To clarify the optimal water management in large-scale fields under high temperatures at the ripening period, effective water managements during this period for improvement of yield, appearance quality and palatability were investigated. Compared with intermittent irrigation and flooded irrigation, the soil temperature with saturated irrigation remained low throughout the day, and the decrease rate of the bleeding rate of hills was the lowest. These results suggested that the saturated irrigation maintained root activity. For the three irrigation types, the number of spikelets per m2 and 1000-grain weight were similar, however, saturated irrigation resulted in significantly higher rice yield due to improvement in the percentage of ripened grains. The saturated irrigation produced a high percentage of perfect rice grains and thicker brown rice grain, furthermore, the palatability of cooked rice was excellent because protein content and hardness/adhesion ratio were both low. Thus, under high-temperature ripening conditions, soil temperature was lowered and root activity was maintained when applying saturated irrigation after heading time. The results indicated that saturated irrigation is an effective countermeasure against high-temperature ripening damage.

The production of cellulosic bioethanol from non-edible plants is a potential countermeasure against global warming. Erianthus species provide cellulosic raw material for bioethanol because they have high biomass productivity and high tolerance to environmental stress, associated with their large, deep root systems. However, it is difficult to select Erianthus species for breeding by direct observation of their root systems because the roots are widely dispersed in the soil. Instead, we examined shoot morphological traits that could be closely related to root morphology to find effective reference indices for selection. The potential to evaluate root structure and function in Erianthus according to bleeding rate was also examined. An analysis of root–shoot relationships in seedlings indicated that root number and mean length were closely related to stem number and diameter, respectively. These results suggest that root–shoot relationships may provide useful criteria for selective breeding of root systems in Erianthus.

Erianthus species are perennial C4 grasses with such high biomass productivity and high tolerance to environmental stresses that they can be grown in marginal land to supply raw material for cellulosic bioethanol. Because high biomass production and strong tolerance to environmental stresses might be based on their large and deep-root system, we closely examined the morphology and anatomy of roots in first-year seedlings of field-grown Erianthus arundinaceus. The deep-root system of E. arundinaceus consists of many nodal roots growing with steep growth angles. Diameter of nodal roots with large variations (0.5 - 5 mm) correlates with the size and number of large xylem vessels. The microscopic observation shows that the nodal roots with dense root hairs developed soil sheath, hypodermis with lignified sclerenchyma in the outer cortex, and aerenchyma in the mid-cortex. In addition, starch grains were densely accumulated in the stele of nodal roots in winter. In the first year, E. arundinaceus developed less lateral roots than other reported grass species. The lateral roots formed a large xylem vessel in the center of the stele and no hypodermis in the outer cortex. Morphology and anatomy of E. arundinaceus root were discussed with reference to strong tolerance to environmental stresses.

Wetland plants, such as rice, develop aerenchyma, which is formed due to cell collapse, in their roots as pathways for diffusion of oxygen. Understanding of aerenchyma development in their plants is essential to elucidate the resistance mechanism of these plants to waterlogging stress. Synchrotron X-ray micro-computed tomography (micro-CT) is powerful for in-situ three-dimensional visualization of aerenchyma [1]. In this study, we have employed refraction contrast X-ray micro-CT was performed at a bending magnet beamline BL20B2 of SPring-8 to observe when and where aerenchyma starts to form and how they expand. Imbibed rice (Oryza sativa L. ssp. japonica cv. Nipponbare) caryopses were placed and roots were grown in darkness for 2 to 4 days in plastic tubes filled with agar containing Hoagland medium. The effective pixel size of the detector was 2.33 or 4.86 μm/pixel. Dark areas in a tomographic slice of a root were confirmed to correspond to air spaces formed due to cell collapse. Frequency distribution of location of collapsed cells showed it was the highest in the 5th and the 6th tiers from the outside of the endodermis. Air spaces formed due to collapse of a single cell were frequently observed, indicating that aerenchyma initiates at independent locations and then expand. Frequency of location of an adjacent collapsed cell to an existing collapsed cell tended to be higher in the radial and longitudinal direction. Volume of air space including aerenchyma, which were estimated from isosurface models created using tomograms, was confirmed to increase over a period of time. [1] I Karahara et al, Ann Bot 110 (2012) 503-509. C2-O-04 doi:10.1093/jmicro/dfv186

