Periodic P fertilizer application is recommended for small-holder farmers in Northeast China: evidence from a 12-year study

Phosphorus (P) fertilizer prices rose more than 150 % in the past two decades, thus periodic P fertilization (purchasing and applying superphosphate periodically) could be economically beneficial to small-holder farmers. Still, it is necessary to determine if periodic P fertilization could sustain corn production compared to annual P fertilization. Corn ( Zea mays L.) obtains P for its growth and development from soil solution, which is replenished by soil P fractions associated with the soil minerals (inorganic P, Pi) and organic matter (organic P, Po). It is expected that P fertilization regimes (annual vs. periodic applications) will influence the concentration of soil P fractions contributing to corn P nutrition. The objective of the study was to evaluate soil Pi and Po fractions and P uptake in corn agroecosystems of Northeast China under two fertilizer regimes: triple-superphosphate applied annually at 0, 25 or 75 kg P ha −1 , or applied periodically (once every 6 years) as 150 or 450 kg P ha −1 . During the two 6-year periods (1997–2002 and 2003–2008), both periodic and annual triple-superphosphate application significantly ( P