Switchgrass Winter Yield, Year‐Round Elemental Concentrations, and Associated Soil Nutrients in a Zero Input Environment

Abstract

The maximum biomass yield of switchgrass (Panicum virgatum L.) usually is achieved with one seasonal autumn harvest. However, information is limited on the influences of winter harvesting on annual biomass yield and on quality parameters impacting conversion into bioethanol. Accordingly, the objectives of this study were to assess: (i) yield of standing field cured biomass at monthly intervals through winter, (ii) year‐round elemental composition of biomass, and (iii) associated year‐round soil nutrient status. An unfertilized ‘Kanlow’ switchgrass planting established in 1998 was used for this study conducted from November 2007 to October 2010. The experimental treatment was monthly harvest from November to the following March and year‐round monthly sampling of biomass (except April) and soil for chemical analyses. The 3‐yr mean dry matter yield of winter harvests was 5.94Mg ha−1, ranging from 3.88 Mg ha−1 in the winter of 2007–2008 to 7.55 Mg ha−1 in 2009–2010. Monthly biomass yield differences were significant in Years 1 and 3 but not in Year 2. Concentrations of biomass elements and soil nutrients changed with various degrees over the 3 yr. Concentrations of ash, cell wall components, and mineral nutrients, except P, K, and S, did not change appreciably across winter months. Early winter harvests resulted in less yield loss compared to late winter harvests. These findings will be valuable in harvest management for switchgrass biomass production.

Switchgrass Growth and Effects on Biomass Accumulation, Moisture Content, and Nutrient Removal

“…Yield increased during leaf emergence and stem elongation and peaked at DAY 246 to 254 (2-yr mean yield of 12.1 Mg ha -1 ) at the onset of seed maturation. Declines in harvestable biomass over winter are consistent with other studies in the U.S. upper southern United States using lowland cultivars in Tennessee with Alamo , and in Oklahoma with cultivar Kanlow (Makaju et al, 2013).…”

Changes in Nutrient Characteristics of Switchgrass for Bioenergy

“…In most cases, researchers have noted that N decreases throughout the growing season. Values for N have been observed from approximately 11 to 35 g kg −1 in May, and they continue to decline to about 3 to 6 g kg −1 by October (Waramit et al, 2011; Makaju et al, 2013; Wilson et al, 2013b). Mulkey et al (2006) observed a reduction in total N of 4.8 to 7.7 g kg −1 between anthesis (August) and killing frost (October) harvests of switchgrass‐dominated plots, which is similar to the trends in this study between the reproductive growth and senescence periods in 2011.…”

“…There has been research on the quality changes that occur within switchgrass during and between growing seasons, although intensive studies of these changes are few. In most cases, N, P, K, metals, and moisture concentrations have been observed to decrease significantly throughout the growing season due to translocation of nutrients from shoots to roots and senescence (Reynolds et al, 2000; Mulkey et al, 2006; Ogden et al, 2010; Makaju et al, 2013; Sadeghpour et al, 2014). These quality characteristics (except for N and Ca) generally continue to decline between killing frost and the following spring (Adler et al, 2006; Lindsey et al, 2013; Makaju et al, 2013; Sadeghpour et al, 2014).…”

Nitrogen fertilizer and landscape position impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass

“…Different fertilization rates did not significantly influence SOC because it was measured in June 2009 before fertilizer application. However, the influence of the effect of nitrogen on switchgrass biomass yield is likely to depend on various factors including antecedent soil nitrogen, type of fertilizer, time of application, switchgrass cultivar, soil series, time of harvest, and local climate (Lee et al, 2007;Makaju et al, 2013). Depending upon initial N levels and time of application, a large amount of N can be lost through nitrification, vaporization, and leaching, and thus not necessarily translate into higher biomass.…”