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: 3/10/2011
Publication Date: 3/22/2011
Citation: Kovar, J.L., Karlen, D.L. 2011. Fluid fertilizer's role in sustaining soils used for bio-energy feedstock production. In: Leikam, D.F. (ed). Fluid Fertilizer Foundation Symposium Proceedings. Fluid Fertilizer Forum, Feb. 20-22, 2011, Scottsdale, AZ. Volume 28. Available: http://www.fluidfertilizer.com/fertilizer_forum_proceedings2011.html.

Interpretive Summary: Growing crops for bio-energy 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 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 that nitrogen (N) fertilizer applications were less than needed to carry the corn crop through the growing season. Plant populations, tillage intensity, application of biochar, and use of cover crops 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 2010 grain yields. In a separate laboratory study, 20-day-old plants grown in soil with only 100 lb. P2O5/A produced more dry matter than those grown in soil amended with biochar. 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 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 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, the short- and long-term effects of both increasing grain yields and removing stover on soil nutrient cycling, physical properties, and biological activity must be understood to ensure that soil productivity and ecosystem services are maintained. Our objectives for 2010 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. Analysis of whole plants at V6 and ear leaves at mid-silk indicated that management scenario, tillage, and the amount of stover removed from the field with the 2009 harvest did not affect uptake of most nutrients. Nitrogen concentrations in ear-leaf tissue, however, were below the critical value for all treatments. 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. We suspect that this is a short-term effect. The wet growing conditions in central Iowa during June and early July may have caused significant nitrate leaching and denitrification, thus limiting N availability and decreasing yields of all treatments. If wet weather patterns continue, mid-season N applications may become necessary. In a separate controlled-climate chamber study, 20-day-old 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 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. Continued generation of plant growth and nutrient uptake data should provide a clearer picture of the value of the biochar, any biochar-fertilizer interactions, and whether legacy or fresh biochar affects the nutrition of juvenile corn in different ways.