Seasonal dynamics of soil CO₂ efflux in a conventional tilled wheat field of the Loess Plateau, China

Abstract

An automated chamber system was employed to measure the soil CO 2 efflux (SCE) in situ for 2 years in a conventional wheat field of the Loess Plateau, China under semi-arid conditions. The annual mean SCE values were 2.44 ± 2.52 lmol m À2 s À1 in 2006 and 2.37 ± 2.33 lmol m À2 s À1 in 2007. Distinct seasonality in the SCE was observed, with significant differences occurring among four periods divided by harvesting, tillage and sowing. In the period from tillage to sowing, the mean SCE values were 2.82 and 2.69 times the annual mean values in 2006 and 2007, respectively, and SCE accounted for 39% and 48% of the annual total within 14% and 18% of the days of the years. Although there were significant exponential correlations between the SCE and soil temperature, and significant linear correlations between the SCE and soil moisture for measurements conducted in the periods before tillage and after sowing each year, the SCE from tillage to sowing was significantly beyond the correlation curves. These findings indicated that seasonal variation in the SCE in a conventional field was controlled not only by soil temperature and moisture, but also by tillage practice. The confounding effects of climate and practice on SCE should be considered when developing ways to mitigate soil carbon loss in conventional cropland in semi-arid regions.

Soil respiration after tillage under different fertiliser treatments – implications for modelling and balancing

“…For instance, the investigations by Kessavalou et al (1998),Al-Kaisi andYin (2005), Quincke et al (2007) and Morell et al (2010) revealed effluxes and post/pre-tillage ratios in accordance with our results. However, higher effluxes and ratios were observed in other studies (Zhang et al, 2011b;Cid et al, 2013), although the mean climatic properties were comparable to (2)) and experimental data for three selected periods of all treatments. Day 36 is assumed to present the bare soil in undisturbed condition.…”

“…In contrast, in the BR treatment a good model fit was attained already from the period "day 13, 15, 27". As the air temperature differed only slightly around a mean of 16.5 C (SD of 1.1) from day 4 till day 14, the transient and exceptionally good model fit for the period "day 4, 5, 7" indicates a high sensitivity of the disturbed soil to changing environmental parameters (e.g., soil moisture), rather than to temperature (Zhang et al, 2011b). The quality parameters of the treatment MFBR generally ranged between those of the other two treatments, but were insufficient until day 36, similar as in the MF treatment.…”

Soil Carbon Dioxide Respiration in Switch Grass Fields: Assessing Annual, Seasonal and Daily Flux Patterns

“…This equates to a loss of 20.14 Mg C ha-1 y-1. The total annual soil CO2 flux measured here for switchgrass is significantly greater than estimations of annual soil CO2 efflux reported for other perennial grasses (Zhang et al 2011;Maljanen et al 2001). Comparative to other crop grasses, annual loss of CO2-C flux for switchgrass is five times greater than has been observed for barley, 4.0 Mg C ha-1 y-1 and more than two times greater than reports for crops such as wheatgrass, 8.65 Mg C ha-1 y-1 (Zhang et al 2011).…”

“…The total annual soil CO2 flux measured here for switchgrass is significantly greater than estimations of annual soil CO2 efflux reported for other perennial grasses (Zhang et al 2011;Maljanen et al 2001). Comparative to other crop grasses, annual loss of CO2-C flux for switchgrass is five times greater than has been observed for barley, 4.0 Mg C ha-1 y-1 and more than two times greater than reports for crops such as wheatgrass, 8.65 Mg C ha-1 y-1 (Zhang et al 2011). In some instances, however, annual soil flux under annual and perennial crop grasses have been shown to range between 14.8 MgCO2-C ha-1 y-1 and 20.3 MgCO2-C ha-1 y-1 during the growing season alone (Sainju et al 2010).…”

Tillage, Mulch and N Fertilizer Affect Emissions of CO2 under the Rain Fed Condition

“…According to these findings [39], instead of microbial activity, the basic reason for higher CO 2 emissions immediately after the tillage was actually the release of entrapped CO 2 from the soil pores as a result of physical operations. The other reasons for these higher emissions might be that (1) tillage operations break soil aggregates and expose their organic matter to microbial attack [44], [45]; (2) tillage operations encourage the mineralization of soil organic matter by incorporating crops residues into the soil [46]; and (3) tillage operations enhance soil aeration [43]. In our study, the tillage methods had significant effects on the CO 2 emissions and, overall, the rotary tillage and mold board plow tillage methods led to higher CO 2 emissions compared to the chisel plow and zero tillage planting methods (Fig.…”