An internet-based smart irrigation approach for limiting phosphorus release from organic fertilizer-amended paddy soil

We are still challenged to fully understand to what extent controlling irrigation inputs is important for limiting phosphorus (P) losses from paddy soils and how this affects the contribution of dissolved P (DP), particulate P (PP), and colloidal P (P-coll) fractions in P losses. For this investigation, an internet-based smart irrigation system was developed to precisely implement different irrigation scenarios-flooding irrigation (FI) and two water-saving irrigation (WSI) scenarios of intermittent (II) and controlled irrigation (CI). A simulation experiment was conducted and the concentrations of total P (TP), DP, PP, and P-coll released to floodwater (FW) and leachate (LW) were determined during a rice season after the addition of different P forms (chemical fertilizer (CP), biogas slurry (BP), and manure (MP)) at a rate of 40 kg P.ha(-1). The results revealed that the CI scenario effectively decreased P losses in FW (similar to 51%) and LW (similar to 63%) with a positive WSI ratio (39.1%), while II reduced it in FW by similar to 11% and in LW by similar to 27% with a WSI ratio of 11.0% compared with FI. The BP and MP additions caused a higher risk of P losses than CP under FI, with lower risk under WSI. DP largely contributed to P losses (FW: 30%-71%; LW: 42%-66%); however, more PP was released to FW under II (37%-54% of TP). The Pcoll (FW: 5%-23% and LW: 6%-24%) was more sensitive to release at initial periods after fertilization on account PP. This work provides a promising approach to timely control irrigation inputs, which could limit P losses from paddy soil; however, there remains a need to assess and generalize our initial evidence at field scales. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the importance of controlling irrigation inputs in limiting phosphorus losses from paddy soils. Results show that the controlled irrigation scenario effectively decreases phosphorus losses compared to flooding irrigation, especially under water-saving irrigation scenarios. Different forms of phosphorus have varying risks of phosphorus losses, with biogas slurry and manure showing higher risks under flooding irrigation but lower risks under water-saving irrigation.