Japan Agricultural Research Quarterly: JARQ
Online ISSN : 2185-8896
Print ISSN : 0021-3551
ISSN-L : 0021-3551
Current issue
Showing 1-9 articles out of 9 articles from the selected issue
REVIEW
Agricultural Engineering
  • Yuki YONEDA
    Type: review-article
    2021 Volume 55 Issue 3 Pages 201-208
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    A closed-type plant factory (plant factory) can control growth environments in confined spaces with artificial lights and hydroponic systems. The growth environment of a plant factory can be modulated without having to consider the natural climate, so that high value plants rich in useful compounds or low in toxic compounds can be uniformly and consistently produced. However, the process of optimizing growth condition settings to increase or decrease the target compounds tends to be complicated, given the various control parameters in a plant factory. An efficient optimization process for producing high value plants was shown using physiological and genetic information in the case of Stevia rebaudiana (stevia). This case study was conducted to determine the optimal conditions for producing stevia rich in sweet steviol glycosides (SGs) compounds. All environmental condition settings were selected based on previous studies relating to the biosynthesis of such SGs as stevioside (Stev) or rebaudioside-A (Reb-A). A yield evaluation of Stev and Reb-A was conducted based on the transcription levels of SGs-related genes. The process of producing SGs-rich stevia provides an example of an efficient optimization process for producing high value plants with increased or decreased target compounds in a plant factory system.

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ARTICLES
Crop Science
  • Hiroaki SAMEJIMA, Keisuke KATSURA, Mayumi KIKUTA, Symon Mugo NJINJU, ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 209-216
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    A decrease in the filled grain ratio (FGR) under high nitrogen (N) conditions inhibits the increase in rice yield in the tropical highlands of equatorial East Africa. We hypothesized that, under high N fertilization, the decrease in FGR is due to low temperatures during the reproductive growth stages, and that high grain yield can be achieved using cold tolerant varieties. Two cold-susceptible varieties (BW196 and Komboka) and a cold-tolerant variety (NERICA 1) were grown under 57, 114, and 171 kg N ha−1 of N fertilization. Grain yield increased with a higher N fertilization rate only in NERICA 1. Shoot dry weight and total spikelet number increased in all varieties under high N conditions. Although FGR decreased with increases in N fertilization rate in all varieties, the adverse effects of high N fertilization on FGR were least observed in NERICA 1. However, temperature did not affect FGR in all N treatments, growth stages, and varieties, except for Komboka during the ripening stage under high N conditions. The findings did not support the hypothesis that high-N-induced decreases in FGR are due to low temperatures. High-N-induced decreases in FGR in Komboka were mainly attributable to the poor filling of spikelets during the ripening stage due to excess total spikelets. Factors other than filling high-N-promoted increases in total spikelet number may affect FGR in BW196 and NERICA 1 under high N conditions in Mwea.

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  • Motohiko KONDO, Yoshiko IIZUMI, Takeshi WATANABE, Luu Hong MAN, Nguyen ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 217-224
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    This study aimed to determine the rice (Oryza sativa L.) yield under double cropping in the Mekong Delta, Vietnam, and identify which climatic factors cause a reduced yield in the wet season (WS) compared with the dry season (DS). A series of field experiments was conducted in the field from 2014 to 2017, along with a supplementary pot experiment, by using the rice variety OM 6976. The yield was 38% lower in WS than in DS, mainly due to a decrease in the spikelet number per panicle and percentage of ripening. This yield reduction observed in WS was most closely related to lower radiation at 51-80 days after transplanting, and was also related to higher temperature. These results suggest that low radiation and high temperature during the reproductive to grain-filling stages were mainly responsible for causing a low yield in WS. In addition, a need to further consider soil reduction was suggested based on more extensive root damage and sulfide levels on roots observed in WS as compared with DS.

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Agricultural Environment
  • Shumpei HASHIMOTO, Mai FURUYA, Xiaodong YOU, Genki WANIBUCHI, Hayato T ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 225-232
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    Vermicomposting technology is an environmentally friendly, sustainable, and low-cost tool used to convert agronomical and food waste into manure, facilitated by the decomposition and digestion by earthworms. In this study, we evaluated the chemical properties and microbial diversity of vermicompost (VC) derived from school lunch waste, which has long been a serious problem in many countries including Japan. The results revealed that 18-week-old VC promoted the root elongation of plants, and also showed a higher germination index (GI) and higher cation exchange capacity (CEC), indicating that vermicompost made from school food waste is an acceptable manure. As a result of the microbiome analysis by the sequencing of 16S ribosomal DNA (rDNA) using next generation sequencing (NGS), higher ratios of Bacillus, Pseudomonas, and Paenibacillus species, which may include beneficial bacteria for plant growth, were detected in VC than in the control compost (CC). These results demonstrate the significance of vermicompost in utilizing waste from school lunch, suggesting the possibility of implementing a waste recycling system that leads to reducing and recycling food waste in schools.

