An improved model to simulate soil water and heat: A case study for drip-irrigated tomato grown in a greenhouse

Soil physical, chemical, and biological processes are influenced by soil water and heat conditions, which greatly depend on the crop root systems in different soil layers. Hence, understanding root distribution, soil water and heat dynamics is essential to improve water and nutrient use efficiency. A case study of tomato grown in a greenhouse with drip irrigation was conducted to test an improved two-dimensional (2D) model, namely UZflow-2D, for simulating the soil water and heat dynamics. The performance of UZflow-2D model was also compared with the well-known Hydrus-2D model. A 2D root length density (RLD) function, as a main subsidiary model of UZflow-2D, was proposed by investigating the roots distribution from lateral and radial latitudes at the four main growth stages (seedling, flowering, fruit-setting, and picking). Experimental data in 2015 was used to calibrate the parameters of UZflow-2D and Hydrus-2D models, and validated using the data of 2016. Results showed that more than 70% of the total RLD was concentrated in soil layers of 0-20 cm during the seedling, 0-40 cm during the flowering, and 0-60 cm during the fruit-setting and picking stages. The 2D RLD function perform well for locations within and between two rows, with determination coefficients higher than 0.77. Both UZflow-2D and Hydrus-2D models perform well in simulating soil water and soil temperature dynamics, while UZflow-2D model produced improved accuracy in modeling the soil water and heat dynamics within and between two rows of drip-irrigated tomato plants. The overall root mean square error (RMSE) was-0.008 cm3 cm-3 for soil water con-tents, and-0.434 degrees C for soil temperature for UZflow-2D model. However, the overall RMSE was-0.012 cm3 cm-3 for soil water contents, and-0.504 degrees C for soil temperature for Hydrus-2D model. Hence, the UZflow-2D model can be served as an alternatively useful tool to simulate water and heat dynamics.