Soil‐phosphorus distribution and availability as affected by greenhouse subsurface irrigation

Abstract

AbstractVertical distribution and plant availability of soil P under subsurface irrigation were investigated in a 5‐year tomato‐grown‐greenhouse experiment. Irrigation was applied when soil water condition reached the predefined maximum allowable depletion (MAD) for different treatments, e.g., –10 kPa, –16 kPa, –25 kPa, –40 kPa, and –63 kPa. Results show that P distribution with soil depth was significantly affected by irrigation schedules. The general trend is that concentrations of soil total P and inorganic P were greater in topsoil than in subsoil, whereas the concentrations of soil organic P were larger at the depths of 0–10 cm, 30–40 cm, and 40–60 cm than at other soil depths. Comparison of different irrigation schedules indicates that more soil organic P was retained in the soils under the MAD of –25 kPa, –40 kPa, and –63 kPa, implying that irrigation of relatively low frequency and large water quantity of each irrigation event favored the accumulation of organic P in soils. In addition, we found that the concentrations of plant‐available P decreased with soil depth and were largest under the MAD of –16 kPa and –25 kPa. This result suggests that irrigation of relatively high frequency and low water quantity of each irrigation event led to greater P availability for plant uptake. Overall, this study suggests that the transformation and plant availability of soil P can be manipulated, to some degree, by soil‐water management. Maximum allowable depletion controlled between –16 kPa and –25 kPa could result in high availability of soil P in clay‐textured soils.