OICC PRESS Quality of seedlings of different pepper genotypes grown in millicompost: An organic substrate generated by millipedes’ activity Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Quality of seedlings of different pepper genotypes grown in millicompost: An organic substrate generated by millipedes’ activity 10.30486/ijrowa.2021.1908263.1126 EN Talita Dos Santos Ferreira Institute of Agronomy, Federal Rural University of Rio de Janeiro, Seropédica, Brazil 0000-0001-6796-1656 Rogério Gomes Pêgo epartment of Crop Science, Institute of Agronomy, Federal Rural University of Rio de Janeiro, Seropédica, Brazil Luiz Fernando De Sousa Antunes Federal Rural University of Rio de Janeiro, Seropédica, Rio de Janeiro, Brazil 0000-0001-8315-4213 Maria Elizabeth Fernandes Correia Embrapa Agrobiologia, Rio de Janeiro, Seropédica, Brazil 0000-0003-1919-6659 Rosária Da Costa Faria Martins Institute of Agronomy, Federal Rural University of Rio de Janeiro, Seropédica, Brazil 0000-0001-7590-2939 Margarida Goréte Ferreira Do Carmo Department of Crop Science, Institute of Agronomy, Federal Rural University of Rio de Janeiro, Seropédica, Brazil 0000-0002-0955-091X Journal Article 2023 10 22 Purpose To evaluate the production and the quality of seedlings of different pepper genotypes produced on millicompost as an organic substrate. Method Three experiments were carried out, one for each pepper genotype (ENAS-5007, ENAS-5031 and ENAS-5032) in which three substrates were evaluated: 100% Millicompost (S1); Millicompost MIX (50% millicompost + 50% powdered coconut fiber) (S2) and Carolina organic® commercial substrate (S3). Variables evaluated: shoot and root dry mass (SDM and RDM), number of leaves (NL), plant height (PH), seedling vigor (SV) and clod stability (CS). The data were subjected to the analysis of variance and the means were compared by the Tukey’s test at 5% probability level. Results For the ENAS-5007 and ENAS-5032 genotypes, there was a significant difference in all the variables analyzed, being S1 and S3 the substrates with the highest and the lowest performances, respectively. In the ENAS-5031 genotype, SDM and RDM did not differ between S1 and S2. For ENAS-5031, there were significant differences in PH, NL and SV, in which S1 promoted the best results; however, no significant difference was observed for CS. Conclusion The 100% millicompost substrate promoted the best development of pepper seedlings in all the three genotypes evaluated. However, the combination of the millicompost MIX has the potential to be used, as it promotes seedlings of superior quality in comparison to the commercial substrate, maximizing the use of millicompost as a substrate for the production of organic pepper seedlings. Highlights The organic compound produced by the action of millipedes can be used as substrate; The millicompost has adequate physicochemical properties to produce pepper seedlings; Pepper genotypes show high vigor when grown in organic substrates.

OICC PRESS Influence of non-edible oil-cakes and their composts on growth, yield and Alternaria leaf spot disease in chilli Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Influence of non-edible oil-cakes and their composts on growth, yield and Alternaria leaf spot disease in chilli 10.30486/ijrowa.2021.1912158.1150 EN VasudhaUdupa A Department of PG Studies and Research in Applied Botany, Jnana Sahyadri, Kuvempu University, Shankaraghatta – 577 451, Shimoga Dist. India Balakrishna Gowda Department of Forestry and Environmental Science, University of Agricultural Sciences, GKVK Campus, Bangalore- 560065 India Shivanna M.B Department of PG Studies and Research in Applied Botany, Jnana Sahyadri, Kuvempu University, Shankaraghatta – 577 451, Shimoga Dist. India Journal Article 2023 10 22 Purpose Raw and composted oil-cakes of neem, madhuca and simarouba were evaluated for their effect on plant growth, yield, and management of Alternaria tenuissima leaf spot disease, and rhizosphere microorganisms in chilli crop. Method The oil-cakes were composted in simple pits containing a mixture (6:1:1) of individual oil-cake, soil and rice straw. Growth promotion and disease incidence were assessed in plants grown in soil amended with raw or composted oil-cakes of neem, madhuca and simarouba in pot and field. Rhizosphere microflora was also determined in all treatments. Result Raw oil-cakes and their composts increased plant growth and yield and considerably decreased disease incidence and severity of A. tenuissima leaf spot in chilli grown in pot and field. The composted oil-cakes of simarouba were most effective in improving