S-map parameters for APSIM

Abstract

Agroecosystem models have become an important tool for impact assessment studies, and their results are often used for management and policy decisions. Soil information is a key input for these models, yet site-specific soil property data are often not available, and soil databases are increasingly being used to provide input parameters. For New Zealand, the digital spatial soil information system S-map provides geospatial data on a range of soil characteristics, including estimates of soil water properties. We describe a protocol for how properties from S-map can be used as input parameters for the APSIM (Agricultural Production Systems sIMulator) framework. Finally, we investigate how changes in the physical description of soil layers, and soil organic matter pools, affect the various outputs of APSIM.•This paper presents a description of how information from S-map, a digital soil map of New Zealand, can be used for building a soil description for APSIM.•A sensitivity analysis shows the effect of soil layering and the set-up setup, size, and distribution of SOM pools on model outputs, including plant growth and N leaching.

Keywords: Digital spatial soil information; Process-based modelling; Sensitivity analysis.

Graphical abstract

Fig. 1

Measured and simulated cumulative drainage from lysimeters (with depths of 70 cm) under a ryegrass/white clover pasture, with a representative generic soil description of a Horotiu silt loam, with (a) showing the effect of layering with SWCON of 0.5 (Layering 1: 0–20 cm, 20–60 cm, 60–70 cm and Layering 2: 0–15 cm, 15–30 cm, 30–45 cm, 45–60 cm, 60–70 cm), and (b) the effect of SWCON, either set to different values (0.3, 0.5 or 0.7) or calculated based on hydraulic properties and layer thickness, using Layering 2. Simulations in c) are based on S-map descriptions (Otor_70a.1) with different layering (Layering1: 0–31 cm, 31–55 cm, 55–70 cm, Layering 2: 0–6 cm, 6–31 cm, 31–55 cm, 55–70 cm, and Layering 3: 0–6 cm, 6–17 cm, 17–31 cm, 31–61 cm, 61–70 cm)

Fig. 2

Measured and APSIM simulated soil water content from seven different sites and periods (labelled Series 1 to 7) of field experiments done on the Horotiu soil in the Waikato region of New Zealand. APSIM simulations were done with soil descriptions based on representative generic descriptions of the Horotiu soil (a and c) and S-map (b). Measurements were done at a depth from 0–75 mm (a and b), and from 20–60 cm (c). For the Horotiu soil the layering was Layering1: 0–20 cm, 20–60 cm, 60–70 cm and Layering 2: 0–15 cm, 15–30 cm, 30–45 cm, 45–60 cm, 60–70 cm; and for S-map descriptions Layering1: 0–31 cm, 31–55 cm, 55–70 cm, Layering 2: 0–6 cm, 6–31 cm, 31–55 cm, 55–70 cm, and Layering 3: 0–6 cm, 6–17 cm, 17–31 cm, 31–61 cm, 61–70 cm).