Modeling soil water flow and quantification of root water extraction from different soil layers under multi-chemicals application in dry land field

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The combined application of different functional chemicals creates challenges both in modeling water flow in soil and quantification of water extraction by crops in dry land farming. In the present study, 2-year laboratory and field experiments were conducted in a typical dry land of northern China in order to: (i) develop a model to describe patterns of water flow in soil under two typical chemicals Superabsorbent polymer (SAP) and Fulvic acid (FA) combined applied in the soil-maize system and (ii) use the stable hydrogen and oxygen analysis method to further quantify the soil water extraction by crops as affected by SAP and FA. Two root water extraction (RWE) terms based on density of root length (DRL) and density of root nitrogen mass (DRNM), respectively, were established to describe the rate of RWE, demonstrating that the values simulated from DRNM were verified to be closer to measured values. A particular model was further developed to simulate flow of water in different soil layers, and its authenticity was confirmed for describing the patterns of soil water flow under multi-chemicals application. The results of hydrogen and oxygen isotope abundance estimated from multi-source mass balance method (IsoSource model) suggested that main depth of water extraction as affected by multi-chemicals decreased first and then increased, and mainly concentrated in the shallow soil layers, 0–20 cm soil layer for jointing stage, 20–40 cm soil layer for heading stage, 0–20 cm soil layer for grain filling stage. Combined application of SAP and FA played a synergistic role in promoting the rainfall WUE of maize.