Water supply from pearl millet by hydraulic lift can mitigate drought stress and improve productivity of rice by the close mixed planting

The authors have proposed the close mixed planting technique using mixed seedlings of two different crop species that results in close tangling of their root systems. Especially, the combination of drought-adaptive upland crops (e.g. pearl millet or sorghum) and flood-adaptive lowland crop of rice would be beneficial to overcome the drought and flood conditions and to reduce the risks of crop failure. In our previous studies, we found that upland crop yield losses by flood stress was mitigated by mix-cropped rice, owing to the oxygen gas released from the rice roots into the aqueous rhizosphere. In the present study, we conducted two experiments to assess whether mixed cropping a drought-resistant cereal, pearl millet, would improve the performance of co-growing drought-susceptible crop, rice under drought conditions. In the field experiment, some grains were obtained from the rice plants mix-cropped with pearl millet under drought condition. However, no rice matured in the single cropping system. In the model experiment using deuterium analysis, it was confirmed that water absorbed by pearl millet roots from deep soil layer was utilized by rice, suggesting that mix-cropped rice could withstand drought stress and complete grain filling using water released into the upper soil layer by hydraulic lift.     

Short-term evaluation of oxygen transfer from rice (Oryza sativa) to mixed planted drought-adapted upland crops under hydroponic culture

Mixed cropping is a cultivation method widely practiced in tropical regions. The newly developed close mixed planting technique mitigates the flood stress of drought-adapted upland cereal species by co-growing rice (Oryza sativa) plants under field flood conditions. We tested the hypothesis that O₂ was transferred from rice to upland crops using the model system of hydroponic culture. To confirm the hypothesis, the phenomena of O₂ absorption and release by plants were evaluated in a water culture condition without soil. Experiments were conducted in a climate chamber to estimate the amount of O₂ released from the roots of rice and pearl millet (Pennisetum glaucum) under both O₂-rich (20.0 ± .0% conc. in phase I) and O₂-free dark (.8 ± .0% conc. in phase II) conditions. The total O₂ change (between the two phases) in a single planting of rice and pearl millet was significantly higher than that of the mixed planting of rice and pearl millet, which indicated that O₂ was transferred from rice to pearl millet under a water culture condition. The result indicated that approximately 7 μM O₂ g fresh root weight^?1 h^?1 was transferred between the two plant species. O₂ transfer was confirmed between the two plant species in a mix cultured in water, implying its contribution to the phenomenon that improved the physiological status of drought-adapted upland crops under field flood conditions.     

Pearl Millet Developed Deep Roots and Changed Water Sources by Competition with Intercropped Cowpea in the Semiarid Environment of Northern Namibia

abstract

The practice of intercropping pearl millet with cowpea is widespread among subsistence farmers in northern Namibia. In this region, the scarce and erratic rainfall may enhance competition for the limited soil water between intercropped plants. Trials were conducted on a field of the University of Namibia (on-station) and on a farmer’s field (off-station) to determine the effects of competition between pearl millet and cowpea on the water sources and plant growth of each crop. The deuterium analysis showed that pearl millet, intercropped with cowpea, significantly increased its dependence on the recently supplied labeled irrigation water. Intercropped cowpea also showed an increased trend of the dependence but it was not statistically significant. At the university field, intercropped pearl millet showed higher dependence on the irrigation water than monocropped pearl millet. At the farmer’s field, the dependence of intercropped pearl millet on the irrigation water was low in the pearl millet-dominant zone. In contrast, the dependence on the irrigation water was high in the cowpea-dominant zone, indicating that the dependence on the irrigation water changes according to the size of the pearl millet canopy. The water sources of cowpea did not show a significant difference at either pearl millet-dominant or cowpea-dominant zone, indicating a stable water uptake trend under competitive conditions. Competition with cowpea significantly increased the root-weight density of intercropped pearl millet in the deep soil layers, but decreased that in the shallow layers. The root-weight density of intercropped cowpea, however, was reduced in most of the soil layers. In conclusion, cowpea has a higher ability to acquire existing soil water, forcing pearl millet to develop deep roots and shift to the surface irrigation water.     

