Using the Aquacrop Model to Assess the Long-Term Performance of Replacing Summer Fallow in Montana's Wheat-Based Systems.

Water is the greatest constraint on dryland wheat production throughout Montana. Farmers typically utilize a wheat-fallow system to conserve soil moisture and  reduce the risk of crop failure from annual cropping and unreliable precipitation. However advances in no-till farming have improved precipitation capture and storage, and the risk of cropping intensification has begun to decline. Cropping intensification could generate greater economic returns while sustaining the environment, but due to the threat of drought, producers are often hesitant to eliminate fallow from their systems. To help measure producer risk, a tool that predicts yields when water limits crop production is needed in Montana. The newly developed AquaCrop model is designed to simulate yield response to water stress, and its ease-of-use and robustness could make it a powerful decision-making tool for Montana producers. The objective of this study is to calibrate and validate AquaCrop for several common grown crops in Montana, and use the model to assess risk by simulating yields of different wheat-based crop rotations. Here we introduce methodology, and present preliminary results testing the robustness of AquaCrop by comparing past spring wheat yield and soil moisture measurements with simulated AquaCrop predictions.