Share

Cycles

The model Cycles simulates the productivity and the water, carbon and nitrogen balance of soil-crop systems subject to climate conditions and a large array of management constraints.
Cycles simulates the response of vegetation to nutrients and atmospheric forcings. The picure shows a canola canopy. Photo credit S. Mazzilli.

Cycles simulates the response of vegetation to nutrients and atmospheric forcings. The picure shows a canola canopy. Photo credit S. Mazzilli.

Cycles is an agroecosystem simulation model. It is a multi-year, multi-crop, multi-soil-layered, one-dimensional, daily or sub-daily time step platform that simulates water, carbon and nitrogen balance of the soil-crop system subject to climate conditions and a large array of management forcings. It belongs to the family of mechanistic or process-based models.

Cycles needs inputs of initial soil properties, climate forcings at a daily time step, and the management practices or forcings imposed by the farm operator such as crop sequence, fertilization rates and timing, irrigation and tillage. Based on these inputs, Cycles simulates crop growth and nutrient cycling and predicts agricultural performance metrics for annual and perennial crops (grain and forage yield, nutrient and water use efficiency), and environmental performance metrics such as nutrient losses through different pathways to the environment.

Many modules in Cycles are related to the model CropSyst (Stöckle et al, 2014), and the fundamental heat and water transport algorithms are adapted from Campbell (1985) Soil Physics with Basic landmark book. The Cycles code is modularized and easily unplugged from the main interface, which permits an efficient addition / removal of algorithms and coupling with watershed simulation models. Cycles has unique solutions to the coupled cycling of carbon, nitrogen and water in the soil-plant-atmospheric system. Among the original components in Cycles are new developments in carbon and nitrogen saturation theory (soil), and an old but robust implementation of stomatal optimization theory (vegetation) to simulate plant growth, water use efficiency, and the response of crops to increasing carbon dioxide, and the simulation of polycultures (multispecies pastures and silage crops, cover crops, an more).

The philosophy behind Cycles is that the outcomes of interest must emerge from fundamental principles. The model is meant to provide a framework and insights to address disciplinary and multidisciplinary questions, and as a component of decision support tools for improved agricultural management and environmental stewardship. Current developments focus on integrating Cycles to PIHM for a tridimensional representation of the landscape that includes rivers, lakes and groundwater. This integration will remove simplifications needed to operate in one dimension and will expand the model's domain of application as landscape properties become intrinsic components of the simulations.

Cycles control interface

Cycles control interface. The main screen gives access to the weather file for a given location, and let the user define the name and location of the output files. It also allows importing all simulations stored in Excel. Another version of Cycles, coded in C, can be run on the Penn State Linux Cluster.

Cycles Crop Description interface
Cycles Crop Description interface. Cycles has a generic plant growth and development model that simulates grasses and other herbaceous crops, legumes or non-legumes, perennial and annual crops, and woody crops. It requires minimum inputs from the user.

Cycles Tillage setup interface
Cycles Tillage setup interface. Cycles allows the user to select operations from dozens of tillage tools. These tools disturb the soil, mixing soil layers and all the components in them, breaking up residues, and accelerating soil organic matter turnover. Cycles simulates till and no-till conditions, manure additions, and all the properties that affect soil surface processes.