Gray Lowland Soil Research Articles

The effect of slow adsorption of phosphate on its transport during the infiltration process in saturated agricultural soils

ABSTRACT Assessment of phosphorus (P)-infiltrating croplands is essential for the preservation of the water environment. It has been pointed out that a huge discrepancy lies in the different evaluation methods of P adsorption, such as batch experiments and column experiments, which makes it difficult to demonstrate P mobility under flow conditions. The objective of this study was to evaluate the applicability of the convective-dispersion equation using the parameters of the Langmuir-type isotherm obtained from batch experiments with different reaction times: the adsorption capacity of soil (q max) = 0.112 (g kg−1) for a Gray lowland soil with 24 h reaction time, q max = 0.484 (g kg−1) for an Andosol (volcanic ash soil) with 24 h reaction time, and q max = 1.17 (g kg−1) for an Andosol with 32 d reaction time, for describing P mobility in typical Japanese agricultural soils under fast flow conditions. The breakthrough curves of P infiltrating the soil columns demonstrate nonequilibrium P adsorption by the soil. The chemical nonequilibrium model, with a kinetic adsorption rate of α = 0.40 (Gray lowland soil) and 0.098 (Andosol), succeeded in describing the observations in the column experiments. Compared with Gray lowland soil, which is relatively rich in iron oxide, P mobility was largely affected by kinetic sorption in Andosol, which is relatively rich in allophane. It is suggested that the P adsorption capacity of soils should be evaluated reflecting the soil composition in order to simulate the P mobility under flow conditions. In particular, the slow adsorption (long-lasting adsorption) of P by the soil should be considered in the estimation of the P transport.

Bacterial Community Composition Under Paddy Conditions Is More Strongly Affected by the Difference in Soil Type than by Field Management.

In this study, we aimed to investigate the effects of soil type and field management on bacterial communities in paddy soils, taking into account the differences in soil physicochemical properties. We collected soil samples from 51 paddy fields in six prefectures in Japan. The paddy fields were managed under organic regimes (26 fields), natural-farming regimes (12 fields), or conventional regimes (13 fields). The paddy fields were classified into four soil types: andosol, gray lowland soil, gley soil, and gray upland soil. Soil DNA was extracted from the soil samples collected 2 to 10 weeks after the flooding, and the 16S rRNA gene amplicon sequencing analysis was performed. The bacterial community compositions were dominated by the phylum Proteobacteria, Chloroflexi, Actinobacteria, Acidobacteria, and Firmicutes in all fields. The difference in soil type had significant effects on α-diversities of the bacterial communities, although the field management had no effect. The soil bacterial communities in the gley soils and gray upland soils individually formed different groups from those in the other soils, while the andosol and gray lowland soils tended to form relatively similar bacterial communities. On the other hand, the effects of the field management were estimated to be smaller than those of soil type. The β-diversity of the bacterial community compositions were significantly correlated with soil pH, total nitrogen content, total carbon content, and divalent iron content. Our results suggest that the soil microbial community in paddy fields may be strongly influenced by soil physiochemical properties derived from differences in soil type.

Factors causing the increase in arsenic concentration in brown rice due to high temperatures during the ripening period and its reduction by applying converted furnace slag

It has been pointed out that the concentration of arsenic (As) in brown rice increases due to high temperatures during the ripening period, and fertilization that can reduce As in brown rice even under high-temperature is required. The effectiveness of using converted furnace slag (CFS) to reduce the As concentration in brown rice was investigated. Rice plants were cultivated in Wagner pots (1/5000a) filled with gray lowland soil added CFS under ambient conditions up to 1 week after heading. Those pots were moved to a temperature gradient chamber set at four temperature levels (ambient, mildly-high, moderate-high, and super-high) and kept until harvest. An analysis of covariance using the mean daytime temperature as a covariate showed significant linearity of regression for As concentrations, indicating that high temperature increased the concentration of As in brown rice. The application of 30 g of CFS significantly reduced 20% of the As concentration in the rice, suggesting that CFS can be an effective countermeasure to reduce the As concentration in brown rice under high-temperature conditions. Since inorganic As flows into brown rice through sieve tubes, the cause of the increase in As concentration in brown rice due to high temperature was investigated by comparing the concentrations with carbon dynamics. The significant positive correlation between the As/carbon ratio and the As concentration in brown rice was observed, suggesting that high temperature reduces the rate of carbon translocation which is one of the essential factors in the increase in As concentration in brown rice due to high temperature.

