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Soil carbon sequestration in agricultural lands has been deemed a sustainable option to mitigate rising atmospheric CO2 levels. In this context, the effects of different tillage and C input management (residue management and manure application) practices on crop yields, residue C and annual changes in total soil organic C (SOC) (0–30 cm depth) were investigated over one cycle of a 4-year crop rotation (2003–2006) on a cropped Andisol in northern Japan. For tillage practices, the effects of reduced tillage (no deep plowing, a single shallow harrowing for seedbed preparation [RT]) and conventional deep moldboard plow tillage (CT) were compared. The combination of RT, residue return and manure application (20 Mg ha−1 in each year) increased spring wheat and potato yields significantly; however, soybean and sugar beet yields were not influenced by tillage practices. For all crops studied, manure application enhanced the production of above-ground residue C. Thus, manure application served not only as a direct input of C to the soil, but the greater crop biomass production engendered enhanced subsequent C inputs to the soil from residues. The SOC contents in both the 0–5 cm and 5–10 cm layers of the soil profile were greater under RT than under CT treatments because the crop residue and manure were densely incorporated into the shallow soil layers. Comparatively, neither tillage nor C input management practices had significant effects on annual changes in SOC content in either the 10–20 cm or 20–30 cm layers of the soil profile. When soil C sequestration rates, as represented by annual changes in total SOC (0–30 cm), were assessed on a total soil mass basis, ananova showed that tillage practices had no significant effect on total C sequestration, but C input management practices had significant positive effects ( P ≤ 0.05). These results indicate that continuous C input to the soil through crop residue return and manure application is a crucial practice for enhancing crop yields and soil C sequestration in the Andisol region of northern Japan. [ABSTRACT FROM AUTHOR]

In the context of sustainable and less energy-dependent agricultural biomass production, an energy balance was developed for a conventional rotation of winter wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L. subsp. vulgaris), adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and potato (Solanum tuberosum L.) under the highly fuel-dependent and material-intensive farming systems in the Tokachi region of Hokkaido, northern Japan. As annual energy inputs, tractor operations, truck transportations and grain drying for adzuki bean and winter wheat consumed the equivalent of 6.09 and 11.50GJha−1 year−1 in fossil fuels, respectively. Input–output table estimates of the energy consumption resulting from the use of materials necessary to agricultural production (chemical fertilizers, biocides and agricultural machines) ranged between 11.01±0.26GJha−1 year−1 for winter wheat and 24.38±0.35GJha−1 year−1 for sugar beet. Thus, total annual energy inputs for fuel and materials consumed in cultivation and transportation steps amounted to 22.51±0.26, 32.97±0.35, 20.71±1.58 and 24.44±0.41GJha−1 year−1 for winter wheat, sugar beet, adzuki bean and potato production, respectively. Chemical fertilizer consumption contributed significantly to the energy use, representing 25–43% of the total energy inputs. Based on regional crop production statistics (1999–2003), total energy outputs as yield and crop residue biomass were estimated at 151.3±18.1, 346.1±17.9, 42.0±18.1 and 163.8±11.6GJha−1 year−1 for winter wheat, sugar beet, adzuki bean and potato production, respectively, resulting in regional conventional cropping energy output/input ratios of 6.72, 10.50, 2.03 and 6.70. Sugar beet is the most promising biomass-derived energy feedstock crop in this region, due to its high energy output/input ratio and net energy gain (energy output–input). However, for the full sugar beet-based bioethanol production system, a much lower energy output/input ratio and net energy gain were expected, given the greater energy inputs required in the transformation process. In addition to altering agronomic practices, transformation technologies less dependent on fossil fuels are crucial to developing sustainable bioethanol production systems in northern Japan. [Copyright &y& Elsevier]

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO2, N2O and CH4) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO2 emissions from on-farm and off-farm fossil fuel consumption, soil CO2 emissions induced by the decomposition of soil organic matter, direct and indirect N2O emissions from arable lands and CH4 uptake by soils, which were then aggregated in CO2-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO2 emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO2 ha−1 year−1 for adzuki bean to 0.826 Mg CO2 ha−1 year−1 for winter wheat. Off-farm CO2 emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO2 ha−1 year−1 for winter wheat to 1.724 Mg CO2 ha−1 year−1 for sugar beet. Direct N2O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO2-equivalents, ranged from 0.041 Mg CO2 ha−1 year−1 for potato to 0.382 Mg CO2 ha−1 year−1 for cabbage. Indirect N2O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO2 ha−1 year−1 for adzuki bean to 0.381 Mg CO2 ha−1 year−1 for cabbage. The rates of CH4 removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO2 ha−1 year−1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO2 emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO2 ha−1 year−1, respectively. In total, CO2-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO2 ha−1 year−1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO2 emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing. [ABSTRACT FROM AUTHOR]