Direct-seeded Rice Cultivation Research Articles

Influence of Nitrogen Levels and Microbial Inoculation on Growth, Yield and Straw of Direct Seeded Basmati Rice (Oryza sativa L.)

Background: Rice, a staple cereal, serves as the primary food for almost 50% of the world¢s population. Nitrogen is the predominant mineral element found in crops and serves as the primary constraint on Rice production. Direct-seeded rice cultivation has emerged as a potential alternative to traditional transplanting method. The goal is to provide insights that may be used to build sustainable agricultural methods that are specifically designed for Basmati rice production. Methods: This study aim to evaluate the effect of different N application levels (M1: 0 kg ha-1, M2: 40 kg ha-1 and M3: 60 kg ha-1) options as first factor with four microbial inoculation treatments (S1-Control, S2-Azosprillum (618g/ha) + Streptomyces’s (618g/ha), S3- Consortium (1235 g/ha) and S4-AMF (1235 g/ha). The experiment was conducted using a split-plot design (SPD) with three replications. Result: The study revealed that the maximum yield and yield attributes viz. plant height (116.47 cm), effective tillers ( 354.13 m2),leaf area index (2.64), no. of grains per panicle(84.17), length of panicle (24.66 cm), no. of filled grains per panicle (125.0), grain yield (54.30 q ha-1), straw yield ( 80.42 q ha-1), biological yield (134.72 q ha-1) and 1000-grain weight (24.64 g), maximum protein content (%) in grains (8.73%), straw (5.78%) was recorded in M3S2 i.e. 60 kg N ha-1 with azosprillum (618 g/ha) + streptomyces's (618 g/ha) significantly highest compared to other nitrogen levels and microbial inoculation treatments. Hence, the application of N @ 60 kg ha-1 along with azosprillum (618 g/ha)+Streptomyces¢s (618 g/ha) can be suggested to achieve higher rice grain yield, yield attributes and nitrogen content in grain and straw in DSR.

Ecology and Management of Sedges in Direct-seeded Rice: A Review

Sedges, resilient weeds from the Cyperaceae family, pose a significant threat to direct-seeded rice cultivation due to their perennial nature and robust propagules, which endure harsh conditions. Their emergence, growth and seed production during fallow periods contribute significantly to seed banks, making their management challenging compared to other weed types. Water levels in paddy fields dictate weed composition, favouring sedges and grasses under saturated conditions but shifting to grass weeds during cropping seasons, influenced by factors like soil conditions and rainfall. Managing sedges requires a multifaceted approach due to their perennial hydrophilic and pro-alkaline nature with extensive propagules. Sedges possessing strong root system with morphological similarities necessitate continuous weed control throughout the cropping season during the critical period ranging from 15 to 60 days after sowing for wet and dry direct-seeded rice. Effective weed management practices proved crucial for minimizing yield losses caused by infestation of Cyperus difformis, Fimbristylis miliacea and Schoenoplectus juncoides by many researchers. Various methods, including cultural practices like stale seedbeds, physical methods like summer tillage, biological approaches such as integrating poultry and chemical interventions like herbicide application, are utilized for sedge management in rice fields. Higher efficacy of ethoxysulfuron for management of majority of sedge weeds in rice has been reported by many workers. However, relying on a single strategy is insufficient to keep sedge populations below the threshold, necessitating a comprehensive and adaptable approach to weed control in rice cultivation.

Identification of a Promising Novel Genetic Source for Rice Root-Knot Nematode Resistance through Markers Associated with Trait-Specific Quantitative Trait Loci.

