Shifting from N-based to P-based manure management maintains soil test phosphorus dynamics in a long-term corn and alfalfa rotation
2017
Sadeghpour, Amir | Ketterings, QuirineM. | Godwin, GregoryS. | Czymmek, KarlJ.
Multiyear repeated dairy manure application based on nitrogen (N) needs of corn (Zea mays L.) increases soil test phosphorus (P) concentration and risk of P runoff over time. A P removal based application of manure adds less P but could impact yield. A corn field trial was implemented in New York in 2001 and rotated into alfalfa (Medicago sativa L.) in 2006 to examine soil test P dynamics over a corn-alfalfa rotation (2001 to 2011). Treatments were annual spring applications of N-based versus P removal based compost (74 and 46 Mg ha⁻¹, respectively), liquid dairy manure (196 and 68 m³ ha⁻¹, respectively), and two control treatments (0 N and 112 kg ha⁻¹ sidedress N). No manure or compost was applied during the alfalfa years. In the five corn years, Morgan-extractable soil test P concentrations increased 4- and 2-fold for N-based and P-based manure and 6- and 4-fold for N-based and P-based compost, respectively, consistent with greater P balances possibly combined with differences in P fractions in each source. Soil test P concentrations declined in the alfalfa years but reached initial concentration only in the P-based manure system. Our findings show, for the first time in dairy forage rotations, the long-term sustainability benefits of P-based manure management and emphasize the importance of rotation fertility management rather than single-year P management. In conclusion, we demonstrated that a shift from N- to P-based manure allocation in corn years is a good approach to maintaining soil test P concentrations over the rotation while for higher application rates, a greater number of years in alfalfa than corn might be needed to prevent soil test P from building over the rotation.
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