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

Author:
Ruth H. Burke, Kenneth J. Moore, Martin J. Shipitalo, Fernando E. Miguez, Emily A. Heaton
Source:
BioEnergy research 2017 v.10 no.2 pp. 305-316
ISSN:
1939-1234
Subject:
Panicum virgatum, bioenergy, calcium, canopy, feedstocks, frost, grasses, leaching, leaves, magnesium, nitrogen, nutrient content, nutrients, perennials, phosphorus, potassium, rain, rainfall simulation, resorption, winter
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⁻¹ dry 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.
Agid:
5728364
Handle:
10113/5728364