Purpose This study was conducted to investigate the effects of different fertilization regimes, including chemical fertilizer, biochar, and their combined application, on soil nutrient dynamics and enzymatic activity profiles in a Casuarina equisetifolia plantation ecosystem. Materials and methods The experimental site is characterized by a maritime subtropical monsoon climate, with soil classified as aeolian sandy soil. A 7-year-old Casuarina equisetifolia plantation was subjected to four fertilization regimes: a control with no fertilization (CK), application of NPK fertilizer (F), biochar alone (B), and a combination of NPK fertilizer with biochar (FB). Soil samples were periodically collected at three-month intervals following fertilization, corresponding to four distinct sampling stages (S1-S4), to assess temporal variations in soil mineral nutrient concentrations and enzymatic activities. Results and discussion Soil elements responded differentially to fertilization. Macronutrients (K, Mg, Ca) exhibited pronounced seasonal fluctuations. In topsoil, FB treatment significantly (p < 0.05) increased K by 59.81% at S2. B treatment significantly (p < 0.05) elevated Mn and Fe by 65.56% and 67.31% at S3, and significantly (p < 0.05) increased Mg and Ca by 154.07% and 97.85% at S4. In subsoil, FB significantly (p < 0.05) enhanced Mg, Ca, Zn, and Fe by 46.98%, 82.23%, 133.69%, and 35.25% at S4. Under FB treatment, topsoil urease activity significantly (p < 0.05) increased by 32.53%-229.17%, neutral phosphatase by 41.72%-545.50%, and sucrase by 156.91% at S4. Subsoil urease activity significantly (p < 0.05) increased by 235.24%-238.76% during S3-S4. Correlations among elements and enzymes were influenced by season and soil depth. In topsoil at S1, Mn and Fe positively correlated with sucrase and phosphatase. K and urease were positively correlated at S2 but negatively at S3. ANOVA showed significant interactive effects significantly (p < 0.05) of treatment, season, and soil layer. Conclusions Fertilization affected enzyme activities more markedly than element contents. Season was the dominant variation driver, though fertilization impact on some enzymes exceeded seasonal effects, highlighting its significant role in regulating soil biochemical processes.

Biochar-NPK interactions improve soil nutrients and enzyme activity in Casuarina equisetifolia

期刊论文
发表日期：

2026年3月6日

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Qiping Qiu,
Bin Xie,
Lin Zhao,
Han Lin,
Anqiang Xie,
Dongyang Wu,
Can Chen

摘要

Purpose

This study was conducted to investigate the effects of different fertilization regimes, including chemical fertilizer, biochar, and their combined application, on soil nutrient dynamics and enzymatic activity profiles in a Casuarina equisetifolia plantation ecosystem.

Materials and methods

The experimental site is characterized by a maritime subtropical monsoon climate, with soil classified as aeolian sandy soil. A 7-year-old Casuarina equisetifolia plantation was subjected to four fertilization regimes: a control with no fertilization (CK), application of NPK fertilizer (F), biochar alone (B), and a combination of NPK fertilizer with biochar (FB). Soil samples were periodically collected at three-month intervals following fertilization, corresponding to four distinct sampling stages (S1-S4), to assess temporal variations in soil mineral nutrient concentrations and enzymatic activities.

Results and discussion

Soil elements responded differentially to fertilization. Macronutrients (K, Mg, Ca) exhibited pronounced seasonal fluctuations. In topsoil, FB treatment significantly (p < 0.05) increased K by 59.81% at S2. B treatment significantly (p < 0.05) elevated Mn and Fe by 65.56% and 67.31% at S3, and significantly (p < 0.05) increased Mg and Ca by 154.07% and 97.85% at S4. In subsoil, FB significantly (p < 0.05) enhanced Mg, Ca, Zn, and Fe by 46.98%, 82.23%, 133.69%, and 35.25% at S4. Under FB treatment, topsoil urease activity significantly (p < 0.05) increased by 32.53%-229.17%, neutral phosphatase by 41.72%-545.50%, and sucrase by 156.91% at S4. Subsoil urease activity significantly (p < 0.05) increased by 235.24%-238.76% during S3-S4. Correlations among elements and enzymes were influenced by season and soil depth. In topsoil at S1, Mn and Fe positively correlated with sucrase and phosphatase. K and urease were positively correlated at S2 but negatively at S3. ANOVA showed significant interactive effects significantly (p < 0.05) of treatment, season, and soil layer.

Conclusions

Fertilization affected enzyme activities more markedly than element contents. Season was the dominant variation driver, though fertilization impact on some enzymes exceeded seasonal effects, highlighting its significant role in regulating soil biochemical processes.