Aerobic Rice System Research Articles

Soil greenhouse gas emissions under enhanced efficiency and urea nitrogen fertilizer from Australian irrigated aerobic rice production

AbstractAerobic rice production offers a promising solution to improve water use efficiency and reduce methane (CH4) emissions by minimizing water inundation. However, alternate water‐saving methods for rice cultivation can lead to “trade‐off” emissions of nitrous oxide (N2O). A field experiment was conducted over one season measuring soil‐derived greenhouse gas emissions in irrigated aerobic rice (Oryza sativa L.) under different N fertilizer management at a rate of 220 kg N ha−1, including a nil treatment (“control”); slow release (180 days) polymer‐coated urea (“N180”); banded urea applied upfront (“urea”); and three applications of broadcast urea (“urea‐split”). The N180 treatment reduced soil N2O emissions compared with urea (p < 0.001), with mean cumulative N2O emissions of 4.36 ± 1.07 kg N ha−1 and 27.9 ± 5.70 kg N ha−1, respectively. Soil N2O fluxes were high, reaching up to 1916 and 2900 µg N m2 h−1 after urea application and irrigation/rain events, and were similar to other irrigated crops grown on heavy textured soils. Fertilizer N management had no effect on soil CH4 emissions, which were negligible across all treatments ranging from 1.28 to 2.75 kg C ha−1 over the growing season. Cumulative soil carbon dioxide emissions ranged from 1936 to 3071 kg C ha−1 and were greatest in N180. This case study provides the first evidence in Australia that enhanced efficiency nitrogen fertilizer can substantially reduce N2O emissions from soils in an aerobic rice system. Our findings reinforce the CH4 mitigation potential of water saving rice approaches and demonstrate the need to consider N fertilizer management to control N2O emissions.

Interactions of Microbial Inoculations with Fertilization Options and Crop Establishment Methods on Modulation of Soil Microbial Properties and Productivity of Rice

A field investigation was undertaken to assess the interactive effects of different crop establishment methods (CEMs) and microbial formulations in field conditions. The two year experiment was carried out in kharif season (June to October) of both 2013–14 and 2014–15 at Research Farm of ICAR-Indian Agricultural Research Institute, New Delhi India. The CEMs studied consist of puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS); while microbial formulations consist of Anabaena sp. (CR1)+Providencia sp. (PR3) consortium (MC1) and Anabaena–Pseudomonas biofilm formulation (MC2). The microbial inoculation was applied with 75% recommended dose of nutrients (RDN) (90 kg nitrogen ha-1 and 19.35 kg phosphorus ha-1) and compared with 100% RDN. Soil microbiological properties showed significantly higher values in SRI in the first year; while in the second year, SRI and PTR remained on par and superior to ARS. Among the combinations of nutrient supplements, application of Anabaena–Pseudomonas biofilm formulation (MC2) with 75% RDN was superior in terms of all microbiological attributes studied [acetylene reduction activity (ARA), soil chlorophyll, soil dehydrogenase activity, microbial biomass carbon and alkaline phosphatase activity]. Application of microbial inoculation led to an increase in milled rice yield from 230 to 240 kg ha-1. Among the different combinations of CEMs and inputs investigated the application of 75% RDN+MC2+zinc (Zn) (soil applied 5 kg Zn ha-1 through zinc sulphate heptahydrate) in SRI can be a judicious option to maximize rice yield and soil health.

Assessing aerobic rice systems for saving irrigation water and paddy yield at regional scale

Assessing aerobic rice systems for saving irrigation water and paddy yield at regional scale

Major challenges in widespread adaptation of aerobic rice system and potential opportunities for future sustainability

