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Title: Fluid Fertilizer’s Role in Sustaining Soils Used for Bio-fuel Feedstock Production

item Kovar, John
item Karlen, Douglas

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/17/2009
Publication Date: 2/17/2009
Citation: Kovar, J.L., Karlen, D.L. 2009. Fluid Fertilizer’s Role in Sustaining Soils Used for Bio-fuel Feedstock Production. In: Fluid Fertilizer Foundation Symposium Proceedings. Fluid Fertilizer Forum, Feb. 15-17, 2009, Scottsdale, AZ 2009 CDROM.

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 three 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, below-normal rainfall during part of each growing season and significant soil variability at both 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. The results of this research will benefit 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 on potassium (K) and sulfur (S) requirements of corn (Zea mays L.) grown for bio-energy feedstock production. Our objectives for 2008 were to: i) evaluate the performance of several S fertilizers, including liquid ammonium thiosulfate (12-0-0-26S), as S sources for corn grown in Iowa, and ii) establish a comprehensive tillage, nutrient management, crop residue removal, and cover crop study. As in 2006 and 2007, S fertility trials targeted low organic matter soils found on eroded hill slopes. On a Clarion loam in 2008, application of 30 lb S/A increased mean plant dry weight and whole-plant S concentrations at the V5 growth stage. By mid-silk, however, S concentrations were below the sufficiency range, even when S fertilizer had been applied. In 2008, application of 30 lb S/A as 13-33-0-15S significantly (p<0.05) increased grain yield by more than 12 bu/A, compared with the control. Stover yield increased 1.2 tons/A after application of 30 lb S/A as 12-0-0-26S. Based on current pricing, the replacement cost of S removed with the grain and stover is still relatively low. A 25-acre field study was also initiated at the ISU Agronomy & Agricultural/Biosystems Engineering Research Center. Continuous corn will be grown using a variety of soil and crop management systems including a 30"-row spacing, standard fertility management treatment and a twin-row, high-population treatment with increased nutrient addition in split-applications. Analysis of V6 whole plant and ear-leaf samples indicated nitrogen (N) levels for both systems were lower than desired at both growth stages, S was approaching the lower level at V6, and K concentrations at anthesis were approaching the lower level – presumably because Ca levels were above the high rating (0.4%). Grain yield for the 30" and twin-row planting configurations averaged 171 and 183 bu/A, respectively. Corn stover was harvested at two heights (just below the ear shank and at a stubble height of approximately 4 inches). The amount of dry stover collected averaged 2.5, 2.9, 2.8, and 3.1 tons/A for the high and low cuts of the two configurations, respectively. Residue samples collected at harvest are currently being processed to determine dry matter production and nutrient composition, so that the amount of residue returned to the soil and the amounts of nutrients removed can be calculated.