Fungal N₂O production in an arable peat soil in Central Kalimantan, Indonesia     

Yosuke YANAI  Koki TOYOTA  Tomoaki MORISHITA  Fumiaki TAKAKAI  Ryusuke HATANO  Suwido H. LIMIN  Untung DARUNG  Salampak DOHONG 《Soil Science and Plant Nutrition》2007,53(6):806-811

  相似文献   

Mild drying of sandy soil can physically limit the uptake of phosphorus by rainfed lowland rice in northeast Thailand     

Ryoya Seto  Kazuhiko Fujisao  Akiko Toriumi  Koki Homma  Ryosuke Tajima 《Soil Science and Plant Nutrition》2013,59(6):677-685

ABSTRACT

Poor response of rice to phosphorus (P) fertilization and low phytoavailability of soil P have been reported in sandy rainfed fields in northeast Thailand. In order to evaluate the effects of mild soil drying on the uptake of P by rainfed lowland rice, we carried out nutrient omission trials for nitrogen (N) and P at Ubon Ratchathani Rice Research Center under rainfed and flooded conditions. The surface soil was classified as sandy loam. To avoid severe soil drying and drought stress in the rainfed field, soil water potential at a depth of 20 cm was maintained at the field capacity (> ?20 kPa) by flush irrigation. The effects of flooding and drying on the soil properties were also evaluated in the laboratory using soils with diverse textures in and around the center. In the field experiments, the above-ground biomass of rice plants (RD6) did not respond significantly to P fertilization in the rainfed field, although it responded positively to N fertilization. Root length in the surface 10 cm under the rainfed condition was significantly smaller than that under the flooded condition due partly to the increased soil hardness upon drying, but this could not quantitatively explain the large discrepancy of P uptake observed between the rainfed and flooded conditions. Under the rainfed condition, the P uptake did not increase significantly, even when the concentration of soil Bray P was tripled by transferring the surface soil from the flooded to the rainfed field. From the laboratory experiments, it was further suggested that soil P was supplied mainly by diffusion and that the effective diffusion coefficient for P can become less than one-tenth of the value in the flooded field when the sandy soil with clay at around 10% dried to ?100 kPa. Our results suggest that the uptake of P by the rainfed lowland rice grown in sandy soil can be limited physically by mild soil drying that reduces the supply of P to roots by diffusion rather than the chemical extractability of soil P.  相似文献   

Soil management: The key factors for higher productivity in the fields utilizing the system of rice intensification (SRI) in the central highland of Madagascar   总被引：1，自引：0，他引：1  

Yasuhiro Tsujimoto  Takeshi Horie  Hamon Randriamihary  Tatsuhiko Shiraiwa  Koki Homma   《Agricultural Systems》2009,100(1-3):61-71

The system of rice intensification (SRI) developed in Madagascar in the 1980s has been promoted as an integrated crop and resource management approach to rice-cultivation, especially for resource-limited smallholder farms. While advocates have claimed that SRI could boost rice yields with less external input, many criticisms have challenged its effectiveness regarding yields and applicability to larger-scale rice farming systems. In this study, we conducted a field survey and on-farm experiments to assess rice yield performance and key management practices on a few of the early SRI-practicing smallholder farms in the central highland of Madagascar.Rice grain yields at the survey fields were 9.9 t ha⁻¹ maximum without using mineral fertilizer. Deep plowing to the depth of 25–30 cm as well as SRI practices have been conducted continuously since the early 1990s. In addition, an effective drainage system facilitated intensive water management at these high-yielding fields. On-farm experiments demonstrated some yield increases with no interaction for the examined SRI practices, though the effects were not great enough to explain the high yields at these fields. The soils of these high-yielding fields contained relatively large amounts of soil organic carbon (SOC) from the surface to the deep soil layers, and the soil mineralizable nitrogen was closely correlated with rice grain yields.The results indicated that the high yields at the fields of those who were early to adopt SRI were mainly due to the soil fertility associated with great nitrogen-supplying ability, rather than ‘synergetic effects’ of the SRI components. This high N-supplying ability of the soil and accumulated SOC from surface to deep soil layers were attributable to the long-term combined practices of extensive organic applications and deep plowing. Soil hydrology could be another key factor stimulating high rates of soil N-mineralization.These management practices were, however, only applied to the limited numbers of fields within less than 1.0 ha of total landholdings of these farmers due to the great demand in labor and organic resources and the difficulty in controlling irrigation water. Intensive weeding and widely spaced transplanting of young seedlings were also performed in the fields with irrigation and drainage systems sufficient to avoid yield losses from flooding and drought. Although extensive and long-term systematic research is further required to fully assess the benefits of this sort of intensive management as opposed to conventional methods, the preferential allocation of intensive management by the successful SRI-adopters might be the implication of its location-specificity and difficulty in scaling up even within the resource-limited smallholder farms.  相似文献   