Climate change and diminishing resources are the major challenges in sustainable rice production. The aerobic rice system can be a transformational approach to replace conventional rice in the face of climate change and scarcity of resources due to its high input-use efficiency. However, it could not be adapted widely yet due to several challenges like higher weed infestation and low nitrogen (N) use efficiencies. This transformed system can only be adapted at a wider scale through investigation of associated constraints and risks and provision of potential adjustive measures. Aerobic rice crop failure can be reduced if the availability of suitable and stress-resistant cultivars with early improved vigour, and short-duration characteristics are ensured for maintaining the reproductive capability under resource stressed environment. This transformed rice system exhibits limited response to applied N because of increased losses due to higher volatilization and rapid coupled nitrification-denitrification processes under alternate wetting and drying systems. Shifting from the flooded to aerobic rice system bringing changes in crop water demand, organic matter (OM) turnover, N dynamics, weed flora, and greenhouse gases (GHGs) emissions. Along with N-losses, continuous monocropping, higher weed infestation, weedy rice emergence, nitrous oxide (N2O) emissions, nutrient disorders, higher prevalence of pathogens and diseases, increased panicle sterility, and an increase in soilborne pathogens lodging are other major constraints negatively impacting the widespread adaptation of aerobic rice. This article reviews the climate change status, its associated impacts on the sustainability of traditional rice systems, and the rationale for transforming from traditional to aerobic rice systems. Furthermore, it describes the major challenges associated with the aerobic rice system, thereby presenting management strategies ensuring its wider adaptation for sustainable rice production in the face of projected climate change and scarcity of resources.

Recent trends in nitrogen cycle and eco-efficient nitrogen management strategies in aerobic rice system.

Rice (Oryza sativa L.) is considered as a staple food for more than half of the global population, and sustaining productivity under a scarcity of resources is challenging to meet the future food demands of the inflating global population. The aerobic rice system can be considered as a transformational replacement for traditional rice, but the widespread adaptation of this innovative approach has been challenged due to higher losses of nitrogen (N) and reduced N-use efficiency (NUE). For normal growth and developmental processes in crop plants, N is required in higher amounts. N is a mineral nutrient and an important constituent of amino acids, nucleic acids, and many photosynthetic metabolites, and hence is essential for normal plant growth and metabolism. Excessive application of N fertilizers improves aerobic rice growth and yield, but compromises economic and environmental sustainability. Irregular and uncontrolled use of N fertilizers have elevated several environmental issues linked to higher N losses in the form of nitrous oxide (N2O), ammonia (NH3), and nitrate (NO3–), thereby threatening environmental sustainability due to higher warming potential, ozone depletion capacities, and abilities to eutrophicate the water resources. Hence, enhancing NUE in aerobic rice has become an urgent need for the development of a sustainable production system. This article was designed to investigate the major challenge of low NUE and evaluate recent advances in pathways of the N cycle under the aerobic rice system, and thereby suggest the agronomic management approaches to improve NUE. The major objective of this review is about optimizing the application of N inputs while sustaining rice productivity and ensuring environmental safety. This review elaborates that different soil conditions significantly shift the N dynamics via changes in major pathways of the N cycle and comprehensively reviews the facts why N losses are high under the aerobic rice system, which factors hinder in attaining high NUE, and how it can become an eco-efficient production system through agronomic managements. Moreover, it explores the interactive mechanisms of how proper management of N cycle pathways can be accomplished via optimized N fertilizer amendments. Meanwhile, this study suggests several agricultural and agronomic approaches, such as site-specific N management, integrated nutrient management (INM), and incorporation of N fertilizers with enhanced use efficiency that may interactively improve the NUE and thereby plant N uptake in the aerobic rice system. Additionally, resource conservation practices, such as plant residue management, green manuring, improved genetic breeding, and precision farming, are essential to enhance NUE. Deep insights into the recent advances in the pathways of the N cycle under the aerobic rice system necessarily suggest the incorporation of the suggested agronomic adjustments to reduce N losses and enhance NUE while sustaining rice productivity and environmental safety. Future research on N dynamics is encouraged under the aerobic rice system focusing on the interactive evaluation of shifts among activities and diversity in microbial communities, NUE, and plant demands while applying N management measures, which is necessary for its widespread adaptation in face of the projected climate change and scarcity of resources.

Improving Nitrogen Use Efficiency in Aerobic Rice Based on Insights Into the Ecophysiology of Archaeal and Bacterial Ammonia Oxidizers.

