cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.14453992
title: A modeling approach to estimating N<sub>2</sub>O emission derived from loss of soil organic matter for the Japanese greenhouse gas inventory

description: We designed a new approach for modeling the nitrous oxide (N<sub>2</sub>O) derived from nitrogen (N) mineralization associated with loss of soil organic matter (SOM) that meets the current IPCC guidelines (GL) because the method currently used in the National GHG Inventory Report (NIR) of Japan does not. Loss of soil carbon (C) was calculated by using the previously developed nationwide soil C calculation system for agricultural soils. We conducted a zero-C-input soil C modeling experiment, which is a one-year simulation without C input after a long-term ‘normal’ simulation with C input. Because no new organic matter was added to the system in the one-year simulation, we considered that C loss was equal to the C loss from SOM loss. Next, the amount of C loss was divided by the soil C/N ratio for each soil and agricultural land use type to calculate the amount of N mineralization. Finally, N mineralization quantity was converted to N<sub>2</sub>O emission by using an empirical model. Because the use of this empirical model cannot be justified for paddy fields, the use of IPCC default emission factor should be recommended instead of the empirical model-derived emission. We consider that these calculated N<sub>2</sub>O is derived from N mineralization associated with SOM loss. Our new approach, however, was not yet validated against field observation. The results are therefore only tentative and waiting for the field validation.
DOI: 10.6084/m9.figshare.14453992.v1
title: A modeling approach to estimating N<sub>2</sub>O emission derived from loss of soil organic matter for the Japanese greenhouse gas inventory

description: We designed a new approach for modeling the nitrous oxide (N<sub>2</sub>O) derived from nitrogen (N) mineralization associated with loss of soil organic matter (SOM) that meets the current IPCC guidelines (GL) because the method currently used in the National GHG Inventory Report (NIR) of Japan does not. Loss of soil carbon (C) was calculated by using the previously developed nationwide soil C calculation system for agricultural soils. We conducted a zero-C-input soil C modeling experiment, which is a one-year simulation without C input after a long-term ‘normal’ simulation with C input. Because no new organic matter was added to the system in the one-year simulation, we considered that C loss was equal to the C loss from SOM loss. Next, the amount of C loss was divided by the soil C/N ratio for each soil and agricultural land use type to calculate the amount of N mineralization. Finally, N mineralization quantity was converted to N<sub>2</sub>O emission by using an empirical model. Because the use of this empirical model cannot be justified for paddy fields, the use of IPCC default emission factor should be recommended instead of the empirical model-derived emission. We consider that these calculated N<sub>2</sub>O is derived from N mineralization associated with SOM loss. Our new approach, however, was not yet validated against field observation. The results are therefore only tentative and waiting for the field validation.
DOI: 10.6084/m9.figshare.15124365.v1
title: Amelioration in manganese uptake by a low-cadmium rice cultivar with application of several manganese fertilizers

description: We evaluated the use of manganese-containing amendments (Mn amendments) to improve the Mn uptake of a low-cadmium (Cd) rice cultivar, Koshihikari Kan No.1 <i>(Oryza sativa</i> L.), with a loss of function in the OsNramp5 that transports Mn and Cd, which was developed from an elite <i>japonica</i> cultivar Koshihikari. A flooded soil incubation experiment demonstrated that an increase of dissolved Mn in soils was induced by adding all 14 Mn amendments and was highly dependent on the citric acid-extractable Mn in the amendment. From the result of the incubation experiment, we selected three Mn amendments, namely, SM-1 (remarkably high Mn availability), FME-2 (high Mn availability), and SM-3 (moderate Mn availability) for a pot experiment. The pot experiment was carried out using two kinds of Mn-deficient soils with different pH (soil A and B). Manganese uptake by Koshihikari Kan No.1 was only less than one-tenth of that by Koshihikari grown on the same kinds of control soils. Dissolved Mn in soils and Mn uptake by Koshihikari Kan No.1 were substantially improved with the application of Mn amendments in the order SM-1 &gt; FME-2 &gt; SM-3; however, the magnitude was much more prominent in soil A than soil B. Lower soil solution pH of soil A would promote Mn dissolution from amendments and prevent dissolved Mn from adsorption on solid phase. Manganese uptake by Koshihikari Kan No.1 increased linearly with the increased dissolved Mn in the observed range (<i>R<sup>2</sup></i> = 0.972, <i>p</i> &lt; 0.001 for soil A and <i>R<sup>2</sup></i> = 0.978, <i>p</i> &lt; 0.001 for soil B). We concluded that the application of Mn amendment to Mn-deficient soils would be a promising countermeasure to ensure the healthy growth of Koshihikari Kan No.1. Additionally, soil pH control along with the application of Mn amendment would be of significance to improve the effectiveness of the application. The findings provide useful information for soil management to enhance Mn uptake by using the existing and future low-Cd cultivars with the mutant <i>osnramp5</i> allele.
DOI: 10.6084/m9.figshare.14069513
title: Depth profile of plant nutrients and acidity in a non-allophanic Andosol as affected by a half-century of fertilization