Mixed Planting with Legumes Modified the Water Source and Water Use of Pearl Millet

Abstract

In semi-arid areas, pearl millet is an important staple food crop that is traditionally intercropped with cowpea. This study evaluated the water competition between pearl millet and cowpea using deuterated water. At vegetative stage, pearl millet biomass production was lower in the pearl millet-cowpea (PM-CP) combination than in the pearl millet-pigeon pea (PM-PP) and pearl millet-bambara nut (PM-BN) combinations. PM-CP used more water than PM-PP and PM-BN under well-watered conditions; however, all combinations used similar amounts of water under dry conditions. The biomass production, photosynthetic rates, transpiration rates, and midday leaf water potential of pearl millet at early flowering stage were not significantly reduced by mixed planting with cowpea sown two weeks later as compared with single planted pearl millet. When pearl millet and cowpea were sown at the same time, mix planting significantly increased the recovery rates of recently irrigated heavy water in pearl millet, but not in cowpea in both vegetative and early flowering stages. Midday leaf water potential and transpiration rates in pearl millet were lowered by mixed planting but those in cowpea were not. These indicate that the water source of pearl millet is shifted to the recently irrigated and easily accessible water. By contrast, when cowpea was sown two weeks later than pearl millet, this trend was not observed. These results provide new evidence on water competition in the PM-CP intercropping system; cowpea has higher ability to acquire existing soil water than pearl millet when both crops are sown at the same time.     

Growth of Roots Emerged from Excised Phytomers of Three Gramineous Species under a Low Osmotic Potential

Abstract

The growth of crown and lateral roots emerged from the excised phytomers of pearl millet (Pennisetum typhoideum Rich.), barnyard millet (Echinochloa frumentacea Link.) and maize (Zea mays L.) was studied under normal and low osmotic potential conditions. The plants were grown in two solutions with osmotic potentials of –0.02 and –0.54 MPa for 6 days. The relative growth rate of the roots in total length (RGR_L) , was not affected by osmotic stress in pearl and barnyard millets, but that in stressed maize was reduced to 64% of the control. Similarly, the relative growth rate of the roots in dry weight (RGR_W), was not affected by osmotic stress in pearl and barnyard millets, but significantly reduced in maize. Osmotic stress increased the specific root length of the lateral roots in pearl and barnyard millets, but did not affect that of maize. The photosynthetic rate (Pr) in the two millets was decreased to ca. 60% of the control by the stress, and that in maize was reduced to 21%. Under the stress, Pr in the three species was limited mainly by low stomatal conductance, but no clear relationship was found between Pr and osmotic adjustment of the leaf. The relative water content of the leaf was lower in maize than in the two millets. The resistance to water flow through the phytomer (R) was significantly increased by osmotic stress in maize, but not significantly in the two millets. The mean root length (RL) was decreased by the stress in maize, but not in the two millets. The maintenance of RGR_L in the two millets was associated with sustained R, RL and also with the maintenance of Pr and allocation of assimilates to roots.     

Cover Crops as Affecting Soil Chemical and Physical Properties and Development of Upland Rice and Soybean Cultivated in Rotation

Cover crops can provide changes in soil chemical and physical properties, which could allow a sustainable development of soybean and upland rice rotation in Brazilian Cerrado. The objective of this study was to determine the effects of cover crops(cultivated in the offseason) in the soybean-upland rice rotation(cultivated in the summer season) on the soil chemical and physical properties, yield components and grain yield of the cash crops. The experimental design was a randomized block design in factorial scheme 4 × 2 with six replications. Treatments were composed by four cover crops: fallow, millet(Pennisetum glaucum) + Crotalaria ochroleuca, millet + pigeon pea(Cajanus cajans), and millet + pigeon pea + Urochola ruziziensis in the offseason with one or two cycles of cover crops, with rice(Oryza sativa)or soybean(Glycine max) in the summer season. Cover crops alone provided no changes in soil chemical properties. However, the rotation cover crops/cash crops/cover crops/cash crops reduced p H, Al and H + Al and increased Ca, Mg, K and Fe contents in the soil. The cover crops millet + pigeon pea and millet + pigeon pea + U. ruziziensis improved soil physical properties in relation to fallow,especially in the 0–0.10 m soil layer. In spite of the improvement of the soil physical properties after two years of rotation with cover crops and cash crops, the soil physical quality was still below the recommended level, showing values of macroporosity, S index and soil aeration capacity lower than 0.10 m3/m3, 0.035 and 0.34, respectively. Upland rice production was higher under mixtures of cover crops than under fallow, mainly because of soil physical changes done by these mixtures of cover crops.Soybean grain yield was similar under all cover crops tested, but was higher after the rotation cover crops/upland rice/cover crops than after only one cycle of cover crops.     

