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"soil phosphorus"
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Soil chemical fumigation alters soil phosphorus cycling: effects and potential mechanisms
Soil chemical fumigation is an effective and popular method to increase agricultural productivity. However, the broad-spectrum bioactivity of fumigants causes harm to soil beneficial microorganisms involved in the soil phosphorous cycle, such as soil phosphorus solubilizing microorganisms (PSMs). We review the effects of soil chemical fumigation on soil phosphorus cycling, and the potential underlying mechanisms that ultimately lead to altered phosphorus availability for crops. These complex processes involve the highly diverse PSM community and a plethora of soil phosphorus forms. We discuss phosphatizing amendments aimed at counteracting the possible negative effects of fumigation on phosphorus availability, phosphorus use efficiency, and crop yields. We also emphasize distinguishing between the effects on soil phosphorus cycling caused by the chemical fumigants, and those caused by the fumigation process (e.g. plastic mulching). These are typically conflated in the literature; distinguishing them is critical for identifying appropriate amendments to remediate possible post-fumigation soil phosphorus deficiencies.
Journal Article
Eleven-Year Canopy Nitrogen Addition Enhances the Uptake of Phosphorus by Plants and Accelerates Its Depletion in Soil
Soil phosphorus (P) is a critical factor that limits plant productivity. Enhanced nitrogen (N) deposition has the potential to modify P transformation and availability, thereby potentially affecting the long-term productivity of forests. Here, we conducted an 11-year-long field experiment to simulate N deposition by adding N to the forest canopy in a N-limited northern subtropical forest in central China and assessed the changes in soil organic P mineralization, P fractions, microbial biomass P content, phosphatase activity, and plant P content under N deposition. Our objective was to establish a theoretical framework for addressing the P supply and sustaining plant productivity in soils with low P availability, particularly in a changing global setting. The results demonstrated a substantial reduction in the levels of total, organic, and available P owing to the canopy addition of N. Furthermore, there was a marked decrease in the proportion of organic P in the total P pool. However, no substantial changes were observed in the soil inorganic P content or the proportion of inorganic P within the total P across different treatments. Canopy N addition significantly enhanced the microbial biomass P content, phosphatase activity, and organic P mineralization rate, suggesting that in soils with limited P availability, the primary source of P was derived from the mineralization of organic P. Canopy N addition substantially increased the P content in leaves and fine roots while concurrently causing a considerable decrease in the N:P ratio. This indicates that N deposition increases P demand in plants. Correlation analysis revealed a significant negative association among the total, organic, and available P levels in the soil and plant P concentrations (p < 0.05). This suggests that the primary cause of the reduced fractions of P was plant uptake following canopy N addition. Various studies have demonstrated that N deposition induces an augmented P demand in plants and expedites the utilization of available P. A substantial reduction in potentially accessible soil P caused by N deposition is likely to exacerbate regional P depletion, thereby exerting adverse impacts on forest ecosystem productivity.
Journal Article
Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities
Background The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction. Scope We asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research. Conclusions We identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems.
Journal Article
Impacts of long-term plant biomass management on soil phosphorus under temperate grassland
Aims We assessed and quantified the cumulative impact of 20 years of biomass management on the nature and bioavailability of soil phosphorus (P) accumulated from antecedent fertiliser inputs. Methods Soil (0–2.5, 2.5–5, 5–10 cm) and plant samples were taken from replicate plots in a grassland field experiment maintained for 20 years under contrasting plant biomass regimen- biomass retained or removed after mowing. Analyses included dry matter production and P uptake, root biomass, total soil carbon (C), total nitrogen (N), total P, soil P fractionation, and 31P NMR spectroscopy. Results Contemporary plant production and P uptake were over 2-fold higher for the biomass retained compared with the biomass removed regimes. Soil C, total P, soluble and labile forms of inorganic and organic soil P were significantly higher under biomass retention than removal. Conclusions Reserves of soluble and labile inorganic P in soil were significantly depleted in response to continued long-term removal of P in plant biomass compared to retention. However, this was only sufficient to sustain plant production at half the level observed for the biomass retention after 20 years, which was partly attributed to limited mobilisation of organic P in response to P removal.
Journal Article
Phosphorus Environmental Risk Assessment in Wetland Soil
At the interface between agricultural fields and water bodies there are wetlands constituted by hydromorphic soils. Our hypothesis is that hydromorphic soil acts a P sink and the P buffer capacity increases over time. To test our hypothesis, we apply tools to evaluate the P environmental risk via i) maximum phosphorus adsorption capacity (PMAC); ii) environmental soil phosphorus thresholds (P-threshold); iii) soil phosphorus storage capacity (SPSC) in hydromorphic soil (Histosol) and a non-hydromorphic soil (Cambisol) under application of mineral P. The PMAC was estimated by the Langmuir model in soil samples collected at four depths (0–10, 10–20, 20–40 and 40–60 cm). Soil samples were incubated for 30, 60 and 120 days with mineral P equivalent to 0, 25, 50, 75 and 100% of the PMAC. The P-threshold was determined from the degree of phosphorus saturation (DPS), estimated using PMAC and Fe + Al extracted with Mehlich-1. The SPSC was obtained from the 0–60 cm depth using the DPS%
M1(CMAP)
. The PMAC values ranged from 2321 to 3539 mg kg
−1
with higher values in the Histosol compared to the Cambisol. The Histosol presented a P-threshold of 19% DPS (609 mg kg
−1
), while in the Cambisol it was 24% DPS (582 mg kg
−1
of P Mehlich-1). According to the SPSC tool, the soil acted as a source of P when P Mehlich-1 exceeded 887 mg kg
−1
in Histosol, while in Cambisol it was 773 mg kg
−1
. Overall, the P buffering capacity was higher in the Histosol, indicating the importance of preserving wetlands for water quality.