description: To clarify the effects of long-term fertilization on the depth profile of plant nutrients and soil acidity in non-allophanic Andosols, a soil survey was conducted on fertilized grassland and adjacent secondary forest in Kuju highland, Oita Prefecture, Japan. Both of the experimental plots had been managed as a semi-natural grassland (managed by cutting, mowing, and burning for raising cows) before mid of the 1960s, and then, the former had been converted into reclaimed grassland with applying agricultural materials such as fertilizers, manure, and lime, and the latter had been abandoned which resulted in secondary succession into the secondary forest. The comparison of the depth profiles between the two plots revealed that the applied Ca<sup>2+</sup> and Mg<sup>2+</sup> reached at least 100 cm depth of the non-allophanic Andosol profile. The soil pH was increased at least at the depth of 100 cm, and the plant-toxic level of soil acidity (≥12 mmol kg<sup>−1</sup>), which is one of the characteristic properties of non-allophanic Andosols, was decreased in the fertilized grassland soil. Soil available P was also observed to be increased at least 80 to 100 cm depth, although the mobility was smaller than those of exchangeable cations and soil acidity. Other soil chemical properties, such as cation exchange capacity, total C and N contents, pyrophosphate-extractable Al (Al<sub>p</sub>) and Fe (Fe<sub>p</sub>), acid-oxalate-extractable Al (Al<sub>o</sub>), Fe (Fe<sub>o</sub>), and Si (Si<sub>o</sub>), Al<sub>p</sub>/Al<sub>o</sub> ratio, and Al<sub>o</sub> + 1/2 Fe<sub>o</sub>, were not significantly altered by the modern grassland management activities. This study reveals considerable loss of plant nutrients from the fertilized grassland soil of a non-allophanic Andosol during a half-century. The loss of plant nutrients should be reduced for sustainable agriculture and conserving the natural environment.
DOI: 10.6084/m9.figshare.14069513.v1
title: Depth profile of plant nutrients and acidity in a non-allophanic Andosol as affected by a half-century of fertilization

description: To clarify the effects of long-term fertilization on the depth profile of plant nutrients and soil acidity in non-allophanic Andosols, a soil survey was conducted on fertilized grassland and adjacent secondary forest in Kuju highland, Oita Prefecture, Japan. Both of the experimental plots had been managed as a semi-natural grassland (managed by cutting, mowing, and burning for raising cows) before mid of the 1960s, and then, the former had been converted into reclaimed grassland with applying agricultural materials such as fertilizers, manure, and lime, and the latter had been abandoned which resulted in secondary succession into the secondary forest. The comparison of the depth profiles between the two plots revealed that the applied Ca<sup>2+</sup> and Mg<sup>2+</sup> reached at least 100 cm depth of the non-allophanic Andosol profile. The soil pH was increased at least at the depth of 100 cm, and the plant-toxic level of soil acidity (≥12 mmol kg<sup>−1</sup>), which is one of the characteristic properties of non-allophanic Andosols, was decreased in the fertilized grassland soil. Soil available P was also observed to be increased at least 80 to 100 cm depth, although the mobility was smaller than those of exchangeable cations and soil acidity. Other soil chemical properties, such as cation exchange capacity, total C and N contents, pyrophosphate-extractable Al (Al<sub>p</sub>) and Fe (Fe<sub>p</sub>), acid-oxalate-extractable Al (Al<sub>o</sub>), Fe (Fe<sub>o</sub>), and Si (Si<sub>o</sub>), Al<sub>p</sub>/Al<sub>o</sub> ratio, and Al<sub>o</sub> + 1/2 Fe<sub>o</sub>, were not significantly altered by the modern grassland management activities. This study reveals considerable loss of plant nutrients from the fertilized grassland soil of a non-allophanic Andosol during a half-century. The loss of plant nutrients should be reduced for sustainable agriculture and conserving the natural environment.
DOI: 10.6084/m9.figshare.14417688
title: Dynamics of fractionated rhizosphere soil P and plant P uptake under maize/P-mobilizing legumes intercropping in strongly weathered soil of Tanzania

