Modeling evapotranspiration and evaporation in corn/tomato intercropping ecosystem using a modified ERIN model considering plastic film mulching

Highlights

• A modified ET model (MERIN) for intercropping ecosystem was proposed.

• The accuracy performance of the MERIN model was better than other ET models.

• Water competition between crops mainly occurred in elongation and tasseling stages.

• The variation of water competition under different irrigation levels was similar.

Abstract

Intercropping planting pattern under plastic film mulching (PFM) has been widely adopted in the arid regions to reduce soil evaporation (E), improve land-use efficiency, and increase crop yield. However, water competition between intercropping components in the soil-plant-atmosphere continuum remains largely unexplored. The evaporation and radiation interception using the neighboring species model (ERIN) can effectively estimate evapotranspiration (ET) in a different intercropping ecosystem. However, the effects of soil surface resistance in the mulching area on ET are not considered in the ERIN model. Thus, the existing ET models do not accurately estimate ET in the intercropping ecosystem with PFM. In this study, we proposed a modified ERIN model (MERIN). In the MERIN model, soil surface resistance in the mulching area was taken into account, and its performance was compared to ERIN and Penman-Monteith (PM) models. These models were validated against observed ET and E using the water balance method and micro-lysimeters in a corn intercropped tomato experiment under high (HI: 30 mm for corn and 22.5 mm for tomato, a locally recommended irrigation depth), medium (MI: 22.5 mm for corn and 16.9 mm for tomato, 25% of HI), and low irrigation depth (LI: 15 mm for corn and 11.25 mm for tomato, 50% of HI) during 2018-2019, respectively. The outcomes of this study showed that the MERIN model could accurately estimate ET and E variation for a corn-tomato intercropping ecosystem under PFM during the entire crop growth season compared to the other examined models. The most intense water competition between corn and tomato was observed in stage II (the elongation and tasseling stages for corn; the flowering and fruiting stages for tomato). T of corn generally was higher than tomato, but an opposite result was also observed in stage II. Additionally, the variation of water competition under different irrigation levels was similar in the intercropping ecosystem. When irrigation depth decreased to 22.5 and 15 mm from 30 mm, average T for corn decreased by 10.7% and 16.3%, respectively, and by 12.9% and 22.4% for tomato, respectively, in both years.

Introduction

Intercropping planting pattern involves simultaneous cultivation of two or more plant species in the same field (Bolo et al., 2021, Costa et al., 2021, Salehi et al., 2018). It is widely used in agronomic production worldwide as it increases the land-use efficiency (Crusciol et al., 2021), yield of dominant plant species (Berghuijs et al., 2021), and other natural resources (Jardim et al., 2020). Currently, the incorporation of cereals and cash crops in the cropping system is widely employed, for instance, corn-wheat Ma et al., 2020a, Ma et al., 2020b, corn-soybean (Rodehorst et al., 2020), and the corn-tomato intercropping patterns (Li et al., 2017). Inter-specific competition in different intercropping planting patterns varies significantly. Ma et al., 2020a, Ma et al., 2020b demonstrated that wheat plants are more competitive than corn plants in absorbing soil moisture during the intercropping co-growth period. In a study by Ahmed et al. (2020), a decreased co-growth duration increased growth rate and resilience in soybean crops against the size-asymmetric competition in the corn-soybean intercropping pattern. Chen et al. (2020b) evaluated the differences in the competition between corn and tomato crops for soil nitrate. They found that soil nitrate exchange between corn and bare soil regions was lower than between the tomato and bare soil regions due to the lower concentration gradients of soil nitrate in the rhizosphere. Previous studies have systematically elucidated the inter-species competition in different intercropping planting patterns. These studies were primarily focused on the competition between soil water and nutrients between different crop species in the vadose zone. However, water competition between intercropping components in the soil-plant-atmosphere continuum (SPAC) needs to be explored further.

