Graphical abstract Highlights ► Algal ponds and macrophyte wetlands in widespread use for wastewater treatment. ► Harvested algae/macrophytes require <1/10 of the area compared to terrestrial crops ...for phosphorus uptake. ► Luxury uptake could be used to increase the phosphorus content of the biomass. ► Multiple opportunities exist (e.g. offshore cultivation) but are still in their infancy. ► Phosphorus recovery via plants has potential to become an important future solution.
Several studies have shown Soluble Reactive Phosphorus (SRP) analyses provide a poor index of dissolved phosphorus (P) bioavailability in natural systems. We tested 21 inorganic and organic P ...containing compounds with series of nutrient uptake and bioavailability bioassay experiments and chemical characterizations. Our results show that in 81% of cases, these compounds did not fit the classic assumption that SRP approximately equals Bioavailable P (BAP). Many organic compounds were classified as non-reactive, but had very rapid uptake kinetics and were nearly entirely bioavailable (e.g., several nucleic acids, ATP, RNA, DNA and phosphatidylcholine). Several inorganic compounds also classified as non-reactive but had high bioavailability (i.e., sodium tripolyphosphate and phosphorus pentoxide). Conversely, apatite was operationally classified as reactive, but had low bioavailability. Due to their tendency to alias as SRP, but recalcitrance and very low bioavailability, humic-(Al/Fe)-phosphorus complexes may play an especially important role in the dissolved phosphorus dynamics of natural systems.
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•We tested 21 P containing compounds with bioassay and chemical speciation.•The acid molybdate method does not consistently predict the bioavailability of P compounds.•The P in humic substances was bounded with Al/Fe and could not be taken up by algal.•A new classification scheme divided P species based on bioavailability and chemical speciation.
SRP is a poor indicator of the bioavailability of many of P containing compounds and much of what is classified as SRP in nature could be associated with humic-metal complexes with low bioavailability.
Root growth is influenced by soil nutrients and neighbouring plants, but how these two drivers affect root interactions and regulate plant growth dynamics is poorly understood. Here, interactions ...between the roots of maize (Zea mays) and faba bean (Vicia faba) are characterized. Maize was grown alone (maize) or with maize (maize/maize) or faba bean (maize/faba bean) as competitors under five levels of phosphorus (P) supply, and with homogeneous or heterogeneous P distribution. Maize had longer root length and greater shoot biomass and P content when grown with faba bean than with maize. At each P supply rate, faba bean had a smaller root system than maize but greater exudation of citrate and acid phosphatase, suggesting a greater capacity to mobilize P in the rhizosphere. Heterogeneous P availability enhanced the root‐length density of maize but not faba bean. Maize root proliferation in the P‐rich patches was associated with increased shoot P uptake. Increased P availability by localized P application or by the presence of faba bean exudation stimulated root morphological plasticity and increased shoot growth in maize in the maize/faba bean mixture, suggesting that root interactions of neighbouring plants can be modified by increased P availability.
•Organic P (OP) availability is strongly driven by OP forms and mineral types.•Ryegrass was able to take up about 3–18% of OP adsorbed to soil minerals.•Adsorbed glycerophosphate was more available ...than the other OP forms.•Montmorillonite-OP showed the highest P uptake and kaolinite-OP the lowest one.•The binding strength of OPs to the mineral surface did not explain P availability.
Organic phosphorus (OP) represents a significant fraction of the total P pool in soils. With the increasing use of organic resources to substitute mineral P fertilizers and the need to recover P from the soil, it is pivotal to gain insight into the interactions between various OP forms and soil minerals and their consequences on P availability. Here, we aim at elucidating the extent to which OP compounds adsorbed onto major soil minerals may be available to plants. Ryegrass (Lolium multiflorum) plants were grown in RHIZOtest devices in the presence of OP including myo-inositol hexakisphosphate (IHP), glycerophosphate (GLY), and glucose-6-phosphate (G6P) and inorganic P (IP) compounds that were previously adsorbed onto Fe and Al oxyhydroxides (goethite and gibbsite, respectively) and clay minerals (montmorillonite and kaolinite). Phosphorus availability and P uptake were then determined through rhizosphere and plant characterization. Irrespective of the type of mineral, ryegrass was able to take up about 3–18 % of adsorbed OP compounds. The magnitude of availability and uptake depended on the OP compounds and the type of soil minerals. The potential availability of OP adsorbed by different minerals was strongly mediated by mineral-OP interaction types and properties. The P uptake increased in the following order: kaolinite-OP ≪ gibbsite-OP ≤ goethite OP ≪ montmorillonite-OP. Phosphorus uptake from adsorbed OP compounds showed contrasting patterns compared to adsorbed IP and depended more on available P concentration in the rhizosphere rather than on the binding strength of OPs to the mineral surface.
