Abstract
Repeated applications of phosphorus (P) fertilizers result in the buildup of P in soil (commonly known as legacy P), a large fraction of which is not immediately available for plant use. Long-term applications and accumulations of soil P is an inefficient use of dwindling P supplies and can result in nutrient runoff, often leading to eutrophication of water bodies. Although soil legacy P is problematic in some regards, it conversely may serve as a source of P for crop use and could potentially decrease dependence on external P fertilizer inputs. This paper reviews the (1) current knowledge on the occurrence and bioaccessibility of different chemical forms of P in soil, (2) legacy P transformations with mineral and organic fertilizer applications in relation to their potential bioaccessibility, and (3) approaches and associated challenges for accessing native soil P that could be used to harness soil legacy P for crop production. We highlight how the occurrence and potential bioaccessibility of different forms of soil inorganic and organic P vary depending on soil properties, such as soil pH and organic matter content. We also found that accumulation of inorganic legacy P forms changes more than organic P species with fertilizer applications and cessations. We also discuss progress and challenges with current approaches for accessing native soil P that could be used for accessing legacy P, including natural and genetically modified plant-based strategies, the use of P-solubilizing microorganisms, and immobilized organic P-hydrolyzing enzymes. It is foreseeable that accessing legacy P will require multidisciplinary approaches to address these limitations.
Highlights
Phosphorus (P) is essential to life on Earth
Repeated P fertilizer applications over time has led to build-up of soil legacy P, which theoretically could be utilized to substitute for, if not eliminate dependence on, mineral P fertilizers
This paper reviewed (1) the occurrence and factors controlling bioaccessibility of different soil P forms, (2) transformation of different legacy P species with P fertilizer additions, and (3) currently studied strategies that could possibly be used for exploiting soil legacy P for crop use
Summary
Phosphorus (P) is essential to life on Earth. It plays critical roles in core biological systems associated with energy storage, cell replication, and protein synthesis [1]. Technologies and strategies for transformation from mineral and animal waste fertilizers into these soil P chemical forms is necessary to maximize the contributions of legacy P as a complement or substitute for externally added P fertilizers. Technologies and strategies for potentially enhancing the capacity to dissolve potentially enhancing the capacity to dissolve inorganic legacy P or hydrolyze organic legacy P, referred to as bioaccessibility, that are feasible on a large scale are not yet available In light of these challenges, this paper aims to review (1) the chemical forms of P in soil and their variation with chemically relevant soil properties (Section 2), (2) the transformation of P into different proportions of various chemical species after mineral and organic P fertilizer applications (Section 3), and (3) different plant- and microbial-based approaches for accessing native soil P and potentially legacy P and associated challenges (Section 4). We conclude with an overall outlook on legacy P as a currently untapped resource that could potentially decrease the dependence on external fertilizer applications in the future as research and technology advances, with the generation of plant cultivars with more efficient P mobilization and utilization processes/capabilities, and with the use of P-solubilizing microorganisms (Section 5)
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