Phosphorus activators contribute to legacy phosphorus availability in agricultural soils: A review

TLDR: 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.

About: This article is published in Science of The Total Environment.The article was published on 2018-01-15 and is currently open access. It has received 336 citations till now. The article focuses on the topics: Crop residue.

Figures

Fig. 5. Schematic illustration of the recycling of phosphorus between agricultural residues and soil, including the application 61 of biochar. Pi is inorganic phosphorus, Po is organic phosphorus. 62 63

Fig. 6 Schematic summary of different approaches to modify zeolite. 68 69

Table 2 10 Examples of common phosphate solubilizing microorganisms in agricultural soils (Behera et al., 2014; Bolan, 1991; 11 Thingstrup et al., 2000). 12

Fig. 2 Potential mechanisms for the solubilization of insoluble P by phosphate solubilizing microorganisms (PSMs). PSF: 18 phosphate solubilizing fungi; PSB: phosphate solubilizing bacteria; PSA: phosphate solubilizing actinomycete; VAM: 19 vesicular-arbuscular mycorrhizae (modified after Khan et al., 2010).20

Fig. 1. The physicochemical and biological transformations of P in soil-plant and soil-solution systems (modified after Frossard et al., 2011). Po: orgainc P; Pi: inorganic P. The dotted arrow 7 indicates external phosphorus input and the solid arrow shows the internal phosphorus transformations.8

Fig. 7. Illustration of different mechanisms involved in the solubilization and mineralization of insoluble P by P activators in soils. (A) Enlarged drawing of root; (B) Metal ions and metal oxides 72 which easily form P-O-M compounds in soil. (a) Effect of soil pH on sparingly soluble Pi (inorganic phosphorus) minerals; (b) Formation of complexes with (B) to release phosphate; (c) 73 Competition for sorption sites with phosphate in soil; (d) Adsorption of metal and metal oxides to release phosphate; (e) Sheltering sorption sites in soil; (f) Hydrolysis of Po (organic phosphorus) 74 and Pi; (g) Strengthening of phosphatase enzyme activity; (h) Promotion of root growth; (i) Biochar increasing mycorrhizal-plant associations; (j) Exchange-induced dissolution; (k) Production 75 of organic acids by microbial processes; (m) Po & Pi retention and release. ABT rooting powder: have the ability to promote rooting and to increase the survival rate of plants under abiotic stress.76

Frequently asked questions

Q1. What have the authors contributed in "Phosphorus activators contribute to legacy phosphorus availability in agricultural soils: a review" ?

In this paper, the authors try to clear up the potential for making 6 use of legacy P in soils for crop growth potentially alleviating the global P resource shortage. Specifically, 7 the authors try to clear up the potential of soil “ P activators ” for releasing fixed P. P activators accelerate and 8 strengthen process which transform P into bio-available forms via a range of chemical reactions and 9 biological interactions. Although reported performance is variable, there is growing evidence that P activators can 12 promote the release of phosphate from soil and, hence, have potential for mitigating the impending global P 13 crisis. Further basic and applied research is required to better understand the mechanisms of interaction of P 14 activators with natural soils and to maximize activator efficacy. 

Q2. What enzymes can hydrolyze the phosphate diester bond in nucleic acids?

247 Phosphodiesterase and phosphomonoesterase may act sequentially in the mineralization of Po: 248 phosphomonoesterase can dissociate the phosphate group from phosphate monoester compounds and 249 phosphodiesterase can hydrolyze the phosphate diester bond in nucleic acids. 

Q3. What are some of the common types of soil P activators?

These include PSMs, phosphatase enzymes, enzyme activators, low molecular weight organic 519 acids, humic acids, lignin, crop residues, manure, biochar, zeolites, fly and wood ash, water-dissolved 520organic polymers, bentonite, mugineic acid and ABT rooting powder. 

Q4. What enzymes can release inorganic phosphates from sugar phosphates?

Wanner (1996) found that 232many enzymes can function as organic phosphoester scavengers, releasing inorganic phosphates from 233 nucleotides and sugar phosphates. 

Q5. What is the effect of biochar on P availability?

Biochar may also alter P availability through sorption of chelating organic 455 molecules like phenolic acids, amino acids and complex proteins or carbohydrates (Joseph et al., 2010). 

Q6. What are the common fungi known to enhance P availability in soil?

