Paddy Fields Research Articles

Impact of pressure and temperature on the hydration resistance of rice

Crop soaking, a hydration process driven by diffusion, is essential for applications such as milling and germination. This study investigated the moisture absorption of rice kernels during soaking, considering factors like pressure and temperature. The experimental data were analyzed using the Peleg model to understand hydration kinetics, revealing a strong correlation between empirical and regression data, with determination coefficients mostly exceeding 0.99. The study also assessed soaking hydration resistance, identifying contributions from various rice layers, including the husk and bran. Moisture content increased gradually with soaking time, with higher temperatures enhancing absorption. Under normal pressure, white rice absorbed water faster than paddy and brown rice, with brown rice exhibiting higher hydration resistance. Interestingly, paddy rice soaked faster than brown rice under certain conditions due to the air layer between husk and bran, which was eliminated under vacuum or higher temperatures, though the water replacing the air remained unabsorbed. This study aggregated hydration resistance from each kernel to determine layer resistance and specific diffusivity of husk and bran.

In-situ induced formation of Fe-OM association in soil: Theory and practice of remediation of cadmium contaminated paddy fields in high cadmium geological background areas

Cadmium (Cd) pollution in rice paddies, attributable to high geological Cd backgrounds, has emerged as a global concern. This study leverages the passivation mechanism of bioavailable Cd by iron-organic matter associations (Fe-OM) to explore a novel strategy for Cd immobilization. We examined the adsorptive capacity and removal efficiency of Cd by laccase-mediated Fe-OM association and assessed their natural stability using 57Fe isotopic tracing. Additionally, we conducted in-situ remediation trials in a Cd-enriched paddy soil. Our results indicate that the theoretical maximum adsorption capacity for Cd by the laccase-mediated Fe-OM is 100.0 mg/g, which is a 15% improvement over the common Fe-OM and a 150% enhancement over inorganic iron oxides (ferrihydrite). The 57Fe isotope tracing test showed that the affinity of laccase-modified organic matter for iron increased by 55.6%, and it exhibited better stability than common Fe-OM under anaerobic conditions. The field-scale remediation, predicated on the in situ synthesis of Fe-OM association, effectively reduced the bioavailable Cd concentration in the soil from 0.91 mg/kg to 0.40 mg/kg. Concurrently, the Cd concentration in rice grains was lowered from 0.63 mg/kg to 0.15 mg/kg, thus falling beneath the national safety threshold. This study represents a significant advancement in the safe reclamation and utilization of agricultural soils with elevated geological Cd burdens.

Design and implementation of tilting‐plate drainage equipment for paddy field

AbstractDrainage equipment is an important part of paddy field drainage and irrigation system, and its performance research and application are conducive to the promotion and implementation of high‐standard farmland construction. Aiming at the different water demand of rice in different growing stages, low water level control precision, large manual operation and extensive management of existing drainage machinery, a tilting‐plate drainage equipment using upper overflow mode was proposed in this paper. Based on the Geneva mechanism principle, a unique linkage mechanism is designed, which can realize water retaining operation and silt discharge operation through a single motor drive, and the relationship between the motor angle and the water retaining height is established. Through mechanical analysis and dynamic simulation of the mechanism, the motion characteristics of the water baffle, silt plate and the change of the motor torque are studied. A remote control system based on a 4G module is designed to control the drainage equipment easily through the user layer. The performance test of the prototype shows that the precision error of the optimized water retaining height control is less than 3.75%. The maximum height of water retaining operation is 180 mm, and the maximum load of silt discharge operation is 10 kg, which can meet the actual operation requirements. The design is beneficial to improve the precision and intelligence level of paddy field drainage management, and the research process can provide some help for the development and application of this kind of equipment.

Assessment of the utilization of modern agricultural machinery in rice production and its problems: A case from San Leonardo, Philippines

This study examines the relationship between the utilization of modern agricultural machinery and the business technical aspect of rice production of paddy field farmers in San Leonardo, Nueva Ecija, Philippines. The objective of this study is to assess the effectiveness of modern machinery on the business technical aspect of the farmers and the paddy field owners. The study utilized descriptive analysis to assess the use of modern agricultural machinery in rice production and its problems. The design was quantitative, using percentage, frequencies, and weighted mean. The results revealed that the majority of respondents have been operating for 11 to 20 years, owned 1 hectare of land that cultivate 2 times a year and harvest 86 rice sacks per hectare. Rice cultivation is happened during wet and dry season. To maximizing the land, farmers can try other crops while waiting for the season of rice cultivation. In agricultural mechanization, it concluded that plowing machines helps remove clods from the soil, transplanting rice seedlings and applying chemicals using machine can saves time. Harvester machine is suitable in small and large farmland for harvesting and may help farmers to save time, effort and total cost requirements. Local Government Unit to support through grants and funding the local rice farmers in maximizing utilization of machines that shows positive effect.