Abstracts of Nippon Dojohiryogaku Zasshi     

Erika Sato  Yuko Suga  Chihiro Kisaki  Koki Toyota  Kazuto Miyake  Atsushi Takada 《Soil Science and Plant Nutrition》2013,59(2):213-222

Abstract

The humus composition was analyzed and the humic acid characterized by UV and visible absorption spectroscopy in order to investigate the rotting and maturing process of city refuse compost according to the method of Kumada et al. During the composting process, the following findings were obtained: (1) the HT value was almost constant, but the HE/HT ratio varied somewhat, (2) HA increased with decrease in FA, and the PQ value so increased clearly, (3) the shoulder-like absorption at a wavelength near 270 nm weakened, and (4) the RF value of humic acid increased, whereas the Δ log K value seldom varied.

The IR spectrum of humic acid gradually changed as follows: (1) the absorption band in the 1700-1600 cm^-1 region and in the 1550-1500 cm^-1 region increased slightly, (2) the band in the 1100-1000 cm^-1 region decreased, and (3) the bands at 835 and 710 cm^-1 com pletely disappeared. On the whole, the shape of the IR spectrum of the city refuse compost became featureless. These changes were probably due to the oxidation which occurred in the composting process.  相似文献   

Suppression of Ralstonia solanacearum in soil following colonization by other strains of R. solanacearum     

Koki Toyota  Makoto Kimura 《Soil Science and Plant Nutrition》2013,59(2):449-459

The effect of prior colonization of a sterile loam soil and a sterile clay loam soil by individual soil bacteria on the subsequent growth of a bacterial wilt pathogen Ralstonia solanacearum YU1Rif43 (tRNA type III: Seal et al. 1992: Appl. Environ. Microbiol., 58, 3759–3761) was investigated. Various strains, belonging to the same type, the same species, the same genus, Gram-negative, Grampositive, or fungi, were used. The degree of suppression of the growth of R. solanacearum YU1Rif43 was markedly different depending on the species that had previously colonized the soil, hereafter referred to as priorcolonists. All the strains belonging to R. solanacearum type III suppressed the growth of R. solanacearum YU1Rif43 markedly, while strains of R. solanacearum type I and type II showed a moderate suppressive effect on R. solanacearum YU1Rif43. The suppressive effect of the strains belonging to species other than R. solanacearum, including fungal strains, was relatively limited, or some strains did not show any suppressive effect. The production of bacteriocin did not appear to be related to the strong suppressive effect of the R. solanacearum type III strains. Possible mechanisms for the suppressive effect of priorcolonists on R. solanacearum YU1Rif43 are discussed in relation to nutrients and physical sites in soil available for growth.  相似文献   

Basin-scale distribution pattern and biomass estimation of Japanese anchovy Engraulis japonicus in the western North Pacific     

Hiroto Murase  Atsushi Kawabata  Hiroshi Kubota  Masayasu Nakagami  Kazuo Amakasu  Koki Abe  Kazushi Miyashita  Yoshioki Oozeki 《Fisheries Science》2012,78(4):761-773

The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35°N and west of 170°E) were studied using a quantitative echosounder. This is the first attempt at such a study in this region. Data were collected in summer from 2004 to 2007. The biomass was estimated using data collected at 38?kHz. Species compositions in the backscatterings from pelagic fish were assigned based on the results of trawl hauls taking account of sea surface temperature (SST). Japanese anchovy tended to be high density to the west of 153°E and were distributed in an SST range of 9?C24?°C. Although the temporal and spatial coverage of the survey differed each year, at least 1.5?C3.4 million tons of Japanese anchovy were present in the survey area between 2004 and 2007. To take account of the spatial coverage of the survey each year, the most reliable biomass estimate for this region in the time period was 3.4 million tons (coefficient of variation?0.22).  相似文献   

Spatiotemporal distribution of Flavobacterium psychrophilum and ayu Plecoglossus altivelis in rivers revealed by environmental DNA analysis     