plant growth and yield and decreasing leaf spot disease in chilli, followed by madhuca and neem oil-cake compost. Fruit yield and vitamin C content were also high in simarouba compost. All composted oil-cakes increased beneficial microbial population in the rhizosphere, including phosphate solubilizers, free-living N2 fixers and Trichoderma species. The compost amendment decreased A. tenuissima population in the soil at the same time. Conclusion The growth promotion, yield increase and disease reduction in chilli were attributed to chemical compounds in oil-cakes and stimulation of beneficial microbes in the rhizosphere by raw or composted oil-cakes. This study demonstrated that composted non-edible oil-cakes could be used for soil amendment in place of agrochemicals to increase productivity, manage soil-borne diseases and improve soil health. Highlights Alternaria tenuissima cause leaf spot disease in chilli crop and is the cause of reduced yield. The first study on the use of oil-cakes of neem, madhuca and simarouba in controlling leaf spot in chilli; The oil-cake application inducing systemic resistance in chilli plants; Providing baseline information on the application of composted oil-cakes for yield improvement and disease management in chilli crop

OICC PRESS Laser-induced breakdown spectroscopy applied to cattle compost for phosphorus quantification Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Laser-induced breakdown spectroscopy applied to cattle compost for phosphorus quantification 10.30486/ijrowa.2021.1917918.1178 EN Alberto Lencina Laboratorio de Análisis de Suelos, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina 0000-0002-4834-7543 Gustavo Romagnoli CRESCA, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina Andrea Alonso CIISAS, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina Noelia Ramos CRESCA, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina Cristian D’Angelo Instituto de Física Arroyo Seco, IFAS (UNCPBA) and CIFICEN (UNCPBA-CICPBA-CONICET), Buenos Aires, Argentina Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Buenos Aires, Argentina Lina Lett CIISAS, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina Silvia Mestelan Laboratorio de Análisis de Suelos, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina CIISAS, Facultad de Agronomía, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina Journal Article 2023 10 22 Purpose Agronomic and environmental reasons force farmers to know the total P concentration of composted cattle manure. Laser-Induced Breakdown Spectroscopy seems proper to obtain such information. For logistic reasons (carriage, storage, field application, etc.), a dry matter characterization is also needed. Method Thirty samples of feedlot compost at different stages of stability and maturity were studied. Samples were dried at 50°C for dry matter characterization. As a reference method to determine total P concentration, wet digestion and colorimetry were employed. The area of the P I line emission obtained by laser-induced ablation of the samples was measured to estimate the total P concentration. Randomized calibrations through a modified version of the Kennard-Stone algorithm based on the Mahalanobis distance were performed. Results Dry matter varied from 40% to 90%, and no pattern was found related to compost origin, maturity, or stability. The total P concentration of the studied compost ranged from 1800 ppm up to 11200 ppm. Almost 80% of the calibration fittings have an R2 ≥ 0.895. The mean validation error was less than 22% for about 80% of the calibrations, with a mean prediction error bound to 40%. Discarding outliers, the errors were reduced to 19% and 30%, respectively. Conclusion Water content must be considered in addition to other characterizations due to logistic implications. Calibrations with a 30 percent of prediction error were achieved, which seems enough as a first approximation to predict the total P content in compost for utilization in farms to recycle nutrients. Highlights Agronomic and environmental reasons force farmers to know the total P concentration of composted cattle manure. Laser-Induced Breakdown Spectroscopy seems proper to obtain such information. As a reference method to determine total P concentration, wet digestion and colorimetry were employed. Randomized calibrations through a modified version of the Kennard-Stone algorithm based on the Mahalanobis distance were performed. Discarding outliers, 80% of the calibration fittings have an R2 ≥ 0.92 and the mean validation and prediction errors were reduced to 19% and 30%, respectively.

