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Fertilizer application, especially their physical and chemical composition, substantially regulates crop growth and development. The form in which fertilizers are applied to the soil has always been regarded as a crucial factor regulating nutrient availability. However, the properties and release characteristics of Mg fertilizers, i.e., fast-release Mg (F-Mg) and slow-release Mg (S-Mg), have not been fully elucidated in acidic soils. This study characterized the different Mg fertilizers, and their release characteristics were verified through pot (using soybean) and field (using pomelo) experiments. The results showed that, despite the differences between different Mg fertilizers, the same functional group peaks were recorded among them. F-Mg fertilizers had a low pH and low Mg purity, while S-Mg fertilizers had a high pH and high Mg purity. The release rate and leaching characteristics of the F-Mg fertilizers were higher than the S-Mg fertilizers. The pot experiment showed that the yield and growth of soybean were higher under the S-Mg fertilizer than the F-Mg fertilizer. However, MgSO4·7H2O and MgO had the best effect among the F-Mg and S-Mg fertilizers, respectively. The effects of these two fertilizers were further validated using field experiments, and it was found that MgSO4·7H2O and MgO fertilizers substantially improved the yield and quality of pomelo. However, MgO showed a better effect than MgSO4·7H2O. This study can provide a sound theoretical basis for selecting the most efficient type of Mg fertilizer for acid soils. It can contribute valuable information regarding farmland management strategies and may result in sustainable agricultural productivity. [ABSTRACT FROM AUTHOR]

Soil fungi play a critical role in plant performance and soil nutrient cycling. However, the understanding of soil fungal community composition and functions in response to different nutrients management practices in red soils remains largely unknown. Here, we investigated the responses of soil fungal communities and functions under conventional farmer fertilization practice (FFP) and different nutrient management practices, i.e., optimization of NPK fertilizer (O) with soil conditioner (O + C), with lime and mushroom residue (O + L + M), and with lime and magnesium fertilizer (O + L + Mg). Illumina high-throughput sequencing was used for fungal identification, while the functional groups were inferred with FUNGuild. Nutrient management practices significantly raised the soil pH to 4.79–5.31 compared with FFP (3.69), and soil pH had the most significant effect (0.989 ***) on fungal communities. Predominant phyla, including Ascomycota, Basidiomycota, and Mortierellomycota were identified in all treatments and accounted for 94% of all fungal communities. The alpha diversity indices significantly increased under nutrients management practices compared with FFP. Co-occurrence network analysis revealed the keystone fungal species in the red soil, i.e., Ascomycota (54.04%), Basidiomycota (7.58%), Rozellomycota (4.55%), and Chytridiomycota (4.04%). FUNGuild showed that the relative abundance of arbuscular mycorrhizal fungi and ectomycorrhizal fungi was higher, while pathogenic fungi were lower under nutrient management practices compared with FFP. Our findings have important implications for the understanding of improvement of acidic soils that could significantly improve the soil fungal diversity and functioning in acidic soils. [ABSTRACT FROM AUTHOR]

Soil fungi play a vital role in soil nutrient dynamics, but knowledge of their diversity and community composition in response to biochar addition into red soil is either limited or inconsistent. Therefore, we determined the impact of bamboo biochar (BB) with increasing concentrations (0, 5, 20, and 80 g kg−1 of soil, referred to as B0, BB5, BB20, and BB80, respectively) on soil physicochemical properties and fungal communities (Illumina high-throughput sequencing) in red soil under Fokenia hodginsii (Fujian cypress). We found that increasing BB levels effectively raised the soil pH and soil nutrients, particularly under BB80. BB addition significantly increased the relative abundance of important genera, i.e., Basidiomycota, Mucoromycota, and Chytridiomycota that could play a key role in ecological functioning, e.g., wood degradation and litter decomposition, improvement in plant nutrients uptake, and resistance to several abiotic stress factors. Soil amended with BB exhibited a substantial ability to increase the fungal richness and diversity; BB80 > BB20 > BB5 > B0. Basidiomycota, Mucoromycota, Glomeromycota, Rozellomycota, Aphelidiomycota, Kickxellomycota, and Planctomycetes were positively associated with soil pH, total nitrogen, phosphorous, and carbon, and available potassium and phosphorous. Besides, the correlation analysis between the soil fungal communities and soil properties also showed that soil pH was the most influential factor in shaping the soil fungal communities in the red soil. These findings have significant implications for a comprehensive understanding of how to ameliorate acidic soils with BB addition, as well as for future research on sustainable forest management, which might increase soil fungi richness, diversity, and functionality in acidic soils. [ABSTRACT FROM AUTHOR]