Direct-seeded rice (DSR) is gaining popularity among farmers due to its environmentally safe and resource-efficient production system. However, managing the rice root-knot nematode (RRKN), Meloidogyne graminicola, remains a major challenge in DSR cultivation. Developing genetic resistance is a pragmatic and effective approach compared to using hazardous pesticides. Pusa Basmati 1121 (PB1121) is the most popular Basmati rice variety, but it is highly susceptible to RRKN. In contrast, Phule Radha (PR) has shown highly resistant reaction to RRKN, as reported in our earlier study. We generated an F2:3 population from the cross of PB1121/PR and evaluated it for RRKN resistance-related traits under artificial inoculation conditions. The distribution pattern of traits in the F2:3 population indicated that resistance may be governed by a few major-effect genes and many minor-effect genes. The molecular markers reported to be associated with QTLs governing RRKN resistance traits were used to test in the current population. Although the simple linear regression identified significant associations between the markers and RRKN resistance-associated traits, these associations were spurious as the LOD score was below the threshold limit. This indicates that PR possesses novel genomic regions for resistance to RRKN as it does not possess any of the earlier reported QTLs.

Analysis of energy input-output in direct seeded and transplantation cultivation of rice under different irrigation systems

Energy input-output assessment for crop production processes is becoming increasingly important due to increased energy demand. This study explored the energy consumption for puddled transplanted (PTR), un-puddled transplanted (UPTR), and direct-seeded rice (DSR) cultivation methods under sprinkler, flood and drip irrigation systems in Golestan province, Iran, during 2019 and 2020. The energy of inputs and outputs were calculated using energy equivalents. Then, using input energy values, the global warming potential (GWP) was determined based on the equivalent of carbon dioxide (CO2). According to the results, the highest amount of yield was obtained for permanent flood irrigation with PTR. The results of mean comparison of cultivation method showed that the highest and lowest amounts of energy input were obtained for PTR (32418 MJ/ha) and UPTR (28175 MJ/ha), respectively. Also, the amounts of indices of energy use efficiency (EUE), energy productivity (EP) and net energy (NE) in DSR were lower than transplanted treatments. The results of mean comparison showed that the lowest amount of GWP was related to UPTR. The results of this study showed that drip irrigation with UPTR cultivation (due to less energy input and a yield close to PTR) can be a technology to save water and energy.

The impact on Cd bioavailability and accumulation in rice (Oryza sativa L.) induced by dry direct-seeding cultivation method in field-scale experiments

Dry direct-seeded rice cultivation has gained popularity and expanded its cultivated area due to reduced labor requirements and water consumption. However, the impact of this cultivation method on cadmium (Cd) bioavailability in soil and the accumulation levels in grains remains uncertain. Field experiments were conducted in acidic soils at two locations in southern China to compare rice varieties and evaluate the dry direct-seeding method alongside the wet direct-seeding and traditional transplanting methods. Dry direct-seeded rice reached significantly higher Cd concentrations in its tissues starting from the heading stage than transplanted rice. Cd accumulation levels by the maturation stage in the brown rice of dry direct-seeded rice were 18.33 %–150.69 % higher than those of wet direct-seeded and transplanted rice, with a considerable ability to translocate Cd into brown rice. Furthermore, dry direct seeding decreased iron plaque formation, particularly in the amorphous Fe form; it resulted in high soil temperature and low moisture content during tillering, elevating Cd availability in the soil. Additionally, the proportion of ions and more labile forms of Cd in the soil solution was high. Moreover, the soil under dry direct seeding had high urease and acid phosphatase enzyme activities. However, low richness and diversity in the bacterial community were characterized by a significant increase in the relative abundance of Actinobacteria and Gammaproteobacteria at the class level, while exhibiting decreased relative abundances of Alphaproteobacteria, Bacilli, and KD4-96, along with fewer biomarkers. Nonetheless, these differences are gradually reduced during the maturation stage. Overall, although dry direct seeding offers several advantages, it is crucial to implement additional measures to mitigate the increased health risks linked to rice cultivation through this approach in Cd-contaminated areas.

