the loss of soil exchangeable Ca2+ and Mg2+. However, DAP application did not compensate for the loss of Ca2+ or Mg2+. With an increase in the proportion of DAP replacing FCMP, soil exchangeable Ca2+ and Mg2+ decreased and soil exchangeable Al3+ increased simultaneously. The accumulation of soil exchangeable Al3+ and loss of exchangeable (Ca2+ + Mg2+) were negatively correlated. And its impact on long-term sugarcane productivity warrants further study and careful management. The finding can provide important reference basis for decision-making in China’s fertilizer and sugarcane industries. And underscore the critical role of balanced fertilization in maintaining soil health and ensuring sustainable sugarcane production in acidic soils, offering actionable insights for policymakers and agricultural practitioners to optimize nutrient management strategies.