The abundance and structural composition of nitrogen (N) transformation-related microbial communities under certain environmental conditions provide sufficient information about N cycle under different soil conditions. This study aims to explore the major challenge of low N use efficiency (NUE) and N dynamics in aerobic rice systems and reveal the agronomic-adjustive measures to increase NUE through insights into the ecophysiology of ammonia oxidizers. Water-saving practices, like alternate wetting and drying (AWD), dry direct seeded rice (DDSR), wet direct seeding, and saturated soil culture (SSC), have been evaluated in lowland rice; however, only few studies have been conducted on N dynamics in aerobic rice systems. Biological ammonia oxidation is majorly conducted by two types of microorganisms, ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). This review focuses on how diversified are ammonia oxidizers (AOA and AOB), whose factors affect their activities and abundance under different soil conditions. It summarizes findings on pathways of N cycle, rationalize recent research on ammonia oxidizers in N-cycle, and thereby suggests adjustive agronomic measures to reduce N losses. This review also suggests that variations in soil properties significantly impact the structural composition and abundance of ammonia oxidizers. Nitrification inhibitors (NIs) especially nitrapyrin, reduce the nitrification rate and inhibit the abundance of bacterial amoA without impacting archaeal amoA. In contrast, some NIs confine the hydrolysis of synthetic N and, therefore, keep low NH4+-N concentrations that exhibit no or very slight impact on ammonia oxidizers. Variations in soil properties are more influential in the community structure and abundance of ammonia oxidizers than application of synthetic N fertilizers and NIs. Biological nitrification inhibitors (BNIs) are natural bioactive compounds released from roots of certain plant species, such as sorghum, and could be commercialized to suppress the capacity of nitrifying soil microbes. Mixed application of synthetic and organic N fertilizers enhances NUE and plant N-uptake by reducing ammonia N losses. High salt concentration promotes community abundance while limiting the diversity of AOB and vice versa for AOA, whereas AOA have lower rate for potential nitrification than AOB, and denitrification accounts for higher N2 production. Archaeal abundance, diversity, and structural composition change along an elevation gradient and mainly depend on various soil factors, such as soil saturation, availability of NH4+, and organic matter contents. Microbial abundance and structural analyses revealed that the structural composition of AOA was not highly responsive to changes in soil conditions or N amendment. Further studies are suggested to cultivate AOA and AOB in controlled-environment experiments to understand the mechanisms of AOA and AOB under different conditions. Together, this evaluation will better facilitate the projections and interpretations of ammonia oxidizer community structural composition with provision of a strong basis to establish robust testable hypotheses on the competitiveness between AOB and AOA. Moreover, after this evaluation, managing soils agronomically for potential utilization of metabolic functions of ammonia oxidizers would be easier.

Effect of Crop Establishment Methods and Microbial Inoculations on Augmenting the Energy Efficiency and Nutritional Status of Rice and Wheat in Cropping System Mode

A field experiment was conducted for two consecutive years with the aim to quantify the role of different nutrient management variables such as microbial inoculation, zinc (Zn) fertilization and optimal and sub-optimal fertilization of nitrogen and phosphorus on the energetic and nutritional status of the rice–wheat cropping system (RWCS). The said nutrient management variables were applied over six different crop establishment methods (CEMs) in RWCS viz. puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS) in rice and conventional drill-sown wheat (CDW), system of wheat intensification (SWI) and zero-tillage wheat (ZTW) in wheat. Two microbial consortia viz. Anabaena sp. (CR1) + Providencia sp. (PR3) consortia (MC1) and Anabaena-Pseudomonas biofilmed formulations (MC2) were used in this study, while recommended dose of nitrogen (N) and phosphorus (P) (RDN) (120 kg N ha−1 and 25.8 kg P ha−1), 75% RDN and Zn fertilization (soil applied 5 kg Zn ha−1 through zinc sulphate heptahydrate) were the other variables. The contribution of microbial consortia, Zn fertilization and RDN (over 75% RDN) to net energy production of RWCS was 12.9–16.1 × 103 MJ ha−1, 10.1–11.0 × 103 MJ ha−1 and 11.7–15.3 × 103 MJ ha−1. Among the CEMs, the highest gross and net energy production was recorded in ARS–ZTW with lowest energy required for production of one tonne of system yield (2366–2523 MJ). The system protein yield varies from 494.1 to 957.7 kg ha−1 with highest protein yield in 75% RDN + MC2 + Zn applied ARS–ZTW. Among micronutrients, the uptake of Zn and iron (Fe) is sensitive to all studied variables, while manganese (Mn) and cupper (Cu) uptake was found significantly affected by CEMs alone. The combination of 75% RDN + MC2 + Zn in ARS–ZTW was found superior in all respects with 288.3 and 286.9 MJ ha−1 net energy production and 2320 and 2473 MJ energy required for production of one tonne system yield in the first and second year of study, respectively.