Tenma  Hinako  Tsunekawa  Koki  Fujiyoshi  Riho  Takai  Hajime  Hirose  Masae  Masai  Nanami  Sumi  Kosuke  Takihana  Yuta  Yanagisawa  Sogen  Tsuchida  Kota  Ohara  Kenichi  Jo  Toshiaki  Takagi  Masaki  Ota  Akiko  Iwata  Hiroyoshi  Yaoi  Yuichi  Minamoto  Toshifumi 《Fisheries Science》2021,87(3):321-330

Outbreaks of bacterial cold-water disease (BCWD), caused by Flavobacterium psychrophilum, are widespread in Japan, especially among ayu Plecoglossus altivelis. There are few investigations of F. psychrophilum in river water, and its seasonal distribution has not been clarified. We aimed to identify the spatiotemporal dynamics of F. psychrophilum and ayu to provide information that is useful for establishing a countermeasure for BCWD. Quantitative analysis of environmental DNA (eDNA) was used to clarify the year-round dynamics of ayu and F. psychrophilum. We sampled river water from the Nagara and Ibi rivers in Japan, and conducted monthly water sampling and eDNA quantification. Changes in the eDNA concentration of ayu were consistent with the known life histories of the fish. There was a strong negative correlation between the eDNA concentration of F. psychrophilum and water temperature, suggesting a strong dependence of F. psychrophilum dynamics in the river on water temperature. Furthermore, relatively high eDNA concentrations were recorded for both organisms in early summer and fall, suggesting that ayu is infected with F. psychrophilum during these seasons when experiencing up- and downmigration, respectively.

  相似文献   

Transgenic apple (Malus x domestica) shoot showing low browning potential     

Murata M  Haruta M  Murai N  Tanikawa N  Nishimura M  Homma S  Itoh Y 《Journal of agricultural and food chemistry》2000,48(11):5243-5248

Transgenic apple shoots were prepared from leaf disks by using Agrobacterium tumefaciens carrying the kanamycin (KM) resistance gene and antisense polyphenol oxidase (PPO) DNA. Four transgenic apple lines that grew on the medium containing 50 microgram/mL KM were obtained. They contained the KM resistance gene and grew stably on the medium for >3 years. Two transgenic shoot lines containing antisense PPO DNA in which PPO activity was repressed showed a lower browning potential than a control shoot.  相似文献   

Detection of changes in taste of japonica and indica brown and milled rice (Oryza sativa L.) during storage using physicochemical analyses and a taste sensing system     

Tran TU  Suzuki K  Okadome H  Ikezaki H  Homma S  Ohtsubo K 《Journal of agricultural and food chemistry》2005,53(4):1108-1118

Changes in the taste of japonica, hybrid, and indica brown and milled rice, stored for 10 months at low (5 degrees C, 65-70% relative humidity) and room temperatures were observed by physicochemical analyses and a novel method using a taste sensing system. During storage, some properties increased or decreased while others were fairly constant. The main taste components of cooked rice such as sweetness (sucrose) and umami tastes (glutamic acid and aspartic acid) were reduced during storage, whereas glucose and fructose increased. The increase of fat acidity and consequent decrease of the pH value of the cooking solution may contribute to the off-taste of cooked stored rice. A taste sensing system with 10 lipid membrane sensors was also used to classify new and old rice samples using principal component analysis. Fresh and room temperature stored japonica and indica rice could be clearly distinguished; however, it was not possible to differentiate the samples stored at low temperature.  相似文献   

Effect of roasting on properties of the zinc-chelating substance in coffee brews     

Wen X  Enokizo A  Hattori H  Kobayashi S  Murata M  Homma S 《Journal of agricultural and food chemistry》2005,53(7):2684-2689

ApV is a brownish polymer with zinc-chelating activity in brewed coffee. We investigated in this study the effects of roasting on the zinc-chelating, reducing, and antioxidative activities of ApV from light-, medium-, and dark-roasted coffee. We also discuss the effect on the zinc-chelating activity of adding milk to the brewed coffee. The chelating activities of ApVs were evaluated by the tetramethyl murexide method. As the intensity of roasting increased, the yield of ApV increased, and the brown color and molecular weight of ApV respectively became darker and higher. Increasing the degree of roasting also decreased the zinc-chelating activity of ApV. The reducing activities of ApVs estimated by the indophenol method were stronger than those of ascorbic acid. Both the antioxidative activity estimated by the ABTS assay and the reducing activity of ApV increased with roasting. When milk was added to instant coffee and its ApV was prepared, the zinc-chelating activity of ApV was not changed.  相似文献