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Relationships between Immobilized Phosphorus Uptake in Two Grain Legumes and Soil Bioactive Phosphorus Pools in Fertilized and Manure‐Amended Soil
Author(s) -
Rao S. C.,
Dao T. H.
Publication year - 2008
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2007.0405
Subject(s) - manure , phosphorus , chemistry , agronomy , loam , mineralization (soil science) , soil water , dry matter , nutrient , organic matter , growing season , zoology , nitrogen , biology , ecology , organic chemistry
Mixing P‐immobilizing additives with manure has raised concerns of irreversible reduction in P availability to growing crops. A potted plant growth experiment was conducted to characterize cattle manure P mineralization as modified by iron amendments and uptake by pigeon pea ( Cajanus cajan L. Millsp.) and soybean [ Glycine max (L.) Merr.]. Triple superphosphate, untreated, or manure amended with Fe at 1:1 or 1:3 molar ratio of manure P:Fe, was applied to Dale silt loam (fine‐silty, mixed, superactive, thermic Pachic Haplustolls) at the rate of 20 mg kg −1 . Whole plants were harvested at three stages of development (vegetative, flowering, and physiological maturity) to determine and correlate P uptake to changes in soil bioactive P pools over the growing season. Dry matter production was unaffected by Fe at both application rates. Phosphorus solubility and plant uptake were reduced at the 1:3 P:Fe molar ratio rate, in spite of the legumes' reported ability to secrete siderophores. Within‐season changes in bioactive P fractions indicated that P was taken up from the inorganic (water‐extractable P [WEP] + inorganic ligand‐exchangeable P [EEP i ]) pools. Comparing soil P pools in cropped and noncropped soils, the decrease in the organic phosphohydrolase‐labile P (PHP) pool corroborated the fact that the PHP pool replenished the WEP + EEP i fractions. Although Mehlich 3 P and EEP i were related, the Mehlich 3 P pool showed no significant relationship with whole plant or any plant part P. The latter did not perform as well as the EEP i pool in assessing plant availability and enzymatically mediated turnover of immobilized P.