Rasu, E. 2020. Innovative approaches to gauge resilience of managed rainfed agricultural systems. Dissertation, Michigan State University, East Lansing, MI.
Increasing climate extremes have devastated both crop yields and farm economies, especially in the rainfed agricultural systems of the Midwestern United States. Furthermore, these extreme events are projected to increase in the future due to climate change. As a result, alternative agricultural practices are becoming more common in efforts to mitigate the impacts of extreme climatological events. Nevertheless, the level of resiliency of these practices has not yet been adequately quantified due to the lack of robust metrics available to address the complexity of agricultural systems while being simple enough to be measured at different scales. To this end, three studies were conducted and compiled into this dissertation. These studies were carried out in a long-term cropping system experiment at the W.K. Kellogg Biological Station and the Kalamazoo River Watershed located in the Southwestern Michigan of the United States.
The first study was designed to evaluate the applicability of soil moisture metrics to gauge resiliency of four differently managed rainfed agricultural treatments at the field scale. The robustness of these metrics was assessed over a long-period (1993-2018) for a corn-soybean-wheat rotation by monitoring crop growth and yield in response to climate variability. Results demonstrated that the soil moisture metrics can be used as indicators of resilience at the field scale. The no-till treatment had the highest level of resilience as quantified by soil moisture retention, effectiveness of reducing drought severity, crop yields, and stability of yields. Although the organic treatment substantially improved resiliency in terms of soil moisture conservation and drought mitigation than the conventional treatment, the limitation of available nitrogen significantly reduced corn and wheat yields. Meanwhile, the reduced input treatment was the least resilient as it was vulnerable during extreme climate conditions.
The second study was performed to evaluate the climate resilience of four rainfed agricultural treatments in terms of profitability and farm risks for the same corn-soybean-wheat rotation. Crop production and management data were used to conduct enterprise budgeting and risk analysis. The means and volatility of estimated net returns and risk preferences were used as the evaluation metrics. According to the results of this study, the organic and the no-till treatments had higher resilience than the conventional and the reduced input treatments as they were projected to generate greater net revenues with higher stability. Furthermore, these treatments were promising to cater to a large group of farmers with different risk preferences. Meantime, conventional and reduced inputs treatments were found to be adversely affected by climate extremes.
The goal of the third study was to examine the impacts of large-scale adaptation of conservation agricultural practices (i.e., no-till treatment) on resilience in comparison to traditional practices (i.e., conventional treatment). Similar to the previous two studies, the corn-soybean-wheat rotation was applied on all agricultural land use in the Kalamazoo River Watershed during the period of 1993-2019. Crop and groundwater models were integrated to derive the resilience metrics, namely recharge, groundwater level, soil moisture, yield, and net return. Results showed clear improvement in all metrics under the no-till treatment. Therefore, the adoption of the no-till could improve the overall resilience of the corn-soybean-wheat rotation.
Together, these studies present a set of robust metrics to quantify the resilience of diverse rainfed agricultural systems both at the field and watershed scale.
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