Restoring Soil Fertility on Degraded Lands to Meet Food, Fuel, and Climate Security Needs via Perennialization

A continuously growing pressure to increase food, fiber, and fuel production to meet worldwide demand and achieve zero hunger has put severe pressure on soil resources. Abandoned, degraded, and marginal lands with significant agricultural constraints—many still used for agricultural production—result from inappropriately intensive management, insufficient attention to soil conservation, and climate change. Continued use for agricultural production will often require ever more external inputs such as fertilizers and herbicides, further exacerbating soil degradation and impeding nutrient recycling and retention. Growing evidence suggests that degraded lands have a large potential for restoration, perhaps most effectively via perennial cropping systems that can simultaneously provide additional ecosystem services. Here we synthesize the advantages of and potentials for using perennial vegetation to restore soil fertility on degraded croplands, by summarizing the principal mechanisms underpinning soil carbon stabilization and nitrogen and phosphorus availability and retention. We illustrate restoration potentials with example systems that deliver climate mitigation (cellulosic bioenergy), animal production (intensive rotational grazing), and biodiversity conservation (natural ecological succession). Perennialization has substantial promise for restoring fertility to degraded croplands, helping to meet future food security needs.

Quantifying the peak yields of four cellulosic bioenergy crops in the East-Central Poland.

Through the six successive years (2010–2015), from the 5th to the 10th year of cultivation, research was carried out on yielding and species characteristics of 4 perennial vegetatively propagated energy crops. These were: 2 species of Miscanthus, Sida hermaphrodita, and 2 Salix viminalis clones (1047 and 1054), cultivated side-by-side. The height and shoot number, yield and biomass moisture were evaluated. The highest shoot density of Miscanthus sacchariflorus was found, while the largest yield of Miscanthus × giganteus. Salix viminalis and Miscanthus × giganteus biomass was characterized by the highest content of accumulated moisture (on average 50%). The Sida hermaphrodita plants were appeared as the tallest ones on the six-year average. It is worth mentioning, we have concluded that yield of Miscanthus, and Sida is high and stable in the long-term study. However, in the average yields of these 2 species (Miscanthus × giganteus and Sida hermaphrodita) no statistically significant differences were found. Results can strengthen the improved species diversity in perennial energy crops cultivation.

Cellulosic biofuel contributions to a sustainable energy future: Choices and outcomes

Cellulosic crops are projected to provide a large fraction of transportation energy needs by mid-century. However, the anticipated land requirements are substantial, which creates a potential for environmental harm if trade-offs are not sufficiently well understood to create appropriately prescriptive policy. Recent empirical findings show that cellulosic bioenergy concerns related to climate mitigation, biodiversity, reactive nitrogen loss, and crop water use can be addressed with appropriate crop, placement, and management choices. In particular, growing native perennial species on marginal lands not currently farmed provides substantial potential for climate mitigation and other benefits.

Effects of Giant Foxtail (Setaria faberi) and Yellow Foxtail (Setaria pumila) Competition on Establishment and Productivity of Switchgrass

Switchgrass is a potential feedstock for cellulosic bioenergy production. Weed competition from annual grass during the establishment year can reduce switchgrass establishment and resulting productivity, but the relationship between early season grass densities and outcomes of competition are not well understood. We measured how a range of giant and yellow foxtail densities in the establishment year influenced switchgrass establishment and resulting productivity in the first production year (second year of the growing season). In two of the three site–yr more than four foxtail plants m−2reduced switchgrass plant densities below documented thresholds of establishment success. A lesser effect of foxtails in the third site–year suggested that higher switchgrass emergence rates reduced foxtail competitive ability during establishment. Effects on yield were consistent over the three site–yr. The yield (10.96 Mg ha−1± 0.77) decreased rapidly as foxtail density increased. One foxtail plant m−2reduced switchgrass yield in the first production year by 25%, and yield loss was 90% or greater at densities > 50 foxtail plants m−2. Although switchgrass can establish in the presence of foxtail competition, these weed species should be controlled to maximize yields in the first production year.