OICC PRESS Animal manure application effects on soil properties and okra ( Abelmoschus esculentus L) growth and yield performance Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Animal manure application effects on soil properties and okra ( Abelmoschus esculentus L) growth and yield performance 10.30486/ijrowa.2022.1910512.1137 EN Benedict O. Unagwu Department of Soil Science, University of Nigeria, Nsukka 410001, Enugu State, Nigeria 0000-0003-4383-2811 Roseline U Ayogu Department of Soil Science, University of Nigeria Nsukka, Nigeria Journal Article 2023 10 22 Purpose Increase in global population and food demands have necessitated the need to enhance the health status of agricultural soils to overcome retrogresses in crop yields. Thus, amply use of animal manures is critical to improving low fertility status that characterised most agricultural soils in the tropics. Method This study investigated the effects of various animal manure types on soil properties and performance of okra (Abelmoschus esculentus L) grown on a degraded coarse-textured ultisol. The treatments were: T1, poultry manure; T2, cow manure; T3, pig manure applied at 702 g pot-1 (equivalent to 30 t ha-1) to a 10 kg potted soil and T4, control unamended soil. Results Amended treatments had 0.73-10.9% increase in organic matter, 191-370% increase in soil N, 30.4-170% and 25.5-76.5% increase in soil P and K, respectively relative to the control treatment. Amended treatments recorded significantly higher (p <0.05) plant height, stem girth, okra biomass and yields compared with the control treatment. Poultry manure showed superiority over cow manure and pig manure for pH, soil nutrients, okra yield, okra growth and yield parameters measured. Conclusion The results indicate that animal manure application increased okra yield and enhanced the fertility status of a degraded coarse-textured ultisol. Thus, application of animal manures can help overcome low fertility challenges associated with degraded tropical soils. Highlights Animal manure application had positive effects on most of the plant parameters (okra height, number of okra leaves, pod yields etc.) measured and significantly reduced the duration of flowering and fruiting in okra plant. Animal manured treatments significantly improved soil nutrients (NPK) and organic matter content relative to the control treatment. Comparatively, neither poultry manure nor pig manure application outperformed (p < 0.05) each other based on the okra yield components measured. Applying 30 t ha-1 of either poultry manure or pig manure enhanced okra production in a degraded coarse-textured ultisol.

OICC PRESS Banana residue could be a viable rice straw alternative for Pleurotus mushroom production Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Banana residue could be a viable rice straw alternative for Pleurotus mushroom production 10.30486/ijrowa.2022.1923511.1204 EN Hend Ahmed Hamed Department of Horticulture, Faculty of Agriculture, Sohag University, Egypt 0000-0002-4013-5191 Mohamed Fouad Mohamed Department of Olericulture, Faculty of Agriculture, Assiut University, Egypt 0000-0001-7657-6223 Khalid Ahmed Elshaikh Department of Horticulture, Faculty of Agriculture, Sohag University, Egypt Maher Hassan Hosseney Department of Horticulture, Faculty of Agriculture, Sohag University, Egypt Journal Article 2023 10 22 Purpose Oyster mushroom (Pleurotus ostreatus) is becoming more popular as an efficient biotechnological procedure for upcycling agricultural by-products into valuable human food. This study looked into the possibility of employing banana residue (BR) and sorghum stalks (SS) as localized feasible rice straw (RS) substitutes for cultivating P. ostreatus. This has the potential to improve the livelihoods of rural agricultural communities in Egypt, as well as those in other parts of the world. Method For two successive trials, three sole substrates (BR, SS, and RS) and six various combinations of SS and BR each with rice straw at 1:1, 1:2, and 2:1 ratio were tested. Agronomic features, antioxidant capacity, and crude protein contents of mushroom basidiocarps were measured.  The chemical profile of the three raw and spent sole substrates was also studied. Results The sole BR substrate was superior to both RS and SS in terms of basidiocarps yield and both exterior (average cap weight, diameter, and thickness) and interior (crude protein and total antioxidant activity, phenols and flavonoids contents) quality attributes. The yield of basidiocarps developed on the sole SS substrate was far lower than that of the other substrates. It is worth mentioning that, BR tended to contain high initial potassium, phosphorus, cellulose, and total carbohydrates concentration. Conclusion Sole BR could entirely substitute sole RS as a substrate for the production of Pleurotus ostreatus. Highlights Banana wastes can serve as alternative of rice straw to cultivate oyster mushrooms, which would help rural agricultural communities better their livelihoods. Sole banana residue (BR) could completely replace sole rice straw (RS) as a substrate for Pleurotus ostreatus and if both BR and RS substrates are plentifully available, their mixture can be used gainfully. The potassium, phosphorus, cellulose, and total carbohydrates concentrations in Banana Residue tends to be high. Sorghum stalks are not suited as a growing medium for oyster mushrooms on their own.