エリアンサスとネピアグラスは，多年生でC4 型光合成経路を有する大型のイネ科草本である．私達は，セルロース系バイオエタノールの原料作物として利用するため，両植物種の栽培技術を研究している．原料作物は食糧生産と競合しないように荒廃地などの非農地でも栽培されるため，劣悪土壌から養水分を獲得する根の能力が必要である．また，地上部全量を系外へ持ち出してしまうため，土壌に還元される唯一の有機物となる根が土壌生産性の向上に果たす役割が非常に大きい．そこで，私達は両植物種の栽培技術だけではなく，根も同時に調査した．両植物種は，浅い土層に多くの根を発達させつつ，かなり深い土層まで到達するような根の分布を示す．その結果，単位面積当たりの現存根量が主要な食用作物と比較して非常に多い．同時に多量の根を土壌中へ脱落させている．節根は太く，多数の導管を有する中心柱には秋頃にデンプン粒が多量に蓄積する．外皮，内皮，中心柱は，他のイネ科植物とは異なる特殊な構造を示す．根毛が密に発達することでsoil sheath が付着し，皮層には空隙も形成される．硬く痩せた土地や湛水条件下で栽培しても旺盛に根を発達させ，大きな地上部を支えるための養水分を良く獲得する．さらに，地上部全量を系外へ持ち出しても土壌炭素濃度は増加する．以上のように，エリアンサスとネピアグラスは，巨大な地上部バイオマスだけではなく，根の機能面からも原料作物に適している．

Cellulosic bioethanol produced from non-edible plants avoids food-fuel competition. Growing such plants on marginal non-arable lands also avoids the use of farmland. In this study, attempts were made to identify potential field sites for cellulosic bioethanol production in Asia. In this study, GIS databases containing information about requirements such as land use, landform, and climate were superimposed. Areas with terrestrial constraints were then removed from the candidate field sites using a terrain slope database. The remaining lands were evaluated using a net primary production (NPP) database. Of these areas, southern and eastern India, northeastern Thailand, and southern Sumatra (Indonesia) had high NPP. In the 2nd phase, local information regarding infrastructure, and agriculture were analyzed. Field-establishment feasibility was high for eastern India and southern Sumatra. Potential field sites were then located in satellite images of these two areas. In the 3rd phase, soils around potential sites were evaluated. Local residents were interviewed to estimate the cost of producing plants for biomass energy. Sites selected using this simple method are suitable for biomass production. Keywords: bioethanol, biomass, cellulosic energy plants, geographic information system, unused land DOI: 10.3965/j.ijabe.20140703.008 Citation: Sekiya N, Hattori T, Shiotsu F, Abe J, Morita S. Identifying potential field sites for production of cellulosic energy plants in Asia. Int J Agric & Biol Eng, 2014; 7(3): 59－67.

The production of cellulosic bioethanol from non-edible plants is drawing increasing attention, as it potentially avoids food-fuel competition. Because growing such plants on farmland indirectly reduces food availability, the plants should be grown on marginal, non-arable lands. In this study, we evaluated the growth of cellulosic energy crops at a former mining site in Indonesia. This mine was abandoned because it contained few mineral deposits, and exposed subsoils rather than toxic soils prevented revegetation. In the first trial, growths of two energy plant species Erianthus spp. and Napier grass (Pennisetum purpureum) were compared with that of maize (Zea mays) at the mine site and a nearby degraded farm. Erianthus and Napier grass produced 11.7 and 22.5 t·ha-1 of shoot dry matter at 8 months after planting (MAP) in the farm respectively while maize plants failed to establish, but none of the three species grew at the mine. In the second trial, two-week-old seedlings of Erianthus and Napier grass rather than stem cuttings as used in the first trial were planted at the mine site. Erianthus and Napier grass produced 16.3 and 24.0 t·ha-1 of shoot dry matter over the course of 18 months, respectively. Application of organic fertilizer significantly increased shoot dry matter to 18.9 and 39.6 t·ha-1 in Erianthus and Napier grass, respectively. During the 18-month growth period, both of the energy plants significantly increased soil carbon at the 0 - 0.3 m depth from 0.33% to 1.15% - 1.23% when chemical fertilizer was applied and to 0.67% - 0.69% when both chemical and organic fertilizers were applied. From 0 - 5 MAP, soil surface level dropped by 28.0 - 34.7 mm in plots without plants due to soil erosion. In contrast, both of the energy plants significantly reduced the drop of soil surface level to 16.0 - 19.3 mm in plots with chemical fertilizer alone and to 18.0 - 20.7 mm in plots with chemical and organic fertilizers. Proportions of small soil particles, that would be easily detached and transported by water flow compared with large particles, were larger in the planted plots than the no-plant plots at 16 MAP. The results suggest that successful cultivation of energy plants on abandoned mine sites is possible, particularly if seedlings are transplanted and the crops are fertilized with organic fertilizer. In addition, the cultivation of Erianthus and Napier grass has positive impacts on soil quality that may contribute to their sustainability as crops and to the conservation of the local ecosystem.