Biodegradation of Chlorpyrifos in Paddy Rice Soil in the Mekong Delta, Vietnam

Biodegradation of Chlorpyrifos in Paddy Rice Soil in the Mekong Delta, Vietnam

Effects of tillage management on soil organic carbon mineralization under double cropping rice system of southern China

Soil organic carbon (SOC) plays a vital role in maintaining or enhancing soil fertility and quality of paddy field, but there is still limited information about how SOC mineralization responds to different tillage managements under the double-cropping rice (Oryza sativa L.) system in southern of China. Therefore, this study was designed to explore the changes in SOC content, soil enzyme activities (invertase, cellulose and urease), SOC mineralization at 0–10 cm and 10–20 cm layers and its relationship with 7-years tillage management under the double-cropping rice system of southern China. The experiment included four tillage managements: rotary tillage with all residues removed as a control (RTO), conventional tillage with residue incorporation (CT), rotary tillage with residue incorporation (RT), and no-tillage with residue retention (NT). The results indicated that SOC and soil labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with CT and RT treatments were significantly higher than the RTO treatment. Compared to the RTO treatment, SOC mineralization and accumulation at 0–10 cm and 10–20 cm layers in paddy field with CT, RT and NT treatments were increased. SOC accumulation and potential mineralization at 0–10 cm layer with NT treatment were significantly higher than the CT, RT and RTO treatments. Soil mineralization constant at 10–20 cm layer with CT treatment was significantly higher than those of RT, NT and RTO treatments. This result indicated SOC mineralization rate and accumulation at 10–20 cm layer of CT, RT, NT and RTO treatments were lower than those of treatments at 0–10 cm layer. Compared to RTO treatment, soil invertase, cellulose and urease activities with CT and RT treatments were significantly increased. Compared to RTO treatment, soil invertase, cellulose and urease activities at 0–20 cm layer of CT treatment increased by 22.6%, 46.2% and 89.0%, respectively. There was significantly positive correlation between SOC accumulation and SOC content, soil invertase, cellulose, urease activities, but SOC accumulation was significantly negative correlated with soil pH, bulk density. Therefore, CT and RT treatments were beneficial managements to improve SOC content and SOC mineralization in the double-cropping rice field of southern China.

Impact of Dolomite Liming on Ammonia-Oxidizing Microbial Populations and Soil Biochemistry in Acidic Rice Paddy Soils

Background and Aims: Over the last few decades, rampant nitrogen fertilization has exacerbated soil acidification in agricultural ecosystems. To counteract this, liming has become an essential technique for rehabilitating fertility in acid-degraded agricultural soils. Our research aimed to shed light on the response of ammonia oxidizers to liming in acidic soils within a controlled rice paddy experiment. We conducted a pot experiment with rice, featuring three different treatments: a control with only soil, a low dolomite dose (LD), and a high dolomite dose (HD). Various soil properties were investigated throughout the study. Under flooding, soil pH values rose across the treatments, from 5.4 in the control to 6.8 in HD. Ammonium and nitrate levels peaked in the HD treatment, reaching 30 and 22 mg kg−1, respectively. Similarly, dissolved organic carbon and microbial biomass carbon surged at mid-season aeration, hitting highs of 101 and 30 mg kg−1, respectively, in the HD treatment. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) were responsive to dolomite-lime application, with distinct reactions; AOB abundance and potential nitrification rates were positively affected by higher lime doses, whereas AOA numbers decreased over time and with dolomite application. Additionally, soil enzymes such as urease, catalase, invertase, phenol oxidase, and phosphatase also increased progressively, mirroring the rise in soil pH. This study identified increased soil pH as the critical factor influencing various soil parameters, especially the balance between AOA and AOB populations. Both AOB and AOA were sensitive to liming; AOA decreased while liming stimulated AOB abundance.