Effects of winter flooding on weedy rice (Oryza sativa L.)

Weedy rice (Oryza sativa L.), characterised by competitiveness, seed longevity, and dormancy is a troublesome weed to rice fields. Furthermore, its close botanical affinity to cultivated rice makes its control particularly difficult. However, winter flooding of rice fields can be an efficient technique to control weedy rice infestation by promoting weed seed decay, animal predation, or germination.     

Wind erosion control using crop residue II. Effects on millet establishment and yields

Effects of three levels of millet stover residue (0, 500, and 2000 kg ha⁻¹) on establishment and growth of pearl millet (Pennisetum glaucum (L.) R.Br) were determined in a wind-erosion-affected area in Niger, West Africa, during 1991 and 1992. The extent of millet seedlings buried by blown soil in plots with 500 kg ha⁻¹ residues was similar to that of control plots. A residue amount of 2000 kg ha⁻¹ reduced the extent of covered millet, but did not provide complete protection during severe sand storms. Partial covering of millet seedlings by blown soil decreased biomass yields compared to uncovered millet. Grain production, averaged over two years, was about 500 kg ha⁻¹ for the control, 570 kg ha⁻¹ with 500 kg ha⁻¹ residue, and 730 kg ha⁻¹ with 2000 kg ha⁻¹ residue. Increased yields were caused by both wind erosion protection and direct growth stimulating effects of residue. Stover yields for all treatments in both years were less than 2000 kg ha⁻¹ and thus insufficient to sustain the levels required for protection of crops against wind erosion damages. An increase in dry matter left in the field or the implementation of alternative wind erosion control measures is needed for sustainable crop production in wind-erosion-affected areas.     

Studies on Ancient Rice—Where Botanists, Agronomists, Archeologists, Linguists, and Ethnologists Meet

Taiwan’s aboriginal peoples are thought to be related to ancestral Austronesian-speaking peoples. Currently, Taiwan has 14 officially acknowledged aboriginal tribes. The major crops currently farmed in aboriginal areas are rice (Oryza sativa) and foxtail millet (Setaria italica). Archeologists recently excavated the remains of several early cultures in Taiwan. The most plentiful plant remains were carbonated rice and foxtail millet grains. The earliest ¹⁴C date of these excavation sites is ～5,000 bp. These settlements may be those of the earliest ancestral Austronesian speakers in Taiwan. Rice domestication is a complex story. In this study, we identified the functional nucleotide polymorphisms of 16 domestication-related genes using 60 landraces collected from aboriginal Taiwanese villages about 100 years ago. We also screened the phenotypes of these landraces. By integrating pheno- and genotypic data, together with data from archeologists and linguists, we may be able to better understand the history of rice cultivation in Taiwan and nearby areas.     