description: Intercropping with cereal and phosphorus (P)-mobilizing leguminous crops is a traditional agricultural practice in Sub-Saharan Africa. It is essential to evaluate the effect of intercropping (i.e., rhizosphere sharing) on fractionated rhizosphere soil P dynamics under the various soil P conditions and legumes, to improve the soil-plant P dynamics in this region. This study aimed to identify the effect of rhizosphere sharing of maize (MZ)/P-mobilizing legumes intercropping on fractionated rhizosphere soil P dynamics and plant P uptake under different P fertilization rates in strongly weathered cropland soil of Tanzania. We conducted 60-day MZ and P-mobilizing legumes intercropping pot experiments under different P-fertilized conditions (0, 50, and 100 kg P ha<sup>−1</sup>) with two legumes (pigeon pea (PP) and groundnut (GN)) by using three different root-separation treatments (no separation (NS) for rhizosphere sharing, nylon mesh separation (MS), and complete separation (CS)), to compare the effect of rhizosphere sharing in one pot. We evaluated the Hedley-fractionated P of rhizosphere soil and plant P uptake in each pot. We found that both P-efficient legumes did not clearly decrease the less labile P (NaOH-P) of rhizosphere soil in no P treatment, while these clearly decreased the less labile P in 100 kg P ha<sup>−1</sup> treatment. It indicates that P-efficient legumes can solubilize the fertilized P but not native less labile P of the soil. The NS treatment increased the labile P of rhizosphere compared with CS by solubilizing the fertilized P, except for MZ/GN intercropping at 50 kg P ha<sup>−1</sup>. Relative to CS, MZ/PP intercropping increased the total plant P uptake per pot (20%–40%) under P-fertilized conditions, whereas MZ/GN intercropping decreased it (17%) at 50 kg P ha<sup>−1</sup> or showed no change at 100 kg P ha<sup>−1</sup>. MZ/PP intercropping improved P fertilizer recovery efficiency, whereas MZ/GN intercropping did not. Enhanced P use efficiency through intercropping with P-mobilizing legumes is dependent on P-solubilizing characteristics of each P-mobilizing legume.
DOI: 10.6084/m9.figshare.14417688.v1
title: Dynamics of fractionated rhizosphere soil P and plant P uptake under maize/P-mobilizing legumes intercropping in strongly weathered soil of Tanzania

description: Intercropping with cereal and phosphorus (P)-mobilizing leguminous crops is a traditional agricultural practice in Sub-Saharan Africa. It is essential to evaluate the effect of intercropping (i.e., rhizosphere sharing) on fractionated rhizosphere soil P dynamics under the various soil P conditions and legumes, to improve the soil-plant P dynamics in this region. This study aimed to identify the effect of rhizosphere sharing of maize (MZ)/P-mobilizing legumes intercropping on fractionated rhizosphere soil P dynamics and plant P uptake under different P fertilization rates in strongly weathered cropland soil of Tanzania. We conducted 60-day MZ and P-mobilizing legumes intercropping pot experiments under different P-fertilized conditions (0, 50, and 100 kg P ha<sup>−1</sup>) with two legumes (pigeon pea (PP) and groundnut (GN)) by using three different root-separation treatments (no separation (NS) for rhizosphere sharing, nylon mesh separation (MS), and complete separation (CS)), to compare the effect of rhizosphere sharing in one pot. We evaluated the Hedley-fractionated P of rhizosphere soil and plant P uptake in each pot. We found that both P-efficient legumes did not clearly decrease the less labile P (NaOH-P) of rhizosphere soil in no P treatment, while these clearly decreased the less labile P in 100 kg P ha<sup>−1</sup> treatment. It indicates that P-efficient legumes can solubilize the fertilized P but not native less labile P of the soil. The NS treatment increased the labile P of rhizosphere compared with CS by solubilizing the fertilized P, except for MZ/GN intercropping at 50 kg P ha<sup>−1</sup>. Relative to CS, MZ/PP intercropping increased the total plant P uptake per pot (20%–40%) under P-fertilized conditions, whereas MZ/GN intercropping decreased it (17%) at 50 kg P ha<sup>−1</sup> or showed no change at 100 kg P ha<sup>−1</sup>. MZ/PP intercropping improved P fertilizer recovery efficiency, whereas MZ/GN intercropping did not. Enhanced P use efficiency through intercropping with P-mobilizing legumes is dependent on P-solubilizing characteristics of each P-mobilizing legume.
DOI: 10.6084/m9.figshare.14046112
title: Enhancement of the nitrogen-fixing activity of paddy soils owing to iron application