Low soil fertility and high fertilizer costs are constraints to wheat production, which may be resolved with integrating fertilizer phosphorus (P) and farm-yard manure (FYM). Study objectives were to ...evaluate P source impacts on soil, P efficiency, and wheat growth in a calcareous soil.
Treatments included P fertilizer (0, 17, 26, or 39 kg P ha-1) and/or FYM (0 or 10 T ha-1) in a: 1) incubation experiment and 2) wheat (Triticum aestivum spp.) field experiment.
Soil organic matter increased (30-72%) linearly for both fertilizer and FYM, whereas pH decreased (0.1-0.3 units) with fertilizer only. Addition of fertilizer and FYM increased plant available P (AB-DTPA extractable soil P) an average of 0.5 mg P kg-1 soil week-1 with incubation. The initial increase was 1-9 mg P kg-1, with further increase after 84 d of ~3-17 mg P kg-1. There was also a significant increase of available P in the soil supporting plants in the field study, although the magnitude of the increase was only 2 mg kg-1 at most for the highest fertilizer rate + FYM. Grain (66 to 119%) and straw (25-65%) yield increased significantly, peaking at 26 kg P ha-1 + FYM. The P Absorption Efficiency (PAE), P Balance (PB), and P Uptake (PU) increased linearly with P rate, with the highest levels at the highest P rate. The P Use Efficiency (PUE) was highest at the lowest rates of P, with general decreases with increasing P, although not consistently. Principal component analysis revealed that 94.34 % of the total variance was accounted for with PC1 (84.04 %) and PC2 (10.33 %), with grain straw yield significantly correlated to SOM, PU, and PAE. Regression analysis showed highly significant correlation of PB with P-input (R2= 0.99), plant available P (R2= 0.85), and PU (R2= 0.80). The combination of FYM at the rate of 10 T ha-1 and fertilizer P at 26 kg P ha-1 was found as the optimum dose that significantly increased yield. It is concluded that FYM concoction with fertilizer-P not only improved SOM and residual soil P, but also enhanced wheat yields with reasonable P efficiency.
The continued supply of phosphate fertilizers that underpin global food production is an imminent crisis. The rock phosphate deposits on which the world depends are not only finite, but some are ...contaminated, and many are located in geopolitically unstable areas, meaning that fundamental changes will have to take place in order to maintain food production for a growing global population. No single solution exists, but a combination of approaches to phosphorus management is required not only to extend the lifespan of the remaining non-renewable rock phosphate reserves, but to result in a more efficient, sustainable phosphorus cycle. Solutions include improving the efficiency of fertilizer applications to agricultural land, alongside a better understanding of phosphorus cycling in soil-plant systems, and the interactions between soil physics, chemistry and biology, coupled with plant traits. Opportunities exist for the development of plants that can access different forms of soil phosphorus (e.g., organic phosphorus) and that use internal phosphorus more efficiently. The development of different sources of phosphorus fertilizers are inevitably required given the finite nature of the rock phosphate supplies. Clear opportunities exist, and it is now important that a concerted effort to make advances in phosphorus use efficiency is prioritized.
• Many Proteaceae are highly phosphorus (P)-sensitive and occur exclusively on old nutrient-impoverished acidic soils (calcifuge), whilst a few also occur on young calcareous soils (soil-indifferent) ...that are higher in available calcium (Ca) and P. Calcium increases the severity of P-toxicity symptoms, but its underlying mechanisms are unknown. We propose that Ca-enhanced P toxicity explains the calcifuge habit of most Proteaceae.
• Four calcifuge and four soil-indifferent Proteaceae from South-Western Australia were grown in hydroponics, at a range of P and Ca concentrations.
• Calcium increased the severity of P-toxicity symptoms in all species. Calcifuge Proteaceae were more sensitive to Ca-enhanced P toxicity than soil-indifferent ones. Calcifuges shared these traits: low leaf zinc concentration (Zn), low Zn allocation to leaves, low leaf Zn:P, low root : shoot ratio, and high seed P content, compared with soil-indifferent species.