Graphical Abstract
Journal Article
Nitrogen-Fixing Plants Enhance Soil Phosphorus Availability by Promoting Transformations Among Phosphorus Fractions in a Subtropical Karst Forest
Nitrogen (N)-fixing plants are commonly employed in the restoration of degraded terrestrial ecosystems due to their ability to increase soil N capital and boost ecosystem productivity. Given the close coupling between N and phosphorus (P) in soil, the effects of N-fixing plants on soil P fractions and availability in karst forests remain largely unexplored. Herein, we compared soil P pools, fractions, and availability in the rhizosphere and non-rhizosphere soils of N-fixing and non-N-fixing plants, and explored associated drivers, such as soil, microbial, and plant properties, in a subtropical karst forest. The results showed that the N-fixing plants increased total P, inorganic P, and available P in both the rhizosphere and non-rhizosphere soils. The nitrogen-fixing plants increased soil labile P (LP) and non-labile P (NLP), but decreased moderately labile P (MLP), particularly in the rhizosphere soils, due to transformations among different soil P fractions. Soil P fractions were primarily influenced by soil inorganic P, root and leaf N, and microbial biomass N in the N-fixing plant treatment, whereas soil inorganic P, dissolved organic carbon (DOC), and dissolved organic N (DON) were the key factors in the non-N-fixing plant treatment. Consequently, soil properties, microbial attributes, plant nutrients, and soil P fractions collectively exerted both direct and indirect effects to increase soil P availability in the N-fixing plant treatment. In contrast, soil P fractions directly and soil properties indirectly influenced soil P availability in the non-N-fixing plant treatment. Our results revealed the unique role of N-fixing plants in driving soil P availability in subtropical karst forests. These findings are essential for developing effective strategies for P nutrient management and guiding the selection of appropriate plant species for vegetation restoration in karst regions.
Journal Article
Comparative Analysis of Four Methods for Accurate Estimation of Soil Phosphorus Storage Capacity: a Case Study in a Typical Red Soil
Efficient utilization of agricultural soil phosphorus (P) and mitigation of loss risks necessitate a precise evaluation of soil P storage capacity (SPSC). This study compared the effectiveness of four soil test P methods (Oxalate, Bray, Olsen, and Mehlich-1) to accurately estimate SPSC and simplify P loss risk assessment of soils located in a typical red soil in the Sunjia Watershed, Yingtan, Jiangxi Province, China. The extraction efficiencies of these methods for Fe, Al, P, and P saturation ratio (PSR) were compared, and conversion equations between SPSC
Ox
(extracted using Oxalate) and soil test P (Bray, Olsen, and Mehlich-1) were derived through fitting analysis. The results underscored Oxalate as the optimal extractant for gauging P loss risk in red soils. Structural equation modeling (SEM) unveiled the substantial impact of amorphous iron-aluminum oxides (Fe
o
, Al
o
) on SPSC, with Fe
o
exerting a more pronounced influence than Al
o
. Among soil physicochemical properties, total carbon emerged as the most influential, and a strong interaction was noted between the physicochemical properties and Fe
o
and Al
o
. The study delineated three crucial P concentration ranges for practical P management in red soils. When Bray-P < 48.2 mg kg
–1
, the soil acted as a P sink with no P loss risk, allowing for continued P application to augment crop yield. Conversely, within 48.2 mg kg
–1
< Bray-P ≤ 55.2 mg kg
–1
, the soil attained its maximum secure P capacity; further P application significantly escalated the peril of P loss. Subsequently, when Bray-P > 55.2 mg kg
–1
, the soil turns into a source of P release. This signifies an escalated risk of P loss, demanding the immediate implementation of environmental protective measures.
Journal Article
Regional-scale phosphorus flows and budgets within France: The importance of agricultural production systems
Large-scale studies at the regional, national and global scales are increasingly needed to assess nutrient flows in agroecoystems and to identify their drivers. In this study, we aimed to quantify the extent to which regional phosphorus (P) flows and soil P budget depend on agricultural production systems. Phosphorus was taken as a case study due to its sorbing properties in soil and to the many questions concerning its future availability. The issue was studied from two different stages: (1) for the 21 administrative regions of France; and (2) by selecting four contrasting French regions—the Centre region (a crop farming region), Brittany (an animal farming region) and Lorraine and Aquitaine (mixed farming regions). Phosphorus flows and soil P budgets were quantified on a yearly basis for the 21 regions from 1990 to 2006, whereas a 5-year average was calculated for the years 2002–2006 to compare the four selected regions. At the beginning of the study (1990), the calculated P budget was positive for all regions averaging 17.5 kg P ha
−1
year
−1
which declined over years to 4.4 kg P ha
−1
year
−1
in 2006, but huge differences between the 21 regions were observed, confirming the heterogeneity of the regional P flows. Agricultural production systems strongly influenced the P flows through feed, fodder and animal excretion, while P fertiliser consumption was only partially influenced. As a consequence, both the regional soil P budgets and the magnitude of soil P inflows and outflows were strongly dependent on the regional agricultural production systems. A balanced soil P budget could be obtained in crop farming regions, but it strongly relied on P fertiliser use. The animal farming regions continued to accumulate P in the soil, and further use of P fertilisers in these regions is questionable. Finally, there was no simple rule between the mixed farming systems and the soil P budget. This study offers some initial elements for understanding the drivers of mineral P fertiliser use, i.e. the factors governing P fertiliser use by the farmers. It may also contribute to the redesign of regional farming systems oriented towards more effective use of nutrients at the global scale.
Journal Article