Development, Testing, and Application of a Process-based Crop Simulation Model for Garlic

Crop simulation models are essential tools for assessing climate impacts on crops, assisting crop breeding and management decisions, optimizing agricultural inputs and resources, and forecasting crop yield for policy decisions, as well as developing adaptive cropping solutions in a changing climate. With a long history of cultivation, garlic (Allium sativum) is an important crop that has been incorporated into cuisines around the world and widely used as a health supplement and at times a panacea. It is critical to evaluate the impacts of climate change on garlic production with site specificity and develop climate adaptation strategies such as identifying suitable production sites under the future climate scenarios. We have developed a process-based crop model for simulating potential growth, phenology, and bulb yield formation of hard-neck garlic. The model responds to temperature, solar radiation, CO₂, and humidity in predicting crop development, biomass accumulation, growth, and bulb yield. Our model incorporates a modified beta function for modeling non-linear phenological responses to temperature, and applies a coupled photosynthesis and transpiration model for predicting crop carbon gain and water use. The model is designed based on the object-oriented scheme in which each organ is an object of a class with properties and methods. This scheme allows for tracking the development and growth of individual organs including leaves, roots, scape, and bulb, and examining the interactions between different organs. Expansion and senescence of individual leaves are simulated separately for each leaf as a function of cardinal temperature, physiological age, and carbon availability. The model has been calibrated and tested using experimental data from the greenhouse and field studies performed in the United States and Korea. We discuss a case study for linking the model with a GIS tool to evaluate site-climate-crop suitability in a changing climate.