Nobuhisa Koga

Life cycle inventory-based analysis of greenhouse gas emissions from arable land farming systems in Hokkaido, northern Japan

Abstract 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.

Effects of reduced tillage, crop residue management and manure application practices on crop yields and soil carbon sequestration on an Andisol in northern Japan

Abstract 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, an anova 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.

Nitrous oxide emissions under a four-year crop rotation system in northern Japan: impacts of reduced tillage, composted cattle manure application and increased plant residue input

In the context of their role in global warming, nitrous oxide (N2O) emissions from agricultural soil under different management practices were studied in Hokkaido, northern Japan. To assess the impacts of reduced tillage, composted cattle manure-based fertilization and amendments with crop residues and green manure on N2O emissions from soil, a field experiment was conducted under a four-year crop rotation on a well-drained Andisol. The crop rotation included potato (Solanum tuberosum L.) or sweet corn (Zea mays L.), winter wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L. subsp. vulgaris) and soybean (Glycine max (L.) Merr.). The cumulative N2O emissions for the four-year study period differed widely (0.33 to 4.90 kg N ha−1), depending on the treatments imposed, being the greatest for a combination of conventional moldboard plow tillage, composted cattle manure-based fertilization and increased plant residue input, and the lowest for a combination of conventional tillage, chemical fertilizer-based fertilization and normal plant residue input treatments. The cumulative N2O emissions under reduced tillage were all small, irrespective of fertilization and plant residue input treatments. Composted cattle manure-based fertilization (P ≤ 0.01) and increased plant residue input (P ≤ 0.01) significantly increased cumulative N2O emissions. Tillage showed a significant interaction with fertilization and plant residue input, indicating that N2O emissions were enhanced when composted cattle manure, crop residues and green manure were incorporated by conventional tillage. In the present study, the N2O emission factors for chemical fertilizer, composted cattle manure and crop residues were 0.26 ± 0.44, 0.11 ± 0.16 and −0.03 ± 0.52%, respectively, all much lower than the country-specific emission factor for Japans well-drained soils (0.62%) and the default emission factor used in the IPCC guideline (1%).

Potential agronomic options for energy-efficient sugar beet-based bioethanol production in northern Japan

Sugar beet (Beta vulgaris L. subsp. vulgaris) is deemed to be one of the most promising bioethanol feedstock crops in northern Japan. To establish viable sugar beet‐based bioethanol production systems, energy‐efficient protocols in sugar beet cultivation are being intensively sought. On this basis, the effects of alternative agronomic practices for sugar beet production on total energy inputs (from fuels and agricultural materials during cultivation and transportation) and ethanol yields (estimated from sugar yields) were assessed in terms of (i) direct drilling, (ii) reduced tillage (no moldboard plowing), (iii) no‐fungicide application, (iv) using a high‐yielding beet genotype, (v) delayed harvesting and (vi) root+crown harvesting. Compared with the conventional sugar beet production system used in the Tokachi region of Hokkaido, northern Japan, which makes use of transplants, direct drilling and no‐fungicide application contributed to reduced energy inputs from raising seedlings and fungicides, respectively, but sugar (or ethanol) yields were also reduced by these practices, to a greater equivalent extent than the reductions in energy inputs. Consequently, direct drilling (6.84 MJ L−1) and no‐fungicide application (7.78 MJ L−1) worsened the energy efficiency (total energy inputs to produce 1 L of ethanol), compared with conventional sugar beet production practices (5.82 MJ L−1). Sugar yields under conventional plow‐based tillage and reduced tillage practices were similar, but total energy inputs were reduced as a result of reduced fuel consumption from not plowing. Hence, reduced tillage showed improved energy efficiency (5.36 MJ L−1). The energy efficiency was also improved by using a high‐yielding genotype (5.23 MJ L−1) and root+crown harvesting (5.21 MJ L−1). For these practices, no major changes in total energy inputs were noted, but sugar yields were consistently increased. Neither total energy inputs nor ethanol yields were affected by extending the vegetative growing period by delaying harvesting.

Newly developed system based on multiple enzyme restriction fragment length polymorphism – an application to proteolytic bacterial flora analysis

Abstract To assist assignment of bacterial phylogeny based on multiple enzyme restriction fragment length polymorphism (MERFLP) analysis, new programs were developed; one program was used to construct reference database of theoretical multiple enzyme restriction fragment (MERF) data, which were edited from DNA sequence of various kinds of bacteria; the other program was used to search the theoretical MERF having the highest similarity to the measured MERF based on pairwise distance according to Nei and Li. Using proteolytic bacteria (96 strains) isolated from various field soils and 25 reference strains, the factors that affected accurate phylogenetic estimation were evaluated. Bacterial strains from the genus Bacillus were successfully separated into species using the MERF with HaeIII and HhaI as the restriction enzymes. Genera Xanthomonas, Pseudomonas, and Alcaligenes were affiliated with the corresponding genus, but precise affiliation under genus level was not always possible. Differentiation among genera in the Enterobacteriaceae may be possible using the other restriction enzymes (HhaI, RsaI and ScrF1). The method was found to be useful for the analysis of bacterial flora because the differentiation, grouping and phylogeny assignment of bacteria, including various genera, were easily accomplished without preliminary information. Most (97.8%) of the proteolytic bacteria isolated from field soils applied with chemical fertilizer or no fertilizer were affiliated with Bacillus spp., whereas the ratios were low in those isolated from field soils applied with liquid livestock feces.