Herbicide Strategies for Weed Control in Rice Cultivation: Current Practices and Future Directions

Rice, as a staple food for more than half of the world's population, plays a crucial role in global food security. However, weed competition poses a significant challenge to rice cultivation, affecting yield and quality. To address this challenge, rice farmers have increasingly turned to chemical herbicides as a cost-effective alternative to labor-intensive manual weeding. This review paper explores the current practices and future directions in herbicide strategies for weed control in rice cultivation, with a specific focus on diverse approaches adopted in various agro-ecological regions, particularly in Pakistan. The paper begins by highlighting the importance of rice cultivation in global agriculture and the economic significance of the crop, emphasizing the need for effective weed management to ensure sustainable production. It discusses the impact of labor shortages and rising labor costs on weed control practices, driving the adoption of chemical herbicides, especially in direct-seeded rice cultivation. Additionally, the review underscores the importance of integrated weed management systems, which combine cultural practices, targeted herbicide applications, and legislative measures to optimize crop productivity while minimizing environmental impact. Furthermore, the paper evaluates the efficacy of different herbicides and their timing of application in managing weeds and maximizing rice yield. It synthesizes findings from recent studies to provide insights into the effectiveness of pre-emergence and post-emergence herbicides, as well as their impact on weed-crop competition and overall crop health. By analyzing the strengths and limitations of existing herbicide strategies, the review identifies opportunities for innovation and improvement in weed management practices. Overall, this review paper offers a comprehensive overview of herbicide strategies for weed control in rice cultivation, highlighting the need for sustainable and integrated approaches to address weed challenges while ensuring food security and environmental sustainability in rice-producing regions.

Dry Direct-Seeded Rice Yield and Water Use Efficiency as Affected by Biodegradable Film Mulching in the Northeastern Region of China

In the realm of agriculture, biodegradable films are emerging as a promising substitute for traditional polyethylene (PE) films. Despite their potential, there has been a notable lack of extensive research on their effectiveness in the context of dry direct-seeded rice cultivation. Addressing this gap, a comprehensive biennial study was conducted in the northeastern regions of China, focusing on the ‘Baonong 5’ rice variety. This study meticulously compared three distinct cultivation methods: (1) employing biodegradable film mulching, (2) using conventional plastic film mulching, and (3) cultivating without any mulch. The findings revealed that biodegradable film mulching significantly enhanced soil moisture control, increased leaf area, and improved rice yield and water utilization efficiency (p < 0.05) compared to the plots without mulch. Notably, there was no marked difference in outcomes between the plastic film mulching and the unmulched plots. This research underscores the profound benefits of biodegradable film in rice cultivation, particularly from an environmental sustainability perspective. This innovative method not only boosts agricultural productivity but also addresses critical environmental challenges like climate change and water conservation. The application of biodegradable mulch has proven to be remarkably effective in improving irrigation efficiency and crop water conservation, leading to enhanced rice development and higher yields. The study recorded a substantial increase in water productivity—30% in 2021 and between 52.85% and 60% in 2022—compared to traditional cultivation practices. Furthermore, the use of biodegradable mulch resulted in significantly higher rice yields than the non-mulched plots, thus contributing to increased profitability. Such methods not only yield higher crop outputs but also mitigate environmental issues like water pollution and help alleviate prevalent water shortages in rice farming.

Screening of potential donors for anaerobic stress tolerance during germination in rice.