Root system plays a crucial role in plant growth and development by uptake of soil nutrients, which is affected by intensive use of NPK fertilizer. However, it is unknown how integrated nutrient management (INM) could affect the root growth and its nutrient uptake in the red soils of southern China. For this, the impacts of different INM practices on root morphological traits and root nutrient uptake were investigated in the pomelo tree. First, we investigated the spatial root distribution of various tree ages (i.e., 8, 13, 18, and 23 years old) and found the optimum root growth at 20–80 cm around the tree trunk in topsoil (0–20 cm). Hence, the pomelo trees were fertilized at 20–80 cm around the trunk, i.e., FFP (farmer fertilization practice), optimization NPK fertilizer (O) combined with lime (L) and mushroom residue (M) known as O+L+M treatment, and O+L combined with Mg fertilizer called as O+L+Mg treatment. We found that root length (RL) significantly increased by application of O+L+M (108.5 and 219.1 cm) and O+L+Mg (73.6, 66.8 cm) in topsoil and subsoil, respectively, in 2019. Similarly, root surface area (RSA) was significantly higher under INM, i.e., O+L+Mg > O+L+M > FFP. For root diameter (RD), O+L+M (0.8 mm) and O+L+Mg (1.5 mm) showed significantly lower diameter than FFP (2.54 mm). The root tips (RT) also improved considerably under INM practices compared with FFP. Besides, root nutrient contents (N, P, K, Ca, and Mg) also significantly improved under O+L+M and O+L+Mg over FFP. Similar trends of root growth and nutrients uptake were recorded in 2020. Overall, these findings suggest that INM plays a significant role in root development and nutrient uptake under acidic soil, which could be useful for maximizing crop productivity. [ABSTRACT FROM AUTHOR]

• Lime+Mg application increased the availability of N, P, Ca, Mg in acidic soils. • Lime+Mg increased edible rate, soluble solids, and reduced titratable acidity. • Pomelo yield increased by 30.5% under Lime+Mg application. • Lime+Mg application increased annual net income by 37.4%. Magnesium (Mg) is an essential mineral nutrient for plant growth, and its deficiency in citrus orchards has been widely observed in the acidic soils of southern China. Lime amendments have been proposed as potential solution to mitigate the soil pH and improve the soil quality. Therefore, we evaluated the effects of lime and Mg fertilizer on soil physicochemical properties, nutrients uptake, pomelo quality and yield, and economic benefits in the pomelo production area. For this, a field experiment was conducted during 2017–2019 using three treatment combinations; (i) control with no lime and Mg fertilizer (CK), (ii) Mg fertilizer with no lime (+Mg), and (iii) lime combined with Mg fertilizer (Lime+Mg). We found that Lime+Mg treatment significantly increased pomelo yield by 34.2% and 26.8% in 2018 and 2019, respectively over CK. Economically, Lime+Mg application increased the annual net income by 37.4%. Under Lime+Mg treatment, the concentration of N, K, Ca, and Mg was increased, while Fe and Mn decreased in leaf, peel, and pulp. Lime+Mg application significantly increased the edible rate, and total soluble solids (TSS) by 7.2% and 4.2%, respectively, while decreased the titratable acid (TA) by 11.7% in pomelo. Lime+Mg treatment also raised the soil pH, available N, P, Ca, and Mg concentrations significantly. Our results demonstrate that Lime+Mg incorporation to acidic soils of pomelo orchard alleviates the soil acidification, improves the nutrients availability, yield and fruit quality, and results in more economic benefits. [Display omitted] [ABSTRACT FROM AUTHOR]

Soil amendments, including lime, biochar, industrial by-products, manure, and straw are used to alleviate soil acidification and improve crop productivity. Quantitative insight in the effect of these amendments on soil pH is limited, hampering their appropriate use. Until now, there is no comprehensive evaluation of the effects of soil amendments on soil acidity and yield, accounting for differences in soil properties. We synthesized 832 observations from 142 papers to explore the impact of these amendments on crop yield, soil pH and soil properties, focusing on acidic soils with a pH value below 6.5. Application of lime, biochar, by-products, manure, straw and combinations of them significantly increased soil pH by 15%, 12%, 15%, 13%, 5% and 17%, and increased crop yield by 29%, 57%, 50%, 55%, 9%, and 52%, respectively. The increase of soil pH was positively correlated with the increase in crop yield, but the relationship varied among crop types. The most substantial increases in soil pH and yield in response to soil amendments were found under long-term applications (>6 year) in strongly acidic (pH < 5.0) sandy soils with a low cation exchange capacity (CEC, <100 mmol c kg−1) and low soil organic matter content (SOM, <12 g kg−1). Most amendments increased soil CEC, SOM and base saturation (BS) and decreased soil bulk density (BD), but lime application increased soil BD (1%) induced by soil compaction. Soil pH and yield were positively correlated with CEC, SOM and BS, while yield declined when soils became compacted. Considering the impact of the amendments on soil pH, soil properties and crop yield as well as their costs, the addition of lime, manure and straw seem most appropriate in acidic soils with an initial pH range from <5.0, 5.0–6.0 and 6.0–6.5, respectively. [Display omitted] • Soil amendments increased soil pH and crop yield by ca. 13% and 36%, respectively. • Amendments increased soil CEC, OM and base saturation and decreased bulk density. • Lime is the most economical while biochar is the most expensive for raising pH. • Lime, manure and straw are recommended at pH < 5.0, 5.0–6.0 and 6.0–6.5, respectively. [ABSTRACT FROM AUTHOR]