Effect of Greenhouse Subsurface Irrigation on Soil Phosphatase Activity

Abstract

In this study, tomato plants were grown in a greenhouse and were subjected to five subsurface irrigation treatments with maximum allowable depletion (MAD) of −10, −16, −25, −40, and −63 kPa in soil water potentials, respectively. The long‐term effect of subsurface irrigation schedules on soil neutral phosphatase activities at five soil depths (0–10, 10–20, 20–30, 30–40, and 40–60 cm) were investigated in 2004. Results showed that subsurface irrigation could enhance soil neutral phosphatase activity in the treatment with higher irrigation maximum allowable depletion. Neutral phosphatase acitivties were higher at topsoil than subsoil, with heightened phosphatase activities at the depth of 10–20 cm in the soil profile in subsurface irrigation. Neutral phosphatase activity presented significantly positive liner relationships with available phosphorus (P) and contributed to the increase of available P in soil. Phosphatase activity could be an effective indicator to assess the plant‐available P under greenhouse subsurface irrigation. Irrigation management could be applied to adjust phosphatase activity and maximum allowable depletion of −10 to −16 kPa is an advisable subsurface irrigation schedule to heighten phosphatase activity, thereby contributing to higher P availability in soil.

Keywords:

• Irrigation scheduling
• soil phosphatase activity
• subsurface irrigation
• tomato

Acknowledgments

This study was funded by the National High Technology Research and Development Program of China (Program 863, No. 2002AA2Z4321) and the key project of Agricultural Water‐Saving Irrigation (Liaoning Province of China, No. 2001212001). The authors give special thanks to Fulai Liu of the Royal Veterinary and Agricultural University, Denmark, for his valuable suggestions on the manuscript.