The rising cost of transplanting rice has made direct seeding an affordable alternative for rice establishment, particularly in Africa. However, direct seeding, while cost-effective, faces crop establishment challenges due to flooding. Uncontrolled water, driven by erratic rains in low-lying areas or uneven fields, limit germination. Rice possesses the unique ability of anaerobic germination, enabling it to sprout and emerge in oxygen-deprived conditions. Understanding rice's response to anaerobic stress during germination is crucial for resilience breeding. Africa, although relying on direct seeding, has made limited progress in addressing flooding during germination compared to Asia. Anaerobic stress tolerance ensures successful crop emergence even in oxygen-limited environments and can help suppress weeds, a significant challenge in direct-seeded rice cultivation. This study aims to contribute by screening for potential rice donors exhibiting anaerobic stress tolerance. We screened 200 rice genotypes at Sokoine University of Agriculture (SUA) in Morogoro, Tanzania, primarily focusing on landraces with untapped potential. Using an alpha lattice design, we conducted two anaerobic experiments in September and October 2022, adding 7cm of standing water immediately after dry seeding for flooded and maintaining a 2cm water level after germination in the control for duration of 21 days. We identified potential donors based on selection index computed from genomic estimated breeding values (GEBVs) using eight variables: germination at 14 DAS, germination at 21 DAS, seedling height at 14 DAS, seedling height at 21 DAS, shoot dry matter at 21 DAS, root dry matter at 21 DAS, culm diameter at 21 DAS, and root length at 21DAS. Ten genotypes emerged as the most promising, exhibiting at least 70% germination in floodwater at 21 DAS and greater selection indices. These genotypes were like: Afaa Mwanza 1/159, Rojomena 271/10, Kubwa Jinga, Wahiwahi, Magongo ya Wayungu, Mpaka wa Bibi, Mwangaza, Tarabinzona, IB126-Bug 2013A, and Kanamalia with respective percentages of 75, 74, 71, 86, 75, 80, 71, 80, 70, and 73. These findings contribute to global efforts to mitigate the impacts of flooding during germination. These donors, will be potential to enrich the gene pool for anaerobic germination, providing valuable resources for breeding for flooding tolerance.

Identification of a Seed Vigor–Related QTL Cluster Associated with Weed Competitive Ability in Direct–Seeded Rice (Oryza Sativa L.)

Direct seeding of rice (Oryza sativa L.) is a low-labor and sustainable cultivation method that is used worldwide. Seed vigor and early vigor are important traits associated with seedling stand density (SSD) and weed competitive ability (WCA), which are key factors in direct-seeded rice (DSR) cultivation systems. Here, we developed a set of chromosome segment substitution lines with Xiushui134 as receptor parent and Yangdao6 as donor parent and used these lines as a mapping population to identify quantitative trait loci (QTLs) for seed vigor, which we evaluated based on germinability–related indicators (germination percentage (GP), germination energy (GE), and germination index (GI)) and seedling vigor–related indicators (root number (RN), root length (RL), and shoot length (SL) at 14 days after imbibition) under controlled conditions in an incubator. Ten QTLs were detected across four chromosomes, of which a cluster of QTLs (qGP11, qGE11, qGI11, and qRL11) co-localized on Chr. 11 with high LOD values (12.03, 8.13, 7.14, and 8.75, respectively). Fine mapping narrowed down the QTL cluster to a 0.7-Mb interval between RM26797 and RM6680. Further analysis showed that the QTL cluster has a significant effect (p < 0.01) on early vigor under hydroponic culture (root length, total dry weight) and direct seeding conditions (tiller number, aboveground dry weight). Thus, our combined analysis revealed that the QTL cluster influenced both seed vigor and early vigor. Identifying favorable alleles at this QTL cluster could facilitate the improvement of SSD and WCA, thereby addressing both major factors in DSR cultivation systems.

Identifying Donors for Anaerobic Germination Tolerance and Direct Seeded Rice Cultivation by Exploring Seed and Seedling Traits

Background: Anaerobic conditions in waterlogged soil affect germination rate significantly reducing rice yields. Under wet direct seeded condition, only limited availability of rice genotypes are suitable for anaerobic germination. So, there is an urgent need to identify rice genotypes for enhanced germination even under anoxic stress. Methods: Experiment was conducted in glass house, Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore. In this study, 22 rice germplams with three replications were evaluated for seed and seedling traits underlying anaerobic germination tolerance. Main aim of this study is to explore the starch and sugar relation under anoxic stress and identifying tolerant genotypes for direct seeded rice cultivation. Result: Tolerant genotypes had early emergences, higher shoot and root length along with higher starch degradation and sugar accumulation under waterlogged condition. Cluster analysis revealed that Karuppukavuni, Kalanamak, CBMAS 14065 and Kodavilayan were identified as tolerant genotypes and suitable for wet direct seeded rice cultivation. Finally higher starch degradation coupled with higher accumulation of glucose and fructose were the key traits underlying anaerobic germination tolerance in tolerant genoytpes. Shoot length, root length and sucrose contents had higher genotypic coefficient of variance, phenotypic coefficient of variance coupled with high heritability indicating scope for enhancing anaerobic germination tolerance.

