Hiroyuki Tsuji

Fuel consumption-derived CO2 emissions under conventional and reduced tillage cropping systems in northern Japan

Abstract In the context of their role in net global warming, CO2 emissions were calculated for fuel-consuming processes associated with arable land crop production in Hokkaido, northern Japan. Fuel-consuming processes included tractor-based field operations, transportation of products and materials and grain drying. In conventional tillage (CT) systems, total CO2 emissions from fuel consumption were 826.2, 605.4, 424.2 and 738.7xa0kg CO2xa0ha−1 for winter wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L.), adzuki bean (Vigna angularis (Willd.) Ohwi and Ohashi) and potato (Solanum tuberosum L.) production, respectively. In winter wheat production, 55% of total CO2 emission were released from kerosene and electricity use for grain drying, the remainder from tractor-based field operations. In contrast, for sugar beet, adzuki bean and potato production, field operations were the main contributors to CO2 emissions. Of the field operations, tillage and harvesting required the largest amounts of fuels. Under reduced tillage (RT) systems in which soil preparation in early spring was reduced and plowing after harvesting was omitted, 47.5xa0lxa0ha−1 of diesel oil equivalent to 125.4xa0kg CO2xa0ha−1 could be saved, regardless of crop species. Consequently, total CO2 emissions could be reduced by 15–29%, respectively, in winter wheat and adzuki bean production. In the Tokachi region of Hokkaido, a primary arable crop production region in Japan, annual CO2 emissions under CT and RT for the four crops produced were estimated at 82.7xa0Gg CO2 per year and 67.4xa0Gg CO2 per year, respectively. Besides reduced fuel costs, the use of RT production systems could significantly reduce the large quantities of CO2 released as a result of arable land crop production in northern Japan.

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.

The Effects of Cropping Systems and Fallow Managements on Microarthropod Populations

Abstract The response of microarthropod populations to different combinations of conservations! agricultural practices was investigated in two field experiments. In the first experiment, cropping systems with combinations of tillage (conventional or reduced), biocide application (conventional or reduced), and fertilization (chemical or cattle manure compost) were compared. In the second experiment, five treatments including four fallow managements that received different levels of tillage, biocide, and organic matter input from vegetation were compared. The springtail (Collembola) population was higher with less tillage, less biocide application, and more organic matter input in both experiments, and these effects were additive; there was no specific combination of practices that has an interacting effect. The mite (Acari) population was also higher under most conservations! treatments, and a significant interaction effect between tillage and organic matter application was found. A large increase in the Acari population under the combination of reduced tillage and higher organic matter input suggested that beneficial effects of these practices on the Acari community could be increased by integrating these practices. There was no significant correlation between the microarthropod populations and plant cover or soil chemical/physical properties measured. Slight changes in soil environments caused by agricultural practices may affect microarthropod communities substantially even before the changes in soil properties become detectable.

Response of Soybean, Sugar Beet and Spring Wheat to the Combination of Reduced Tillage and Fertilization Practices

Abstract To evaluate the feasibility of conservation tillage in combination with reduced biocide and fertilization regimes, we conducted a field experiment using conventional and reduced tillage, with or without reduced biocide, and fertilization regimes for growing soybean, sugar beet, and spring wheat in this order for three years. Root biomass and sugar yield of sugar beet did not differ with any combinations of conservation practice. Although leaf biomass was significantly reduced under reduced chemical fertilization (replaced partially with manure compost), it was compensated by a greater specific leaf area. Early crop growth of soybean, and spring wheat was increased to some extent under reduced tillage, which indicated a better nutrient utilization, as well when combined with reduced biocide application. However, reduced fertilization could not supply as much nitrogen as conventional chemical fertilization especially in the combination with reduced tillage. Larger amount or long-term application of organic fertilization may be necessary under reduced tillage compared to the requirement under conventional tillage to compensate for lower rate of nitrogen release from organic matter.

Yielding Performance of “Kita-aoba”, High-yielding Rice Variety for Hokkaido Region, Northern Japan

Abstract The yielding performance of the first high-yielding rice variety for Hokkaido, Kita-aoba, after application of various amounts of nitrogen (9.0 to 23.7 g m-2 in 2008 and 10.5 to 16.5 g m-2 in 2010) and under various planting densities (13.2 to 33.2 hills m-2 in 2008 and 17.5 to 36.8 hills m-2 in 2010) was examined in comparison with that of the common variety, Kirara397. Kita-aoba had higher grain yield than Kirara397 owing to its large sink capacity through larger sink capacity per unit biomass at heading. Kita-aoba had a high yield potential (the maximum grain yield of 1081 g m-2), and achieved a high grain yield even in Hokkaido where the rice-growing season is short. Kita-aoba had a large sink size, but, judging from the relationship between sink capacity and percentage of sink filled, further increase of sink size might not result in increase of grain yield. Kita-aoba showed a great increase in shoot dry matter from heading to maturity, but it was not enough to fill its large sink.

