Silphium integrifolium seed and biomass responses to plant density and N fertilization

Authors: SCHIFFNER, SYDNEY - The Land Institute; Hulke, Brent; JUNGERS, JACOB - University Of Minnesota; SMITH, KEVIN - University Of Minnesota; VAN TASSEL, DAVID - The Land Institute; SCHEAFFER, CRAIG - University Of Minnesota

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2020
Publication Date: 11/26/2020
Publication URL: https://handle.nal.usda.gov/10113/7222873
Citation: Schiffner, S., Hulke, B.S., Jungers, J., Smith, K., Van Tassel, D., Scheaffer, C. 2020. Silphium integrifolium seed and biomass responses to plant density and N fertilization. Agrosystems, Geosciences & Environment. 3:1-12. https://doi.org/10.1002/agg2.20118.
DOI: https://doi.org/10.1002/agg2.20118

Interpretive Summary: Silphium, also known as silflower, is a perennial plant native to North America that is being domesticated for biomass and edible seed oils. The purpose of this study was to understand how to optimize yield of seeds, seed oils, and above-ground biomass by changing plant density and nitrogen fertilizer rate. Results indicate that increasing plant density increases biomass yields, but not necessarily oil yields and seed yields. When grown on sandy soils, increasing nitrogen fertilizer increased seed yield, oil yield, and biomass yield in the first year after establishment, but no effects of fertility were seen after the first year. The results suggest that plants compensate greatly for changes in plant density and may be scavenging nitrogen from the soil in addition to using applied nitrogen, which is generally in keeping with trends that occur in the related crop, sunflower.

Technical Abstract: Silphium integrifolium Michx. (rosinweed; silflower) is a native perennial oilseed crop that can provide ecosystem services but its seed, oil, and biomass yield potential are unknown. The objectives were to determine the effects of planting density and N fertilizer rate on silflower seed and oil yields, biomass production and seed yield components for three years after establishment. Experiments with a selected silflower population evaluated the effect of five planting densities on silt loam and sandy soils, and five N rates and two planting densities on a sandy loam. Averaged over all years and silt loam and sandy soils, a planting density increase from 1181 to 53792 plants ha-1 linearly increased biomass yield, but decreased seed heads per plant and seeds per plant. Planting density had no effect on seed (SY) or oil yield (OY), other seed related variables, or harvest index. On a sandy soil, seed yield, oil yield, and biomass yield increased linearly with N rates from 0 to 179 kg ha in the year after seeding, but were not affected by N fertilization rates in subsequent years. At the 179 kg ha-1 N rate, seed, oil, and biomass yields were 1651, 381 kg ha-1 10.5 Mg ha-1, respectively, in the year following seeding but declined thereafter. Over both experiments SY and OY per hectare were closely related (r= 0.99) and together were associated (r>0.60) with seed heads per plant, seeds per head, and seeds per plant. Biomass yield was only moderately associated with SY, OY and tillers per ha. Relative to annual oilseed crops, seed and oil yields for this new perennial species are low. Germplasm improvement for seed and oil yield per se and breeding and management research to reduce yield decline with plant age will be critical to develop this new perennial oilseed cropping system.