Quantifying enzyme activities under anaerobic germination in traditional rice landraces to identify donors for direct seeded rice cultivation

Climate change has increased environmental risks globally having an adverse effect on agriculture productivity. Among the abiotic stresses, anaerobic germination stress has been identified as a major stress for seed emergence, plant growth and food production. By understanding the manipulation of germination, antioxidant and fermentation enzymes, adaptations to anaerobic conditions can be improved. The ability of rice to emerge under oxygen deprivation is a determinant of anaerobic germination tolerance, critical for successful direct seeding. There is an urge to identify novel rice genotypes associated with better germination and higher enzymatic activities under anaerobic conditions in order to improve seedling establishment. In the present study, twenty-two rice genotypes were characterized for their anaerobic germination potential by assessing the activities of α- amylase, antioxidant enzymes viz., catalase and peroxidase, and fermentative enzyme viz., alcohol dehydrogenase and pyruvate decarboxylase under anoxic stress. α- amylase, catalase, peroxidase, alcohol dehydrogenase and pyruvate decarboxylase activities showed a significant positive association with seed germination under anaerobic conditions. Higher expression of five enzymatic activities confirms anaerobic germination stress tolerance in rice genotypes. This study identified four tolerant genotypes namely Karuppukavuni, Kalanamak, CBMAS 14065, and Kodavilayan, and two moderately tolerant genotypes namely TKM13 and Anna R4 based on principal component analysis and correlation analysis.

Molecular Mechanisms in Understanding Anoxia Tolerance in Rice Seeds under Submergence and Their Implication in Rice Biotechnology

Submergence in rice fields creating inundation stress and realizing anoxia or hypoxia is a problem in agriculture. Seeds under this oxygen deficit are faced with fermentative respiration, where the end product would be poisoning the tissue viability. This is more aggravated in direct seeded rice cultivation with the accumulation of lactate as a poison. This review is concerned with the basic insights into anoxia tolerance in seeds and possible strategies to reduce anoxic shock through the modification of metabolism preceded by gene expression. The major concern of anoxic germination is starch metabolism and downstream physiological realization to facilitate escape or quiescence strategy, overcoming submergence stress. The coleoptiles facing hypoxic stress mated with transcripts for oxidative traits, energy metabolism, and proteins for membrane peroxidation in support of energy metabolism are the most important. Hypoxic genes are recovered from traditional indica and japonica land races of rice, and show changes in glycolytic flux and sugar sensing. Anoxic germination and seedling vigor are based on a combinational regulation of oxidative stress and fermentative catabolism. De novo antioxidant and antioxidative enzyme production can support improved seed germination in this condition. Pre-harvest spouting with seed-coat-induced dormancy, hormonal ratios, and hydrolyses would be of concern. Therefore, comprehensive analysis aimed to understand rice seed priming for better gas exchange, diffusion, temperature sensitivity, ion uptake, redox balance, and others. Still, in-depth insights are being awaited for better understanding the physiological and molecular basis using a multi-omics approach for better seed priming to overcome the anoxic/hypoxic revelation mostly acquainted with submergence stress.

Nitrogen uptake pattern of dry direct-seeded rice and its contribution to yields in northeastern Japan

