Tillage effects on phosphorus composition and phosphatase activities in soil aggregates

• The proportions of organic P in total P were higher under NT than MP.
• NT impelled more soil P stored as monoesters and diesters.
• Soil AlP and PD activities under NT were significantly higher than MP.
• AlP in 0.25–1 mm and PD in < 0.25 mm were more sensitive to tillage.

Phosphorus (P) and phosphatase activities in soil aggregates affected by tillage under cold monsoon climate remain poorly understood. Based on the hypothesis that the distribution of P composition and phosphatase activities in soil aggregates should be affected by different tillage practices, a field experiment was conducted to study the effects of moldboard plow (MP), ridge tillage (RT), and no-tillage (NT) on the distribution of soil P composition determined by 31P nuclear magnetic resonance (NMR) and phosphatase activities in different size fractions of soil aggregates (> 2, 1–2, 0.25–1, and < 0.25 mm) at the 0 to 20 cm depth in northeastern China. NT treatment had significantly higher organic P proportion in total P and larger proportions of monoesters and diesters in extracted total P than the MP treatment, whereas the MP treatment showed higher concentrations of total P, organic P, plant available P, NaOH-EDTA extracted total P, orthophosphate and monoesters. Soil alkaline phosphatase (AlP) and phosphodiesterase (PD) activities under NT were significantly higher than those under MP, and the responses of AlP in 0.25–1 mm size fraction and PD in < 0.25 mm size fraction were more sensitive to tillage treatments. Overall, although NT facilitated more P stored in the organic P form and increased phosphatase activities, soil with NT had lower total and plant available P compared to traditional MP treatment and therefore, MP may be the right practice to conserve soil P under cold monsoon climate.