Results and Discussion

This chapter presents the correlations between drought indices and crop yields, their spatio-temporal variability, and the implication for understanding drought impacts on agricultural productivity. The findings are discussed in detail to highlight the significance of both short- and long-term drought indices for corn and soybean yields. Insights into climatic conditions, spatial patterns, and implications for drought risk management are also explored.

Yearly Correlation of Corn Yields with Drought Indices

Figure 3 illustrates the yearly correlation coefficients between corn yields and various drought indices from 2000–2022. Shorter-term indices, such as SPI-1 and SPEI-1, exhibit greater variability in correlations, with significant swings in positive and negative values. These trends indicate that corn production is susceptible to short-term precipitation variability, particularly during critical growth stages such as silking and grain filling. For instance, corn is highly reliant on moisture availability during its reproductive phase, and a lack of rainfall during these periods can result in substantial yield reductions. In contrast, longer-term indices like SPI-12 and SPEI-12 reflect the cumulative impact of extended moisture conditions. These indices capture broader seasonal or yearly precipitation trends, which align with the water requirements of corn during the entire growing season. Notably, sharp peaks and troughs in 2005, 2012, and 2018 correspond to years of significant climatic anomalies. For example, the severe drought of 2012, widely regarded as one of the most impactful droughts in U.S. history, resulted in significant negative correlations across most indices, underscoring the vulnerability of corn to prolonged droughts.