Balancing energy, conservation, and soil health requirements for plant biomass

The global importance of plant biomass for mitigating water and wind erosion, sustaining soil organic carbon (SOC), and providing animal feed and bedding is well recognized, but those needs are no longer the only factors influencing crop residue management decisions. As fossil energy sources diminish, the need for cellulosic derived liquid fuels is going to increase. Supplying bio-based fuels while simultaneously meeting food, feed, and fiber demands of more than nine billion people will require tremendous grain and biomass yield increases, as well as innovative crop residue management strategies for efficient agricultural operations. Our goal is to examine the challenges farmers, conservationists, and land managers face as they strive to manage crop residues without degrading soil health. Harvesting a portion of our nation’s crop residues, such as corn (Zea mays L.) stover, to simultaneously provide liquid fuels and enhance agricultural operations will occur, provided it is done in a manner that sustains critical ecosystem and soil health services within the landscape. Harvest rates must be site-specific at subfield scales (Bonner et al. 2014a, 2014b) to ensure a sufficient amount of plant biomass remains at every harvest location to protect the soil surface from wind and water erosion and to sustain SOC throughout the profile. Protecting these soil health and ecosystem services before harvesting crop residue for any use is essential because SOC influences numerous chemical processes, including nutrient cycling, retention, and release to plants; physical properties, such as aggregate stability, surface crusting, water infiltration, and retention (Johnson et al. 2010; Wilhelm et al. 2007, 2010); and biological properties and processes, such as fungal:bacterial ratios (Lehman et al. 2014), soil enzyme levels (Stott et al. 2010), and resiliency (Lehman et al. 2015).