Hydrogen Stable Isotope Analysis of Water Acquisition Ability of Deep Roots and Hydraulic Lift in Sixteen Food Crop Species

Abstract

Deep root penetration, which allows access to deep soil water and hydraulic lift, may help plants to overcome drought stress. The aim of this study was to evaluate the ability of sixteen food crop species to take up water from deep soil layers and the extent of hydraulic lift by the use of deuterated water. Plants were grown in pots consisting of two loose soil layers separated by a hardpan and a Vaseline layer. The lower (deep) layers were always kept wet (32%; ψ = –5 kPa), while soil moisture in the upper (topsoil) ones was adjusted to 25% (ψ = –7 kPa) and 12% (ψ = –120 kPa) in the well-watered and drought treatments, respectively. The deuterium labeling of the deep soil water provided evidence that wheat, Job’s tears, finger millet, soybean, barnyard millet, rice, and rye (in decreasing order of D₂O increments) extracted more water from the deep layers under drought than well-watered in topsoil. These species showed significantly greater hydraulic lift under drought, except for soybean. Most of these species also showed increased root length density in deep soil layers and sustained high photosynthetic rates under drought. In contrast, pigeon pea, cowpea, common millet, pearl millet, foxtail millet, maize, barley, and oat did not show a significant increment in either deep-water uptake or hydraulic lift under drought. In summary, increased extraction of deep soil water under drought was closely related with the magnitude of hydraulic lift.     

Response of Yield Traits of Rice (Ⅱ-You 898) to Abrupt Drought-flood Alternation

【Objective】Abnormal global climate change leads to the reoccurrence of abrupt drought-flood alternation (ADFA). In order to national food security and disaster prevention and reduction in crops, we analyzed yield response characteristics of rice to ADFA. 【Method】The experiment was conducted at the Xin-maqiao irrigation experimental station at the Anhui and Huaihe River Institute of Hydraulic Research in China (117°22′E, 33°09′N) between 2017 and 2018. Three drought-flood alternation treatments were designed and compared with normal irrigation conditions. Based on the experimental data, the effects of drought, flood, and ADFA on rice yield and yield components were analyzed, the quantitative indicator R for the compensation or reduction of the early drought and later floods was proposed, and the interaction effects between late flooding stress and early drought stress on yield was revealed.【Result】Compared with the normal group, ADFA stress reduced the rice yield. The yield reduction ranged from 12.38% to 56.15%. Among them, the combination of heavy drought and heavy flood was the most unfavorable for yield. The reduction in the grain number and the grain weight was the main reason for yield reduction under ADFA stress. The drought stress of the ADFA groups compensated the yield under flood conditions, mainly because the grain number per panicle, total grain number and seed setting rate increased during the drought period. The flood stress of the ADFA groups reduced the yield under drought conditions, and the decrease in the grain number per panicle, total grain number, thousand-seed weight and seed setting rate during the flooding period was the main reason. 【Conclusion】The results show that in the case of light and moderate drought stress occurring at the early stage, the damage caused by late-stage flood stress on rice should be avoided as possible; if flooding is predicted to occur in the later period and the drainage facilities can not eliminate its adverse effects, drought treatment can be carried out in advance at the medium-late period of the jointing stage to reduce the loss of rice yield.     

Effects of salt and low light intensity during the vegetative stage on susceptibility of rice to male sterility induced by chilling stress during the reproductive stage

We tested whether exposing rice plants to abiotic stress (salt or shade) during vegetative growth affects the chilling tolerance of reproductive organs, which is one of the most important traits for rice growing in a cool climate; we used two rice cultivars with different tolerance in two growing seasons. We divided the vegetative growth into three phases to clarify the most sensitive period: 7–22 days after transplanting (DAT), 23–38 DAT and 39–54 DAT. Chilling tolerance of the pre-stressed plants was based on the male sterility induced by low temperatures. Shade and salt stress during all three vegetative growth phases significantly reduced stomatal conductance. Shade decreased the specific leaf weight and the leaf sugar and starch contents, but salt had no significant effect, despite causing leaf damage. Low temperatures during the reproductive stage induced spikelet sterility in all plants, but the magnitude was greater in the salt- and shade-stressed plants of both cultivars, especially those stressed late during vegetative growth. The increased spikelet sterility caused by chilling was closely related to the reduction of the total spikelet number per panicle. This is the first study to show that salt and low light stress during vegetative growth increased the susceptibility of rice plants to chilling damage during panicle development.     