Monitoring of Peronospora destructor oospores from field samples using real‐time PCR

AbstractOnion downy mildew caused by Peronospora destructor has been widespread in Japan since 2016. Soil disinfection and use of fungicides have been implemented as control measures against oospores in the soil, which are the primary source of infection. Measurements of oospore density are needed to clarify the risk of disease development and inform disease management. In this study, an experimental system capable of detecting P. destructor DNA from field samples was developed. A TaqMan probe‐type primer was used to target the coxII (cytochrome c oxidase subunit II) region of the mitochondrial genome of P. destructor and no false positives were observed. Using this method, the detection limit was equivalent to 5 oospores of P. destructor/g soil in grey lowland soil and andosol. The correlation coefficient between oospore density and the primary infection rate was investigated by testing soil samples from 115 fields. Although no correlations between oospore density and the primary infection were observed in pesticide‐treated fields, significant correlations were observed in untreated fields. Continuous cropping of onions increased the oospore density. The correlation between primary and secondary infection was relatively weak, and the negative predictive value of primary infection was relatively high (89.0). These results suggest that the disease‐risk potential of onion downy mildew is very high, and thus it is necessary to set a low pathogen detection threshold. The system presented here provides a highly sensitive method for supporting decision‐making aimed at disease control.

Potential of Nitrification Inhibition and Change of Soil Bacterial Community Structure by Biofumigation of <i>Brassica juncea</i> Green Manure in Succeeding Sweet Corn Cultivation under Gray Lowland Soil Conditions

Potential of Nitrification Inhibition and Change of Soil Bacterial Community Structure by Biofumigation of <i>Brassica juncea</i> Green Manure in Succeeding Sweet Corn Cultivation under Gray Lowland Soil Conditions

Factors destabilizing the control of Monochoria vaginalis by rice bran: its conflicting powers influence both suppression and promotion of germination in paddy soil

ABSTRACT Organic paddy rice (Oryza sativa L.) cultivation can be negatively impacted because of the weeds growth like Monochoria vaginalis. Although the rice bran application is useful in combating weed, its performance is not consistent. In this study, laboratory experiments were conducted to elucidate the effects of rice bran on the suppression and promotion of germination of M. vaginalis. Suppression experiments involved incubating mixtures of flooded soil and rice bran. This was followed by a germination experiment in the collected soil solutions. A negative and significant correlation was observed between germination and the electric conductivity (EC) of the solution. None of the seeds germinated when the EC of the Gray Lowland soil was over 130 mS m−1. Conversely, the seeds in the Andosols’ solution germinated even when EC was over 130 mS m−1. Thus, the solutions of the Andosols had different mechanisms of suppression than the Gray Lowland soils. To understand the promotion of germination, air-dried soil was prepared after the flooded incubation of rice bran and soil mixture, simulating a long-term application of rice bran. Germination was analyzed in a filtrate of the mixture of air-dried soil and distilled water. The addition of rice bran significantly promoted germination. There was a negative and significant correlation between germination and dissolved oxygen (DO) suggesting that hardly decomposable components like antioxidants in rice bran decreased O2 and stimulated germination because the seeds of M. vaginalis require very little O2 for germination.

