Ligands and Phytase Hydrolysis of Organic Phosphorus in Soils Amended with Dairy Manure

Abstract

tion of IP6 and other IPs in dairy manure are attributed to the protective effect of IP6 complexation with polyva-Information about orthophosphate and organic phosphorus (P) lent cations that reduces dephosphorylation. As a result, desorption in soil amended with animal manure is needed because a build-up of P following repeated manure applications poses risks of substantial amounts of dietary IP6-P of feed grains are offsite dissolved P discharges. An enzymatic hydrolysis and soil P excreted, contributing to water pollution rather than desorption study was conducted to develop a novel ligand-based phyanimal growth and development. tase-hydrolyzable P (PHP) method and quantify water-extractableIn soils amended with animal manure, IP6 and other uncomplexed and complexed P forms (i.e., bioactive P) in Unicorn organic P are added to the soil P pool, in addition to and Christiana soils (Typic Hapludults). Extractability of inorganic inorganic PO 4 -P. The need for detailed organic P char-P with ligands alone (LEP) increased from 2 and 22 mg kg Ϫ1 (0.3 and acterization studies is critical as orthophosphate mono-3.1 Ϯ 0.16% total P) up to sevenfold with increasing ligand (LIGND) and diesters have been observed to move through soils, concentrations in the order of CDTA ϭ EDTA Ͼ DTPA Ͼ Ͼ oxalate. posing risks of water quality degradation via soil subsur-The LIGNDs nullified the benefits of using an anion sink in soil P face transport (Wild and Oke, 1966; Gerritse and Ekdesorption measurements. Soil organic P was hydrolyzed in situ by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8, corroborat-steen, 1978; Chardon et al., 1997). myo-Inositol hexakis ing the presence of myo-inositol phosphomonoesters including IP6.dihydrogenphosphate and lower phosphomonoesters of Adding CDTA and EDTA increased phytases' efficacy and that of inositol are the most abundant identifiable organic P the PHP assay for measuring previously inaccessible complexed orcompounds, and may make up to 50% of total soil organic P; soil PHP increased from 2.3 and 6.4% to peak at 32.0 Ϯ 0.7 ganic P (Cosgrove, 1962;Wild and Oke, 1966). The and up to 40.8 Ϯ 0.2% of total P in Unicorn and Christiana soils, phosphomonesters have been identified by 31 P nuclear respectively. In long-term manure-amended Christiana silt loam under magnetic resonance (NMR) spectroscopy, using alkaorchardgrass-red clover stands, the LIGND-PHP method showed line extractants such as 0.5 M NaOH or 0.25 M NaOHthat repeated manure applications resulted in soil storage of unextract-0.05 M Na 2 EDTA (Newman and Tate, 1980; Cade-Menun able complexed PHP and a buildup of inorganic LEP. Accumulation

Formas de fósforo no solo após o cultivo de braquiária e tremoço branco

“…A adubação fosfatada resultou em maiores valores de P bioativo (Tabela 1). Os valores de PHP indicam que o solo apresenta quantidade considerável de P orgânico, que está ativo e poderia estar disponível para as plantas, como proposto por DAO (2004). Como não houve diferença entre as espécies, pode-se inferir que essas plantas foram equivalentes quanto ao uso efi ciente do P dessa fração.…”

“…Como não houve diferença entre as espécies, pode-se inferir que essas plantas foram equivalentes quanto ao uso efi ciente do P dessa fração. A utilização de extrator EDTA junto à enzima fi tase resultou em melhoria na determinação do P realmente disponível às plantas em solos americanos, já em solos brasileiros os resultados não foram satisfatórios (DAO, 2004;PAVINATO et al, 2010). As difi culdades de se observar esta fração nos solos brasileiros estão relacionadas aos teores de argila e às quantidades consideráveis de Fe e Al, que consequentemente diminuem a fração de P disponível, devido à maior capacidade de adsorção nos coloides.…”

“…Após a agitação, estas foram centrifugadas a 10.000rpm por 10min e foi tomado o sobrenadante para análise. Na fração EDTA, foram adicionadas posteriormente a enzima fi tase (EC 3.1.3.8 Sigma-Aldrich), com agitação por 18h em agitador horizontal, com posterior centrifugação e coleta do sobrenadante (DAO, 2004). A fi tase é usada para degradação de parte da fração orgânica do P do solo, e então é determinado o P orgânico.…”

“…A fi tase é usada para degradação de parte da fração orgânica do P do solo, e então é determinado o P orgânico. A fração determinada após a adição da fi tase é o chamado P bioativo do solo e é considerado disponível para as plantas (DAO, 2004).…”

A Discussion on Mehlich-3 Phosphorus Extraction from the Perspective of Governing Chemical Reactions and Phases: Impact of Soil pH

“…Aluminum and Fe-phytate extraction with M3 will behave similar to inorganic P bound with Fe and Al under acid conditions. Specifically, phytate will mostly exist as Al and Fe-phytate in low pH soils, making it insoluble in water and mostly non-available to plants [37][38][39]. The extreme acid conditions of M3 solution along with added EDTA and F − will remove Al and some Fe [38] from the phytate ring (IP6) and convert it to phytic acid as it protonates at low pH.…”