Phosphorus in all its forms Howarth, Robert W
Science (American Association for the Advancement of Science),
03/2023, Volume:
379, Issue:
6637
Journal Article
Peer reviewed
Limited availability and unwanted effects render the mineral’s future uncertain, despite its agricultural importance
Low availability of inorganic phosphorus (P) is considered a major constraint for crop productivity worldwide. A unique set of 266 chickpea (Cicer arietinum L.) genotypes, originating from 29 ...countries and with diverse genetic background, were used to study P‐use efficiency. Plants were grown in pots containing sterilized river sand supplied with P at a rate of 10 μg P g−1 soil as FePO4, a poorly soluble form of P. The results showed large genotypic variation in plant growth, shoot P content, physiological P‐use efficiency, and P‐utilization efficiency in response to low P supply. Further investigation of a subset of 100 chickpea genotypes with contrasting growth performance showed significant differences in photosynthetic rate and photosynthetic P‐use efficiency. A positive correlation was found between leaf P concentration and transpiration rate of the young fully expanded leaves. For the first time, our study has suggested a role of leaf transpiration in P acquisition, consistent with transpiration‐driven mass flow in chickpea grown in low‐P sandy soils. The identification of 6 genotypes with high plant growth, P‐acquisition, and P‐utilization efficiency suggests that the chickpea reference set can be used in breeding programmes to improve both P‐acquisition and P‐utilization efficiency under low‐P conditions.
Low availability of phosphorus (P) is a major constraint for crop productivity worldwide, and there is a need to improve P‐use efficiency. Using a unique set of 266 chickpea genotypes, our study identified 6 genotypes with high P‐acquisition and P‐utilization efficiency, suggesting that the chickpea reference set can be used in breeding programs to improve P‐use efficiency under low‐P conditions. For the first time, our study has demonstrated the significance of leaf transpiration in P acquisition likely via mass flow in chickpea grown in low‐P sandy soils.
Wetland soils act as a sink or source of phosphorus (P) to the overlaying water due to phosphorus sorption-desorption processes. Litter information is available on sorption and desorption behaviors ...of phosphorus in coastal wetlands with different flooding conditions. Laboratory experiments were conducted to investigate phosphorus sorption-desorption processes, fractions of adsorbed phosphorus, and the effects of salinity, pH and temperature on phosphorus sorption on soils in tidal-flooding wetlands (TW), freshwater-flooding wetlands (FW) and seasonal-flooding wetlands (SW) in the Yellow River Delta. Our results showed that the freshly adsorbed phosphorus dominantly exists in Occluded-P and Fe/AlP and their percentages increased with increasing phosphorus adsorbed. Phosphorus sorption isotherms could be better described by the modified Langmuir model than by the modified Freundlich model. A binomial equation could be properly used to describe the effects of salinity, pH, and temperature on phosphorus sorption. Phosphorus sorption generally increased with increasing salinity, pH, and temperature at lower ranges, while decreased in excess of some threshold values. The maximum phosphorus sorption capacity (Qmax) was larger for FW soils (256 mg/kg) compared with TW (218 mg/kg) and SW soils (235 mg/kg) (p < 0.05). The percentage of phosphorus desorption (Pdes) in the FW soils (7.5–63.5%) was much lower than those in TW (27.7–124.9%) and SW soils (19.2–108.5%). The initial soil organic matter, pH and the exchangeable Al, Fe and Cd contents were important factors influencing P sorption and desorption. The findings of this study indicate that freshwater restoration can contribute to controlling the eutrophication status of water bodies through increasing P sorption.
•P sorption isotherms could be better fitted using the modified Langmuir model.•Freshwater input improved maximum P sorption capacity and reduced desorption rate.•The freshly adsorbed phosphorus was nominated by Occluded P and Fe/Al P forms.•Effects of salinity, pH and temperature could be described by a binomial equation.•SOM, pH and exchangeable Al, Fe, Ca were the important factors influencing Pmax.
There has been much soil phosphorus (P) research in the last decades, but few basic publications exist summarizing the current state of knowledge on ecologically relevant P forms and their reactions ...in soils. The present paper aims at giving such a literature overview. The major P forms occurring in soils are presented. Organic P results from biogenic processes when organisms take up P from the soil. After their death, this P is returned into the soil and has to be mineralized before the next uptake. Mineralization intensity depends on the concentration of dissolved inorganic P in the soil solution. Only this soil P fraction can be taken up by plants and microorganisms and enter the food chain. Thus, it is critical for ecosystem nutrition. Dissolved P is highly affine for binding to the soil matrix and strives for equilibrium with bonded P forms. On the one hand, there is sorbed P, regularly forming quickly and being easily exchanged back into the soil solution. Sorbed P strongly depends on which and how many sorption sites a soil offers. Some of these sites are not easily accessible. Thus, P needs time to be sorbed there and is slightly soluble afterwards. This fraction is termed “occluded P”. It is considered fixed and not bioavailable for long times. On the other hand, there is mineral P, resulting from the precipitation of P anions and metal cations when the soil solution is oversaturated with these ions. The stability of mineral P depends on its degree of order, amorphous phases being less stable than highly crystalline minerals. Organic, sorbed and mineral P are tightly interconnected with dissolved P and strive for equilibrium with it. Due to changes in temperature, precipitation and vegetation/edaphic patterns such equilibrium is hardly attained and soil P reactions must dynamically adjust to present conditions.