Radiocesium transfer from Andosols to brown rice in the northern and northwest areas of Tochigi Prefecture, in the first 3 years following the 2011 Fukushima Daiichi nuclear power plant accident

ABSTRACT Following the Fukushima Daiichi Nuclear Power Plant accident of 2011, the potential for radiocesium transfer from contaminated soils, such as Andosols, to agricultural crops became a significant concern. Andosols account for up to 70％ of paddy soils in the northern and northwest areas of Tochigi Prefecture, where the radiocesium concentration is 1000 Bq kg−1 or greater in the soil of some fields. The present study was carried out in order to determine the phytoavailability of radiocesium in Andosols by comparing it with that of gray lowland soils in the first 3 years following the accident. The transfer factor (TF) tended to be higher in Andosols than in gray lowland soils, leading to higher radiocesium concentrations in brown rice grown in Andosols. The exchangeable potassium (Ex-K2O) in Andosols was highly and negatively correlated with TF, followed by clay. The Ex-K2O value was positively correlated with the clay/total carbon (T-C) value, suggesting that a high T–C ratio could weaken K2O adsorption on clay mineral sites; hence, the low clay/T-C values can partially explain the relatively large TF values of Andosols. Samples with Ex-K2O contents less than 200 mg kg−1 and with low clay/T-C values showed striking decreases in TF values from 2011 to 2012. However, the decrease from 2012 to 2013 was quite small; radiocesium in these samples was potentially available for rice uptake for a long time, likely due to the reversible adsorption and fixation characteristics of allophane. Most gray lowland soil samples showed very low TF values over the 3 years of the study, except for those with TF values greater than 0.1 due to low Ex-K2O and clay contents; the geometric mean (GM) value of TF was below 0.01 in 2012. The extraction of exchangeable radiocesium (Ex-Cs) with a 1 mol L−1 ammonium acetate solution may not be an appropriate method for explaining the variability in radiocesium TF in Andosols. This is because the Ex-Cs value was significantly correlated with Ex-K2O in Andosols, but not in gray lowland soils, indicating that Ex-K2O explained this variability in relation to Ex-Cs.

Effects of mitigation strategies on greenhouse gas emissions from a paddy field on gray lowland soil under a paddy-upland rotation system with four-crops over three-years

Effects of mitigation strategies on greenhouse gas emissions from a paddy field on gray lowland soil under a paddy-upland rotation system with four-crops over three-years

Fate of Fertilizer-Derived N Applied to Enhance Rice Straw Decomposition in a Paddy Field during the Fallow Season under Cool Temperature Conditions

A field experiment was conducted to evaluate the fate of nitrogen (N) derived from fertilizer (fertilizer-derived N) applied to a paddy field after rice harvesting to promote rice straw decomposition during the fallow season, and to determine its effect on soil N fertility in northern Japan. A frame containing soil mixed with rice straw and 15N-labeled fertilizer (4.3 g N m−2 ammonium sulfate [AS] or lime-nitrogen [LN]) was placed into a paddy field on a gray lowland soil during the fallow season (October–April), and the following rice-growing season (May–September). Before cultivation (April), the percentages of fertilizer-derived N in soil + straw were higher for LN (55–72%) than for AS (41–63%). At the harvesting stage (September), the percentages of fertilizer-derived N in plants were significantly higher for LN (4.9–6.2%) than for AS (3.4–5.3%), and the percentages in soil were also significantly higher for LN (42–61%) than for AS (31–38%). This could be attributed to the nitrification inhibitory effect of LN and result in the suppression of N losses via leaching. Consequently, fertilizer-derived N could contribute to the maintenance of soil N fertility, and this effect could be higher for LN than AS.