Ⅱ优898产量对旱涝急转的响应规律研究

【目的】全球气候变化异常导致旱涝急转事件频发,为保障国家粮食安全,做好农作物的防灾减灾工作,研究了旱涝急转条件下水稻的减产特征。【方法】以淮北平原区水稻为试验对象,在淮委水利科学研究院新马桥农水试验站(117°22′E,33°09′N)开展了为期两年(2017–2018年)的水稻旱涝急转胁迫试验,分析了不同旱涝胁迫程度、不同胁迫持续时间的单一干旱、单一淹涝、旱涝急转胁迫对水稻产量及产量构成的影响,提出先期旱与后期涝的补偿、削减作用量化指标R,揭示了旱涝急转后期淹涝胁迫与前期干旱胁迫对水稻产量影响的交互作用新规律。【结果】拔节期发生旱涝急转产量普遍减少,减产范围12.38%~56.15%。其中,重旱重涝组合对产量最为不利,粒数与粒重减少是旱涝急转胁迫条件下水稻减产主要原因;旱涝急转处理下前期适度干旱可减轻后期淹涝导致的减产,即旱涝急转旱胁迫对涝胁迫具有产量上的补偿效应,主要是提高了每穗粒数、总粒数和结实率;而后期淹涝对前期干旱具有协同作用,表现出产量上的削减效应,主要是每穗粒数、总粒数、千粒质量、结实率的减少。【结论】前期已经发生了轻、中旱胁迫,应尽量避免后期淹涝对水稻的二次损伤;若预测到后期将出现洪涝,并且短时间内田间排水设施无法消除其不利影响,则可提前在水稻拔节中、后期进行旱锻炼以减轻水稻产量损失。     

Effect of fermentation on protein,fat, minerals and thiamine content of pearl millet

Natural as well as single, mixed and sequential pure cutlure (S. diastaticus, S. cerevisiae, L. brevis andL. fermentum) fermentations of pearl millet flour for 72h lowered pH and raised titratable acidity. The fermentation either decreased or did not change the protein content of pearl millet flour. Natural fermentation increased whereas pure culture fermentation decreased the fat content. Ash content did not change. Natural fermentation at 20°C and 25°C increased whereas at 30°C it decreased the thiamine content of the pearl millet flour. Yeast fermentation raised the level of thiamine two- to three-fold, while lactobacilli fermentation lowered it significantly.     

淹水缓解直播早籼稻苗期低温冷害的生理特性研究

【目的】 探究淹水对低温胁迫下直播早籼稻幼苗生长的影响,为南方稻区直播稻生产与抗逆栽培奠定生理基础。【方法】 以耐冷品种湘早籼6号和冷敏感品种中嘉早17为材料,设置低温处理(8℃)、低温淹水处理(8℃ + 淹水)与常温对照(25℃)3个处理(处理3 d),分析秧苗农艺性状、抗氧化酶活性、渗透调节物质含量、光合酶活性和内源激素含量等生理特性。【结果】 与低温处理相比,低温淹水处理3 d后不同耐性品种的苗高、鲜质量、干质量和顶三叶叶长显著增加,根数、最大根长、剑叶叶长、倒2叶叶长也都有不同程度增加,淹水可减轻低温对水稻秧苗农艺性状的影响;耐冷品种湘早籼6号苗期受到伤害的程度小于冷敏感品种中嘉早17。此外,与低温处理相比,低温淹水处理显著降低叶片抗氧化酶活性(SOD、POD、CAT)、可溶性蛋白、渗透调节物质(MDA、脯氨酸)含量和内源生长抑制类激素(ABA)含量,同时显著增加了内源生长促进类激素(GA₃)含量;低温条件下淹水可减少植物体内活性氧的积累,减轻膜脂过氧化,加强了植物体内源激素的调控作用。同时,低温和低温淹水处理显著降低叶片叶绿素和ATP含量,导致光合酶(Rubisco、PEPCK)活性降低;但低温淹水处理的影响低于低温处理,低温淹水可起到缓解作用。且在恢复处理后,低温淹水处理各生理活性指标更接近对照处理,而与冷敏感性品种相比,耐冷性品种可缓解低温胁迫产生的伤害。【结论】 低温处理影响直播早籼稻秧苗生长特性,降低了秧苗光合酶活性;同时提升叶片抗氧化保护酶活性与渗透调节势,但淹水处理有助于缓解低温胁迫造成的叶片生理伤害。     