Rapid change in soil C storage associated with vegetation recovery after cessation of cultivation

The total area of abandoned and fallow agricultural fields in Japan has been increasing annually. The change in agricultural land use can alter belowground carbon (C) stocks associated with changes in the types of plant species. The aim of this study was to investigate how the cessation of cultivation influenced the soil C storage in former agricultural fields. The study sites were previously used for rice (Poaceae, Oriza sativa L.) and wheat (Poaceae, Triticum L.) cultivation, and fallow management practices had been in effect for three years under three different conditions: two treatments involved mowing and either leaving the plant residue on the ground or removing the plant residue, while the third treatment involved simply abandoning the field. We found that the former paddy site invaded by rhizomatous perennial grasses had significantly higher soil C storage compared to former upland fields that was dominated by annual grass species. The cessation of cultivation increased soil C storage by about 1.3 times in former paddies, and decreased the content by 0.83–0.91 times in former uplands. The three-year total belowground production was 2.0–4.7 times greater in former paddies than former uplands for each management condition, suggesting that lower C input from the annual grasses caused a loss in soil C at the upland fields. Aboveground biomass removal of the perennial grasses strongly reduced C input, whereas the C input from their high belowground production led to the significant increases of soil C storage near the surface of the former paddies. Our studies indicate that high belowground productivity of perennial grasses can increase soil C storage after the cessation of cultivation.

Use of a Microchip Electrophoresis System for Estimation of Bacterial Phylogeny and Analysis of NO3 − Reducing Bacterial Flora in Field Soils

Phylogenetic estimation method without determination of DNA sequence was developed. By this method, fragment length polymorphism separately digested with multiple restriction enzymes was measured using microchip electrophoresis and affiliated with those calculated from corresponding DNA sequence in the theoretical database. The phylogenies of 129 NO3 − reducing bacteria newly isolated from field soils were estimated by this method, and were compared to those by carbon source utilization profiles and by comparative sequence analysis of 16S rDNA. Various bacteria such as Micrococcus sp. (one isolate), Acidovorax delofieldii (one isolate), Cupriavidus necator (one isolate), Burkholderia sp., (seven isolates), Commamonas acidovorans (two isolates), Herbaspirillum seropedicae (two isolates), Ralstonia sp. (six isolates), Pseudomonas spp. (14 isolates), and Acinetobacter spp. (one isolate), were affiliated as similar to those by sequence analysis of 16S rDNA, while exact affiliation of genus was difficult for those belonging to Enterobacteriaceae.

Differences in CO2 and N2O emission rates following crop residue incorporation with or without field burning: A case study of adzuki bean residue and wheat straw

Abstract In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO2) and nitrous oxide (N2O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha–1) and nitrogen (5.97 ± 0.76 kg N ha–1) from burned wheat straw into the soil, neither CO2 nor N2O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO2, methane (CH4) and N2O emission during wheat straw burning showed that CO2-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.

Tillage, fertilizer type, and plant residue input impacts on soil carbon sequestration rates on a Japanese Andosol

ABSTRACT To identify efficient field management practices for enhanced soil carbon sequestration suited to crop rotation-based Andosol fields in northern Japan, the impacts of a combination of tillage, fertilizer type, and plant residue input on soil carbon sequestration rates were studied in a 4-year field experiment (April 2007 to March 2011). The rates of changes in soil organic carbon over the entire study period were determined by soil carbon stock change and by net ecosystem carbon budget. Across eight field management treatments and two replicates for each treatment, the rates of changes in soil organic carbon determined by net ecosystem carbon budget were positively correlated with the rates determined by soil carbon stock change (r = 0.766, n = 16). The arithmetic means of the rates determined by net ecosystem carbon budget (1.24 Mg C ha−1 year−1) were greater than those determined by soil carbon stock change (−0.18 Mg C ha−1 year−1) because decomposing crop residues and composted cattle manure in soil were included in the calculation of the net ecosystem carbon budget but were excluded in the calculation of soil carbon stock change (decomposing crop residues and composted cattle manure in soil samples were removed by sieving in measuring the soil carbon stock change). Both methods led to the same conclusion that soil carbon sequestration was significantly enhanced by composted cattle manure application and increased input of plant carbon from crop residues and green manure but was not enhanced by reduced tillage. The p values for net ecosystem carbon budget were smaller than those for soil carbon stock change in analysis of variance; therefore, the net ecosystem carbon budget was more sensitive to field management practice than the soil carbon stock change.

Biochar Impacts on Crop Productivity and Greenhouse Gas Emissions from an Andosol

To assess the impacts of biochar application on crop productivity and global warming mitigation, a 4-yr field experiment was conducted in a well-drained Andosol in northern Japan. Wood residue-derived biochar (pyrolyzed at >800°C) was applied at rates of 0, 10, 20, and 40 Mg ha for potatoes, winter wheat, sugar beet, and soybeans cultivated in rotation, and CO, NO, and CH emissions from the soil and yield and quality of the harvested materials were measured. Biochar application, regardless of rate, had no significant impact on yield and quality of the harvested materials, except for soybean grain yield. It also had no effect on cumulative CO, NO, and CH emissions from the soil. Andosols are inherently highly porous, and biochar application increased soil porosity only at the highest amendment level. The small changes in soil properties and the recalcitrance of the biochars C components probably account for the unchanged soil-associated greenhouse gas emissions and the minimal impact on crop yield and quality. Because soil CO emission was not increased, the net ecosystem C budget during the study period increased with the rate of biochar application from -3.55 ± 0.19 Mg C ha without biochar application to 4.89 ± 0.46, 13.4 ± 0.3, and 29.9 ± 0.4 Mg C ha at application rates of 10, 20, and 40 Mg ha, respectively; therefore, application of wood residue-derived biochar to an Andosol has great potential for mitigating global warming through enhanced soil C sequestration without sacrificing crop productivity.