Allelopathic Potential of Cassava (Manihot esculenta L.) Extracts on Germination and Seedling Growth of Selected Weeds and Aerobic Rice

Weed infestation is a major problem in the aerobic rice system due to the lack of standing water that could prevent the growth of weeds. To reduce heavy reliance on herbicide, this research aims to determine the potential of cassava allelopathy for inhibition of weeds in aerobic rice. The allelopathic potential of cassava extracts on the germination and growth of tested weed species (Eleusine indica, Ageratum conyzoides, and Cyperus distans) and aerobic rice (Oryza sativa) was conducted in the laboratory. The results showed that increasing the aqueous extract concentrations of cassava extracts inhibited the germination and seedling growth of tested weeds, suggesting the allelopathic effects of cassava extracts are concentration dependent. The degree of phytotoxicity of different vegetative parts of cassava can be classified in order of decreasing inhibition as follows: leaf, stem, tuber, and tuber peel. Aqueous leaf extract of cassava at a concentration of 0.5% (w/v) provided complete inhibition on A. conyzoides, E. indica, and C. distansgermination whereas 25% to 100% inhibition on the shoot growth was recorded. By contrast, the shoot growth and germination of aerobic rice were not affected. These results suggest that the cassava leaf extracts contain water-soluble allelochemicals for inhibition on A. conyzoides, E. indica, and C. distans in aerobic rice.

The Effect of Additional Effective Microorganisms in Vegetative Growth of Aerobic Paddy

The influence of effective microorganisms (EM), microbial inoculant containing yeasts, fungi, bacteria and actinomycetes was evaluated in field trials of Aerob 1 paddy cultivation in Jasin, Melaka. Aerobic paddy is a new way of rice cultivation in areas where water resources have been scare and affected by the climate change. As water shortage and climate change is becoming severe, the technology of growing rice with aerobic rice systems need to be further refined or developed to ensure the quality of rice production in water-short areas. The objective of this study was to determine the effect of additional EM on the growth pattern, and to evaluate the efficiency of EM uptake on the aerobic plant. This experiment was carried out by using random controlled Randomized Controlled Block Design (RCBD) consisted of three treatments with two replications in four blocks. Aerobic seed cv. Aeron1 was used as planting materials and has been applied by three different treatments of EM during vegetative growth. The treatment for this study was T1 = 1.8 g NPK with urea (control) while T2 was 1.8 g NPK and T3, with 0.9 g NP with 100 mL of EM respectively during 15 (early vegetative stage) and 45 DAS (late vegetative stage). The RCBD experimental design was used with two replications in each treatment in four blocks. There are three series of harvesting (35, 50 and 60 DAS) was conducted throughout this study. The growth parameter studied was shoot and root dry biomass, number of tillers, RGR at each of harvesting. Our finding revealed that the application of EM did not improve plant growth parameter but the growth pattern of T2 and T3 showed steady improvement, although not significant compared to T1. The application of EM at different growth stages did not enhance the relative plant growth rate of Aeron 1 under aerobic condition, but in comparison to T1 and T2, T3 treatment with 50% reduction of NPK and EM could significantly reduce the cost of land management and fertilizer.

Aerobic Rice Weed Management Optimization through Agro Techniques O. Sativa L.