Growth and yield potential of Oryza sativa and O. glaberrima upland rice cultivars and their interspecific progenies

A recent breakthrough in generating fertile progeny from Oryza sativa×O. glaberrima crosses gives rice breeders access to a broader range of germplasm. Interspecific crosses might provide new solutions to the low productivity of upland rice systems prone to weed competition. Two field and one pot experiments conducted during 1995 and 1996 served to characterize growth and yield potential of CG14 (O. glaberrima), WAB56-104 (O. sativa) and their progeny. During the 1995 wet season and the 1996 dry and wet seasons, the lines were seeded in a well-drained upland field in Ivory Coast with supplemental sprinkler irrigation. A randomized complete-block design with three replications was used, with cultivar and nitrogen levels as sub-plots. Specific leaf area (SLA), leaf area index (LAI), leaf chlorophyll content (SPAD method) and tiller number were measured at 2-week intervals until flowering. Grain yield and yield components were measured at maturity. In all environments, CG14 produced two to three times the LAI and tiller numbers as WAB56-104. This was associated with a high SLA and low leaf chlorophyll content. Grain yields of CG14 did not respond to N inputs, although the sink potential did. The difference was mainly caused by grain shattering. The progenies had intermediate LAI, SLA and leaf chlorophyll content, but their grain yields, tiller numbers and resistance to lodging and grain shattering were similar to WAB56-104. Across lines, LAI and SLA were significantly correlated. A paddy field experiment confirmed the relationship between LAI and SLA for a wider range of rice cultivars and interspecific progenies. A pot experiment demonstrated that leaf net CO₂ assimilation rates (A_max) followed a common linear function of areal leaf chlorophyll content across cultivars. The main common cause of differential LAI and A_max appeared to have been genotypic patterns of SLA, which might be an important determinant of growth vigor and competitiveness with weeds. The possibility is discussed of combining, in a single line, high SLA during vegetative growth (for weed competitiveness) with low SLA during the reproductive growth phase (for high yield potential), to produce an efficient plant type for low-management conditions.     

Genetic Characterization of Indigenous Rice Varieties in Eastern Himalayan Region of Northeast India

The eastern Himalayan region of Northeast （NE） India is home to a large number of indigenous rice varieties, which are traditionally classified as Oryza sativa subspecies indica, japonica or intermediate types. The classification based on traditional Cheng’s index is often inconclusive due to phenotypic plasticity of morphological characters, which are influenced by environmental conditions. We used molecular markers specific for indica and japonica subspecies to assess the degree of genetic relatedness of indigenous rice varieties in NE India. The results revealed that majority of upland （jum） and glutinous rice varieties, traditionally considered as japonica, were genetically close to the subspecies indica. All varieties of boro ecotype were found to be indica type, and only a few varieties cultivated in lowland and upland areas were japonica type. Some of the lowland varieties of the sali ecotype were intermediate between indica and japonica, and they showed a closer genetic affinity to O. rufipogon.     

Countermeasures for heat damage in rice grain quality under climate change

Climate change has been an increasingly significant factor behind fluctuations in the yield and quality of rice (Oryza sativa L.), particularly regarding chalky (white-back, basal-white, and milky-white) grain, immature thin grain, and cracked grain. The development and use of heat-tolerant varieties is an effective way to reduce each type of grain damage based on the existence of each varietal difference. Cultivation methods that increase the available assimilate supply per grain, such as deep-flood irrigation, are effective for diminishing the occurrence of milky-white grains under high temperature and low solar radiation conditions. The application of sufficient nitrogen during the reproductive stage is important to reduce the occurrence of most heat damage with the exception of milky-white grain. In regard to developing measures for heat-induced poor palatability of cooked rice, a sensory parameter, the hardness/adhesion ratio may be useful as an indicator of palatability within a relatively wide air–temperature range during ripening. Methods for heat damage to rice can be classified as either avoidance or tolerance measures. The timing of the measures is further divided into preventive and prompt types. The use of heat-tolerant varieties and late transplanting are preventive measures, whereas the application of sufficient nitrogen as a top dressing and irrigation techniques during the reproductive stage are prompt types which may function to lower the canopy temperature by enhancing evapotranspiration. Trials combining the different types of techniques will contribute towards obtaining more efficient and steady countermeasures against heat damage under conditions of climate change.     

