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Title: A comparison of corn residue and its biochar on soil C and plant growth

Author
item Calderon, Francisco
item Benjamin, Joseph
item Vigil, Merle

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 4/2/2015
Publication URL: http://handle.nal.usda.gov/10113/62025
Citation: Calderon, F.J., Benjamin, J.G., Vigil, M.F. 2015. A comparison of corn residue and its biochar on soil C and plant growth. PLoS One. doi:10.1371/journal.pone.0121006.

Interpretive Summary: In this publication, we show how incorporating corn residues compare to incorporating chars made from them in terms of soil C sequestration efficiency. The paper includes data from two separate projects: a long-term laboratory mineralization of the chars, and a growth chamber experiment to test the effect of the chars on plant growth. Infrared spectroscopy was used to evaluate the charring process, as well as to indicate changes in soil C and biochars as they decomposed.

Technical Abstract: Biochar amendment can be beneficial to soils because it contains mostly recalcitrant forms of C, and biochar contributes base cations that can remedy nutrient deficiencies on acid soils. However, the benefits of biochars on neutral or calcareous soils needs to be assessed. In order to properly determine the value of charring crop residues, the C use efficiency and effects on crop performance of biochar needs to be compared to the crop residues. In this study we compared the addition of corn stalks to soil, with equivalent additions of charred (300 °C and 500 °C ) corn residues. Two experiments were conducted: a long term laboratory mineralization, and a growth chamber trial with proso millet plants. In the laboratory, we measured soil mineral N dynamics, C use efficiency, and soil organic matter (SOM) chemical changes via infrared spectroscopy. The 300 °C biochar decreased plant biomass relative to a nothing added control. The 500°C biochar had little to no effect on plant biomass. With incubation we measured less lower soil NO3 content in the corn stalk treatment than in the biochar-amended soils, suggesting that the millet growth reduction in the stalk treatment was mainly driven by N limitation, whereas other factors contributed to the biomass yield reductions in the biochar treatments. Corn stalks had a C sequestration use efficiency of up to 0.26, but charring enhanced C sequestration to values that ranged from 0.64 to 1.0. Infrared spectroscopy of the soils as they mineralized showed that absorbance at 3400, 2925-2850, 1737 cm-1, and 1656 cm-1 decreased during the incubation and can be regarded as labile SOM, corn residue, or biochar bands. Absorbances near 1600, 1500-1420, and 1345 cm-1 represented the more refractory SOM moieties.