OICC PRESS Organic fertilizer produced from chicken carcasses on soybean production Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Organic fertilizer produced from chicken carcasses on soybean production 10.30486/ijrowa.2021.1918036.1172 EN Willian Silva Melo Western Paraná State University, Department of Energy Engineering in Agriculture, Cascavel, Paraná, Brazil https://orcid.org/00 Natalia Pereira Western Paraná State University, Department of Agricultural Engineering, Cascavel, Paraná, Brazil Edna Aparecida de Andrade Western Paraná State University, Department of Energy Engineering in Agriculture, Cascavel, Paraná, Brazil Reginaldo Ferreira Santos Western Paraná State University, Department of Energy Engineering in Agriculture, Cascavel, Paraná, Brazil Luiz Antônio Zanão Júnior Rural Development Institute of Paraná, Department of Soil Science, Santa Teresa do Oeste, Paraná, Brazil Journal Article 2023 10 22 Purpose The objective of this study was to evaluate soybean production and nutrient availability in the soil using doses of organic fertilizer formed from chicken carcasses, compared to the use of mineral fertilizer. Method The evaluated treatments, produced from chicken carcasses, were calculated to provide 0, 30, 60, 90, 120 kg ha-1 of P2O5, that is, 0; 3.37; 6.71; 10.11 and 13.48 t ha-1, respectively. We also evaluated an additional treatment, in which 60 kg ha-1 of P2O5 were applied, through 400 kg ha-1 of NPK 10-15-15; this was carried out in a rural area located in the municipality of Ubiratã, Western Paraná. After harvest, the plant production components of soybean were evaluated, as well as the P content in the soil. The data were submitted to analysis of variance (ANOVA). The effect of the organic compost doses was evaluated by regression analysis and the additional treatment was compared by contrast analysis. Results The use of organic compost doses based on chicken carcass in soybean cultivation resulted in linear increase in plant height, number of pods per plant, thousand grain weight productivity and oil content in the grains. It was also efficient in increasing P levels of the soil. Compared to mineral fertilizer, the use of organic compost resulted in greater amount of P available in the soil but had a lower productivity. Conclusion Organic fertilizer from chicken carcass was able to increase the production components of soybean as well as to increase the soil P availability. Highlights Soybean is one of the most important cultivated oilseeds in the world and to ensure high grain yield, it is essential to properly supply the nutrients through soil fertilization, which is usually done with mineral fertilizers. Organic fertilizers are an option mainly in regions with high production of poultry and pigs, where it is possible to take advantage of both manure and carcasses, as well as for their value in relation to mineral fertilizer. An organic compost based on chicken carcass with significant amounts of nutrients was obtained. Nutrients supply in the soil, via organic compost, resulted in taller plants and greater number of pods per plant, higher productivity, and higher grain oil content. The organic compost also resulted in a higher P content in the soil compared to the use of mineral fertilizer.

OICC PRESS Effect of cow vermicompost on growth, fruit yield, and quality of hot pepper (Capsicum annuum var. Red chili) Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Effect of cow vermicompost on growth, fruit yield, and quality of hot pepper (Capsicum annuum var. Red chili) 10.30486/ijrowa.2021.1913049.1154 EN Mohammad Hossein Aminifard Department of Horticultural Science and Special Plants Regional Research Center, College of Agriculture, University of Birjand, Iran Journal Article 2023 10 22 Purpose This study evaluated the response of hot pepper (Capsicum annuum var. Red chili) towards cow vermicompost application under field conditions. Method Cow vermicompost was supplied in four levels (0, 5, 10, and 15 t ha-1) across the two growing seasons in 2017 and 2018. Results Vermicompost application significantly increased the plant height, internode distance, and the number of lateral branches in both seasons. It was noticed that manuring with 15 t ha-1 of cow vermicompost resulted with enhanced chlorophyll