灰色低地土の水田転換畑におけるラッカセイ大粒品種'おおまさり’導入の可能性

灰色低地土の水田転換畑におけるラッカセイ大粒品種'おおまさり’導入の可能性

Effect of phenolic acids on the formation and stabilization of soil aggregates

ABSTRACTTo examine the effects of phenolic acids, which are generated by the decomposition of cell walls in plant residues, and other constituents on the stability of soil aggregates, phenolic acids and carbohydrates were mixed into three different types of soil. After a 1-month incubation, the plot containing soil mixed with phenolic acids showed the greatest mean weight diameter of all the soils. In the treated soils, before incubation, the decline of saturated water permeability during continuous water percolation was mitigated in the plot containing soil mixed with phenolic acids compared with that in the other plots. Soil aggregates were synthesized with the addition of phenolic acids and carbohydrates using two methods (mixing and surface brushing) and were incubated for 153 days. The aggregate stability was greatest in the plots surface-brushed with phenolic acids for Andosol and gray lowland soil, whereas the aggregate stability was most stable in the plots mixed with phenolic acids for yellow soil. This difference in the effectiveness of application methods is rationalized by the densities of the active Al and Fe contents, the carbon content, and the specific surface area of the soils. The phenolic acids also affected sandy soil. In a similar experiment using a gray lowland soil, mixing a portion of p-coumaric acid into synthetic aggregates was found to shift the molecular weight distribution of substances to larger molecular weights, as determined by size exclusion chromatography of the liquid extracted from the aggregates, which was likely accompanied by an increase in aggregate stability. The effects of fungi and bacteria on soil long-term stability were not greater than those of phenolic acids. Our findings and previous results show that microorganisms aid in soil-aggregate formation during the early stages, and phenolic acids not only aid in the formation of aggregates but also strongly stabilize them.

Effect of Flooding and the nosZ Gene in Bradyrhizobia on Bradyrhizobial Community Structure in the Soil.

We investigated the effects of the water status (flooded or non-flooded) and presence of the nosZ gene in bradyrhizobia on the bradyrhizobial community structure in a factorial experiment that examined three temperature levels (20°C, 25°C, and 30°C) and two soil types (andosol and gray lowland soil) using microcosm incubations. All microcosms were inoculated with Bradyrhizobium japonicum USDA6T, B. japonicum USDA123, and B. elkanii USDA76T, which do not possess the nosZ gene, and then half received B. diazoefficiens USDA110Twt (wt for the wild-type) and the other half received B. diazoefficiens USDA110ΔnosZ. USDA110Twt possesses the nosZ gene, which encodes N2O reductase; 110ΔnosZ, a mutant variant, does not. Changes in the community structure after 30- and 60-d incubations were investigated by denaturing-gradient gel electrophoresis and an image analysis. USDA6T and 76T strains slightly increased in non-flooded soil regardless of which USDA110T strain was present. In flooded microcosms with the USDA110Twt strain, USDA110Twt became dominant, whereas in microcosms with the USDA110ΔnosZ, a similar change in the community structure occurred to that in non-flooded microcosms. These results suggest that possession of the nosZ gene confers a competitive advantage to B. diazoefficiens USDA110T in flooded soil. We herein demonstrated that the dominance of B. diazoefficiens USDA110Twt within the soil bradyrhizobial population may be enhanced by periods of flooding or waterlogging systems such as paddy–soybean rotations because it appears to have the ability to thrive in moderately anaerobic soil.

Consideration of Snow Cover and Snowmelt upon the Inorganic Nitrogen Leaching Characteristics of an Apple Orchard in a Gray Lowland Soil

Consideration of Snow Cover and Snowmelt upon the Inorganic Nitrogen Leaching Characteristics of an Apple Orchard in a Gray Lowland Soil

Effect of controlled release fertilizer on nitrous oxide emission from gray lowland soil of a wheat–soybean cropping system

Effect of controlled release fertilizer on nitrous oxide emission from gray lowland soil of a wheat–soybean cropping system

大区画圃場における水稲の表面散播栽培に関する研究 : 第 1 報沖積砂壌土において数種類の除草剤が水稲の初期生育に及ぼす影響

大区画圃場における水稲の表面散播栽培に関する研究 : 第 1 報沖積砂壌土において数種類の除草剤が水稲の初期生育に及ぼす影響

Evaluation of available silicon content and its determining factors of agricultural soils in Japan

