PS 43-149 - When do legacy effects matter?: Exploring the impact of current and legacy effects of precipitation on growth and nutrition in contrasting crops

Abstract: Among the many climate change variables, precipitation is a key driver of plant performance through direct and indirect impacts. The direct effect of moisture stress on plant physiology is well-studied in natural and agricultural systems. Dry conditions can reduce leaf-level photosynthesis and plant growth and can cause shifts in foliar chemistry important to consumers. Typically, outcomes are examined as a consequence of current water stress without consideration of accumulated moisture-induced changes in soil properties that accrue over many seasons (legacy effects). These long-term modifications of the chemical, physical and biological makeup of soils are expected to mediate performance in subsequent years. Yet, the relationship between current and legacy effects is largely unexplored. To explore these connections, the infrastructure of the Boston Area Climate Experiment (BACE) was leveraged to examine the responses of kale (Brassica oleracea), oat (Avena sativa) and beans (Phaseolus vulgaris) to three levels of precipitation (ambient, 75% of ambient, and 50% of ambient) when grown in legacy soils obtained from 10 years of differential precipitation inputs. We chose these crops as representative of contrasting crops: a green leafy vegetable, a legume seed crop, and a grain. We hypothesized that low water legacy soils would limit crop growth and that these differences would be most pronounced when current water availability is low. We further predicted that bionutrient composition of leaves and seeds would also be lower under these conditions. Plant growth was measured weekly and nutritional differences within the edible portions of each crop were assessed at the end of the season. We found that current precipitation had a bigger effect on growth than did the legacy of differential precipitation. Our results supported our hypothesis that water-limited conditions in the current growing season would depress plant growth but did not support the expectation that current dry conditions would reduce plant nutrient composition for all species. In addition, and contrary to our expectation, legacy soils had varied effects on growth and nutrient composition. Although legacy effects were relatively minor for growth, both current and legacy treatments impacted foliar nutrients of kale, while only current precipitation treatments affected the nutrient composition of bean seeds and oat grains. Perhaps the nutritional quality of seed/grain producing crops is less sensitive to changes in soil conditions. Future work could explore the underlying mechanisms.