contents, fruit yield, and fruit number in both years. In both seasons, the highest leaf number, fruit weight, and total soluble solids are related to the third treatment (10 t ha-1 of cow vermicompost). The results showed that 1000-seed weight and vitamin C content were affected by cow vermicompost. Data showed that manuring with vermicompost (5 t ha-1) caused the best quality components in 2017 and 2018. Conclusion It was concluded that the application of vermicompost had a significant impact on vegetative and reproductive growth and fruit quality of hot pepper. Highlights Treatments receiving cow vermicompost at 10 and 15 t ha-1 recorded the best growth, fruit yield, and quality in hot pepper. Cow vermicompost has a strong impact on vegetative and reproductive growth, and fruit quality of hot pepper. Cow vermicompost is a suitable alternative for inorganic fertilizers to sustain hot pepper growth

OICC PRESS Differential growth and productivity of oyster mushroom ( Pleurotus pulmonarius ) on agro-waste substrates in semi-arid regions of Kenya Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Differential growth and productivity of oyster mushroom ( Pleurotus pulmonarius ) on agro-waste substrates in semi-arid regions of Kenya 10.30486/ijrowa.2022.1931154.1252 EN Judy Wanjira Wachira School of Agriculture and Veterinary Sciences, South Eastern Kenya University, Kitui, Kenya Simon Nguluu School of Agriculture and Veterinary Sciences, South Eastern Kenya University, Kitui, Kenya Josphert Kimatu School of Pure and Applied Sciences, Department of Life Sciences, South Eastern Kenya University, Kitui, Kenya Journal Article 2023 10 22 Purpose Food insecurity and poverty are common challenges in arid and semi-arid regions.  Diversification into low input agriculture like mushroom cultivation can help address these challenges. However, recommended mushroom substrates in Kenya (rice and wheat straws) are not widely available cheaply. Crop residues found in semi-arid areas can serve as alternative substrates, but their efficiency has not been adequately evaluated. This study evaluated the potential of various agro-waste materials as alternative substrates for cultivation of phoenix oyster mushrooms (Pleurotus pulmonarius) in semi-arid regions. Method Five agro-waste materials and their combinations were tested: maize stalks, beans straw, maize cobs, rice straw, and Melia volkensii leaves. The study assessed the effects of these substrates on different mushroom growth and productivity parameters. The experiment was set in a randomized complete block design, under relative humidity of 80 - 90% and temperatures of 23 - 24°C, over a 75 day period. Results Substrates containing M. volkensii failed to colonize fully except in their combination with bean straw, which yielded little. Yields varied significantly by substrate, ranging from 136.2 g/kg of wet substrate in bean straw + Melia volkensii to 434.9 g/kg of wet substrate in rice straw. Mushroom yields from maize stalks + bean straw and maize stalks + maize cobs substrates were not significantly different from those of rice straw, the control substrate. Conclusion The study showed that combinations of maize stalks, bean straw and maize cobs are suitable alternatives to rice straw, as substrates for oyster mushroom production. Highlights The study showed that Melia volkensii leaves are not a suitable substrate for oyster mushroom production. Combining maize cobs with rice straws, maize stalks with maize cobs and maize stalks with bean straw, can hasten the days to mushroom fruiting compared to pure substrates. The study further showed that the mean weight, biological efficiency and productivity of oyster mushrooms depend on the substrate type used. The performance of the substrates in terms of yields can be arranged in order of decreasing suitability as follows; rice straw, maize stalks + bean straw, maize stalks + maize cobs, maize cobs, bean straw + maize cobs, maize cobs + rice straw, bean straw, maize stalks + rice straw, bean straw + rice straw, maize stalks and bean straw + volkensii. It can therefore be concluded that some of the locally available materials in the semi-arid areas, viz maize stalks, bean straw and maize cobs and their combinations are suitable substrates for oyster mushroom production.