フィールドで栽培した作物の根系の形態や分布を把握するために，改良塹壕法＋コアサンプリング法を利用することを，以前に提案した．ただし，この方法で把握できるのは，ある生育段階における根系形態でしかない．根系の機能を考察するためには，根の発生と枯死・脱落を含めた根系の形成過程を把握することが必要である．このような根系動態を把握するために，これまでにいくつかの方法が開発・利用されてきたが，本稿ではその中からイングロース・コア法（あるいはメッシュバッグ法）を利用することを提案する．この方法では，調査時点における根の現存量のほか，土壌中に埋め込んだメッシュバッグに入り込んだ根量を測定するが，根の発生と枯死・脱落の収支として現存量が決まるという考え方に基づいている．土壌の撹乱など若干の問題点もあるが，この方法を利用することで，根系形成を定量的に把握することができる．牧草の根の生長や，林木の細根の動態を調査するために利用されてきた方法であるが，1年生作物の根系研究に利用することにも意義がある．イングロース・コア法を用いて根の動態に関する研究が進めば，炭素を中心とする物質循環に関する理解が深まり，例えば，地球温暖化対策につながる可能性もある．

For the promotion of environment-friendly agriculture, use of organic fertilizers and green materials is increasingly attempted in rice farming. Although effects of organic fertilizers on soil bacteria in the rhizosphere can differ from those in non-rhizosphere soil, microbiological studies that specifically address the rice rhizosphere still limited. This study was undertaken to investigate the impact of organic fertilizers on soil bacteria communities through comparison of rhizosphere soils and bulk soils. Effects of soil types and seasonal change were also analyzed. Rice plants (Oryza sativa L. cv. Nipponbare) were cultivated in a lowland paddy field of Andosol soil. Applications of compost and rice bran in combination with chemical fertilizer were compared with control soil (chemical fertilizer only). Soil 16S rDNA extracted from rhizosphere soil collected using ultrasonic treatment of rice roots and from bulk soils were analyzed using PCR-denaturing gradient gel electrophoresis (DGGE). Principal component analysis based on PCR-DGGE profiles revealed clear differences in the community structures of soil bacteria between rhizosphere and bulk soils. Furthermore, rhizosphere bacterial community structures of compost and rice bran treatments were plainly different from that of control, and changed with the seasons. The organic fertilizers showed pronounced effects on bacterial communities until mid-summer, but small effects in autumn. Results of this study suggest that the rhizosphere microorganisms in paddy fields can be modified through organic fertilizer management. Moreover, effects of organic fertilizer application, soil type, and phenology on soil bacteria appear depending on interaction with the rice rhizosphere effects in paddy fields.

Water-saving rice-winter crop rotation systems were repeated for 4 cycles from 2000 to 2004 in an urban area, Nishitokyo, Japan, to assess the effects of water-saving (i.e. non-flooded vs. flooded) on grain yield of rice (Oryza sativa L.) and chemical constituents of percolating water. The effects of pre-rice winter cropping compared with fallow on rice yield were also examined. The pre-cultivated crops were wheat (Triticum aestivum L.), italian ryegrass (Lolium multiflorum Lam.) or spinach (Spinacea oleracea L.) with their above-ground parts removed, chinese milk vetch (Astragalus sinicus L.) or rapeseed (Brassica napus L.) with their above-ground parts incorporated before rice transplanting. Neither winter cropping effects nor its interaction with water-saving were significant for rice yield, although the yield after rapeseed incorporation tended to be 9% higher than that after fallow. In 2001, 2003 and 2004, when more than 70% of irrigation water was saved in the non-flooded trial, average yield in non-flooded trial was 58 % of flooded trial, but water productivity increased (from 0.10 to 0.16 kg m(-1)). Among the 3 years, yield in non-floodcd trial was highest in 2004 when the amounts of irrigation and total water supply was larger, the frequency of dry spells was the lowest, and 2 seedlings were transplanted per hill. The nitrate and nitrite concentrations in the percolating water were far below the environmental standard values by WHO. The study showed that incorporation of winter crops had no negative effects on water-saving rice production at least for the first 4 years, and that under extreme water-saving, irrigation and planting methods could minimize yield reduction.