ABSTRACTTo evaluate the available silicon (Si) content in agricultural soils in Japan and to investigate the determining factors of this content, we collected 180 soil samples from the surface layer of paddies and upland fields in Japan and determined their available Si contents. A phosphate buffer (PB; 0.02 M, pH 6.9) or an acetate buffer (AB; 0.1 M, pH 4.0) was used to extract available Si from the soil samples, and the Si concentrations in the extracts were determined by inductively coupled plasma-atomic emissions spectroscopy (ICP-AES). The total Si content and selected physicochemical properties were also determined for the soil samples. The median values of the available Si contents by the PB and AB methods were 48.8 and 79.7 mg kg−1 and corresponded to 0.017% and 0.027% of the total Si content, respectively. The overall data showed log-normal distributions. The available Si content of the upland soils was significantly higher than that of the paddy soils by both the PB (p < 0.01) and AB methods (p < 0.05). The available Si contents by the PB and AB methods had a significant positive correlation (p < 0.01) and they had significant negative correlation with the total Si content (p < 0.01). The values of the available Si contents by the PB and AB methods correlated positively with the pH, total carbon (C) content, and dithionite-citrate bicarbonate extractable iron (Fed) and aluminum (Ald), acid oxalate extractable iron (Feo) and aluminum (Alo), Fed-Feo and Alo+1/2Feo values (p < 0.01). A multi-regression analysis indicated that pH, amorphous minerals and crystalline iron (Fe) oxides were the dominant determining factors of available Si in the soils, and these three variables explained approximately two thirds of the variation of available Si content in agricultural soils in Japan. In terms of soil type, Terrestrial Regosols, Dark Red soils and Andosols had relatively high available Si contents, whereas Sand-dune Regosols, Red soils and Gray Lowland soils had relatively low contents. In terms of region, the soils in the Kanto and Okinawa regions had relatively high available Si contents and those in the Kinki, Shikoku and Chugoku regions had relatively low contents. In conclusion, the available Si content and its determining factors for agricultural soils in Japan were quantitatively elucidated, and this will contribute to the establishment of rational soil management —including the application of silicate materials, taking into account the Si-supplying power of the relevant soils—for sustainable and productive agriculture in Japan.

Effect of the application of polluted wheat (Triticum aestivum L. Thell.) straw during plowing on the transfer of radiocesium from the soil to komatsuna (Brassica rapa L. var. perviridis)

ABSTRACTRadioactive substances were released into the environment after the nuclear accident at the Fukushima Daiichi Nuclear Power Station; this led to the contamination of the soil at Fukushima Prefecture. Mixing of organic matter with soil during plowing is known to influence radiocesium (134Cs and 137Cs) absorption by crops. However, the effect of mixing organic matter polluted by radioactive substances during plowing on radiocesium absorption by plants is not yet known. The aim of this study was to investigate the effect on the radiocesium absorption by komatsuna (Brassica rapa L. var. perviridis) cultivated in a 45-L container containing Andosol (14,300 Bq kg−1) or Gray Lowland soil (33,500 Bq kg−1) mixed with polluted wheat (Triticum aestivum L. Thell.) straw (2080 Bq kg−1). The radiocesium concentration of the plants and the soil and the amount of exchangeable radiocesium in the soil were determined using a germanium semiconductor. The transfer of radiocesium from the soil to plants decreased by 53 and 27% in Andosol and Gray Lowland soil, respectively, after the application of 10 t ha−1 polluted wheat straw. This reduction in the level of radiocesium transfer might be attributed to potassium contained in the wheat straw, which might compete with cesium during membrane transport and thereby block the transport of cesium from the soil solution to the roots and from the roots to the shoots. Alternatively, the applied wheat straw probably absorbed radiocesium and decreased the amount of exchangeable radiocesium in the soil. Our findings suggest that the mixing of polluted wheat straw with contaminated soil might influence the absorption of radiocesium content by agricultural products. Further studies are warranted to determine the long-term effects of the application of polluted wheat straw on the rate of radiocesium transfer to crops.

Effect of liming using a partial mixing technique on reductions in the seed cadmium levels for soybeans (Glycine max (L.) Merr.) under field conditions

