Agroecosystem models need to reliably simulate all biophysical processes that control crop growth, particularly the soil water fluxes and nutrient dynamics. As a result of the erosion history, truncated and colluvial soil profiles coexist in arable fields. The erosion-affected field-scale soil spatial heterogeneity may limit agroecosystem model predictions. The objective was to identify the variation in the importance of soil properties and soil profile modifications in agroecosystem models for both agronomic and environmental performance. Four lysimeters with different soil types were used that cover the range of soil variability in an erosion-affected hummocky agricultural landscape. Twelve models were calibrated on crop phenological stages, and model performance was tested against observed grain yield, aboveground biomass, leaf area index, actual evapotranspiration, drainage, and soil water content. Despite considering identical input data, the predictive capability among models was highly diverse. Neither a single crop model nor the multi-model mean was able to capture the observed differences between the four soil profiles in agronomic and environmental

Consequently, some of the agrochemicals can bypass the soil matrix and its capacity to store, absorb, and transform the solute. Thus, agrochemicals and nutrients can be carried to great depths, where degradation is limited (Boesten et al., 2000), possibly increasing the total amounts leached to groundwater. The preferential processes usually take place in what is often called macropores (Beven and Germann, 1982, 2013; Jarvis, 2007). In the literature, the term macropores is arbitrarily used for soil structural components like cracks, fissures, root channels, and earthworm borrows (Beven and German, 1982, 2013). These generally occur in soils with well-developed structures, that is, soils with silt or clay texture (Beven, 2018; Jarvis, 2007). Jarvis (2007) distinguishes between biologically induced macropores (e.g., root channels and earthworm borrows) termed biopores and macropores as a result of soil aggregation (e.g., fissures and cracks). In this work, the term biopores will be used to describe root channels, and earthworm borrows in which capillary effects are negligible. Artificial drainage is a common agricultural practice, which allows a field to be cultivated and increases crop production, but simultaneously can create new pathways for leaching of nutrients and agrochemicals to surface water (

The use of pesticides is associated with a risk to the water quality of streams and lakes in agricultural areas. The main processes transporting pesticides from the fields to nearby streams are spray-drift, run-off, and drainage (Brown & van Beinum, 2009;Reichenberger et al., 2007). Among those, drainage concentrations are the most challenging to quantify, as these are a result of solute transport and reactions in both the soil matrix and the preferential flow paths. Preferential flow paths are common in fine-textured soils, composed of cracks, fissures, root channels, and earthworm borrows, the latter two often referred to as biopores (Beven & Germann, 1982. Preferential water flow is an important pathway for pesticide transport to drainpipes and deeper soil layers, affecting both the timing and amount of pesticides in drain water (Jarvis, 2007).

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Crop model intercomparison studies have mostly focused on the assessment of predictive capabilities for crop development using weather and basic soil data from the same location. Still challenging is the model performance when considering complex interrelations between soil and crop dynamics under a changing climate. The objective of this study was to test the agronomic crop and environmental flux‐related performance of a set of crop models. The aim was to predict weighing lysimeter‐based crop (i.e., agronomic) and water‐related flux or state data (i.e., environmental) obtained for the same soil monoliths that were taken from their original environment and translocated to regions with different climatic conditions, after model calibration at the original site. Eleven models were deployed in the study. The lysimeter data (2014–2018) were from the Dedelow (Dd), Bad Lauchstädt (BL), and Selhausen (Se) sites of the TERENO (TERrestrial ENvironmental Observatories) SOILCan network. Soil monoliths from Dd were transferred to the drier and warmer BL site and the wetter and warmer Se site, which allowed a comparison of similar soil and crop under varying climatic conditions. The model parameters were calibrated using an identical set of crop‐ and soil‐related data from Dd. Environmental fluxes and crop growth of Dd soil were predicted for conditions at BL and Se sites using the calibrated models. The comparison of predicted and measured data of Dd lysimeters at BL and Se revealed differences among models. At site BL, the crop models predicted agronomic and environmental components similarly well. Model performance values indicate that the environmental components at site Se were better predicted than agronomic ones. The multi‐model mean was for most observations the better predictor compared with those of individual models. For Se site conditions, crop models failed to predict site‐specific crop development indicating that climatic conditions (i.e., heat stress) were outside the range of variation in the data sets considered for model calibration. For improving predictive ability of crop models (i.e., productivity and fluxes), more attention should be paid to soil‐related data (i.e., water fluxes and system states) when simulating soil–crop–climate interrelations in changing climatic conditions.

<p>Biopores and cracks in soils act as fast transport ways for water and solute, potentially leading to pesticide leaching shortly after application. The biopore module in the agro-hydrological model Daisy was developed to simulate preferential water flow directly to drains, in drain-connecting biopores, and to deeper soil layers, in matrix-terminating biopores.Daisy offers a coherent representation of the soil-plant-atmosphere system, including preferential solute transport, for pesticide fate assessment in agricultural fields. We test the biopore module in Daisy against field measurements of water flow and the behavior of bentazone and imidacloprid after application to a cracking clay field in the Netherlands. We generated two model concepts, DCB with drain-connecting biopores and DCMTB with both drain-connecting and matrix-terminating biopores. Parameters describing the biopores were estimated by inverse modelling to observations of water flow and pesticide concentrations in drains. The results showed that data of water flow and pesticide concentrations in drains contained enough information to parameterize the biopore module in Daisy. Furthermore, both models could simulate the water flow and pesticide leaching to drains well after calibration. Especially, the models were able to describe the high concentration of bentazone in drain water shortly after application. Solute transport in drain-connecting biopores explained the fast break through of pesticides in drains shortly after application. We attributed the discrepancies between observations and simulations in the beginning of the drainage season to the limitations that arise when simulating dynamic preferential flow paths, such as shrinkage cracks, with a static model, such as the biopore model in Daisy. The pesticide distribution in the field over time was represented satisfactorily, especially by the DCMTB-model. We therefore conclude that Daisy can simulate fast break through of pesticides in drain water and describe very well pesticide concentration in drain water throughout the drainage season.</p>

<p>Preferential water flow and solute transport in agricultural systems affects not only the quality of groundwater but also the quality of surface waters like streams and lakes. This is due to the rapid transport of agrochemicals, immediately after application, through subsurface drainpipes and surface water. Experimental evidence attributes this to the occurrence of continuously connected pathways, connecting the soil surface directly with the drainpipes. We developed a physically-based model describing preferential flow and transport in biopores and implemented it in the agroecological model Daisy. The model simulates the often observed rapid transport of chemicals from   the upper soil layers to the drainpipes or to deeper layers of the soil matrix. Based on field investigations, biopores with specific characteristics can be parameterized as classes with different vertical and horizontal distributions. The model was tested against experimental data from a column experiment with an artificial biopore and showed good results in simulating preferential flow dynamics. We illustrate the performance of the new approach, by conducting five simulations assuming a two-dimensional simulation domain with different biopore parametrizations, from none to several different classes. The simulation results agreed with experimental observations reported in the literature, indicating rapid transport from the soil to the drainpipes. Furthermore, the different biopore parametrizations resulted in distinctly different leaching patterns, raising the expectation that biopore properties could be estimated or constrained based on observed leaching data and direct measurements.</p>

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