• This is the first demonstration of Ca-enhanced P toxicity across multiple species. Calcium-enhanced P toxicity provides an explanation for the calcifuge habit of most Proteaceae and is critical for the management of this iconic Australian family. This study represents a major advance towards an understanding of the physiological mechanisms of P toxicity and its role in the distribution of Proteaceae.
Myriad field, laboratory, and modeling studies show that nutrient availability plays a fundamental role in regulating CO2 exchange between the Earth's biosphere and atmosphere, and in determining how ...carbon pools and fluxes respond to climatic change. Accordingly, global models that incorporate coupled climate–carbon cycle feedbacks made a significant advance with the introduction of a prognostic nitrogen cycle. Here we propose that incorporating phosphorus cycling represents an important next step in coupled climate–carbon cycling model development, particularly for lowland tropical forests where phosphorus availability is often presumed to limit primary production. We highlight challenges to including phosphorus in modeling efforts and provide suggestions for how to move forward.
Phosphorus (P) availability is often limiting for rice (Oryza sativa) production. Improving internal P-use efficiency (PUE) is crucial to sustainable food production, particularly in low-input ...systems. A critical aspect of PUE in plants, and one that remains poorly understood, is the investment of leaf P in different chemical P fractions (nucleic acid-P, lipid-P, inorganic-P, metabolite-P and residual-P). The overarching objective of this study was to understand how these key P fractions influence PUE.
Three high-PUE and two low-PUE rice genotypes were grown in hydroponics with contrasting P supplies. We measured PUE, total P, P fractions, photosynthesis and biomass.
Low investment in lipid-P was strongly associated with increased photosynthetic PUE (PPUE), achieved by reducing total leaf P concentration while maintaining rapid photosynthetic rates. All low-P plants exhibited a low investment in inorganic-P and lipid-P, but not nucleic acid-P. In addition, whole-plant PUE was strongly associated with reduced total P concentration, increased biomass and increased preferential allocation of resources to the youngest mature leaves.
Lipid remodelling has been shown in rice before, but we show for the first time that reduced lipid-P investment improves PUE in rice without reducing photosynthesis. This presents a novel pathway for increasing PUE by targeting varieties with reduced lipid-P investment. This will benefit rice production in low-P soils and in areas where fertilizer use is limited, improving global food security by reducing P fertilizer demands and food production costs.
Climate is predicted to change over the 21st century. However, little is known about how climate change can affect soil phosphorus (P) cycle and availability in global terrestrial ecosystems, where P ...is a key limiting nutrient. With a global database of Hedley P fractions and key‐associated physiochemical properties of 760 (seminatural) natural soils compiled from 96 published studies, this study evaluated how climate pattern affected soil P cycle and availability in global terrestrial ecosystems. Overall, soil available P, indexed by Hedley labile inorganic P fraction, significantly decreased with increasing mean annual temperature (MAT) and precipitation (MAP). Hypothesis‐oriented path model analysis suggests that MAT negatively affected soil available P mainly by decreasing soil organic P and primary mineral P and increasing soil sand content. MAP negatively affected soil available P both directly and indirectly through decreasing soil primary mineral P; however, these negative effects were offset by the positive effects of MAP on soil organic P and fine soil particles, resulting in a relatively minor total MAP effect on soil available P. As aridity degree was mainly determined by MAP, aridity also had a relatively minor total effect on soil available P. These global patterns generally hold true irrespective of soil depth (≤10 cm or >10 cm) or site aridity index (≤1.0 or >1.0), and were also true for the low‐sand (≤50%) soils. In contrast, available P of the high‐sand (>50%) soils was positively affected by MAT and aridity and negatively affected by MAP. Our results suggest that temperature and precipitation have contrasting effects on soil P availability and can interact with soil particle size to control soil P availability.
Soil phosphorus cycle is an important component of terrestrial biogeochemical cycles; however, little is known about climatic effects on soil phosphorus cycle. We evaluated how climate pattern affected soil phosphorus dynamics and availability in natural terrestrial ecosystems using a global database of soil phosphorus fractions. Our results suggest that temperature and precipitation have contrasting effects on soil phosphorus dynamics and can interact with soil particle size to control soil phosphorus availability.
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