CROP ROTATION DIVERSITY DRIVES RESILIENCE TO ENVIRONMENTAL AND ECONOMIC VARIABILITY, AND IMPROVES NUTRITION OUTCOMES

Our long-term goal is to reduce barriers to adoption of crop rotational diversity by defining positive and negative effects over a range of locations, soil types, and production systems for multiple stakeholders in the agrifood system. Building on our previous work, we will model risks from adverse weather explicitly and develop new metrics for evaluating system performance. We will quantify the impacts of increased rotational diversity on agronomic, economic, and nutritional performance of cropping systems in a changing climate by testing three hypotheses: Hypothesis 1: Negative impacts of adverse weather on crop productivity are reduced with increasing crop rotation diversity because crops differ in their sensitivity and exposure to weather events, thereby spreading risk in diverse rotations (Objs. 1.1, 1.2, 1.3). Hypothesis 2: Farmer economic stability improves with increasing crop rotation diversity due to diffused risk of yearly volatility in yields, crop prices, and input costs (Obj. 2). Hypothesis 3: Nutritive output for people improves with increasing crop rotation diversity--at the cost of reduced caloric output--due to different crops having different nutrient profiles (Obj. 3).Objective 1.1 Quantify the inherent vulnerability of crop rotations to adverse weatherTo achieve this objective we will create a vulnerability index for a rotation based on occurrence of adverse weather (e.g., drought, extreme heat, and excessive precipitation) during critical growth periods of crops in four steps: 1) define weather features for each crop and site, 2) quantify the sensitivity of each crop to each weather feature, 3) combine weather features and sensitivity scores from each crop to create rotation-level vulnerability scores, and 4) compare how dispersion of vulnerability scores changes with increasing rotational diversity.Objective 1.2: Quantify the degree crop rotations can buffer against severe weatherRotation-level vulnerability to adverse weather may be reduced because crops grown in more diverse rotations are less affected, possibly due to changes in soil or other agroecosystem components that help buffer crops against stress. To address this objective, we will build on our previous work describing how crop- and rotation-level yields respond to varying rotational diversity and growing conditions (Bybee-Finley et al., 2024). While our previous work modeled growing conditions as site-year-average crop yields, the current work will incorporate crop responses to adverse weather directly, based on historical yield and weather data. We will evaluate how rotations buffer yield responses to weather first by comparing how simple and more diverse rotations perform in statistical model simulations under more- and less-stressful conditions, defined based on crop-specific responses to multiple weather variables.Objective 1.3: Evaluate effects of increasing crop rotation diversity under future climate scenarios. Obj. 1.2 will provide statistical models describing how yield outcomes are influenced by rotational diversity. To examine how rotational diversity may buffer yield responses to future weather, we will use these models to simulate yield outcomes under a set of future weather scenarios.Objective 2: Stabilize producer net returns. We will evaluate how volatility in yields, crop prices, and input costs contribute to the stability of net returns in different crop rotations. Our analysis will use coefficients of variation (CV), which measure the amount of volatility per unit of return and are the inverse of the Sharpe Ratio, commonly used to assess financial stock portfolios. The CV represents a risk-reward ratio, allowing us to compare risk from different rotations after normalizing by net returns. We will use CVs to examine, 1) how the stability of different sources of volatility (yields, crop prices, and input costs) differ among rotations, and 2) how the separate sources of volatility contribute to differences in economic stability among rotations.Objective 3: Nutritive valueWe will evaluate the hypothesis that more diverse crop rotations provide a broader range of consumable macronutrients (protein, fat, carbohydrate) and micronutrients (vitamins and minerals) at the cost of reduced caloric output compared to simpler crop rotations. This analysis will combine DRIVES yield data with nutritional information from the USDA National Nutrient Database for Standard Reference. Nutritional outcomes for humans will be compared across alternate end-uses for each crop, based on their model production systems.