Biomass Yield of Warm‐Season Grasses Affected by Nitrogen and Harvest Management

Abstract

Core Ideas Dry matter yields increased with N inputs although efficiency decreased.Applying nitrogen at 67 kg N ha–1 was superior in both yield and efficiency.Delaying the time of harvest until late fall or a killing frost increased yield. Native perennial warm‐season grasses (NPWSG) have drawn interest as bioenergy feedstocks due to their high productivity with minimal amounts of inputs under a wide range of environments. Nitrogen fertility and harvest timing are critical management practices when optimizing biomass yield of NPWSG. Our objective was to quantify the impact of N fertilizer rate and timing in combination with harvest timing and frequency on NPWSG yield. Research was conducted in 2014 and 2015 on four field‐plot locations in Missouri. The experiment was a split‐plot design with three replications where N rate and harvest timing were the main and sub‐plot treatments, respectively. Nitrogen rates were 0, 34, 67, and 101 kg N ha−1 with two application timings, all early spring and split N (early spring and following first harvest). Harvest timing included two single (September and November) and two double harvests (June followed by September or November) per year. Delaying harvest until November increased yield across sites. November harvest and N rates ≥67 kg ha−1 improved NPWSG biomass yields. Although N fertilization improved yield, partial factor productivity (PFP) of applied N did not increase with annual N rates >34 kg ha−1. Fertilization at 67 kg ha−1 yr−1 provides an opportunity to maintain a balance between yield and N efficiency. These results demonstrated that N fertilization and harvest management of NPWSG were not always independent, and therefore these practices should be simultaneously considered. For example, early‐season harvesting suppressed response to N when the second harvest was not delayed until after frost.

Performance of Panicum virgatum Cultivars in Competition With Bromus inermis and Differing Amounts of N Fertilizer

“…The data collected in this study suggests that that managing competitor species during the establishment period is of the utmost importance to the producer, as nitrogen fertilizer applied once the stand is mature enough to benefit from it is likely to aid and propagate any remaining competitor species like smooth brome. Contrarily, a legume species, when grown in concert with a well-established stand of switchgrass, has been shown to increase switchgrass biomass, as it is able to access nitrogen fixed by the legume species (7). Replicating this experiment in a multi-year random block design study would prove beneficial for gauging the effects of competition and nitrogen fertilizer application at all times in the life cycle of switchgrass produced for cellulosic ethanol, rather than just the establishment period.…”

Effect of Nitrogen Fertilization on N2o Emission in Different Soil Reactions and Grown Grass Species

“…The main threats due to greenhouse gases relate to organic soil, however more and more studies address the issue in relation to mineral Numerous management techniques are introduced for the purpose of limiting N 2 O emission, among others: split application of fertilizer (Weerasekara et al, 2018), introducing legumes to sward (Fuchs et al, 2018), injecting fresh slurry to a specific depth (Webb et al, 2010), control of soil density (Langevin et al, 2015), and the use of nitrification inhibitors (Dai et al, 2013;Duan et al, 2017). Imer et al (2013) report that N 2 O emission is shaped by the type of climatic zone, type of soil and its pH as well as the source of nitrogen supply to soil.…”