Soil eDNA biomonitoring reveals changes in multitrophic biodiversity and ecological health of agroecosystems

Soil health is integral to sustainable agroecosystem management. Current monitoring and assessment practices primarily focus on soil physicochemical properties, yet the perspective of multitrophic biodiversity remains underexplored. Here we used environmental DNA (eDNA) technology to monitor multitrophic biodiversity in four typical agroecosystems, and analyzed the species composition and diversity changes in fungi, bacteria and metazoan, and combined with the traditional physicochemical variables to establish a soil health assessment framework centered on biodiversity data. First, eDNA technology detected rich multitrophic biodiversity in four agroecosystems, including 100 phyla, 273 classes, 611 orders, 1026 families, 1668 genera and 1146 species with annotated classification, and the relative sequence abundance of dominant taxa fluctuates tens of times across agroecosystems. Second, significant differences in soil physicochemical variables such as organic matter (OM), total nitrogen (TN) and available phosphorus (AP) were observed among different agroecosystems, nutrients were higher in cropland and rice paddies, while heavy metals were higher in fish ponds and lotus ponds. Third, biodiversity metrics, including α and β diversity, also showed significant changes across agroecosystems, the soil biota was generally more sensitive to nutrients (e.g., OM, TN or AP), while the fungal communities were mainly affected by heavy metals in October (e.g., Cu and Cr). Finally, we screened 48 sensitive organismal indicators and found significant positive consistency between the developed eDNA indices and the traditional soil quality index (SQI, reaching up to R2 = 0.58). In general, this study demonstrated the potential of eDNA technology in soil health assessment and underscored the importance of a multitrophic perspective for efficient monitoring and managing agroecosystems.

The responses of weed communities to field nutrients and their ecological benefits in rice fields: A review

The responses of weed communities to field nutrients and their ecological benefits in rice fields: A review

Isolation, Screening and Biocidal Activity of Secondary Metabolites from Fungi of Paddy Field Soil Samples in Selected Alanganallur Sub Regions, Madurai, Tamil Nadu

Isolation, Screening and Biocidal Activity of Secondary Metabolites from Fungi of Paddy Field Soil Samples in Selected Alanganallur Sub Regions, Madurai, Tamil Nadu

Simultaneously reducing methane emissions and arsenic mobility by birnessite in flooded paddy soil: Overlooked key role of organic polymerisation

Flooding of paddy fields enhances methane (CH4) emissions and arsenic (As) mobilisation, which are crucial issues for agricultural greenhouse gas emissions and food safety. Birnessite (δ-MnO2) is a common natural oxidant and scavenger for heavy metals. In this study, birnessite was applied to As-contaminated paddy soil. The capacity for simultaneously alleviating CH4 emissions and As mobility was explored. Soil microcosm incubation results indicated that birnessite addition simultaneously reduced CH4 emissions by 47 %–54 % and As release by 38 %–85 %. The addition of birnessite decreased the dissolved organic carbon (DOC) contents and altered its chemical properties. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) results showed that birnessite reduced the labile fractions of proteins, carbohydrates, lignins, tannins, and unsaturated hydrocarbons, however, increased the abundance of condensed aromatic structures, suggesting the polymerisation of dissolved organic matter (DOM) by birnessite. The degradation of labile fractions and the polymerisation of DOM resulted in an inventory of recalcitrant DOM, which is difficult for microbes to metabolise, thus inhibiting methanogenesis. In contrast, birnessite addition increased CH4 oxidation, as the particulate methane monooxygenase (pmoA) gene abundance increased by 30 %. The enhanced polymerisation of DOM by birnessite also increased As complexation with organics, leading to the transfer of As to the organic bound phase. In addition, the decrease in ferrous ion [Fe(II)] concentrations with birnessite indicated that the reductive dissolution of Fe oxides was suppressed, which limited the release of arsenite [As(III)] under reducing conditions. Furthermore, birnessite decreased As methylation and shaped the soil microbial community structure by enriching the metal-reducing bacterium Bacillus. Overall, our results provide a promising method to suppress greenhouse gas emissions and the risk of As contamination in paddy soils, although further studies are needed to verify its efficacy and effectiveness under field conditions.