Nitrogen application method for improving yield and protein content of “Kitanokaori”, a new variety of winter wheat for bread use in Hokkaido

(Jpn. J. Soil Sci.Plant Nutr., 77, 273–281, 2006) “Kitanokaori” is a new variety of winter wheat (Triticum aestivum L.) for bread use bred at the National Agricultural Research Center for Hokkaido Region. The grain protein content of wheat for bread use should be higher than 120 g kg−1. Much nitrogen application is necessary to obtain high grain protein content. Therefore, it is necessary to determine the optimum amount of nitrogen to obtain the required protein content and to prevent nitrogen from remaining in the soil. Field experiments were conducted for four years from sowing in 2000 to study the effect of the amount of nitrogen and the time of top-dressing. In the experiment in which sowing was carried out in 2003, nitrogen treatments were 40, 40–60, 40–60–0–60, 40–60–0–60–30, 40–60–0–60–60, 40–60–60–60, 40–60–60–60–30, 40–60–60–60–60, 40–60–30–30, 40–60–30–30–30 and 40–60–30–30–60 (each value showing the amount of applied nitrogen at sowing · re-growing stage · panicle formation stage · flag leaf stage · full heading stage, kg ha−1). The experiments were conducted in Andosol, which has moderate nitrogen fertility, and in Histosol, which is fertile soil. Kitanokaori did not lodge with high-applied nitrogen, and both yield and protein content increased with an increase in applied nitrogen. In a moderate climate, Kitanokaori reached a protein content of 120 g kg−1 when the amount of absorbed nitrogen was about 190 kg ha−1, and the yield was about 7·8 Mg ha−1 at that time. The top-dressing at the panicle formation stage was effective to raise the yield and the top-dressing at the full heading stage was effective to raise the grain protein content. It is recommended that the amount of applied nitrogen should be 160 kg ha−1 until the flag leaf stage, and additional nitrogen should be applied at the full heading stage to obtain a grain protein content of more than 120 g kg−1. Nutritional diagnosis at the full heading stage will be necessary to determine whether more nitrogen is needed to achieve the required protein content. When the amount of total applied nitrogen did not exceed 220 kg ha−1, the amount of absorbed nitrogen was over 90% of applied nitrogen, and there was little inorganic nitrogen in the soil after harvest. Therefore, it was considered that the residue of nitrogen in the soil was small within 220 kg ha−1 of nitrogen application, while favorable growth and high yield were obtained.

Relationship between plant surviving after spring and seminal root penetration into soil at thaw in spring wheat seeded in early winter

春まきコムギ (品種: 春よ恋) の初冬まき栽培における, 融雪直後の根の状態とその後の生存の関係を圃場試験と屋内試験で検討した. 圃場試験では北海道農業研究センター内の水田転換畑圃場に2003年と2004年の11月に春まきコムギを表面散播し, 散播と同時に除草レーキで土壌表面を攪乱した撹拌区と, 無撹拌区を設けた. 播種翌年の融雪直後に単位面積あたり個体数, 個体の発芽位置 (地中, 地表面), 地表面発芽個体の種子根数と地中貫入根数等を調査し, 春以降の生存率および子実生産量との関係を検討した. 屋内試験では地中に埋設する種子根数と土壌水分が生存率に及ぼす影響を調査した. 圃場試験において, 撹拌区では無撹拌区に比べて地中で発芽する個体の割合が高く多収であった. 地中で発芽した個体の生存率は両年共に90%以上と高く, 土壌表面で発芽した個体のうち, 融雪直後の地中貫入根数2本以上の個体も76～90%と比較的高い生存率を示した. また, 融雪直後の地中貫入根数2本以上の個体では, 1個体当たりの有効穂数, 1穂粒数, 千粒重が地中で発芽した個体とほぼ同等であった. 地中貫入根数は積雪下で伸長する種子根数が多いほど増える傾向が認められた. 屋内試験において, 個体が定着する前の乾燥により地中に貫入する根数とコムギの生存率が低下することが明らかとなった. これらから, 春まきコムギの初冬まき散播栽培では, 覆土により地中で発芽する個体を増やすこと, および積雪下で伸長する種子根数を増すことが, 越冬後の生存率と収量を高める結果につながることが示された.