Modeling of Soybean Plant Sap Flow

Abstract

Soybean ( Glycine max. (L.) Merr.) sap flow during the growth stages in relation to soil moisture, nutrition, and weather conditions determine the plant development. Modeling this process helps to better understand the plant water-nutrition uptake and improve the decisions of efficient irrigation management and other inputs for effective soybean production. Field studies of soybean sap flow took place in 2017-2021 at Marianna, Arkansas using heat balance stem flow gauges to measure the sap flow during the reproductive growth stages R3-R7. Plant water uptake was measured using the lysimeter-container method. The uniform sap flow-based hydraulic system in the soil-root-stem-leaf pathway created negative water tensions with osmotic processes and water surface tensions in stomata cells as water evaporation layers increase are the mechanism of the plant water uptake. Any changes the factors like soil water tension, solar radiation, or air relative humidity immediately, within a few seconds, affect the system’s balance and cause simultaneously appropriate reactions in different parts of the system. The plant water use model was created from plant emergence, vegetative to final reproductive growth stages depending on soil-weather conditions, plant morphology, and biomass. The main factors of the model include solar radiation, air temperature, and air relative humidity. The effective sap flow uptake occurs around 0.8 KPa VPD. Further research is needed to optimize the model’s factors to increase the plant growth dynamics and yield productivity.