Abstract
While the literature is clear about excessive tillage decreasing soil carbon (C) content, there are few experimental studies that document the comparative effects of soil and crop management on C sequestration. Using micrometeorology we measured CO2 flux from a maize crop grown on both no-till and tilled soils in north-central Ohio. We used Bowen Ratio Energy Balance (BREB) systems to quantify the flux between the atmosphere and either the soil surface (at crop planting) or 0.2 m above the canopy once the crop was established and growing. The no-till plot sequestered 263 g CO2 m-2 (90% confidence interval -432.1 to -99.9) while the tilled plot emitted 146 g CO2 m-2 (90% confidence interval -53.3 to 332.2) during 104 days of the 2015 growing season; a net difference of 410 g CO2 m-2. The difference is statistically significant at the 90% confidence level (based on a bootstrap analysis). The results indicate that no-tillage practices can sequester C, maintain soil productivity, and ensure landscape sustainability.
Highlights
The principal sinks for removing CO2 from the atmosphere are usually assumed to be oceans and forests; oceans will absorb less CO2 as they warm (Morrison et al, 2015) and forest area is shrinking due to agriculture and other land use changes (FAO, 2016)
For five days following tillage on DOY 126 the average daytime CO2 flux for till and no-till were similar in magnitude at 0.61 +/- 0.03 and 0.40 +/- 0.02 g CO2 m-2 hr-1 respectively
Greater emission of CO2 is expected following intensive tillage due to aerobic and anaerobic decomposition of exposed organic matter that was occluded in aggregates and unavailable to degradation prior to tillage (Elliott & Coleman, 1988; Beare et al, 1994; Six et al, 2000)
Summary
The principal sinks for removing CO2 from the atmosphere are usually assumed to be oceans and forests; oceans will absorb less CO2 as they warm (Morrison et al, 2015) and forest area is shrinking due to agriculture and other land use changes (FAO, 2016). Jenny’s (1941) classic work provides the basis for the collective understanding of the processes by which soils emit and sequester C through soil-climate-vegetation interactions. These processes depend on many factors including soil type, climate, crop, and agricultural management practices. Studies suggest that tillage can influence plant physiology including increased rooting depth from decreased moisture in surface layers of tilled soil (Dwyer et al, 1996) or decreased mechanical resistance (Cox et al, 1990). Other studies indicate that tillage effects on plant physiology may interact with climate as Yu et al (2016) found that no-till likely increased yield during drought periods by conserving soil moisture.
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