One of the most widely grown crops, rice (Oryza sativa L.) is crucial to the world's food supply. Historically, rice fields have been flooded for the primary purpose of weed suppression. However, non-flooded or decreased water management practises used in aerobic rice farming systems have received attention because to their potential advantages, which include water saving and increased resource use efficiency. The lack of floods, a traditional method of weed control, makes weed management in aerobic rice systems very difficult. The purpose of this research is to examine and improve agrotechniques for weed control in aerobic rice production utilising Oryza sativa L as the model species.

Soil Organic Carbon Sequestration and Carbon Pools in Rice Based Cropping Systems in Indo-Gangetic Plains: An Overview

Carbon sequestration in the agricultural lands is possible through different soil management strategies and could be substantial with widespread implementation. Sequestration of historic carbon emissions is now essential as mitigation alone is not enough to stabilize our atmosphere. There are numerous management strategies for drawing carbon out of the atmosphere and holding it in the soil. Effectiveness of these strategies vary across different climates, soil types, and geographies. Still, it is a controversy about the durability of sequestration in soil and about the precise conditions that maximize drawdown of carbon emissions. Carbon sequestration in soil is the potential strategy which can reduce or mitigate the impacts of the global warming. The Asian countries are having more than 90% of rice fields, they are being blamed for their contribution in the methane emission and associated climate change. A major part of rice is grown under the continuous submergence condition that may influence the active and passive pools of soil carbon besides methane emission. In this paper we have reviewed the carbon sequestration potential of rice-based soils besides discussion on the mechanisms and strategies that promote accumulation of soil carbon while minimizing carbon emissions. The strategies viz. System of Rice Intensification, Integrated Nutrient Management, promoting mycorrhizal symbiosis in aerobic rice system besides enhancement of phytolith-occluded carbon are some of the key areas facilitating better carbon sequestration in rice ecosystem.

Nutrient removal by rice\u2013wheat cropping system as influenced by crop establishment techniques and fertilization options in conjunction with microbial inoculation

Nutrient uptake by the rice–wheat cropping system (RWCS) is an important indicator of soil fertility and plant nutrient status. The hypothesis of this investigation was that the rate and sources of nutrient application can differentially influence nutrient removal and soil nutrient status in different crop establishment techniques (CETs). Cropping system yield was on par in all the CETs evaluated, however, there were significant changes in soil nutrient availability and microbiological aspects. The system nitrogen (N), phosphorus (P), potassium (K) and zinc (Zn) uptake in aerobic rice system followed by zero tillage wheat (ARS-ZTW) was 15.7–17.6 kg ha−1, 0.7–0.9 kg ha−1, 7–9.8 kg ha−1 and 13.5–23.1 g ha−1 and higher than other CETs. The formulations of Anabaena sp. (CR1) + Providencia sp. (PR3) consortium (MC1) and Anabaena–Pseudomonas biofilm (MC2) recorded significantly higher values of soil chlorophyll and microbial biomass carbon and positively affected cropping system nutrient uptake and soil nutrient balance, illustrating the beneficial effect of microbial inoculation through increased supply of biologically fixed N and solubilised P. Zinc fertilization (5 kg Zn ha−1 through ZnSO4·7H2O as soil application) increased soil DTPA-extractable Zn by 4.025–4.836 g ha–1, with enhancement to the tune of 20–24% after two cropping cycles of RWCS. Our investigation recommends the need for change in the present CETs to ARS–ZTW, along with the use of microbial inoculation as a means of significantly enhancing cropping system nutrient uptake and soil nutrient status improvement.