ABSTRACTTo reduce the availability of soil cadmium (Cd) to soybeans (Glycine max (L.) Merr.), we employed a liming by partial mixing (PM) technique in two drained paddy fields on Gray Lowland soils, which had 0.1 mol L–1 hydrochloric acid-extractable Cd concentrations as high as 1.08 and 1.40 mg kg–1. Among the different application methods tested, PM application (PM2) using a width of 20 cm and a depth of 20 cm was found to be most appropriate for reducing the seed Cd concentration and to obtain the optimum yield at Site A. Under PM2, a liming rate of 38% of that for broadcast incorporated into the surface 15 cm layer (Bc) was suitable to reduce the seed Cd concentration at Site A, whereas the lime rate with PM2 was set at 50% of that for Bc (PM2-50) at Site B due to the higher availability of soil Cd. The root system was limited within the range of lime and fertilizer application for PM2 as well as PM2-50; thus, the lime and fertilizer were supplied successfully to the rooting zone. The soil pH value was lower under PM2 at Site A and PM2-50 at Site B compared with Bc, whereas the seed Cd concentration was lower for PM2 and PM2-50. This may be explained by the intensive uptake of calcium and magnesium with PM2 as well as PM2-50. The seed Cd concentration in the cultivar “Ryuhou” at the target pH of 6.5 was approximately 30% lower with PM2-50 than Bc at Site B. In addition, the average seed Cd concentrations in one cultivar and two lines, characterized by the lower Cd uptake with higher retention in roots and higher accumulation in leaves, were approximately 40% lower compared with “Ryuhou.” Thus, the combination of liming with PM2-50 at the target pH of 6.5 and a low-Cd cultivar (or lines) minimized the seed Cd concentration. The highest seed Cd concentration was found in the first year of soybean cultivation, which was considered to be caused by the release of Cd from organic nitrogen compounds during the nitrogen mineralization process.

Nitrous oxide emissions during biological soil disinfestation with different organic matter and plastic mulch films in laboratory-scale tests

Nitrous oxide (N2O), which is a greenhouse gas, may be more emitted as an intermediate product of denitrification during biological soil disinfestation. The biological soil disinfestation is a method to suppress soil-borne pathogens under reductive soil conditions produced by the application of organic matter and water irrigation with plastic film. The objective of the study was to determine the effects of different organic matter and mulch films on N2O emissions during biological soil disinfestation. Grey lowland soil amended with cattle compost plus rice bran (0.2%), rice husk (0.2%) or dent corn (0.1%, 0.2% and 0.4%) was incubated at 100% water-holding capacity with or without plastic films made of polyvinyl chloride (PVC) and triple-layer polyolefin (3PO) for 72 h at 50°C. Permeation of the two films was also measured at 25°C and 50°C. Results showed that incorporation of organic matter increased N2O emissions compared with no organic matter addition at 50°C. Incorporation of rice bran and dent corn with easily decomposable C and low C:N ratios increased N2O emissions for the first 12 h, but thereafter, available C supply from these amendments suppressed N2O emissions. Permeability of mulch films increased at a higher temperature and was larger for PVC than for 3PO. Our study indicated that rice husk should not be used for soil disinfestation and that application rates of organic matter must be determined based on their decomposability. Moreover, mulch film covering would not suppress N2O emission in biological soil disinfestation because of high temperature.

Depth profile and mobility of 129I and 137Cs in soil originating from the Fukushima Dai-ichi Nuclear Power Plant accident

The 129I derived from the FDNPP accident were clearly identified near the surface and showed a trend of rapid decrease with depth. The FDNPP 129I and 137Cs was 51.6 ± 1.7 mBq cm−2 and 88.2 ± 27.1 kBq cm−2 (average of four cores inventory) respectively. On average, 91% of the FDNPP 129I existed within the top 5 g cm−2 and 98% within the top 10 g cm−2 and average of 100% of the FDNPP 137Cs existed within the top 5 g cm−2. From the observation of the temporal variation of depth profiles from the same upland field (Kawauchi village, 20 km away from the FDNPP to the southwest direction), downward migration rates of 0.81 ± 0.32 g cm−2 yr−1 for the FDNPP 129I and 0.19 ± 0.17 g cm−2 yr−1 for the FDNPP 137Cs were estimated. A simple diffusion model was introduced to evaluate the downward mobility of the FDNPP-derived 129I and 137Cs. The apparent diffusion coefficients D of 0.0086 ± 0.0034 and 0.0011 ± 0.0010 g2 cm− 4 d− 1 were obtained for 129I and 137Cs, respectively. These values might be representative for Haplic Gray lowland soils in near the steady state under humid temperate climate.