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Dwindling water resources appear to become a great challenge threatening the future of sustainable rice cultivation as it consumes substantial amount of water available in agricultural farming par se. Ostensibly being a water-guzzling crop, aerobic rice could be a viable option requiring less irrigation water than conventional farming, instead. However, grain yield penalty while grown continuously is becoming a strong demerit for sustainable aerobic rice cultivation. A better understanding of the causes and concerns vis-à-vis alleviation mechanism suggested a long term field experiment studying rotational sequences with different non-rice crops in a system perspective mode. Thus, the current field study was conducted for consecutive five years exploring the potentiality of aerobic rice based crop rotations with maize, ground nut and green gram in view of promoting soil health resiliency for arresting grain yield decline during 2013–14 to 2017–18. The study revealed a perceptible depletion in soil quality parameters at the end of last year/5th year accounting around 2.70% soil organic carbon, 1.70% available nitrogen, 1.60% available phosphorus, 1.39% available potassium, 2.75% iron and 1.35% zinc as compared those in the 1st year of the study. Even the situations also aggravated root nematode populations, especially rice root knot (Meloidogyne graminicola) and root rot nematode (Hirschmanniella oryzae) that inhibited usual root growth pronouncing less volume (26.50 cc plant−1) and density (0.54 g cc−1). As a result, drastic depression in usual growth and development of continuously grown aerobic rice caused more than 50% grain yield (2.04 t ha−1) decline at the 5th year compared to that (4.30 t ha−1) at the initial 1st year. However, no detrimental impacts were visualized on rice while grown in yearly rotation with non-rice crops; instead, grain yield increased significantly, especially in rotation with groundnut or green gram (4.40–4.46 t ha−1). Additionally, rice grain protein content (6.92–7.0%) also enhanced as compared that (6.36%) at pure aerobic rice stands. Thus, implication of this current study could have far reaching consequences ensuring aerobic rice cultivation sustainable in a rotational sequence with ground nut/green gram even under the apprehension of irrigation water deficiency. [ABSTRACT FROM AUTHOR]

In present study, 48 drought tolerant lines along with two susceptible genotypes of upland and lowland rice ecologies were tested at Central Rice Research Institute during dry season of 2011 and 2012, to identify the reproductive stage drought tolerant lines and to exploit the genetic variations. In support of various estimates of morpho-physiological parameters, genotypes Nan Te Hao, Purbachi (Chinese 1), Saita, NSIC Rc 222, Binnatoha, CO18, Ai Jiao Nan Te, Brown Gora, Black Gora (NCS 12), Jhona 349, Kalakeri are adjudged as good donors for reproductive stage drought tolerance in rice. [ABSTRACT FROM AUTHOR]

Twenty five genotypes were evaluated across the year, locations and two water regimes under aerobic vs. irrigated conditions from 2011 to 2012. The objectives of this research were to determine the importance of the genotype x environment interaction (G x E) using statistical parameters for yield and other quantitative characters. Joint regression was used to understand the importance of genotypes and their interaction. Genotype, environment and their interactions influenced significantly the phenotypes for all characteristics of genotypes. IR 79906-B-192-2-1 was identified as stable genotypes by Eberhart & Russell model. The IR 78875-131-B-1-4, IR 80312-6-B-2-B, IR 74371-3-1-1, IR 79899-B-179-2-3, IR 55419-04, IR 80021-B-86-3-4, IR 78878-53-2-2-4, IR 78877-181-B-1-2 and WR 3-2-6-1 were recorded lowest aerobic response index (ARI<1) for seed yield over the seasons. Based on the various parameters, the genotypes IR 74371-1-1, IR 80021-B-86-3-4 and IR 78875-131-B-1-4 may be exploited for commercial cultivation under different water regimes. The genotypes B-6144-F-MR-6-0-0 and IR 55423-01 yielded maximum across the location and water regimes, and even produced acceptable yield under aerobic condition and provided scope for further large scale evaluation at farmer's field. [ABSTRACT FROM AUTHOR]

Yield decline is the major concern in tropical aerobic rice (Oryza sativa L.). Both biotic and abiotic factors were responsible for this phenomenon. No analytical information on actual causes was reported taking into account of responses of root to water stress conditions. In a field experiment at the Central Rice Research Institute, India during 2009 and 2010, five rice genotypes were grown under two soil water conditions, aerobic and semi-aerobic condition, for better understanding of yield penalty vis-à-vis yield stability. Results showed aerobic condition significantly inhibited structural development of root and caused significant variation in biochemical root traits accounting for higher concentration of hydrogen peroxide (24.6%) and proline (20%), and lower concentration of total soluble protein (20%) that resulted in 17% yield decline than semi-aerobic condition. Applying supplementary irrigation at semi-aerobic condition achieved 21% more grain yield compared with aerobic condition due to 21%, 8.3, and 10.4% more root biomass, root volume, and root/shoot ratio, respectively. Interaction of genotypes with soil water conditions revealed that at aerobic condition, better performance could be expected in 'Apo' (4.0 t ha-1) and 'IR 74371-3-1-1' (3.80 t ha-1) with less yield decline (7.0-9.5%); supplementary irrigation enhanced their grain yield (4.3-4.4 t ha-1) at semi-aerobic condition. Therefore, detrimental impact of physical and biochemical root traits' changes on yield decline in aerobic rice could be alleviated with supplementary irrigation at critical growth stages under semi-aerobic condition without compromising with water productivity. [ABSTRACT FROM AUTHOR]

