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- Title
Long‐term dairy manure amendment promotes legacy phosphorus buildup and mobility in calcareous soils.
- Authors
Hu, Ruifang; Leytem, April B.; Moore, Amber D.; Strawn, Daniel G.
- Abstract
Continuous application of dairy manure to soils can lead to excessive phosphorus (P) accumulation (legacy P), which requires understanding for managing nutrient availability and leaching. This study was conducted in Kimberly, ID, where dairy manure or conventional fertilizer was applied to calcareous soil plots under continuous crop rotations for 8 years (2013–2020), followed by 2 years with no amendment. To understand legacy P behavior in the soils, total P, organic/inorganic P, and plant‐available Olsen bicarbonate P and Truog extraction measurements were made from surface and subsurface samples. Additionally, P in soluble and less soluble calcium phosphate (Ca‐P) minerals was estimated using selective extractions, and P desorption was measured in a flow‐through reactor. Manure amendments resulted in increased total soil P and plant‐available P, particularly in the initial 5 years. In the 0‐ to 30‐cm depth, 54%–65% of the soil P added from manure amendments was readily soluble by the Truog P test. Phosphorus released from the 2022 manure‐amended soil in the desorption experiments was about five times greater than the fertilizer‐amended soil, suggesting high leaching potential. After 8 years of manure amendment, subsurface Olsen‐P levels exceeded the 40 mg kg−1 management threshold, suggesting P adsorption potential of the surface had become saturated, allowing for P leaching. In the manure‐amended surface soils, calcium phosphate minerals increased compared to the controls. Even after 2 years without manure amendment, soluble Ca‐P mineral phases persisted in the soils, which can be a long‐term source of P leaching. Core Ideas: Repeated dairy manure application at 52 Mg ha−1 rate led to soil legacy phosphorus (P) buildup in calcareous soils in southern Idaho.Manure‐amended soil P leached downward causing subsurface soil Olsen P levels to exceed the regulatory limit.Manure‐amended soil had about five times greater leachable P than conventional chemical fertilizer‐amended soil.P desorption from manure‐amended surface soil was slower compared to subsurface soil.Slow P release was correlated with poorly crystalline Ca‐P mineral phases in the soils. Plain Language Summary: Continuous application of dairy manure to soils leads to excessive phosphorus (P) accumulation (legacy P), which can contribute to nutrient availability and leaching. This study characterized P pools and measured P availability in calcareous soils amended with either dairy manure or conventional fertilizer for 8 years, followed by 2 years with no amendment. Manure amendments resulted in increased total soil P and plant‐available P. In the 0‐ to 30‐cm depth, 54%–65% of the soil P added from manure amendments was readily available. After 8 years of manure amendment and 2 years of no amendment, P was five times more available to the soil solution than in controls with chemical fertilizer treatments, suggesting high plant availability and leaching potential in the manure‐amended soils.
- Subjects
IDAHO; CALCAREOUS soils; MANURES; SOIL solutions; PHOSPHATE minerals; SOIL leaching
- Publication
Journal of Environmental Quality, 2024, Vol 53, Issue 3, p365
- ISSN
0047-2425
- Publication type
Article
- DOI
10.1002/jeq2.20559