description: <i>Anaeromyxobacter</i> and <i>Geobacter</i>, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria predominant in paddy soils. We hypothesized that adding ferric iron oxide as an electron acceptor for respiration of the iron-reducing bacteria could enhance the nitrogen-fixing activity of <i>Anaeromyxobacter</i> and <i>Geobacter</i> in paddy soils. In the soil microcosm study, soil nitrogen-fixing activity significantly increased after adding ferrihydrite or Fe<sub>2</sub>O<sub>3</sub>, ferric iron oxides, to the soil. In these soils, gene transcripts of <i>nifD</i> from <i>Anaeromyxobacter</i> and <i>Geobacter</i> were detected, whereas those from other general diazotrophs were not detected. <i>Anaeromyxobacter</i> and <i>Geobacter</i> might be involved in the enhanced soil nitrogen-fixing activity. The application of iron powder to paddy field soils also enhanced the soil nitrogen-fixing activity. This study is the first to demonstrate that addition of iron compounds to paddy soil enhanced the soil nitrogen-fixing activity. The results of this study may lead to the development of novel paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with a reduced nitrogen fertilizer input and a lower environmental nitrogen burden.
DOI: 10.6084/m9.figshare.14046112.v1
title: Enhancement of the nitrogen-fixing activity of paddy soils owing to iron application

description: <i>Anaeromyxobacter</i> and <i>Geobacter</i>, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria predominant in paddy soils. We hypothesized that adding ferric iron oxide as an electron acceptor for respiration of the iron-reducing bacteria could enhance the nitrogen-fixing activity of <i>Anaeromyxobacter</i> and <i>Geobacter</i> in paddy soils. In the soil microcosm study, soil nitrogen-fixing activity significantly increased after adding ferrihydrite or Fe<sub>2</sub>O<sub>3</sub>, ferric iron oxides, to the soil. In these soils, gene transcripts of <i>nifD</i> from <i>Anaeromyxobacter</i> and <i>Geobacter</i> were detected, whereas those from other general diazotrophs were not detected. <i>Anaeromyxobacter</i> and <i>Geobacter</i> might be involved in the enhanced soil nitrogen-fixing activity. The application of iron powder to paddy field soils also enhanced the soil nitrogen-fixing activity. This study is the first to demonstrate that addition of iron compounds to paddy soil enhanced the soil nitrogen-fixing activity. The results of this study may lead to the development of novel paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with a reduced nitrogen fertilizer input and a lower environmental nitrogen burden.
DOI: 10.6084/m9.figshare.14923550
title: Changes in lowland paddy soil fertility in the Philippines after 50 years of the Green Revolution

description: The Green Revolution (GR) made a major contribution to increasing the rice yield in the Philippines from 1.3 t ha<sup>−1</sup> in 1966 to 4.0 t ha<sup>−1</sup> in 2018, but the changes in paddy soil fertility that occurred during this 50-year period remain unknown. We collected 37 soil samples from the plow layers of paddy fields in Luzon, Leyte, Panay, and Mindanao in the Philippines in 2016 and 2017 (the ‘2010s’) and compared their fertility-related soil properties with published data for soil samples collected from the same or nearby sampling sites in 1969 (the ‘1960s’). Paddy soils in the Philippines had relatively high exchangeable calcium (Ca) and magnesium (Mg) content, cation exchange capacity (CEC), available silicon (Si) content, and total carbon (C) and nitrogen (N) content, reflecting their indigenous pedological background. We found that the 2010s soils had a lower available N content, particularly in wetter regions, despite the high input of N fertilizers, whereas the available phosphorus (P) showed a six-fold increase from the 1960s to the 2010s. The total potassium (K) content had significantly decreased during this period, possibly due to the mining effect of intensive farming with K-deficient fertilization. The 2010s soils contained a greater silt content and higher proportion of smectite in the clay fraction, which may have been transported from upstream via irrigation water. The increase in smectite corresponded with a significant increase in the cation exchange capacity, despite the organic C and clay contents tending to decrease, and these increases in smectite and soil pH may have contributed to the increase in the available fraction of Si that had not been applied as fertilizers. These findings demonstrate that paddy soil fertility in the Philippines changed in many ways over this 50-year period, largely owing to the direct impact of GR implementation in paddy fields but also potentially due to offsite effects from upland fields. The environmental impact of the nutrient loss and soil organic matter degradation behind the fertility improvement should be assessed holistically for the sustainable development of rice paddy ecosystems. (337 words)
DOI: 10.6084/m9.figshare.14923550.v1
title: Changes in lowland paddy soil fertility in the Philippines after 50 years of the Green Revolution

