Effect of intermittent drainage in reduction of methane emission from paddy soils in Hokkaido,northern Japan

ABSTRACT

Emission of methane (CH₄), a major greenhouse gas, from submerged paddy soils is generally reduced by introducing intermittent drainage in summer, which is a common water management in Japan. However, such a practice is not widely conducted in Hokkaido, a northern region in Japan, to prevent a possible reduction in rice grain yield caused by cold weather. Therefore, the effects of intermittent drainage on CH₄ emission and rice grain yield have not been investigated comprehensively in Hokkaido. In this study, we conducted a three-year field experiment in Hokkaido and measured CH₄ and nitrous oxide (N₂O) fluxes and rice grain yield to elucidate whether the reduction in CH₄ emission can be achieved in Hokkaido as well as other regions in Japan. Four experimental treatments, namely, two soil types [soils of light clay (LiC) and heavy clay (HC) textures] and two water management [continuous flood irrigation (CF), and intermittent drainage (ID)], were used, and CH₄ and N₂O fluxes were measured throughout the rice cultivation periods from 2016 to 2018. Cumulative CH₄ emissions in 2016 were markedly low, suggesting an initially low population of methanogens in the soils presumably due to no soil submergence or crop cultivation in the preceding years, which indicates a possible reduction in CH₄ emission by introducing paddy-upland crop rotation. Cumulative CH₄ emissions in the ID-LiC and ID-HC plots were 21–91% lower than those in the CF-LiC and CF-HC plots, respectively, whereas the cumulative N₂O emissions did not significantly differ between the different water managements. The amount of CH₄ emission reduction by the intermittent drainage was largest in 2018, with a comparatively long period of the first drainage for 12 days in summer. Rice grain yields did not significantly differ between the different water managements for the entire 3 years, although the percentage of well-formed rice grains was reduced by the intermittent drainage in 2018. These results suggest that CH₄ emission from paddy fields can be reduced with no decrease in rice grain yield by the intermittent drainage in Hokkaido. In particular, the first drainage for a long period in summer is expected to reduce CH₄ emission markedly.     

Immunochemical sexing of living yellowfin tuna, Thunnus albacares (Bonnaterre), using a vitellogeninlike protein

Sexing of living yellowfin tuna, Thunnus albacares (Bonnaterre), was carried out based on immunochemical detection of vitellogenin (VTG), a female-specific protein. Tissue samples were taken from swimming fish in a sea pen by a hand-made apparatus. Recently fertilized eggs were also collected before tissue sample trials. A double immunodiffusion pattern showed that the egg homogenate of T. albacares reacted with rabbit antibody against the purified VTG of greater amberjack, Seriola dumerili (Risso). This suggests that the VTG of T albacares has an antigenicity similar to that of S, dumerili and that this antibody can be used to detect T albacares VTG. Immunodot-blotting analysis revealed that, out of the two fish tested, the tissue sample from one, but not the other, reacted with this antibody, suggesting that the former was a mature female, and the latter a male or immature female. Examination of the fish gonads revealed an ovary and a testis, respectively. Immunological and morphological results corresponded completely. Therefore, the method used in the present study is available for discriminating the sexes of T albacares.     

Assessing sexual maturity of feminized Japanese eel Anguilla japonica by measuring eye size

For efficient production of Japanese eel Anguilla japonica eggs, knowledge of the status of the sexual maturity of potential broodstock females is important because this status directly influences the time required to produce mature eggs by successive hormone doses. Here we apply an eye index (relative eye size) to evaluate the gonadal status of feminized A. japonica, which were induced by administration of estradiol-17β. Examination of gonad somatic and eye indexes of 267 feminized eels, cultivated for 12–56 months, revealed a significant correlation between these two indexes. Artificial maturation of 35 feminized eels showed that the number of hormone injections administered before ovulation was significantly lower as the eye index score increased, indicating availability of this noninvasive method of predicting sexual maturity of feminized eel. There was no correlation between eye index and fertilization rate, hatching rate, or larval survival rate, suggesting that sexual maturity before hormonal treatment does not affect egg quality.     

Immunoperoxidase evaluation of pneumonic lesions in calves naturally infected with Pasteurella haemolytica

Immunoperoxidase technique was applied for pathological study on naturally occurring pneumonic tissues of calves from which Pasteurella haemolytica was isolated. Multifocal necrosis occurred in the lungs of 25 out of 42 calves (59.5%) and P. haemolytica antigen was detected in 22 out of the 25 calves (88.0%). The calves were divided into 3 groups according to the number of P. haemolytica isolated. The positive rate of the bacterial antigen detected by the technique was 66.6% (28/42) on the average, reaching up to 85.7% (18/21) in the group from which the largest number of P. haemolytica was isolated.     

Effect of Organic matter application on the fate of 15N-labeled ammonium fertilizer in an upland soil

Abstract

The clay mineral composition of two “terra roxa estruturada” (TRE) soils occurring in the tropical rain forest and tropical forest/savannah transition zone, and a reddish brunizem in the savannah/semi-arid transition zone was studied comparatively in the southeast Amazon region.

Kaolin minerals were dominant in these soils, and hematite and goethite were found in the clay fraction. A small amount of 2 : 1-type clay minerals was found in two soils. The mineral composition of the clay fraction in the TRE soils was hardly influenced by the difference of the meteorological factor or their water condition in this region, and this factor should not control the influence of parent materials derived from basic rocks. The TRE soils were developed under the condition of laterite genesis, and were regarded claymineralogically as a kind of the lateritic soils.     

Metabolite profiling of Komatsuna (Brassica rapa L.) field-grown under different soil organic amendment and fertilization regimes

Among agricultural soil fertility management options, the environmental benefits of organic amendments have recently drawn particular attention. However, little information exists about their effects on crop metabolites or quality. Field plots of Komatsuna (Brassica rapa L. var. perviridis) were planted in a fractional factorial design with the following treatments: soil amendments of cattle manure (0, 2 or 4?kg?m^?2), wheat straw (0, 0.05 or 0.1?kg?m^?2), fast release nitrogen (N) (0, 6 or 12?g?N?m^?2 of ammonium sulfate), slow release N (0, 3 or 6?g?N?m^?2 of coated ammonium nitrate), phosphorus (P) [0, 5 or 10?g phosphorus pentoxide (P₂O₅)?m^?2 of lime superphosphate] and potassium (K) [0, 6 and 12?g potassium oxide (K₂O)?m^?2 as potassium sulfate]. Metabolite profiling was carried out using a gas chromatograph/mass spectrometer (GC/MS), which yielded 62 and 67 metabolites in the leaves and the petioles, respectively. Metabolite peak areas were subjected to principal component analysis (PCA). The first component accounted for 44.1% of the total variance and bore a close relationship to N. The third component accounted for 8.8% of the total variance and was used to distinguish between different levels of manure application. An analysis of variance (ANOVA) of treatment factor effects on individual metabolites showed that the three most significant factors, from highest to lowest, were N absorption, manure amendments and slow release N. The effects of the manure amendments were not fully explained by its attendant N, P or K inputs. This result raises the question as to what mechanisms may bring about the metabolic changes caused by the manure amendment. The current findings will serve to direct further studies on the relationship between crop quality and cultivation procedures and will lead to more efficient quality control methods.