Sensitivity analysis of the AquaCrop parameters for rainfed corn in the South of Brazil

Luiz Carlos Pittol Martini

doi:10.1590/s0100-204x2018000800008

Abstract

Abstract: The objective of this work was to perform a sensitivity analysis of the main input parameters required for the AquaCrop water balance model, using biomass and grain yield data of a rainfed-simulated corn crop, obtained along the climate data series of 1987-2016 in the South of Brazil. The levels of soil-water stress and the depths of maximum effective rooting were the input parameters that most affected the biomass and grain yields simulated by the model, followed by the crop coefficient, water-use efficiency, soil water storage capacity, and contribution of groundwater to water availability in the root zone. The parameters crop cycle duration, plant density, pattern of soil-water extraction, and field surface practices showed little or no impact on the final results. AquaCrop is a robust water balance model, with small or moderate general sensitivity to variations of the main input parameter values, which makes it applicable to situations with field data limitations.

Highlights

Soil-water balance is an important tool for the management of rainfed and irrigated crops that has been receiving quantitative and qualitative improvements
Simulation results of the AquaCrop from the main input plant parameters used in the present work are expressed as mean values of corn relative biomass and grain yield, computed from the 1987-2016 time series (Table 2)
The first and second rows in this table show the results of the plant- and soil-water stress parameters

Summary

Introduction

Soil-water balance is an important tool for the management of rainfed and irrigated crops that has been receiving quantitative and qualitative improvements. Older soil-water balance models are based on simple accounting methods to assess the inflow and outflow of water in the soil-plant-atmosphere system. In these models, a portion of the rain infiltrates the soil, the plants absorb the water stored in the root zone, and the moisture is released back into the atmosphere through transpiration. In the simplest form, like the Thornthwaite-Mather’s classical model (Thornthwaite & Mather, 1955), a soil-water balance is assessed by few input-output variables in a mass conservation equation, and the plant factors are barely considered. Subsequent improvements in classical models added plant parameters, but the plant phenology was synthesized in a single coefficient (Kc) obtained experimentally (Nolz, 2016).

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Conclusion