Screening of rice cultures and mitigation of iron deficiency in aerobic rice

The field experiment was conducted in Water management research block, Department of Agronomy, Agricultural college and Research Institute, Madurai during Rabi’ 2019 to screen rice cultures and to mitigate the iron deficiency in aerobic rice system. The experiment was laid out in split plot design with three replications. The main plot comprised of rice culture namely Apo-1 (M1), CBMAS 14065 (M2) and CBMAS 14110 (M3) and the sub plot comprised of foliar spraying of 0.5% Fe SO4 on 25 & 45 DAS (S1), foliar spraying of 0.5% Fe SO4 on 45 & 65 DAS (S2), foliar spraying of 1% Fe SO4 on 25 & 45 DAS (S3), foliar spraying of 1% Fe SO4 on 45 & 65 DAS (S4), soil application of iron chelates @ 2 kg ha-1(S5) and control (S6 -water spray). The rice culture CBMAS 14110 responded well to the foliar application of FeSO4 at 1% on 45 and 65 DAS (M3S4) as it recorded higher DMP (14260kg/ha). It also registered significantly higher number of panicles (247/m2), filled grains (261/panicle), grain yield (5878 kg/ha) and straw yield (8449 kg/ha). The maximum plant height (126.8 cm) was recorded in Apo-1 which received 1% Fe SO4 foliar spray on 45 and 65 DAS (M1S4).

Foliar Manganese Supply Enhances Crop Productivity, Net Benefits, and Grain Manganese Accumulation in Direct-Seeded and Puddled Transplanted Rice

Manganese (Mn) deficiency in human nutrition is widespread in the rice–wheat cropping system where cereal grains are the staple food. Agronomic biofortification is an innovative and pragmatic approach to tackle Mn malnutrition. A 2-year field study was conducted to investigate the comparative effect of different Mn application methods: (1) No Mn application, (2) Mn seed coating (2 g kg−1 seed), (3) hydro-priming, (4) Mn seed priming (0.1 M Mn solution), (5) soil application (0.5 kg ha−1), (6) foliar water spray, and (7) foliar Mn spray (0.02 M Mn solution) in improving the productivity, profitability, biofortification and Mn-use efficiencies of rice in puddled transplanted flooded rice (FR) and direct-seeded aerobic rice (AR) production systems. Under AR system, soil physical and biological properties, as well as nutrient dynamics were improved. Averaged across 2 years, improvement in total soil porosity (9%), soil organic carbon (12%), soil microbial biomass carbon (6%), soil microbial biomass nitrogen (3%), total nitrogen (13.6%), available phosphorus (10.98%), and exchangeable potassium (7.1%) were noted in AR system over FR system. Regardless of application methods, Mn nutrition substantially improved the yield and related traits and grain Mn concentration in both production systems. Averaged across 2 years, the increase in grain yield under different Mn application treatments was in the order: foliar application (22%) > seed priming (16%) > soil application (12%) > seed coating (12%). Grain Mn concentration was the highest with foliar application of Mn (27% over control) in both production systems. Moreover, the maximum net benefits and benefit–cost ratio were obtained through Mn-foliar application in both production systems. In conclusion, Mn application by either method improved the productivity, profitability, biofortification and Mn-use efficiencies under FR and AR systems; nevertheless, foliar Mn application performed better for all the studied traits.

Significance of zinc fertilization and microbial inoculation on phosphorus nutrition of rice (Oryza sativa)

The present experiment was conducted during rainy season of 2013-14 at ICAR–Indian Agricultural Research Institute, New Delhi, to compare and calculate variations in phosphorus (P) concentration and uptake in rice (Oryza sativa L.) plant as well as soil available P (Olsen’s reagent 0.5 M NaHCO3-extractable) as influenced by three different crop establishment methods (CEMs), rates of nitrogen (N), phosphorus (P) and zinc (Zn) fertilization and microbial inoculations in spilt plot design with three replications. The concentration and uptake of P in puddled transplanted rice (PTR) and system of rice intensification (SRI) was significantly higher than aerobic rice system (ARS) and total uptake was increased by 480 and 540 g/ha in PTR and 580 and 660 g/ha in SRI over ARS in first and second year, respectively. The treatment with 100% recommended dose of nutrients (RDN) (25.8 kg P/ha and 120 kg N/ha) had significantly higher P concentration and uptake than 75% RDN and absolute control. The correlation between milled rice yield and P concentration was found positive (R2= 0.95 and 0.94). Application of microbial inoculation significantly increased P concentration and uptake over fertilizer control (75% RDN) and absolute control which increased in total P uptake by 640 and 680 g/ha due to application of Anabaena–Pseudomonas (An-Ps) biofilmed formulations (MI2) and Anabaena sp. (CR1) + Providencia sp. (PR3) consortia (MI1) over fertilizer control (75% RDN).