Winter forage crops influence soil properties through establishing different arbuscular mycorrhizal fungi communities in paddy field

Winter planting is promising for improving the utilization rate of fallow paddy fields in southern China by establishing arbuscular mycorrhizal fungi (AMF) communities. However, the effects of different winter forage crops on AMF community construction remain unknown. The AMF community establishment of different winter planting forage crops were conducted in oat, rye, Chinese milk vetch, and ryegrass, with winter fallow as a control. The AMF colonization rate, soil AMF spore density, community structure and diversity, and soil physicochemical properties were determined. The results showed that the total nitrogen and available nitrogen in winter Chinese milk vetch were 11.11% and 16.92% higher than those in winter fallow (P < 0.05). After planting winter forage crops, the AMF spore density in winter oat, rye, Chinese milk vetch, and ryegrass soil were 127.90%, 64.37%, 59.91%, and 73.62% higher than that before planting, respectively (P < 0.05). Claroideoglomus was the dominant AMF genus in the soil of winter planting oat, rye, and ryegrass. The average membership function value of winter Chinese milk vetch was the highest, indicating that it had the best comprehensive effect on soil physicochemical properties, AMF community structure and diversity, and fresh forage yield. Winter forage crops could increase the spore pool of soil AMF and improve the soil AMF community structure and diversity. Winter Chinese milk vetch in paddy field had the best comprehensive effect on soil physicochemical properties and soil AMF community according to the comprehensive evaluation. These findings provide a theoretical basis for sustainable development and utilization of the southern rice paddy ecosystem.

ALIH USAHATANI PADI SAWAH KE TANAMAN JERUK NIPIS (Citrus auratifolia) DI DESA TRIDANA MULYA KECAMATAN LANDONO KABUPATEN KONAWE SELATAN

The objective of this study is to ascertain the underlying factors that precipitate the transition from wet-rice farming to lime farming, as well as to examine the impact of such farming conversions among farmers in Tridana Mulya Village. The study population was comprised of two groups: a group of 31 lime farmers and a group of seven rice farmers. The sampling technique employed was the census method, which entailed the inclusion of the entire population, resulting in a research sample of 38 individuals (31 lime farmers and 7 rice paddy farmers). Data were collected through the use of interview techniques, observation, and documentation of media sources in the form of questionnaires. The variables under investigation are the factors that influence the transfer of farming and the impact of such transfer. The data were analyzed using a descriptive method and an income formula. The results demonstrated that the factors that precipitated the transition from paddy rice farming to lime farming were attributable to a confluence of production, economic, and cultivation-related considerations. The production yield factor of lime farming has demonstrated an increase in production compared to paddy rice farming in Tridana Mulya Village. In terms of economic factors, lime farming has been shown to yield higher profits for farmers than paddy rice farming. Additionally, the cultivation factors associated with lime farming are considerably more straightforward, as the land only requires processing once, due to the fact that lime is a long-term crop, in contrast to paddy rice farming, which is dependent on seasonal conditions. The impact of switching farms includes both economic and environmental consequences. From an economic standpoint, farmers' income may change after switching from paddy rice farming to lime crops. This is because lime crops may yield higher profits than paddy rice, depending on various factors. From an environmental standpoint, the lack of use of chemical fertilizers or pesticides in lime farming may reduce the impact on the environment. This is in contrast to the opposite condition observed in paddy rice farming.

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.

Pemanfaatan Sampah Plastik sebagai Material Paving Block

As people's consumption levels increase, the plastic waste produced will also increase. It's normal if in the future it becomes a serious environmental problem. We need a technology that is able to replace plastic waste into products that have a long life so that they do not return to waste in a short time. Making paving block products from plastic waste is another way of utilizing plastic waste over a long period of time, in order to increase utilization efficiency and reduce the environmental burden on plastic waste and form innovative products into building materials. The most important problem with plastic is plastic waste which cannot be decomposed naturally. Cleaning up plastic waste takes a very long time, and also the use of plastic can hardly be regulated. Based on the results of surveys, interviews and observations conducted on the community around Kuala Village, the community's awareness of waste processing is very minimal and there are lots of piles of plastic waste which can have a negative impact on health and disrupt the preservation of environmental functions, including residential environments, forests, rice fields, and rivers. To reduce the volume of plastic waste that is not managed properly, efforts are being made to utilize plastic waste to make paving blocks in Kuala Lemang Village. to explore the potential for using plastic waste as an alternative material in making environmentally friendly and sustainable paving blocks. Plastic waste collected from the surrounding environment is processed into mixed materials in making paving blocks. This process involves chopping, mixing with conventional materials such as sand, and testing the strength of the final product. Public acceptance of plastic-based paving blocks has proven positive, especially after trials in the local environment. This research contributes to better plastic waste management and offers new economic opportunities in the construction sector, while supporting sustainable development.