ABSTRACT Dry direct-seeded rice (DDSR) cultivation is expected to reduce production costs compared with transplanted rice (TPR); however, its low N use efficiency (NUE) has hindered cost reduction. We conducted DDSR field experiments for 3 years using a standard cultivar (‘Akitakomachi’) and a high-yielding cultivar (‘Yumiazusa’) grown with a single application of coated urea (CU) or split applications of normal urea (NU) to determine factors limiting yield and NUE and compared growth and yields of TPR grown in adjacent fields. DDSR yield was lower than that of TPR at comparable N levels by 11% due to low fertilizer recovery rate, crop NUE (CNUE, yield per unit N uptake), and poor grain filling by meteorological factors. Crop N uptake at maturity in DDSR was similar to or even greater than that in TPR, but poor vegetative growth in DDSR and low crop N uptake until panicle formation (PF) resulted in limited spikelet density and CNUE compared with TPR. Analysis of the N uptake pattern suggests that enhancing early leaf development can improve N uptake until PF and thus CNUE in DDSR. NU yielded as much as CU, so it can potentially reduce the cost of production because of its lower price, but the optimal N proportion and application stage in the split application needs scrutinizing. ‘Yumiazusa’ had better initial growth, CNUE, and yield than ‘Akitakomachi’ in DDSR. To leverage these traits for further yield improvements, we also need to consider suitable phenological characteristics to ensure favorable climatic conditions during the grain-filling period.

Transcriptome and DNA Methylome Analysis of Two Contrasting Rice Genotypes under Salt Stress during Germination

With climate change and labor shortages, direct-seeding rice cultivation is becoming popular worldwide, especially in Asia. Salinity stress negatively affects rice seed germination in the direct-seeding process, and the cultivation of suitable direct-seeding rice varieties under salinity stress is necessary. However, little is known about the underlying mechanism of salt responses during seed germination under salt stress. To investigate the salt tolerance mechanism at the seed germination stage, two contrasting rice genotypes differing in salt tolerance, namely, FL478 (salt-tolerant) and IR29 (salt-sensitive), were used in this study. We observed, that compared to IR29, FL478 appeared to be more tolerant to salt stress with a higher germination rate. GD1 (germination defective 1), which was involved in seed germination by regulating alpha-amylase, was upregulated significantly in the salt-sensitive IR29 strain under salt stress during germination. Transcriptomic data showed that salt-responsive genes tended to be up/downregulated in IR29 but not in FL478. Furthermore, we investigated the epigenetic changes in FL478 and IR29 during germination under saline treatment using whole genome bisulfite DNA sequencing (BS-seq) technology. BS-seq data showed that the global CHH methylation level increased dramatically under salinity stress in both strains, and the hyper CHH differentially methylated regions (DMRs) were predominantly located within the transposable elements regions. Compared with FL478, differentially expressed genes with DMRs in IR29 were mainly related to gene ontology terms such as response to water deprivation, response to salt stress, seed germination, and response to hydrogen peroxide pathways. These results may provide valuable insights into the genetic and epigenetic basis of salt tolerance at the seed germination stage, which is important for direct-seeding rice breeding.

Role of geo informatics in achieving sustainable agriculture and it’s scenario in Haryana: An overview

Agricultural sustainability is founded on the belief that we must meet the demands of the present without affecting future generations' ability to fulfill their demands. Sustainable agriculture attempts to maintain equilibrium between the requirement for food production and the conservation of the ecosystem. Geo informatics technologies are helping in many ways like find out the current scenario of anything like cropping pattern, rotation, the land use and land cover and underground water quality and water table depth; it helps to analyses the finding and makes decisions in the way of achieving sustainable agriculture. Secondary data is collected from state agriculture policy (2021), Statistical abstract of Haryana (2021-22) and state budget 2023-24. The main aim of this study is to understand the current scenario of sustainable agriculture and what’s the role of geo informatics in its development.In Haryana, the agricultural sector remains to be very important to the state's economy, generating 14.5 percent of the state's GDP and employing 51 of the total workforce. Many programs and policies are made by Haryana govt. to conserve the water and soil resources and to achieve sustainable agriculture which is essential for the sustainable growth of state. Some current programs are like at least 72,000 acres were planted with direct-seeded rice in Kharif 2022, and farmers received financial aid total of 29 crores (at 4,000 per acre) to encourage direct-seeded rice cultivation, which uses less water that will be beneficial for the underground water resources. A new initiative called

Effect of Biochar on Soil Physiochemical Properties and Bacterial Diversity in Dry Direct-Seeded Rice Paddy Fields