Aerobic rice is considered a viable agro-technology to cope with the looming crisis of water supply that threatens the sustainability of irrigated rice production systems. Rice adapted to aerobic conditions requires less water than that grown under conventional irrigation management. A field study was conducted at Cuttack, India, during the dry season (January-May) in 2005 and 2006 to determine the critical soil moisture regime at the root-zone depth (30 cm) for sustaining optimum growth and grain yield of aerobic rice variety 'Apo' (IR 55423-01). Irrigation at 0, 20 and 40 kPa soil moisture tension resulted in similar grain yields (4.90-5.25 t ha-1 in 2005 and 4.35-4.50 t ha-1 in 2006). The seasonal water requirement in treatments receiving irrigation at 20, 40 and 60 kPa soil moisture tensions was 28.4, 42.8 and 60.7% lower than that at 0 kPa soil moisture tension, but the yield declined significantly at 60 kPa, i.e. by 42.8% in 2005 and 36.7% in 2006. Irrigation at 40 kPa soil moisture tension ensured maximum water productivity of 0.90, 0.47 and 0.53 g grain kg-1 water with respect to evapotranspiration, irrigation plus rainfall and irrigation alone, respectively. Thus, irrigation at 40 kPa soil moisture tension may be considered critical for optimum grain yield and maximum water productivity of aerobic rice in Indian cultivation conditions. [ABSTRACT FROM AUTHOR]

The cultivation of aerobic rice appears to be a potential option while mitigating threats of looming water scarcity for sustainable rice production. Although, severe prevalence of multi-flush weed pressure inhibiting nitrogen utilization for optimum grain yield becomes the crux of the problem for up-scaling this technology. Thus, the hypothesis of the study was that critical period of weed control (CPWC) governs nitrogen accumulation in aerobic soil—plant continuum, which appears to be the major determinant of ultimate grain yield in aerobic rice cultivation. With this view, the field studies were successively conducted in two locations at Panthnagar, Uttar Pradesh during 2015 and at Cuttack, Odisha during 2016 in India. Nitrogen utilization was estimated with varying magnitude of critical period of weed prevalence at 15 days interval since sowing till 75 days of crop growth. Results recorded significantly higher nitrogen uptakes of 106.6 and 106.0 kg ha−1 while maintaining near weed-free situations during initial 75 days of crop growth at Panthnagar and Cuttack respectively, which were however comparable with similar situations maintained also at 60 and 45 days of crop growth in respective location. Consequently, stands at these situations produced comparable grain yield of 5.56 and 5.25 t ha−1, 5.40 and 5.00 t ha−1, and 5.15 and 4.70 t ha−1 at corresponding locations, which were significantly higher than those corresponding weedy stands producing 1.35 and 0.90 t ha−1, 1.48 and 1.10 t ha−1, and 2.86 and 2.45 t ha−1 grain yields in respective locations. Thus, higher nitrogen gains of 0.42 and 0.06%, and 0.31 and 0.03% were attributed to initial 75 and 60 days weed-free stands respectively at Panthnagar and Cuttack. While, nitrogen losses were maximum of 24.99 and 25.69%, and 24.26 and 24.85% at corresponding weedy crop stands; although, initial 15 day's weedy crop stands or initial 45 days weed-free stands recorded the lowest nitrogen losses of 0.64 and 1.35%, and 1.51 and 2.16%, instead. Therefore, the study contributed above novel information explaining the dynamic correlation of nitrogen balance with prevalence and also magnitude of CPWC where N uptake culminated at 45 days weed-free situation ensuring optimum aerobic rice productivity. [ABSTRACT FROM AUTHOR]

Development of high-yielding rice varieties for the rainfed shallow lowland ecosystem of eastern India is a major challenge for plant breeders. Development and release of CR Dhan 407, a high-yielding cultivar, with a potential yield of more than 5 tons per hectare and non-lodging plant type, can address the problem of yield stagnation in this major rice ecosystem of India. With its high yield and excellent grain quality, this variety can significantly enhance the income of rice farmers of eastern India. [ABSTRACT FROM AUTHOR]

A set of 75 rice genotypes were evaluated under reproductive stage drought stress and controlled conditions during kharif 2011 and 2012 to identify stress tolerant genotypes. Drought tolerance indices like stress susceptibility index (SSI), drought tolerance efficiency (DTE), stress tolerance index (STI) and stress tolerance (TOL) and physio-morphological traits responses were employed in screening of the genotypes. Significant yield reduction was observed under drought stress in majority of the rice genotypes studied. Drought stress at reproductive stage caused reduction in grain yield (55.31%), leaf area (34.87%), number of spikelet (15.9%), spikelet fertility (17.13%), plant height (8.87%), relative water content (31.57%), harvest index (29.2%), while increase in sterility percentage (51.5%) and proline content (55.9%). The variation in SSI values ranged from 0.39 - 1.34, DTE from 26.10-78.54%, STI ranged from 0.22-0.74 and TOL varied from 0.91 -3.54. The genotypes with high DTE and STI and low SSI and TOL were identified as drought tolerant genotypes. Based on preliminary screening, rice genotypes IR55419-04, IR84895-B-B-127-CRA-5-1-1, IR83376-B-B-24-2, IR83387-B-B-40-1 and IR83373-B-B-24-3 showed low SSI and TOL and high DTE and STI values were identified as drought tolerant genotypes. These drought tolerant genotypes also showed superior performance with respect to grain yield and desired physiological and biochemical traits viz., relative water content (RWC), chlorophyll content, proline content, stomatal conductance and photosynthetic rate. Significant negative correlation found between grain yield with leaf rolling, leaf drying and spikelet sterility under stress condition. The present study indicate that selection based on stress tolerance indices likes DTE, SSI, STI and TOL will results in identification of drought tolerant genotypes for rainfed ecosystem. [ABSTRACT FROM AUTHOR]