Identification and analysis of low light responsive yield enhancing QTLs in rice

Rice is one of the major food crops grown globally. However, during the wet season, rice suffers significant yield loss due to reduced light intensity caused by overcast clouds when the light intensity is only around 450–500 µmol/m2/s, compared to 1400–1800 µmol/m2/s in summer. This reduction in light intensity leads to a decrease in seed yield, mainly by limiting tiller or panicle numbers. Yield and its attributing parameters were recorded in one hundred thirty RILs for four consecutive wet seasons in ambient light (AL) and low light (LL, 35% light-cut using white shade net). QTL analysis was performed using Inclusive Composite Interval Mapping (ICIM) with all the phenotypic data and 927 polymorphic SNPs identified by the 7 K Infinium chip. The study identified a large QTL influencing panicle numbers and yield exclusively in lowlight on chromosome 1 (qPNLL1.1, qGYLL1.1) in four consecutive seasons with LOD > 10 and PVE > 30%. The favourable alleles are from the tolerant parent, Swarnaprabha. Another grain yield improving QTL was identified on chromosome 6 (qGYLL6.1), with LOD > 3 in three consecutive seasons. In a diverse rice panel of one hundred seventeen genotypes with five different models, association analysis identified the associated marker for panicle numbers and grain yield in LL, which is also the left marker of the newly identified QTLs for the traits under LL condition. A shade-responsive gene, monoculm 2 (MOC2, LOC_Os01g64660) inside the QTL on chromosome 1, upregulated in the tolerant parent and its QTL-carrying RILs, whereas repressed in the susceptible one. Therefore, due to its significant additive effect and validation across various genotypes, the yield-improving QTL on chromosome 1 can be directly utilised in marker-assisted selection (MAS) for developing shade-tolerant rice. This can also help reduce the yield gap between wet and dry-season rice.

Comparative analysis of production and marketing aspects of deficit and surplus paddy production areas in Bangladesh

The study aimed to compare production and marketing aspects in deficit and surplus paddy production areas in Bangladesh. For this study, a face-to-face interview was conducted with a semi-structured questionnaire. The survey was carried out in two districts from February to March 2022. Data were collected from a total of 113 paddy farmers from Brahmanbaria, a deficit district, and 128 farmers from Habiganj, a surplus district. According to this study, farmers in surplus districts have excellent geographic characteristics such as medium-high land and a triple crop area, while farmers in deficit districts suffer unfavorable conditions such as low land and flooding. The study also discovered that there are differences between the districts in terms of land availability, paddy cultivation area, and cropping intensity. In production aspects, the size of the farmland and the productivity differ significantly at the 1% level between the districts. Deficit farmers produce less paddy per acre compared to farmers with surplus districts. In the paddy marketing channel, local paddy assemblers (LPA) are the dominant actors in the deficit and LPB/local paddy brokers in the surplus area. Farmers in surplus areas have more marketing facilities and get higher paddy revenue and profits compared to deficit districts. However, farmers in both districts are mostly dependent on traders to sell their produce. In that case, paddy marketing facilities can accumulate through farmers’ community investment and the organization of cooperative societies. It will help improve farmers’ negotiation power at the village level in both districts. Res. Agric. Livest. Fish. Vol. 11, No. 2, August 2024: 173-183

