Evaluation of soil salt dynamics in a tomato-corn intercropping system with various spatial arrangements: Experiment and modeling

Abstract

Intercropping has been widely practiced around the world due to its apparent advantages. However, the soil salt dynamic in the intercropping system has not yet been fully quantified, especially from the perspective of the combined impacts of brackish water irrigation and groundwater recharge. Therefore, a two-year field experiment was performed in the Bayannur, Inner Mongolia, northwest China, to determine soil salt dynamics in the following cropping systems: sole corn (SC), sole tomatoes (ST), two rows of tomatoes intercropping two rows of corn (IC_2–2), and four rows of tomatoes intercropping two rows of corn (IC_4–2). Moreover, the HYDRUS (2D/3D) model was used to quantify the spatio-temporal distributions, salt fluxes, and soil salt balances in different intercropping systems. The result showed that the HYDRUS (2D/3D) model can accurately describe the soil salt dynamics in the tomato-corn intercropping system with different spatial arrangements, with average MRE , R², and PBIAS of 9.5 %, 0.84, and −0.7 % for electrical conductivities of the saturation paste extract (EC_e). There are apparent spatio-temporal differences in soil salt distributions among different intercropping systems. A clear difference in soil salt distributions was found among different intercropping systems during the middle crop growth stage, especially in the top 0–40 cm soil layer. The highest EC_e in the root zones of corn and tomatoes occurred in the SC and IC_2–2 systems, respectively. The salt fluxes in different intercropping systems were mainly vertical and downward. The average soil salt flux in different intercropping systems from zone I (the 0–40 cm soil layer in the corn root zone) to II (the 40–100 cm soil layer in the corn root zone) was 30.6 mg cm⁻¹, while it was 17.9 mg cm⁻¹ from zone III (the 0–40 cm soil layer in the tomato root zone) to IV (the 40–100 cm soil layer in the tomato root zone). Meanwhile, the soil salt flux in the horizontal direction mainly occurred from the corn root zone to the tomato root zone. The lowest EC_e occurred in the IC_4–2 system due to its higher leaching ratio of soil salts. Therefore, regarding farmland environment protection, the IC_4–2 system can be recommended as the optimal intercropping system for tomatoes and corn. The findings of this study improve the understanding of the mechanisms of soil salt dynamics for inter-species competition conditions. The study also indicates that soil salt stress can be alleviated by optimizing the spatial arrangements of different crops.