The effects of biochar application on dry direct-seeded rice paddies remains unclear. Therefore, we applied biochar to dry direct-seeded rice paddy fields over 3 consecutive years to assess its effects on soil physicochemical properties and bacterial diversity (conventional fertilization [CK]; biochar + conventional fertilization [BC]). BC increased the content of 0.25–5 mm soil water-stable aggregate particles, but decreased that of &lt;0.25 mm soil water-stable aggregates. At different soil depths, BC significantly reduced sand content and increased silt content. Compared to CK, BC significantly increased the available phosphorus and potassium content of the 0–10 and 10–20 cm soil layers. There were no significant differences in pH, organic matter, total nitrogen, total phosphorus, or total potassium content between the treatments at different soil depths. Compared to CK, BC significantly increased soil neutral phosphatase and catalase activities. Furthermore, BC significantly increased bacterial richness, but had no significant effect on bacterial diversity. According to Qualcomm sequencing analysis, BC increased the relative abundance of Verrucomicrobia, Chloroflexi, Bacteroidetes, Nitrospirae, Verrucomicrobiae, Blastocatellia_Subgroup_4, and Anaerolineae in soil compared to CK. The soil bacterial genera in BC had stronger interrelationships than those in CK. According to redundancy analysis, organic matter was the main environmental factor influencing bacterial community structure. Overall, biochar could promote soil nutrient conversion in dry direct-seeded rice paddies, improve soil effective nutrient content, change the composition of soil bacterial communities, and increase soil bacterial richness. Applying biochar in dry direct-seeded rice cultivation could help realize low-carbon agriculture.

Changes in the Physical, Chemical, and Bacterial Community Characteristics of Soil in Response to Short-Term Combined Organic–Inorganic Fertilizers in a Dry Direct-Seeded Paddy Field

Dry direct-seeded rice cultivation is a simple and labor-saving planting method wherein the combined application of organic and inorganic fertilizers can improve yield. However, the effects of combined fertilizers on soil properties and bacteria in dry direct-seeded rice paddy soil are unclear. Here, four treatments, conventional fertilization (NPK), seaweed bio-organic fertilizer + NPK, Jishiwang bio-organic fertilizer + NPK, and attapulgite organic fertilizer + NPK applied for three consecutive years were tested to explore their effects on soil physical, chemical, and bacterial community characteristics in a dry direct-seeded rice paddy field. The combined fertilizers increased alkaline hydrolysis-nitrogen and available potassium while decreasing the bulk density and pH; in addition, a marked increase in the relative abundance of soil macroaggregates (&gt;5 mm) and clay particles and a decrease in that of sand was observed. Urease and neutral phosphatase activities were the highest with the Jishiwang organic fertilizer + NPK, whereas invertase and catalase activities were the highest with attapulgite organic fertilizer + NPK. All combined fertilizers considerably increased the bacterial richness index (ACE) and Chao index; Jishiwang bio-organic fertilizer + NPK also increased the Simpson index, whereas the seaweed bio-organic fertilizer + NPK reduced it. Proteobacteria and Acidobacteria accounted for 54.25–70.49% of the total bacterial relative abundance. The relative abundance of Verrucomicrobia, Chloroflexi, Firmicutes, and Nitrospirae increased with the combined fertilizers. The correlation network analysis showed predominant antagonistic relationships. A redundancy analysis demonstrated that total nitrogen, soil organic matter, urease, and invertase were the main environmental factors affecting bacterial composition. Combined fertilizers may improve soil physical and chemical properties, fertility, and bacterial richness.

Progress of Research on Phytohormone Interaction in Germination of Direct-Seeded Rice under Submergence

