Fluid fertilizer's role in sustaining soils used for bio-energy feedstock production

Authors: Kovar, John; Karlen, Douglas

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2013
Publication Date: 6/1/2013
Citation: Kovar, J.L., Karlen, D.L. 2013. Fluid fertilizer's role in sustaining soils used for bio-energy feedstock production. In: Leikman, D.F., editor. Fluid Fertilizer Foundation Symposium Proceedings, February 18-20, 2013, Scottsdale, Arizona. Available: http://www.fluidfertilizer.com/Forum%.20Presentations/2013/Proceedings/Kovar%202013%20Proceedings.pdf.

Interpretive Summary: Growing crops as a bio-energy feedstock has attracted the attention of many producers – especially in the Corn Belt states. Both corn grain and stover are being evaluated as potential feedstocks. Unfortunately, our understanding of the short- and long-term effects of removing both corn grain and stover on soil nutrient cycling, physical properties, and biological activity is limited. In a field study with a variety of management systems, including both standard fertilizer management and a high-population treatment with increased nutrient additions, we found adequate levels of all nutrients in the growing crop, suggesting that fertilizer applications were sufficient for the two management scenarios. Differences in plant populations and tillage intensity, application of biochar, and use of cover crops did not affect corn grain or stover yields in 2012. In a separate laboratory study, 20-day-old plants grown in soil with 100 lb. P2O5/A produced more dry matter than those grown in soil without phosphorus (P) fertilizer, but our results suggested that the ability of the plants to utilize the fertilizer P was improved by biochar application. As more data are generated with this experiment, we will have a clearer picture of the value of the biochar and any biochar-P fertilizer interactions that may affect the growth and nutrition of young corn plants. The results of this research will benefit commercial growers, as well as the fertilizer and ethanol industries by providing nutrient management guidelines that maximize crop utilization and biomass yields.

Technical Abstract: The use of corn (Zea mays L.) as a bio-energy feedstock has attracted the attention of many producers. Recently, the focus has shifted from grain-based to cellulose-based ethanol production. In addition to biological conversion of corn stover to ethanol, thermal conversion (pyrolysis) of stover is being explored. Regardless of post-harvest processing, it is important to understand the short- and long-term effects of both increasing grain yields and removing stover on soil nutrient cycling, physical properties, and biological activity, so that soil productivity and ecosystem services are maintained. Our objectives for 2012 were to evaluate: (i) the use of surface or subsurface bands of N-P-K-S fluid fertilizers to optimize positional and temporal availability of nutrients; and (ii) the effect of biochar application on P availability and cycling in Clarion-Nicollet-Webster soils. Corn was grown in a field trial under a variety of management systems including 30-inch row spacing with standard fertility management and a twin-row, high-population treatment with increased nutrient additions applied in split-applications. In 2012, whole-plant N concentrations at the V6 growth stage were below the published critical value of 3.5%, regardless of management. At mid-silk, both N and K concentrations in ear-leaf tissue were below the critical values. The hot, dry growing conditions may have limited N and K availability and uptake. In 2012, management scenario, tillage, and previous stover removal affected corn grain yield, although yields were likely influenced by the availability of water. Grain yields tended to be lower when corn stover was not removed than when ~50% or ~90% was removed. Crop rotation had the most striking effect on corn grain yields. Corn grown in rotation with soybean (Glycine max L. Merr.) yielded 174 bu/A compared with a mean grain yield of 143 bu/A for continuous corn. Biochar application and cover crop growth had no effect on grain and stover yields. Dry stover yields were higher for the 90% removal (low cut) treatments of all management scenarios. As during the three previous growing seasons, the intensively managed (twin row) plots did not produce more grain or dry stover than the conventional plots. In a separate controlled-climate chamber study, biochar and P fertilizer amendments affected soil P supply and corn seedling growth during five consecutive production and harvest cycles. Plants grown in soil with only 100 lb. P2O5/A had the highest shoot and root dry matter values, while those grown in soil amended with biochar in 2007 (legacy) without P fertilizer had the lowest values. Addition of 100 lb. P2O5/A numerically increased shoot and root dry matter values regardless of legacy or fresh biochar amendment. Although cumulative shoot dry matter production tended to be higher for treatments without biochar, the overall agronomic efficiency of the P fertilizer was improved by biochar application. Further statistical analysis of plant growth and nutrient uptake data should provide a clearer picture of any biochar-fertilizer interactions. The effect of biochar application on soil supply of nutrients is complex. Current research suggests that marginal soils will benefit most.