Search

Predicting the parameters that influence colloidal phosphorus (CP) release from soils under different land uses is critical for managing the impact on water quality. Traditional modeling approaches, such as linear regression, may fail to represent the intricate relationships that exist between soil qualities and environmental influences. Therefore, in this study, we investigated the major determinants of CP release from different land use/types such as farmland, desert, forest soils, and rivers. The study utilizes the structural equation model (SEM), multiple linear regression (MLR), and three machine learning (ML) models (Random Forest (RF), Support Vector Regression (SVR), and eXtreme Gradient Boosting (XGBoost)) to predict the release of CP from different soils by using soil iron (Fe), aluminum (Al), calcium (Ca), pH, total organic carbon (TOC) and precipitation as independent variables. Results show that colloidal-cations (Fe, Al, Ca) and colloidal-TOC strongly influence CP release, while bioclimatic variables (precipitation) and pH have weaker effects. XGBoost outperforms the other models with an R 2 of 0.94 and RMSE of 0.09. SHapley Additive Explanations described the outcomes since XGBoost is accurate. The relative relevance ranking indicated that colloidal TOC had the highest ranking in predicting CP. This was supported by the analysis of partial dependence plots, which showed that an increase in colloidal TOC increased soil CP release. According to our research, the SHAP XGBoost model provides significant information that can help determine the variables that considerably influence CP contents as compared to RF, SVM, and MLR., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Soil water-dispersible colloidal phosphorus (WCP) presents high mobility, however, the regulatory effect of biochar-coupled organic fertilizer is rarely known, especially under different cropping patterns. This study investigated the P adsorption, soil aggregate stability, and WCP in three paddy and three vegetable fields. These soils were amended with different fertilizers (chemical fertilizer, CF; substitution of solid-sheep manure or liquid-biogas slurry organic fertilizer, SOF/LOF; substitution of biochar-coupled organic fertilizers, BSOF/BLOF). Results presented that the LOF averagely increased the WCP contents by 50.2% across the sites, but the SOF and BSOF/BLOF averagely decreased their contents by 38.5% and 50.7% in comparison with the CF. The WCP decline in the BSOF/BLOF-amended soils was mainly attributed to the intensive P adsorption capacity and soil aggregate stability. The BSOF/BLOF increased the amorphous Fe and Al contents in the fields in comparison with the CF, which improved the adsorption capacity of soil particles, further improving the maximum absorbed P (Q max ) and reducing the dissolved organic matter (DOC), leading to the improvement of > 2 mm water-stable aggregate (WSA >2mm ) and subsequent WCP decrease. This was proved by the remarkable negative associations between the WCP and Q max (R 2  = 0.78, p < 0.01) and WSA >2mm (R 2  = 0.74, p < 0.01). This study manifests that biochar-coupled organic fertilizer could effectively reduce soil WCP content via the improvement of P adsorption and aggregate stability., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Phosphorus (P) availability and loss risk are linked to P species; however, their alternations in the soil amended with biochar-blended organic fertilizer is not well known, particularly under contrasting soil properties and land management. In this study, the variance of soil P species extracted by sequential chemical extraction (SCE) and 31 P NMR techniques, as well as the degree of P saturation (DPS), were investigated throughout three paddy and three vegetable fields. These fields were amended with three different fertilizers at the same P application rate: chemical fertilizer (CF), organic fertilizer substitution (sheep manure/biogas slurry, SM/BS), and biochar-blended organic fertilizer substitution (BSM/BBS). Results showed that the BSM/BBS and SM increased the total P contents by 7.5% and 5.9% (TP) and available P contents by 30.1% and 19.2% (AP), but decreased the DPS values by 19.4% and 11.7%, compared to the CF treatment. Yet, the BS decreased the TP and AP contents but increased the DPS values across the experimental sites. In the BSM/BBS amended soils, high AP contents were due to the increased inorganic P (NaHCO 3 -P i ), while the increased organic P (monoester and DNA) induced low DPS values and reduced soil P loss risk. Our study highlights that biochar-blended organic fertilizer is an effective agronomic way for improving P availability and decreasing P loss risk via the alteration of soil P species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Excessive application of phosphorus (P) fertilizer to the agriculture soil can lead to the P loss to the aquatic ecosystem. Three soils from different land use (tea, paddy, and vegetable soils) were treated with biogas slurry (BS) at rate of 79.8 kg ha -1 , anionic polyacrylamide (PAM) at rate of 12.5, 25 and 50 kg ha -1 , Gypsum (Gy) at rate of 5t ha -1 , and the control (Ck) without treatment, to control P losses in a laboratory batch experiment. The soil solution was analyzed for total P (TP), dissolved reactive P (DRP) and total dissolved P (TDP). Particulate P (PP) and dissolved unreactive P (DURP) were calculated by subtracting DRP from TP and TDP, respectively. The DRP was within a range of 68-98% of TP whereas PP varied in a range of 2-32% of TP and DURP was within a range of 0.1-19% of TP, depending on soil types and different treatments. The addition of PAM at a high rate and Gy together on the soil after BS application reduced the release of TP by 54, 46, and 51% and that of DRP by 61, 49, and 53% for tea, paddy and vegetable soils, respectively. However, the application of BS with PAM alone promoted the release of DRP by 77, 86, 70% for tea, paddy, and vegetable soils, respectively. This study suggests that the synergic application of PAM and Gy on soils after BS addition can be a good strategy to reduce P losses., (Copyright © 2019 Elsevier Ltd. All rights reserved.)