Enhancing Soil Nitrogen Retention Capacity by Biochar Incorporation in the Acidic Soil of Pomelo Orchards: The Crucial Role of pH

Abstract

Biochar is commonly used to improve acidic soil and reduce nitrogen loss. However, the impact of biochar on soil nitrogen retention, especially at varying pH levels, is not fully understood. Soil samples were obtained from an acidic red soil citrus orchard. The soil pH was adjusted using CaO, with five levels (4.0, 5.1, 5.8, 6.6, and 7.2), and two biochar doses (0% and 1%) were applied. The study used 15N-Tracer and Ntrace to investigate biochar’s influence on soil nitrogen retention at different pH levels. The results showed that soil amendment with biochar improved gross mineralization rates (TM) and gross NH4+ immobilization rates (TI), except at pH 4.0 for TI. Biochar enhanced heterotrophic nitrification (ONrec) within pH 4.0–7.4, with a threshold for autotrophic nitrification (ONH4) at pH 6.4. The findings revealed biochar’s positive effect on soil nitrogen retention within pH 4.5–6.4. Biochar had a greater impact on TI than TM and inhibited ONH4, potentially enhancing nitrogen retention in this pH range. These results highlight the significance of considering biochar incorporation for improving nitrogen use efficiency and reducing NO3−-N loss in subtropical pomelo orchards.

Biochar produced at high temperature mitigates N2O emission and promotes nitrogen retention in subtropical forest soils

“…In our study, both soil N mineralization and nitrification rates showed a significant positive correlation with DOC content (Figure S1). It is widely recognized that the process of soil nitrification leads to the production of NO 3 − , which reduces soil pH (Qian et al, 2023;Zhou et al, 2023). In our study, soil net nitrification rates were significantly decreased after the incorporation of biochar, especially those produced at low temperatures (Figure 3c).…”

Effects of Biochar and Arbuscular Mycorrhizal Fungi on Soil Health in Chinese Kale (Brassica oleracea var. alboglabra L.) Cultivation

“…When incorporated into the soil, biochar has the capacity to increase the overall pH of the soil [75]. Simultaneously, adding different concentrations of biochar to the soil induces changes in the pH value, with an increase corresponding to the applied level [76]. These findings are supported by the results of Hailegnaw et al [77], who noted that the highest biochar application rate (8%) was more effective in altering soil properties than lower biochar rates, significantly increasing pH in all incubated soils.…”

‘Soil and Plant Nutrition’—A Section of Agronomy: Advances and Perspectives

“…Nitrogen can be lost from the soil through processes such as leaching, denitrification, and volatilization, which lead to acidification in terrestrial systems, eutrophication of aquatic systems, and decline in biodiversity and contribute to climate change. The most commonly proposed solutions involve optimizing fertilizer doses, as well as considering the form of fertilizers used, such as slow-release fertilizers [6][7][8][9][10][11][12][13][14]. A very promising solution is the application of nitrification inhibitors [15][16][17][18][19][20].…”

“…Biochar is the most intensively investigated amendment and is widely described in the literature, including in the 'Soil and Plant Nutrition' section [6,[21][22][23][33][34][35][36][37][38][39]. Many review papers (1327 reviews indexed in the Web of Science Core Collection in categories related to agronomy) and meta-analyses have already been written on this subject [40][41][42][43][44][45][46][47][48].…”