All Washed Out? Foliar Nutrient Resorption and Leaching in Senescing Switchgrass

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2017-06-01
Authors
Burke, Ruth
Moore, Kenneth
Heaton, Emily
Shipitalo, Martin
Miguez, F.
Heaton, Emily
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Agronomy
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Agronomy
Abstract

Ideal bioenergy feedstocks are low in nutrients that act as anti-quality factors during conversion processes. Research has shown that delaying harvest of temperate perennial grasses until late winter reduces nutrient content, primarily due to end-season resorption, but also indicates a role for foliar nutrient leaching. While end-season resorption has been estimated, foliar nutrient leaching has not, and is a factor that could refine harvest recommendations. Additionally, establishing a baseline of mineral loss during switchgrass senescence will improve our understanding of leaf-level nutrient resorption. Therefore, we applied simulated rainfall to replicated (n = 5) plots within a previously established switchgrass stand to determine if heavy precipitation can induce nutrient leaching in senescing, unharvested foliage. Hour-long simulated rainfalls of ∼120 mm were applied every 2 weeks from early September to a killing frost in 2014 and 2015. Leaf samples were taken from the upper and lower canopy before and after simulated rainfalls and from no-rain controls and analyzed for elemental N, P, K, S, Mg, and Ca. Nutrient resorption estimates ranged from 33 to 82% in control plots. Comparison of rainfall plots to controls indicated that lower canopy leaves, upon reaching ≥50% senescence, were slightly susceptible to foliar nutrient leaching, with losses ranging from 0.3 to 2.8 g kg−1dry matter for K, P, and Mg. Nitrogen, Ca, and S were not susceptible to foliar leaching. Although statistically significant (P ≤ 0.05), these values suggested that foliar leaching was not a strong driver of nutrient loss during senescence.

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This article is published as Burke, R.H., Moore, K.J., Shipitalo, M.J. et al. All Washed Out? Foliar Nutrient Resorption and Leaching in Senescing Switchgrass. Bioenerg. Res. (2017) 10: 305. doi: 10.1007/s12155-017-9819-6. Posted with permission.

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