OICC PRESS Effect of phosphoric rock on the chemical, microbiological and enzymatic quality of poultry, equine and cattle manure compost mix Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Effect of phosphoric rock on the chemical, microbiological and enzymatic quality of poultry, equine and cattle manure compost mix 10.30486/ijrowa.2022.1930622.1247 EN Luis Alexander Paez Facultad de Ciencias Agrarias y Ambientales, Grupo de Investigación en Producción Animal y Tecnologías Agroalimentarias (INPANTA), Tunja-150001, Colombia 0000-0002-4135-3051 Jose Francisco Garcia Facultad de Ciencias Agrarias y Ambientales, Grupo de Investigación en Agricultura, Organizaciones y Frutos (AOF), Tunja-150001, Colombia 0000-0003-3767-6197 Joel David Parra Facualtad de Ciencias Agropecuarias, Grupo de Investigación en Desarrollo y Producción Agraria Sostenible (GIPSO), Tunja-150001, Colombia Leonardo Lozano Jacome Facultad de Ciencias Agrarias y Ambientales, Grupo de Investigación en Agricultura, Organizaciones y Frutos (AOF), Tunja-150001, Colombia Journal Article 2023 10 22 Purpose Phosphorus (P) is one of the key elements in the agricultural sector, allowing improved production yields. Phosphate rock is a natural source of phosphorus; however, its low reactivity limits the release of P available to plants in the short term, conditioning its application in a direct way. Research was conducted to determine the effect of phosphate rock on a manure compost mix by measuring its availability of P and its microorganism activity. Method Cattle manure, equine manure, and poultry manure from three provinces of the department of Boyacá, Colombia, were moistened up to 60% with fermented mineralized liquid and composted with different proportions of phosphate rock. After 60 days of composting, the mineral content and microorganism activity were measured. Results This study revealed three notable results. First, the addition of phosphate rock led to an increase in total and available P and a decrease in water-soluble phosphorus and inhibitory effects of phosphatase activity. Second, composting with the three manures resulted in microorganism activity levels ​​higher than 700*104 CFU, exceeding the NTC’s definition of an inoculant fertilizer in the agricultural process. Third, a strong positive relationship was found between ammonia-oxidizing bacteria and PBII, a medium correlation was found between PSM and TP, and a negative correlation was found between pH and PT. Conclusion Composting manure with phosphoric rock could be a low-cost source of macronutrients, minerals, and microorganisms to promote soil health and crop yields. Highlights Poultry, equine, and cattle manure compost mix enriched with phosphoric rock is a source of low-cost macronutrients, minerals and microorganisms that promote soil health. Adding phosphoric rock to poultry, equine, and cattle manure compost mix affects the population of phosphate solubilizers, phosphatase activity, and ammonium oxidizing bacteria. Adding phosphoric rock to poultry, equine, and cattle manure compost mix has no statistically significant effect on Bray II phosphorus and water-soluble phosphorus.

OICC PRESS Effect of weed residue application on rice-straw decomposition and soil fungi-to-bacteria ratios Volume 11 (2022), IJROWA Issue 3, September 2022 2023 10 22 Effect of weed residue application on rice-straw decomposition and soil fungi-to-bacteria ratios 10.30486/ijrowa.2021.1926389.1229 EN Jin-Feng Lin Graduate School of Agriculture,The Special Postgraduate Program in Biosphere Sustainability Science, Hokkaido University, Sapporo, JAPAN 0000-0002-4703-1475 Yoshitaka Uchida Global Center for Food, Land and Water Resources, Research Faculty of Agriculture, Hokkaido University, Sapporo, JAPAN 0000-0003-4354-7842 Journal Article 2023 10 22 Purpose Undecomposed rice straw incorporated into the soil can negatively impact rice growth, but it is also an important source of soil carbon. The objective of this study was to evaluate whether the addition of weeds that naturally grow in rice paddy ecosystems could accelerate the decomposition rate of rice straw. The microbes that contribute to the decomposition process were also investigated. Method Trifolium pratense (clover) and Rumex obtusifolius (bitter dock) both alone and in combination were decomposed along with rice-straw litterbags in rice paddy soils. The rice-straw decomposition rate was measured using the weight changes of the litterbags. The rice-straw carbon-to-nitrogen ratio and microbial abundance (fungi and bacteria) were also measured, as well as the soil respiration rate every seven days. Results The addition of weed residues increased the soil respiration rates, but it did not influence the rice-straw decomposition rate. However, the carbon-to-nitrogen ratio of the remaining rice-straw and the fungi-to-bacteria ratio in the soil were both affected by the presence of the weeds, and the magnitudes of the effects were dependent on the carbon-to-nitrogen ratio of the added weeds. Conclusion Given that the addition of weeds altered the quality of the remaining rice straw and the soil microbial community composition, longer term studies are required to determine whether the addition of weed residues primes the rice straw for the later stage of decomposition. Highlights The quality of the remaining rice straw residues (i.e., C:N ratio) and the microbial composition involved in the decomposition (i.e., F:B ratio) were influenced by the added weed residues. Microbial biomass‒C was not influenced by the added weed residues, indicating that they were mostly used as a source of respired-C.