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  • Kyi Mon Mon KO, Yasumaru HIRAI, Takeo YAMAKAWA, Eiji INOUE, Takashi OK ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 233-244
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    Leguminous green manure (GM) is a nitrogen (N) resource that can replace chemical fertilizers (CFs) in rice production. The pattern of N mineralization from GM, which changes according to species, growth stage, and the timing of incorporation, affects rice growth and yield. Thus, the characteristics of N mineralization should be clarified to promote the appropriate use of GM. The objectives of this study were to clarify the patterns of N mineralization from flowering- and maturity-stage GMs under flooded conditions after different upland periods, and to evaluate the denitrification loss occurring during the upland periods. Nitrogen mineralized from three species of GMs collected at both the flowering and maturity stages was measured through incubation tests. The three species were hairy vetch (HV), crimson clover (CC), and white clover (WC). The incubation tests included five upland periods (0, 1, 2, 3, and 4 weeks) at 20°C, and each upland period involved eight flooded periods (0, 1, 2, 4, 6, 8, 12, and 16 weeks) at 30°C. The percentage of mineralized N to total N input from the GMs after being flooded for four weeks until after 16 weeks was 1% for flowering-stage HV and 3% for flowering-stage CC, whereas the percentage increased to 41% for maturity-stage HV and 58% for maturity-stage CC. The results indicate that maturity-stage HV and CC slowly mineralize N until the late growth stage of rice. The denitrification loss under upland conditions increased markedly when the upland period extended longer than two weeks. Said loss can likely be attributed to the easily mineralizable fraction of N in the GMs, which is mineralized until having been flooded for four weeks. Thus, maturity-stage GMs, which have a higher C/N ratio than flowering-stage GMs, are advantageous in reducing the denitrification loss during the upland period.

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Agricultural Engineering
  • Tadashi YOSHIHASHI, Yuki ABE, Nariaki IWASAKI, Hiroyuki SAKANAKA, Masa ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 245-251
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    Rice husking is an operation where the husks are peeled from rough rice, and a rubber roll husker conventionally consists of two rubber rolls with different peripheral velocities that rotate to provide the shear stress needed to husk rough rice. Both short- and long-grain rice, which have totally different shapes, affect rice husker performance, especially the husking ratio and wear of the husker roll. The performance with long-grain rice, which accounts for 80% of world rice production, is poorer than with short-grain rice. We analyzed the fundamental mechanisms of the roll husker, and then compared the performance for long- and short- grain rice using a finite element model. A husking simulation based on the constructed model revealed that long-grain rice exhibited more accumulated friction loss (121.6 mJ) than short-grain rice (40.1 mJ). The difference in accumulated friction loss at the roll surface may lead to increased friction heat, which in turn induces wear. Since sufficient shear force is needed with rough rice to achieve a higher husking ratio, the optimum coefficient of friction and Young’s modulus of the husker roll for long-grain rice were calculated based on the model as being 0.8 and 8.1 MPa, respectively. Newly designed polyurethane-elastomer-based husker rolls based on these results showed a better husking ratio and durability than conventional rubber rolls in experiments undertaken in Thailand using long-grain rice. The results provide new opportunities to prepare new materials for the rice roll husker.

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Social Science
Animal Science
  • Naoto AOKI, Zhang YANLI, Syuhei KANDA, Yuzo KUROKAWA, Halima SULTANA, ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 265-271
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    The objective of this study was to evaluate the effects of supplementing a yeast culture (YC; Saccharomyces cerevisiae) on rumen fermentation, nutrient utilization, and milk production in dairy cows. Six Holstein cows were subjected to two dietary treatments in a crossover design. The treatments were control (no yeast culture) and yeast culture (fed at 30 g/head per day). Rumen pH and protozoal counts were similar between both treatments, although the concentration of rumen ammonia-N tended to be lower with YC treatment. Moreover, YC treatment did not affect the concentration of total short-chain fatty acids in the rumen, but tended to reduce the molar proportion of acetic acid (A), while significantly increasing that of propionic acid (P). Therefore, the A/P ratio decreased significantly after 5 hr of YC feeding as compared with the control. The treatments had no effect on the blood plasma concentrations of glucose, urea-N, and non-esterified fatty acids. However, YC treatment resulted in a significantly higher concentration of plasma free lysine, along with higher concentrations of isoleucine, arginine, and total free amino acids. Dry matter intake and milk yield were similar between both treatments, though the percentage of milk protein tended to be higher with YC treatment. In addition, YC treatment did not affect the milk fatty acid composition and somatic cell counts. Overall, the yeast culture had a subtle effect on ruminal fermentation. The higher plasma concentrations of some essential amino acids indicated the positive effect of YC supplementation on the availability of amino acids for milk protein synthesis in the mammary gland of dairy cows.

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Forestry
  • Masaki J. KOBAYASHI, Kevin Kit Siong NG, Soon Leong LEE, Norwati MUHAM ...
    Type: research-article
    2021 Volume 55 Issue 3 Pages 273-283
    Published: July 01, 2021
    Released: July 29, 2021
    JOURNALS FREE ACCESS

    Understanding internode elongation in woody species is the basis of stable timber production. Although trees exhibit coordinated growth between leaves and internodes, it is unclear whether their coordinated growth occurs simply because both organs receive a common signal that triggers their growth or because the growth of one organ is regulated by the other. To test the latter possibility, we defined simple developmental stages and assessed the effect of leaves on the regulation of internode elongation at the phytomer level in the tropical tree Shorea leprosula, which is an important timber tree species in Southeast Asia. Our observation of phytomers showed that leaves and internodes grew coordinately in S. leprosula. A spatiotemporal analysis of internode elongation indicated that internode elongation occurred around young expanding leaves. Furthermore, the excision of expanding leaves significantly reduced internode elongation. These results suggest that expanding leaves positively regulate internode elongation. Therefore, the growth interactions between leaves and internodes must be considered in order to better understand the mechanism of internode elongation in S. leprosula. These results will also form the basis of future studies aimed at sustainable timber production using this species.

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