The productivity of upland rice in Japan as well as in the world is low and unstable owing to scarce and unpredictable rainfall. The objective of this study was to examine whether agronomic methods could enhance grain yield of upland rice. Four field experiments were conducted from 2001 to 2003 in Nishitokyo, Japan, under upland conditions with different water supplies, in order to quantify the effects of deep tillage combined with deep placement of manure (50-cm depth), straw mulch (6tha−1), or their combinations on the growth and grain yield of rice. Mulch kept surface soil moisture higher than without mulch even at reproductive stage, and it increased yield to the greatest extent under the most favourable conditions with much rainfall before heading (i.e., 2003). Deep tillage with deep placement of manure induced deep root proliferation and higher nitrogen uptake, increasing biomass production, and panicle number, and consequently grain yield was enhanced under the two lowest yielding environments with less rainfall before heading. Rice plants with deep tillage with deep manure application without mulch tended to have lower leaf water potential and higher diffusion resistance during drought, and negative effects on grain filling and harvest index in some experiments compared with the control. When deep tillage with deep placement of manure was combined with mulching in two experiments in 2002 and 2003, grain yield always enhanced compared with the control (P<0.10, 6.0tha−1 versus 5.4tha−1 on average), suggesting their synergetic mechanisms for yield increase and stabilization. The results showed that deep tillage or mulching can improve grain yield of rice under drought-prone rainfed upland conditions in a temperate climate on an Andosol, and their combination had more consistent and greater positive effects.

A Deep Root System May Be A Desirable Plant Characteristic In Upland Rice Because It Improves The Plant’s Water Extraction Capacity. The Objective of The Present Study Was To Assess The Deep Root Development of Rice Cultivars In Relation To Soil Moisture Change and Plant Water Status Under Upland Conditions With Moderate Water Deficits In The Field and In Simple Lysimeter Experiments. We Used One Upland Cultivar (‘Yumeno-Hatamochi [Yhm]) and Two Lowland Cultivars (‘Lemont’ [Lmt] and 'Nipponbare’ [Npb]) In The Field Experiment, With No Supplemental Water From 88 To 106 Days After Sowing (Das) and 116 To 145 Das. In The Lysimeter Experiment, We Used Yhm and Npb and Imposed Two Water Stress Periods During The Late Vegetative Stages (71 To 104 Das and 88 To 104 Das). In The Lysimeter Experiment, A Higher Deep-Root Length Ratio (Proportion of The Length of Deep Roots To The Total Root Length) In Yhm Was Associated With A Greater Deep-Root Length Than In Npb. The Difference In Deep Root Development Was Associated With Change In Soil Water Content At The Depths of 45 To 70 Cm Between The Two Cultivars Under The Above Conditions. The Drought In The Field Experiment Was Less Intense Than In The Lysimeter Experiment, and We Observed Greater Varietal Differences In Total Aboveground Biomass Than In Root System Development; This Was Associated With The Change In Soil Water Content During The Initial Drought Period. Lmt, With Smaller Shoots, Tended To Save Water and Maintain Higher Leaf Water Potential and Lower Diffusion Resistance As The Drought Progressed. Our Results Suggest That Deep Root Development of Rice Was Primarily Advantageous For Soil Water Extraction and Plant Water Status Under Moderate Water Stress In Uplands, But That The Advantage of A Deep Root System Was Affected By Total Aboveground Biomass, Which Had Strong Effects On Plant Water Status Under These Conditions.

Click to increase image sizeClick to decrease image sizeKey Words: Deep rootOryza sativaPhytomerPlant architectureRoot diameterUpland rice