Genetic improvement of Aceh local rice variety Sikuneng to produce green super rice lines adaptive to abiotic stresses

The high genetic diversity of rice landraces of Aceh has great potential to contribute to the world’s food security program in the future, especially in adapting to climate changes and environmental degradation. The objective of this research was to develop a new superior rice line adaptive to abiotic stress and maintains high productivity despite limited agricultural inputs. An Aceh’s local variety, Sikuneng, was artificially crossed with an isogenic line IRBB27 and the F1 plants were self-pollinated for two generations. The F3 lines were cultivated in drought stress and high salinity conditions with the application of aerobic rice system and flash irrigation. It was discovered that the F3 lines showed significantly improved plant height, number of panicles per plant, panicle length, grain weight per plant and grain yield potential per hectare. The plant height of the F3 lines varied from 98 to 192 cm, whereas the plant height of Sikuneng was 172 cm. The number of panicles of F3 lines ranged from 10.3 to 43.5, whereas Sikuneng had only 8.7 panicles. The panicle length of F3 lines ranged from 23.9 to 47.3 cm and Sikuneng had only 28.1 cm of panicle length. The grain weight per plant of F3 lines varied from 69.8 to 196.7 g, in contrast to the grain weight of Sikuneng which was 64.5 g. The weight of 1,000 grains of F3 lines ranged from 21.0 to 34.9 g, whereas that of Sikuneng was 26.9 g. While the yield potential of Sikuneng was 7.6 t/ha, the yield potential of the F3 lines varied from 7.2 to 13.9 t/ha. The highest yield potential was shown by Skn-68-1 line. Further evaluation and selection process need to be conducted in the next generations until the improved characters of the new lines are stable.

Partitioning of total soil respiration into root, rhizosphere and basal-soil CO2 fluxes in contrasting rice production systems

Soil respiration contributes significantly to ecosystem respiration and is vital in the context of climate change research. In a season-long experiment we studied total soil respiration (TSR) and its partitioning into root respiration, rhizospheric respiration (RhR) and basal-soil respiration in four contrasting rice production systems: irrigated lowland (IL) (cv. Gayatri); organic nutrient managed irrigated lowland (OIL) (cv. Geetanjali); system of rice intensification (SRI) (cv. Swarna); and aerobic rice system (Aerobic) (cv. APO). We considered TSR to be the sum of root respiration, RhR and basal-soil respiration. Irrespective of the rice production system, TSR was higher at panicle initiation stage. Considering all four systems, the RhR contributed the most (59–83%) and basal-soil respiration the least (10–19%) to the TSR. Mean RhR showed the trend of Aerobic > SRI > IL > OIL across the growing seasons and indicated higher rhizosphere activities in the aerobic system. Mean root respiration showed a trend of IL > OIL > SRI > Aerobic and mean basal-soil respiration had SRI > IL > OIL > Aerobic. Soil labile carbon pools and heterotrophic populations were higher in OIL and dehydrogenase activity was higher in SRI. Microbial biomass carbon, readily mineralisable carbon, dehydrogenase activity and the heterotroph population showed positive correlations with RhR. Hence, regulation of RhR is crucial and can be achieved through rhizosphere modifications linked with labile carbon pools and soil enzymatic activities by plant physiological modification or through soil carbon stabilisation.