Due to rainfall, closed weeding of paddy fields and other reasons, submergence stress often occurs during the germination and emergence stages of direct-seeded rice (Oryza sativa L.), which leads to intensified anaerobic respiration, accelerated consumption of stored nutrients, difficulty in germination of rice seeds, uneven emergence of seedlings and varying yields. Recent advances in the understanding of phytohormone interaction and the regulation of signaling pathways in crops have increased the feasibility of modulating responses to phytohormones in crop plants to enhance adaptation to environmental changes. In this review, we summarize recent advances and progress in the understanding of the regulation of phytohormone signaling pathways and their interactions with diverse internal and external signaling cues under submergence. We also discuss how these physiological modulations of phytohormones and their abundant signaling crosstalk can be applied to enhance the submergence tolerance of direct-seeded rice during germination through the manipulation of seedling morphogenesis and the fine-tuning of stress responses. Finally, we discuss how complex phytohormone signaling pathways could regulate the metabolism of stored nutrients, anaerobic respiration and energy supply in submerged direct-seeded rice seeds, thereby improving their submergence tolerance. This review hopes to provide a basis for studies of the tolerance mechanisms of submerged direct-seeded rice and the promotion of the simplified direct-seeded rice cultivation model.

Ammi Analysis for Yield and Stability in Direct Seeded Rainfed Rice

The genotype × environment interaction and stability performance of 15 rice landraces was studied using the additive mean effects and multiplicative interaction (AMMI) analysis. The overall, results indicated that significant genotype × environmental interaction (GEI) influenced the relative ranking of the rice landraces across the years/seasons. It was evident from AMMI analysis that first two principal components accounted for 91.90%, which is enough to explain the variability among the landraces. The landraces, G8 (Kallurundaikar), G4 (Sivapuchithiraikar) and G5 (Kuruvaikalanjiyam) exhibited high grain yield. The AMMI 2biplot revealed that the rice landraces, G12 (Poongar), G14(Kala namak) and G15 (Kichali samba) are close to the origin indicating non sensitive nature of these genotypes with the years/seasons and highly stable genotypes across the environments with low yield potential when compared to others. According to the polygon view of GGE biplot, the genotype G8 (Kallurundaikar) was the winner in the environments E2 and E5 whereas the genotypes G5 (Kuruvaikalanjium) and G7 (Mattaikar) were the winners in the environment E1, E3 and E4. The landrace, G8 (Kallurundaikar), has high mean yield with stable performance over five environments being the overall best and it may be considered for the direct seeded rice cultivation in the rainfed ecosystem. Bangladesh J. Bot. 51(3): 469-475, 2022 (September)

Weed growth, nutrient removal and yield of direct-seeded rice as influenced by establishment methods and chemical-cum-mechanical weed management practices

Direct seeding of rice (Oryza sativa L.) has since long been viewed as a potential alternative to unsustainable water-intensive transplanted rice (TPR) world-over, but heavy infestation of a variety of weed species limits the large-scale adoption of direct-seeded rice (DSR) cultivation. Hence, a 2-year field investigation was carried-out in a spilt-plot design, at Banaras Hindu University, Varanasi, during rainy seasons of 2016 and 2017 to assess the influence of various crop establishment methods (CEMs) and weed management options (WMs) on diverse weed-flora, nutrient removal by weeds, weed-control efficiency (WCE) and yield of DSR (cv. Rajendra Kasturi). The results revealed that zero-till DSR + residue + Sesbania brown manure (ZTDSR + R + SBM) was most effective in containing crop-weed competition, lowered density of Echinochloa colona (L.) Link, Echinochloa crusgalli (L.) Beauv., Cynodon dactylon (L.) Pers., Eclipta alba (L.) Hassak., Caesulia axillaris Roxb., Cyperus rotundus L., Cyperus iria L., Fimbristylis miliacea (L.) Vahl. by 63.4% and enhanced grain yield by 22.8%. Further, applying pendimethalin at 1000 g ai ha−1 as PRE. and later post-emergence (POST) spray of chlorimuron + metsulfuron at 4 g ai ha−1 each 20 days after sowing (DAS) supplemented with 1 hand-weeding (HW) 45 DAS was found to be a better weed management option as this treatment recorded the lowest density and nutrient depletion by above mentioned weeds and higher WCE, thereby improving rice yield by 3–19.5% over other studied WMs. Also, the combination of this weed management option with ZTDSR + R + SBM suppressed weeds to a greater extent, restricting weeds to deplete nutrients (N, P and K) from the soil and finally fetched the highest DSR yield.