Quantifying interspecies competition for water in tomato-corn intercropping system using an improved evapotranspiration model considering radiation interception by neighboring plants in two-dimensional profile

Intercropping system is widely adopted in agricultural production due its significant advantages. Usually, the radiation interception of plants with low canopy would be decreased in the vertical and horizontal directions because of the heterogeneity of the underlying surface of the intercropping system, which causes reduction in the water consumption of such plants. However, the existing evapotranspiration (ET) models consider the effect of radiation interception on water consumption only in the vertical direction.Thus, the objectives of this study were to quantify water competition between intercropping components in the tomato-corn intercropping system with various spatial arrangements and to determine suitable spatial arrangements. An improved ET model (DERIN) was deducted by inducing a two-dimensional radiation interception model based on ERIN model, and the corresponding accuracy of ET estimation was compared with that of ERIN and MERIN models. Additionally, a 2-year (2018-2019) field experiment was conducted to validate the accuracy of the model and assess interspecies competition for water in the following systems: two rows of tomato intercropping with two rows of corn (IC2-2), four rows of tomato intercropping with two rows of corn (IC4-2), sole corn (SC), and sole tomato (ST). The result showed that the DERIN modelcan precisely quantify the radiation interception by crop canopy in various intercropping systems compared with ERIN and MERIN models. Mean relative error (MRE) of ET estimated by DERIN model in various intercropping systems (i.e., IC2-2 and IC4-2) decreased by 59.9% compared with that estimated by MERIN model. Moreover, the average MRE of evaporation estimated by DERIN model decreased by 53.8% and 79.8% compared with MERIN and ERIN models, respectively. The interspecies competition for water between tomato and corn in various planting systems was similar during the entire crop growth season. The highest water competition ratio for corn (CRc) occurred in IC2-2 system among various intercropping systems, whereas IC4-2 system exhibited the highest land equivalent ratio for water (LERT). Average LERT of IC4-2 system increased by 6.7% and 5.8% compared with IC2-2 system in 2018 and 2019, respectively. Therefore, IC4-2 system can be recommended as the optimal intercropping system for sustainable agriculture development. Collectively, the DERIN model is an important tool to quantify interspecies water competition between commercial and grain crops. Also, the DERIN model is currently available method to optimize spatial arrangements of an intercropping system in different spatial position and planting orientation.

Automated summary

The intercropping system is widely adopted in agriculture due to its advantages. However, existing evapotranspiration models do not consider the horizontal effect of radiation interception on water consumption. In this study, an improved ET model (DERIN) was developed and compared with two other models (ERIN and MERIN) to accurately quantify water competition between intercropping components in the tomato-corn intercropping system. The results showed that the DERIN model is capable of accurately quantifying radiation interception and that the IC4-2 system is recommended as the optimal intercropping system for sustainable agriculture development.