ENHANCING WATER USE EFFICIENCY AND PRODUCTIVITY OF RICE CROP USING MODERN FARMING METHODS IN PUNJAB, PAKISTAN, A BRIEF REVIEW

Rice is the major staple food for billions of people worldwide. It has the social and economic impacts on people lives. Water scarcity is one of the major challenges to rice production and ultimately food security globally. For food security, it is important to explore efficient rice production technology that uses less water. Therefore, in the modern agriculture focus has been shifted towards development of water saving technologies. These methods include direct seeding, alternate wetting and drying, aerobic rice systems, use of mulches etc. These techniques reduce the water requirements and can enhance water use efficiency (W.U.E) of rice. However, yield may be compromised with these techniques, but research has been carried out to reduce yield losses and water use. Biotechnology and breeding approaches are being used to develop rice verities with drought tolerance, improved water use efficiency etc. Development and adoption of these technologies will shift the rice production from anaerobic to completely or partially aerobic systems. These techniques may reduce the water losses. In Pakistan famers are willing to adopt new technologies; however there is a need of dissemination and demonstration to adopt these technologies at farmer level to enhance crop productivity and water use efficiency. Innovative research approaches are required to fill the gaps in technological innovations and adoption

Zinc nutrition of rice as influenced by crop establishment methods, rates of nitrogen and phosphorus fertilization and inoculation with microbial consortia

Zinc (Zn) fertilization in rice is important to enhance productivity and increase Zn concentration in rice grain to improve its nutritional status. A field experiment was conducted in wet seasons of 2013 and 2014 to study Zn nutrition of rice in three different crop establishment methods (CEMs) viz. puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS), under three different rates of nitrogen (N) and phosphorus (P) viz. 0, 75 and 100% of recommended dose of fertilizer (RDF) (120 kg N ha−1 and 25.8 kg P ha−1) and two different sources of N and P viz. chemical fertilizer and microbial inoculation (MI). Concentration and uptake of Zn at different growth stages and in straw and milled rice was significantly higher in PTR and SRI than ARS. Soil DTPA–extractable Zn content of soil was increased by 1142.4, 1140.3 and 755.8 g ha−1 in PTR, SRI and ARS after two year of Zn fertilization (soil application of 5 kg Zn ha−1). Zinc nutrition increase its Zn concentration in straw and milled rice and improvement in total uptake was 38.1, 40.3 and 40.8 g ha−1 when Zn was applied with RDF, 75% RDF + Anabaena sp. (CR1) + Providencia sp (PR3) consortia (MI1) and 75% RDF + Anabaena-Pseudomonas biofilmed bio-fertilizer (MI2), respectively. Positive correlation between milled rice yield and Zn concentration (R2= 0.95 and 0.97) showed the importance of Zn nutrition in improving rice yield. Zinc concentration at 70 days after sowing (DAS) and 100 DAS was also found positively correlated with dehydrogenase activity and microbial biomass carbon in soil.

Nitrogen nutrition and use efficiency in rice as influenced by crop establishment methods, cyanobacterial and phosphate solubilizing bacterial consortia and zinc fertilization

ABSTRACTA field experiment was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi during wet season of 2013 and 2014, involving three crop establishment methods (CEMs) viz. puddled transplanted rice (PTR), system of rice intensification (SRI), and aerobic rice system (ARS). Three rates of nitrogen (N) and phosphorus (P) application (0%, 75%, and 100% of recommended dose of N and P) (RDN) (120 kg N ha–1 and 25.8 kg P ha–1) and two sources of N and P (fertilizer and cyanobacterial-bacterial inoculation) were tested with and without zinc (Zn) fertilization in all CEMs. The concentration of N in PTR and SRI was significantly higher than ARS with higher uptake of 10.3 and 11.1 kg ha–1 in PTR and SRI over ARS. Treatment with 100% RDN led to significantly higher N availability and uptake than 75% RDN and absolute control, i.e. 14.5 and 32.0 kg ha–1, respectively. Application of Anabaena-Pseudomonas biofilm formulation (MC2) in conjunction with 75% RDN increased total uptake of N by 12.7 kg ha–1 compared to 75% RDN only. A positive correlation was found between N concentration and acetylene reductase activity at 70 days after sowing (DAS) (R2 = 0.52) and 100 DAS (R2 = 0.38) based on mean of 2 years study. Zn fertilization significantly increased N concentration in rice straw and milled rice irrespective of the crop establishment methods. Our study signifies the importance of microbial inoculation, optimal N fertilization along with SRI and PTR as more effective crop establishment methods for deriving greater benefits in terms of N nutrition in rice.