Switchgrass growth and pine–switchgrass interactions in established intercropping systems

Abstract

Intercropping switchgrass (Panicum virgatum L.) with loblolly pine (Pinus taeda L.) has been proposed for producing bioenergy feedstock in the southeastern United States. This study investigated switchgrass growth and pine-switchgrass interactions at two established experimental fields (7-year-old Lenoir site and 5-year-old Carteret site) located on the coastal plain of eastern United States. Position effects (edge and center of switchgrass alley in intercropping plots) and treatment effects (intercropping vs. grass-only) on aboveground switchgrass growth were evaluated. Interspecific interactions with respect to capturing resources (light, soil water, and nitrogen) were investigated by measuring photosynthetically active radiation (PAR) above grass canopy, soil moisture, and soil mineral nitrogen contents. Switchgrass growth was significantly (P = 0.001) affected by treatments in Lenoir and by position (P < 0.0001) in both study sites. Relative to the center, PAR above grass canopy at edge in both sites was about 48% less during the growing season. Soil water content during the growing season at the edge of grass alley was significantly (P = 0.0001) lower by 23% than at the center in Lenoir, while no significant (P = 0.42) difference was observed in Carteret, in spite of more grass growth at center at both sites. Soil mineral nitrogen content at the center of intercropping plots in Lenoir (no fertilization during 2015) was significantly (P < 0.07) lower than at the edge during the peak of growing season (June, July, and August), but not during early and late parts of growing season (May, September, and November). Position effects on soil water and mineral nitrogen were less evident under conditions with higher external inputs (rainfall and fertilization) and lower plant uptake during nongrowing seasons. Results from this study contributed to a better understanding of above-and belowground pine-switchgrass interactions which is necessary to properly manage this new cultivation system for bioenergy production in the southeastern United States.

Microtopography‐induced transient waterlogging affects switchgrass (Alamo) growth in the lower coastal plain of North Carolina, USA

“…2d). The study site was initiated to investigate sustainability and productivity of loblolly pine and switchgrass intercropping to produce sawtimber and bioenergy feedstocks (Albaugh et al, 2012;Tian et al, 2015Tian et al, , 2017. Multiple experimental treatments including switchgrass and pine monocultures, and pine-switchgrass intercropping were established in a randomized complete block design (Albaugh et al, 2012).…”

“…The switchgrass received coated urea Arborite â fertilizer (65.6 kg N ha À1 , 6.6 kg P ha À1 , and 0.2 kg boron ha À1 ) during 2010, 2012, and 2014, but not during 2015 and 2016). Detailed descriptions of the study site, experimental design, and treatments can be found elsewhere (Albaugh et al, 2012(Albaugh et al, , 2014Tian et al, 2015Tian et al, , 2017.…”

“…The air temperature and humidity within the cuvettes were kept at ambient conditions (i.e., within 30-38°C and 40-60%, respectively), CO 2 concentration was set to 400 lmol mol À1 , and photosynthetically active radiation (PAR) to 1500 lmol m À2 s À1 , that is, close to light saturated level (Tian et al, 2017). We conducted field measurements biweekly during most of the experiment period and weekly after heavy storm events with a total of 11 field campaigns of gas exchange measurements during the 2015 growing season.…”

Intercropping with Switchgrass Improves Net Greenhouse Gas Balance in Hybrid Poplar Plantations on a Sand Soil

“…A potential solution to offset this concern is to grow dedicated energy crops on marginal lands (Kang et al, 2013;Gelfand et al, 2013) or maximize land use by intercropping or alley cropping with other perennial crops (Blasier et al, 2012;Cacho et al, 2015;Tian et al, 2016). Intercropping is the growing of two or more crops of different species or varieties in close proximity to maximize the capture of photosynthetically active radiation and enhance the yield of both species compared with their growth in monoculture.…”

“…Several studies have shown the benefits of intercropping woody species and switchgrass on yield and soil properties (Blasier et al, 2012;Gamble et al, 2014;Cacho et al, 2015;Muwamba et al, 2015;Tian et al, 2016). These benefits result from a diversification of outputs and a shortened time to reach economic production (Holzmueller and Jose, 2012;Susaeta et al, 2012).…”