The Belief in Pullayar among Agrarian People in Ampara District, Sri Lanka

Worship of deities takes a specific position among the religious beliefs related to agriculture. The Pullayar deity belief with agriculture specially can be seen in Northern Province and Nuwarakalaviya in the North Central Province of Sri Lanka. The study investigates the significance of the Pullayar deity belief among the agricultural community in Ampara District. It also focusses on the ways in which the agricultural practices of farmers, socio-cultural identities, and customs are influenced by the deity belief system. The main objective of the research was to examine the contemporary condition of Pullayar deity belief associated with agriculture in the Ampara District. The two Grama Niladari (GN) divisions of Galahitiyagoda and Udayagiriya belonging to Uhana Divisional Secretariat in Ampara district were used as the study areas. Data required for the research was collected using forty (40) farmers selected from the study area under random sampling method. Participatory observation and unstructured interviews were used to gather data. Pullayar worship is closely linked with the agricultural practices of Ampara district. Here farmers perform specific rituals for a successful harvest. Among the farming folk beliefs of Ampara, the Pullayar deity worship is uniquely adapted to protect the land from fertility and natural calamities. According to the farmers in this area, it is customary to worship the Buddha as well as Gambara Devi before doing any task in the paddy fields. As a special offering for pullayar deity, farmers offer coconut and let the pots overflow with milk as a ritual. It is performed by them for the protection of their fields and cattle. Pullayar rituals foster collective social cohesion. Strengthens community bonds through shared spiritual practices. Worship as well reveals a gendered division of religious duties, with men leading agricultural rituals and women maintaining household shrines. Therefore, this society reflects a balanced role of spiritual practices across genders. Though, Pullayar deity worship can be regarded as a particular cultural aspect that is unique to the agrarian economic system in this area and still exists now.

Sustainable Paddy Farming in Edirne: Evaluating the Impacts of Excessive Fertilizer and Pesticide Use

This study examines the environmental and economic impacts of chemical fertilizer and pesticide use in paddy fields in Edirne Province, Türkiye. Chemical fertilizers, especially nitrogen and phosphorus, are crucial for boosting paddy yield and ensuring food security. However, recent trends indicate significant potassium deficiency and excessive pesticide use, leading to environmental degradation and higher production costs. Incorrect fertilization techniques and pesticide usage can lower product quality and yield, adversely affecting farmers’ incomes and the national economy. Surveying 139 paddy farmers, the research found that farmers apply the herbicidal active ingredients Tefuryltrione, Clomazone, Tembotrione, and Quinclorac at rates of 129.35%, 34.27%, 18.06%, and 155.29% above the recommended levels, respectively. The excessive use of pesticides costs each farmer an additional USD 925.67, totaling USD 5.32 million for Edirne. The majority of farmers (69.2%) do not conduct soil analysis, indicating a potential gap in adopting the best practices for soil management and fertilization. Farmers use 84% less potassium than recommended while applying nitrogen and phosphorus 13% and 14% above the recommended levels, respectively. The extra cost of fertilizer use in Edirne is calculated as USD 833,135.49. This situation harms the economy and may have adverse effects on the environment and potential health effects on consumers.

The herbicidal activity of pre-emergence herbicide cinmethylin and its potential risks on soil ecology: pH, enzyme activities and bacterial community

BackgroundThe herbicide cinmethylin, which was originally registered for use in rice fields, has the potential to control grass weeds in wheat fields before the emergence of wheat. However, its herbicidal activity against various troublesome grass weeds that infest wheat fields in China and its relationships with soil pH, soil enzymes and soil bacteria are not well known. Here, the effects of applying cinmethylin on the soil surface were tested on six grass weeds, and its impacts on soil characteristics, including the soil pH, soil enzymes and bacterial community, were evaluated.ResultsAlopecurus aequalis, A. japonicus and A. myosuroides were highly sensitive to cinmethylin, with GR50 values of 78.77, 61.49 and 119.67 g a.i. ha− 1, respectively. The half-lives of cinmethylin at 1-, 10- and 100-fold the recommended rates were estimated at 26.46 − 52.33 d. Cinmethylin significantly increased the soil pH but decreased the activities of soil sucrase and urease. At 10- and 100-fold the recommended rate of cinmethylin, the bacterial abundance and diversity significantly decreased at 30 and 60 days after cinmethylin treatment. Cinmethylin at 100-fold the recommended rates largely promoted bacterial co-occurrence network complexity. Cinmethylin at high concentrations temporarily inhibited the abundance of the Nitrospira genus, as indicated by the copy numbers of the ammonia-oxidising archaea (AOA) amoA and ammonia-oxidising bacteria (AOB) amoA genes. Further analysis revealed that soil pH was negatively related to soil urease, and a significantly positive correlation was detected between soil urease and soil nitrification.ConclusionCollectively, the application of cinmethylin at the recommended field dose had nearly no effect on the soil ecosystem, but its potential risks at high concentrations deserve further attention.