Fluid Fertilizer's Role in Sustaining Soils Used for Bio-fuels Production

Authors: Kovar, John; Karlen, Douglas

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/14/2010
Publication Date: 2/14/2010
Citation: Kovar, J.L., Karlen, D.L. 2010. Fluid Fertilizer's Role in Sustaining Soils Used for Bio-fuels Production. In: Fluid Fertilizer Foundation Symposium Proceedings. Fluid Fertilizer Forum, Feb. 14-16, 2010, Scottsdale, AZ. 2010 CD-ROM, Volume 27.

Interpretive Summary: Growing crops for bio-fuel feedstock production has attracted the attention of many producers – especially in the Corn Belt states. Both corn grain and stover are being evaluated as potential bio-fuel 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. With a field study, we evaluated the performance of several sulfur (S) fertilizers as S sources for corn grown for bio-fuels in Iowa. After four years, we found that an application of 30 lb S/A increased early-season growth and plant S concentrations compared with untreated areas. We also found that S fertilizer increased grain yield by up to 12 bu./A. In addition, significant soil variability at the research sites probably limited crop response to S. For several reasons including erosion of high-fertility hill slope soils, fewer S impurities in fertilizers, and decreased atmospheric deposition of S throughout the upper Midwest, our results suggest that S may quickly become a limiting nutrient for corn grown to supply bio-fuel feedstocks. In a separate field study, using a variety of management systems including both standard fertilizer management and a high-population treatment with increased nutrient additions, we found that nitrogen (N) and S fertilizer applications were less than needed to carry the corn crop through the growing season. Therefore, crop management did not affect corn grain yields, but plots from which corn stover was not removed during the previous growing season always yielded less than plots from which ~50% or ~90% of the stover was removed. A combination of less fertilizer N and greater tie up in the soil where residues remained probably decreased the 2009 grain yields.The results of this research will benefit both commercial growers and both the fertilizer and ethanol industries by providing nutrient management guidelines that maximize crop utilization and biomass yields.

Technical Abstract: The short- and long-term effects on soil nutrient cycling, physical properties, and biological activity of striving for higher grain yields and removing crop residues for bio-fuels production must be understood to provide more quantitative crop and soil management guidelines. This study focuses primarily on potassium (K) and sulfur (S) response by corn (Zea mays L.) grown for bio-energy feedstock production. Our objectives for 2009 were to evaluate (i) the performance of several S fertilizers, including liquid ammonium thiosulfate (12-0-0-26S), for corn grown in Iowa, and (ii) the use of surface or subsurface bands of N-P-K-S fluid fertilizers to optimize positional and temporal availability of nutrients. The S fertility trials targeted low organic matter Clarion soils found on eroded hill slopes. Application of 30 lb S/A increased mean plant dry weight, but did not increase whole-plant concentrations of S, which were adequate for corn at the five-leaf growth stage (V5). By mid-silk, however, S concentrations were below the sufficiency range, even when S fertilizer had been applied. Application of 30 lb S/A as 13-33-0-15S or 21-0-0-24S significantly increased grain yield more than 7 bu/A, compared to the control. Stover yields were not increased by applying S. In a separate 25-acre field study, also on the Clarion-Nicollet-Webster soil association, corn was grown using a variety of management systems including 30-in. row spacing with standard fertility management and a twin-row, high-population treatment with increased nutrient additions applied in split-applications. Analysis of V6 whole-plant and ear-leaf samples indicated that management scenario, tillage, and the amount of stover removed from the field with the 2008 harvest did not affect nutrient content. However, both N and S concentrations in ear-leaf tissue were below the critical value for all treatments. These results suggest that the soil supply of N and S was not sufficient to meet crop demand. Management scenario and tillage and did not affect corn grain yields, but plots from which corn stover was not removed always yielded less than plots from which ~50% (harvested just below the ear shank) or ~90% (harvested at a stubble height of approximately 4 inches) of the stover was removed. A combination of less fertilizer N, greater immobilization, and less mineralization where residues remained probably decreased the 2009 grain yields. Unlike 2008, the intensively managed (twin row) plots did not produce more dry stover than the standard management (control) plots. The cool, cloudy conditions in central Iowa during the growing season likely limited the performance of the twin-row treatments. Residue samples collected at harvest are currently being processed to determine nutrient composition, so that the quantity of nutrients removed can be calculated.