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•The major soil P fractions and their reactions are presented.•Organic and inorganic P forms (dissolved, sorbed, occluded, mineral) are characterized.•A conceptual model illustrating interconnections between major P fractions is proposed.•Dissolved P is the most dynamic and mobile fraction and determines reactions of the other P pools.•Changes in temperature, precipitation and vegetation/edaphic patterns trigger P reactions.
Limitation of plant productivity by phosphorus (P) supply is widespread and will probably increase in the future. Relatively large amounts of P fertilizer are applied to sustain crop growth and ...development and to achieve high yields. However, with increasing P application, plant P efficiency generally declines, which results in greater losses of P to the environment with detrimental consequences for ecosystems.
A strategy for reducing P input and environmental losses while maintaining or increasing plant performance is the development of crops that take up P effectively from the soil (P acquisition efficiency) or promote productivity per unit of P taken up (P utilization efficiency). In this review, we describe current research on P metabolism and transport and its relevance for improving P utilization efficiency.
Enhanced P utilization efficiency can be achieved by optimal partitioning of cellular P and distributing P effectively between tissues, allowing maximum growth and biomass of harvestable plant parts. Knowledge of the mechanisms involved could help design and breed crops with greater P utilization efficiency.
•Importance of long-term manure application on soil mineralogy.•Changes in soil mineralogy followed by long-term application of manures.•P and Fe K-edge XAFS spectroscopic analysis of diagnostic ...spectral features of manured soils.•P cycling in manured soils as assessed by P desorption kinetics.•Questionable sensitivity of P sorption indices to predict P losses.
Phosphorus (P) K-edge XANES and Fe K-edge EXAFS spectroscopies along with sequential P chemical fractionation and desorption kinetics experiments, were employed to provide micro- and macro-scale information on the long-term fate of manure application on the solid-state speciation, kinetics and distribution of P in highly weathered agricultural soils of southern Brazil.
Soil test P values ranged from 7.3 up to 16.5 times as much higher than the reference soil. A sharp increase in amorphous Fe and Al amounts were observed as an effect of the consecutive application of manures. Whereas our results showed that the P sorption capacity of some manured soils was not significantly affected, P risk assessment indices indicated that P losses should be expected, likely due to the excessive manure rates applied to the soils. The much higher contents of amorphous Fe and Al (hydr)oxides (55% and 80% increase with respect to the reference soil, respectively) in manured soils seem to have counterbalanced the inhibiting effect of soil organic matter on P sorption by creating additional P sorption sites. Accordingly, the newly created P sorbing surfaces were important to prevent an even larger P loss potential. Phosphorus K-edge XANES lent complimentary hints on the loss of crystallinity and transformation of originally present Fe–P minerals into poorly crystalline ones as an effect of manuring, whereas Fe K-edge EXAFS provided insights into the structural changes underwent in the soils upon manure application and soil management.
Phosphorus (P) is one of the most limiting macronutrients for crop productivity and P deficiency is a common phenomenon in agricultural soils worldwide. Despite long-term application of phosphate ...fertilizers to increase crop yields, P availability is often low, due to the high affinity of phosphate for the soil solid phase. It has been suggested that the accumulated (surplus) P in agricultural soils is sufficient to sustain crop yields worldwide for about 100years. In this paper, we try to clear up the potential for making use of legacy P in soils for crop growth potentially alleviating the global P resource shortage. Specifically, we try to clear up the potential of soil “P activators” for releasing fixed P. P activators accelerate and strengthen process which transform P into bio-available forms via a range of chemical reactions and biological interactions. They include phosphate solubilizing microorganisms, phosphatase enzymes and enzyme activators, low molecular weight organic acids, humic acids, lignin, crop residues, biochar and zeolites. Although reported performance is variable, there is growing evidence that P activators can promote the release of phosphate from soil and, hence, have potential for mitigating the impending global P crisis. Further basic and applied research is required to better understand the mechanisms of interaction of P activators with natural soils and to maximize activator efficacy.
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•Legacy phosphorus accumulated in soils is a large secondary global phosphorus source.•Phosphorus activators accelerate and strengthen the phosphorus transformation process.•Phosphorus activators can activate inorganic and organic phosphorus.•Extensive research is needed to understand the interactions of phosphorus activators with natural soil.
• Different phosphorus (P)-acquisition strategies may be relevant for species coexistence and plant performance in terrestrial communities on P-deficient soils. However, how interspecific P ...facilitation functions in natural systems is largely unknown.
• We investigated the root physiological activities for P mobilization across 19 coexisting plant species in steppe vegetation, and then grew plants with various abilities to mobilize sorbed P in a microcosm in a glasshouse.
• We show that P facilitation mediated by rhizosphere processes of P-mobilizing species promoted growth and increased P content of neighbors in a species-specific manner. When roots interacted with a facilitating neighbor, Cleistogenes squarrosa and Bromus inermis tended to show greater plasticity of root proliferation or rhizosheath acid phosphatase activity compared with other non-P-mobilizing species. Greater variation in these root traits was strongly correlated with increased performance in the presence of a facilitator. The results also show, for the first time, that P facilitation was an important mechanism underlying a positive complementarity effect.
• Our study highlights that interspecific P-acquisition facilitation requires that facilitated neighbors exhibit a better match of root traits with a facilitating species. It provides a better understanding of species coexistence in P-limited communities.
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