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Title: Long-term effects of compost and cover crops on soil phosphorus in two California agroecosystems

Author
item MALTAIS-LANNDRY, G. - Stanford University
item SCOW, K. - University Of California
item Brennan, Eric
item VITOUSEK, P. - Stanford University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2015
Publication Date: 3/13/2015
Citation: Maltais-Landry, G., Scow, K., Brennan, E.B., Vitousek, P.M. 2015. Long-term effects of compost and cover crops on soil phosphorus in two California agroecosystems. Soil Science Society of America Journal. 79:688-697.

Interpretive Summary: The effects of cover crops, composted poultry manure, and yard waste compost on soil phosphorus were evaluated in two long-term studies in California. The results suggest that cover crops have a small effect on soil phosphorus and that frequent additions of yard waste compost and composted poultry manure may lead to over application of phosphorus in organic systems, with stronger effects for composted poultry manure.

Technical Abstract: Inefficient P use in agriculture results in soil P accumulation and losses to surrounding ecosystems, highlighting the need to reduce external inputs and use them more efficiently. Composts reduce the need for mineral fertilizers by recycling P from wastes at the regional scale, whereas cover crops reduce soil P losses and have the potential to increase internal soil P recycling by mobilizing soil P “fixed” from previous P applications. We studied the effects of compost and cover crops on soil P in two California experiments, using one to measure the effects of a single cover crop mixture (oat-legumes) and composted poultry manure across different management practices, and the second experiment to evaluate how different cover crops (rye, mustard, or rye-legumes) and yard compost affected soil P dynamics under organic management. We analyzed soils to determine changes in soil P dynamics after 8 to 18 years by measuring chloroform-extractable P, P sorption capacity and P saturation, and Hedley fractions. Cover crops generally increased microbial and organic P, whereas amendment with yard compost increased resin, microbial and organic P, with no impact of cover crops and yard compost on other pools and P sorption. In contrast, addition of composted poultry manure significantly increased all soil pools (microbial, organic, inorganic) and P saturation. Our results suggest a limited, moderate, and strong role of cover crops, yard compost, and composted poultry manure, respectively, in affecting soil P in California agroecosystems.