description: The Green Revolution (GR) made a major contribution to increasing the rice yield in the Philippines from 1.3 t ha<sup>−1</sup> in 1966 to 4.0 t ha<sup>−1</sup> in 2018, but the changes in paddy soil fertility that occurred during this 50-year period remain unknown. We collected 37 soil samples from the plow layers of paddy fields in Luzon, Leyte, Panay, and Mindanao in the Philippines in 2016 and 2017 (the ‘2010s’) and compared their fertility-related soil properties with published data for soil samples collected from the same or nearby sampling sites in 1969 (the ‘1960s’). Paddy soils in the Philippines had relatively high exchangeable calcium (Ca) and magnesium (Mg) content, cation exchange capacity (CEC), available silicon (Si) content, and total carbon (C) and nitrogen (N) content, reflecting their indigenous pedological background. We found that the 2010s soils had a lower available N content, particularly in wetter regions, despite the high input of N fertilizers, whereas the available phosphorus (P) showed a six-fold increase from the 1960s to the 2010s. The total potassium (K) content had significantly decreased during this period, possibly due to the mining effect of intensive farming with K-deficient fertilization. The 2010s soils contained a greater silt content and higher proportion of smectite in the clay fraction, which may have been transported from upstream via irrigation water. The increase in smectite corresponded with a significant increase in the cation exchange capacity, despite the organic C and clay contents tending to decrease, and these increases in smectite and soil pH may have contributed to the increase in the available fraction of Si that had not been applied as fertilizers. These findings demonstrate that paddy soil fertility in the Philippines changed in many ways over this 50-year period, largely owing to the direct impact of GR implementation in paddy fields but also potentially due to offsite effects from upland fields. The environmental impact of the nutrient loss and soil organic matter degradation behind the fertility improvement should be assessed holistically for the sustainable development of rice paddy ecosystems. (337 words)
DOI: 10.6084/m9.figshare.14776188
title: Alternate wetting and drying enhanced the yield of a triple-cropping rice paddy of the Mekong Delta

description: In the Mekong Delta, triple rice cropping is widely spread. The rice cultivation is characterized by a short cropping period and nearly year-round flooding. Putting the soil under an oxidative condition through changing the water regimes during cropping periods might have a potential to increase the rice yield. To test this potential, an experiment was conducted at a typical triple-cropping farmer’s alluvial paddy in a central area of the delta for five years, 15 consecutive cropping seasons. We adopted an intermittent irrigation technique known as alternate wetting and drying (AWD). Under AWD, we irrigated to a depth of 5 cm above the soil surface only when the field water level dropped to 15 cm below the soil surface, with some exceptions. As a control, we prepared a treatment under which the paddy was continuously flooded (CF) except 2 weeks before expected harvest. We also prepared three straw treatments: all raw straw return, all straw-ash return, and no straw return to the paddy. For other field management, we adopted locally conventional methods. Results show that the straw treatment effects on the rice yield were not significant. For water treatments, the soil redox potential under AWD remained higher, in most cases, than that under CF; and the rough rice yield, harvest index, and percentage of ripened grains under AWD respectively became 8.9%, 4.4%, and 3.5% higher (<i>p</i> &lt; 0.01) than those under CF, with lower N contents in rice grains and 43% less irrigation water use. The increase in rice yield by AWD was found with an increase in harvest index and a decrease in aboveground biomass and nitrogen content, indicating that it was due to the promotion of nutrient translocation in rice by AWD. The effect of AWD was enhanced particularly in the winter–spring cropping season, during which the nighttime temperature was the lowest. This piece of evidence that the rice yield of the delta can be increased simply by introducing AWD has the potential to encourage farmers to take voluntary actions that will also lead to a reduction in methane emission from rice paddies.