Bacteria which are known to enhance P 178availability include species of Pseudomonas, Azotobacter, Burkholderia, Bacillus and Rhizobium (Jones 179 and Oburger, 2011). 

Q7. What is the effect of polyvinyl alcohol on soil pH?

Polyvinyl alcohol, polyacrylamide and polyethylene glycol have been shown to 501 increase P sorption and pH in red ferralitic soils (rich in ferric oxide hydrate). 

Q8. What can be used as a source of P?

Crop residues, manure and biochar 406Like chemical phosphate fertilizer, crop residues, manure and biochar (charcoal produced from crop 407 residues) can also act as P sources. 

Q9. What is the effect of biochar on soil P availability?

Xu et al. (2016) reported that biochar application can decrease P 462availability in saline sodic soil due to enhanced P sorption and precipitation. 

Q10. What is the main reason for the low productivity of phosphate fertilizers?

it is likely that remaining reserves will have increasingly lower quality and will be increasingly 43 more costly to extract, which means that the supply of high quality phosphate fertilizer will also become 44progressively more restricted (Cordell et al., 2009). 

Q11. What is the name of the enzyme that can hydrolyze 260pyrophosphate?

In addition, a kind of 259 inorganic phosphatase (pyrophosphate phosphohydrolase) has been identified which can hydrolyze 260pyrophosphate (used as a fertilizer) to Pi (Dick and Tabatabai, 1978). 

Q12. What is the role of phosphatase enzymes in the regulation of Po?

Phosphatase enzyme and enzyme activators 244Phosphatase enzymes are widely distributed in natural environments and play a major role in Po 245 regulation (Fig. 3) by hydrolyzing ester-phosphate bonds in Po, leading to the release of phosphate (Burns 246 and Dick, 2002). 

Q13. What is the predominant method for disposing of 408 agricultural residues?

Land application is the predominant method for disposing of 408agricultural residues, thereby recycling their nutrients Fig. 5) (Dai et al., 2016). 

Q14. what are the common phosphate solubilizing bacteria in soil?

Phosphate solubilizing bacteria (PSB: 170Achromobacter, Aereobacter, Agrobacterium, Alcaligenes, Arthrobacter, Aspergillus, Azotobacter, Bacillus, 171 Bradyrhizobium, Burkholderia, Chromobacterium, Enterbacter, Erwinia, Escherichia, Flavobacterium, 172Klebsiella, Micrococcus, Pantoea agglomerans, Pseudomonas, Rhizobium, Salmonella, Serratia, 173Thiobacillus) and phosphate solubilizing fungi (PSF: Alternaria, Arbuscular mycorrhiza, Aspergillus, 174Fusarium, Helminthosparium, Penicillium, Rhizopus, Sclerotium) make up 1-50% and 0.1-0.5% 175 respectively of the total PSMs in soil with an additional minor role played by phosphate solubilizing 176actinomycetes (PSA: Streptomyces, Nocardia) (Khan et al., 2007). 

Q15. What are the main processes of adsorption and desorption of Pi?

These include desorption and 106solubilization of rapidly exchangeable Pi; uptake of P by soil microorganisms and plants (either through 107 their roots or through mycorrhizal hyphae); the release of Pi from the soil solid phase or from fertilizers, 108 induced by the exudation of phosphatases and organic acids from roots or microorganisms; the release of Pi 109 from plant residues or organic fertilizers to the soil solution; and the release of Pi from organic matter 110 mineralization by microorganisms (Frossard et al., 2011). 

Q16. What is the simplest explanation for the phosphatase activity of organic acids?

It is possible that low molecular weight organic 351 acids could influence the activity of PSMs and, hence, affect the activity of phosphatases secreted by these 352organisms (Turner, 2008).353 3543.2.2. 

Q17. How much of the P in surface-applied residues could be classified as labile?

Results from a 415 dual-labelling experiment suggest that, on average, 16% of the P contained in surface-applied residues 416could be classed as labile P (Noack et al., 2014). 

Q18. What is the effect of zeolites on the pH of soil?

Fig. 6 gives a summary of several methods for the modification of natural zeolites (Dai et al., 2011) 471 to enhance cation exchange capacity (due to the favorable ion-exchange selectivity of natural zeolites for 472certain cations, such as Cs+, Sr2+, and NH4+) and to the pH change induced by zeolites. 

Q19. What are the main factors that have been shown to 154govern the availability of fixed?

153 Although activation processes are complex, several key factors have consistently been demonstrated to 154govern the availability of fixed P.