Char-amended farm soils – effects on soil chemistry and wheat growth

Authors: Griffith, Stephen; Banowetz, Gary; GADY, DAVID - Farm Power Inc

Submitted to: Seed Production Research at Oregon State University
Publication Type: Experiment Station
Publication Acceptance Date: 12/31/2013
Publication Date: 4/30/2013
Citation: Griffith, S.M., Banowetz, G.M., Gady, D. 2013. Char-amended farm soils – effects on soil chemistry and wheat growth. 2012 Seed Production Research at Oregon State University.(143)p.38-40.

Interpretive Summary: On-farm gasification of agricultural residues, the non-food byproducts from crop harvests, could provide a means to generate value-added income from the production of fuel or electrical generation. Char produced during the process also has potential value as a soil amendment to improve several soil quality factors or even serve as a wastewater pollutant sorbent. The Kentucky bluegrass seed screenings (KBss) char under study here was produced in a farm-scale gasifier where the biomass was converted to a syngas containing methane, carbon monoxide, and hydrogen and used to partially fuel a diesel generator that produced electricity. Wood char was also used in the study and was produced under gasification conditions. The objective of the study was to test the hypothesis that acid farm soils can be mitigated using high temperature-produced KBss and wood chars to reduce plant Al uptake and toxicity by effectively raising soil pH to more optimal levels for plant nutrient acquisition and growth of wheat grown under greenhouse conditions. The two cultivated acid farm soils (Freeman and Bernhill soil), used in this greenhouse experiment were obtained near Rockford, WA, from two different fields. Research findings showed that soil-amended with char improved soil pH of low acid soils that in turn reduced aluminum toxicity. The added char also improved plant nutrient uptake that resulted in considerably more wheat growth than plants grown in acid farm soil without amended char. In summary, this study demonstrated benefits to wheat growth when planted in wood or KBss char amended acid soils. It is likely that char amended soils would alleviate crop Al toxicity issues when farm soils become acidic. Overall, improved plant nutrient acquisition was observed in plants grown in char-amended soils.

Technical Abstract: On-farm gasification of agricultural residues, the non-food byproducts from crop harvests, could provide a means to generate value-added income from the production of fuel or electrical generation. Char produced during the process also has potential value as a soil amendment to adjust acid soil pH (and minimize aluminum toxicity) and improve water relations, or even as a wastewater pollutant sorbent. The Kentucky bluegrass seed screenings (KBss) char under study here was produced in a farm-scale gasifier where the biomass was converted to a syngas containing methane, carbon monoxide, and hydrogen and used to partially fuel a diesel generator that produced electricity. The wood char was also produced under gasification conditions. The objective of the study was to test the hypothesis that acid farm soils can be mitigated using high temperature-produced chars to reduce plant Al uptake and toxicity by effectively raising soil pH to more optimal levels for plant nutrient acquisition and growth. The two cultivated acid farm soils (Freeman and Bernhill soil), used in this greenhouse experiment were obtained near Rockford, WA, from two different fields. It was found that acid soils with amended KBss or wood char had higher electrical conductivity and cation exchange capacity, and soil pH increased with increasing char amounts. Wheat shoot dry mass accumulation significantly increased with increasing concentrations of wood or KBss char. At the highest concentration of KBss char (58 g kg-1) shoot dry mass increased by 1.68-fold in the Freeman soil, but root dry mass was unaffected. Amended Bernhill soil with 58 g kg-1 KBss char increased shoot dry mass 1.94-fold and root dry mass 1.46-fold. In contrast, amendment of Freeman soil with wood char at 86 g kg-1 enhanced shoot dry mass by 2.78-fold and root dry mass 2.06-fold. This same level of amendment of Bernhill soil with KBss char increased shoot and root dry mass by 2.43- and 2.79-fold, respectively. Increasing concentrations of KBss char to Freeman or Bernhill soil consistently enhanced shoot K, P, S, Zn, and Mg, and to some extent S, and significantly reduced Ca content compared to plants grown in soil alone. Wood char mixed with Freeman or Bernhill soil had consistently higher concentrations of K, P, and Mn (Bernhill soil only), and P but had lower Ca, Cu, and S concentrations. Iron concentrations were highest in roots over shoots in all treatments and root Fe concentrations were lower with increasing char concentrations. The inverse was true for Ca. Calcium shoot concentrations exceeded root Ca concentrations and Ca concentrations declined in shoot with increased char concentrations, but not in roots. Addition of char lowered Al uptake by wheat in both soils. In summary, this study demonstrated benefits to wheat growth when planted in wood or KBss char amended acid soils. It is likely that char amended soils would alleviate crop Al toxicity issues due to its effect on soil pH but also may have selective metal binding properties that would sequester Al away from plant roots.