Tolerance of foxtail,proso and pearl millets to saflufenacil

Herbicide options for weed control in millets are very limited and hence there is a need for exploring potential herbicides. Field trials were conducted at three locations in Kansas and Nebraska in 2009 to evaluate foxtail millet, proso millet, and pearl millet tolerance to saflufenacil applied preemergence (PRE) at 36, 50, and 100 g ai ha⁻¹. Foxtail millet was the most sensitive of the three millets to saflufenacil. Among experimental sites, saflufenacil at 36 g ha⁻¹ injured foxtail millet 59–99% and reduced plant stands 41–95%; nearly all plants died at 100 g ha⁻¹. Despite early season foliar injury and up to 36% stand reduction, fodder or grain yields of proso and pearl millets were not reduced by any rate of saflufenacil compared to untreated controls. Additional trials were conducted at four locations in Kansas, Nebraska and South Dakota in 2010 and 2011 to refine saflufenacil use rate (36 and 50 g ha⁻¹) and application timing [14 days early preplant (EPP); 7 days preplant (PP); and PRE] for use in proso and pearl millets. Saflufenacil applied EPP or PP, regardless of rate, caused up to 21 and 6% foliar injury and up to 21 and 9% plant stand reduction in proso and pearl millets, respectively. However, yields were not reduced by EPP or PP treatments in either millet crop. PRE applications of saflufenacil caused the highest crop injury and stand reduction in both millets. Saflufenacil PRE at 36 g ha⁻¹ caused up to 57 and 40% foliar injury and up to 42 and 24% stand reductions in proso and pearl millets, respectively; however, yields were not affected. Comparatively, saflufenacil PRE at 50 g ha⁻¹ reduced yields of proso and pearl millets 36 and 52%, respectively, on sandy loam soils with high pH (8.3) and low organic matter content (1.1%). Overall, results indicated that foxtail millet lacks tolerance to saflufenacil, but up to 50 g ha⁻¹ of saflufenacil may be safely applied as near as 7 days before planting proso or pearl millets. If situation demands, saflufenacil at 36 g ha⁻¹ can also be applied PRE to either crop with risk of some crop injury.     

Historical Changes in Urban Rice Production Systems in Tokyo,Japan

Abstract

Historical changes in planting area, yield improvements, and production of both paddy and upland rice (Oryza sativa L.) in Tokyo and the whole of Japan from 1877 to 2003 were reviewed. The area of rice in Tokyo was at its peak (17,000 ha) at the beginning of the 20th century but dramatically reduced thereafter except for the period of 1950s, to200 and 30 ha for paddy and upland rice, respectively, in 2003, due to urbanization. After the 1950s, the land-use efficiency rate in Tokyo was reduced from 180 to 100% and rice self-sufficiency rate from 4 to 0.1%. There was historical yield improvement of paddy rice in Tokyo particularly after 1960s in the Southern and Northern Tama regions, but the current yield level in Tokyo (ca. 400 g m-²) is lower than that in the whole of Japan (more than 500 g m-²) eventhough crop damage due to low temperatures is not serious.The reasons were discussed from the viewpoints of (1) less agricultural inputs and agronomic management, (2) declining rice research after the 1970s, (3) higher elevating air temperature(e.g. 1.4°C for the last 40 years), in Tokyo, and (4) yield component differences. Upland rice in Tokyo has a planting area comparable with paddy rice (ca. 7,000 to 8,000 ha) during the 1950s, but yield improvement during the last 50 yearsis not noticeable (ca. 150 g m-²) with no development of cultivars, and with greater fluctuation of crop situation index due to drought compared with paddy rice. This review paper discusses the importance of urban rice production system, along with a proposal of the alternatives.