Accurate estimation of evapotranspiration (ET) can unravel the water competition mechanism between intercropping components (Qiu et al., 2019). Currently, ET estimation is primarily derived through the use of the estimation method for ET primarily entails crop coefficients with either the, Penman-Monteith (PM) model, and or Shuttleworth-Wallace (SW) models. However, crop coefficient remains to be an indirect calculation method (Allen et al., 1998). Firstly, the crop coefficient is estimated and rectified in this method and then multiplied by reference crop evapotranspiration (ET₀) (Allen et al., 2005, Chen et al., 2019, Pereira et al., 2021, Rallo et al., 2021). Miao et al. (2016) developed a new method for partitioning ET using plant height and fractions of ground covered by crops based on the dual crop coefficient approach in the intercropping ecosystem. Although the estimation accuracy of this method was satisfactory, determining the accurate value for crop coefficients remains a challenging task.

PM and SW models, a direct method, directly estimates ET by calculating latent heat flux based on energy balance using aerodynamic parameters and meteorological data (Monteith, 1981, Shuttleworth and Wallace, 1985). These models have been widely applied in multiple conditions, specifically in uniform underlying surfaces (del Campo et al., 2019; Elfarkh et al., 2021). However, PM and SW models cannot precisely estimate ET in the intercropping ecosystem as interception alters radiation and wind speed within the canopy by neighboring plant species. Thus, there is an urgent need to devise an ET model to estimate the ET of the intercropping ecosystem with the complex underlying surface.

To estimate ET of a cornfield with different plant heights, Kang et al. (2018) proposed an improved PM model (referred to as PM hereinafter) based on Ohm's law by inducing effective aerodynamic and soil surface resistance. This model can also be employed for an accurate estimation of ET in intercropping ecosystem under PFM. However, this model lacks the functional expression for transpiration partitioning in the intercropping ecosystem. An improved model (ERIN) (Wallace, 1997, Wallace, 2000) was developed considering evaporation and radiation interception by neighboring plant species in intercropping ecosystems based on the SW model (Shuttleworth and Wallace, 1985). In a study by Gao et al. (2013), transpiration of maize and soybean was estimated using the ERIN model. The statistical outcome of the study by Gao et al. (2013) demonstrated a sound agreement between the observed and the estimated values, with the mean bias error of 0.06 mm d⁻¹, the root mean square error of 0.23 mm d⁻¹, and the index of agreement of 0.93.

ERIN model primarily estimates the ET in the intercropping ecosystem without PFM. Thus, the effects of PFM on ET were not taken into consideration. In general, PFM reduces soil evaporation, increases plant transpiration, and alters water consumption by increasing soil surface resistance (Li et al., 2013, Zribi et al., 2015, Thakur and Kumar, 2020). The current ET model, which considers PFM, primarily focuses on the sole crop field. For instance, Li et al. (2013) deduced a new ET model for cornfield under PFM using mulched and total area ratio based on the SW model. Chen et al. (2020a) further improved the SW model by importing the disintegration area of biodegradable film and re-estimating the difference in ET between PFM and biodegradable film mulching.

Although ET models under mulching conditions or intercropping ecosystems were previously developed, the ET model for an intercropping ecosystem under PFM could not be deduced simply by the superposition of the existing model parameters. In the ET model for an intercropping ecosystem model, total latent heat in the intercropping ecosystem under PFM needs to be reasonably divided. Thus, it is necessary to devise an ET model for an intercropping ecosystem under PFM (MERIN) and determine the water competition between intercropping components. The development of such a model will overcome the disadvantages of the existing ET theory and provide a theoretical foundation for the formulation of an irrigation strategy.

This study aimed to a) develop the MERIN model based on the ERIN model, b) validate the estimation accuracy of MERIN for ET and E in the corn-tomato intercropping ecosystem, c) compare the estimated ET difference during different crop growth stages between PM, ERIN, and MERIN models, d) evaluate the difference in the simulation of E for ERIN and MERIN models, and e) quantify plant transpiration and water competition between intercropping components under different irrigation depths.