SOIL PHOSPHORUS DYNAMICS IN RESPONSE TO DAIRY MANURE AND INORGANIC FERTILIZER APPLICATIONS: A LABORATORY INCUBATION STUDY

Authors: He, Zhongqi; Griffin, Timothy; Honeycutt, Charles

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2006
Publication Date: 6/20/2006
Citation: He, Z., Griffin, T.S., Honeycutt, C.W. 2006. Soil phosphorus dynamics in response to dairy manure and inorganic fertilizer applications: a laboratory incubation study. Soil Science. Vol 171;598-609

Interpretive Summary: In modern agriculture practices, the application of plant nutrients to soil is usually required for sustained high crop yields. Manure application rates are often calculated to balance N input with crop requirements. The impact of N-based manure application rates on soil P transformations should therefore be evaluated for efficient utilization of both manure N and P. In this study, eleven dairy manures and inorganic fertilizers were added into soils to supply 100 mg organic N kg-1 soil. Our data showed that, in two Maine soils, the general distribution patterns for three P species basically followed the trend of changes for inorganic N amended soil, indicating soil properties played a major role in controlling P dynamics. This work confirmed that a single application of manure impacted soil bioavailable P in a manner similar to fertilizer and did not significantly alter soil P properties. This means growers converting from conventional to organic practices (i.e. where manure is the sole source of N and P) may estimate manure bioavailable P to meet their short-term P needs. Further studies need to be conducted to determine if similar results can be found under field conditions.

Technical Abstract: In modern agriculture practices, the application of plant nutrients to soil is usually required for sustained high crop yields. Manure application rates are often calculated to balance N input with crop requirements. The impact of N-based manure application rates on soil P transformations should therefore be evaluated for efficient utilization of both manure N and P. In this study, eleven dairy manures and inorganic fertilizers were added to soils to supply 100 mg organic N kg-1 soil. Our data showed that, in two Maine soils, the general distribution patterns for three P species, inorganic P (Pi), enzymatically hydrolyzable organic P (Peo), and nonhydrolyzable organic P, basically followed the trend of changes for inorganic N amended soil, indicating soil properties played a major role in controlling P dynamics. In H2O and NaHCO3 fractions, soil bioavailable P (Pi and Peo) was linearly related to added P. NaOH extractable soil P was not closely related to the P applied in the manure. This work confirmed that a single application of manure impacted soil bioavailable P in a manner similar to fertilizer and did not significantly alter soil P properties. This means growers converting from conventional to organic practices (i.e. where manure is the sole source of N and P) may estimate manure bioavailable P to meet their short-term P needs. Further studies need to be conducted to determine if similar results can be found under field conditions.