Influence of 2-chloro-6 (trichloromethyl) pyridine and dicyandiamide on nitrous oxide emission under different soil conditions

Abstract

Two experiments were conducted to evaluate the inhibitory effects of 2-chloro-6 (trichloromethyl) pyridine (nitrapyrin) and dicyandiamide on nitrous oxide (N₂O), a greenhouse gas, emission from soils amended with ammonium sulfate. In the two experiments, samples of an Andosol and a Gray Lowland soil were kept in glass vessels sealed with a butyl rubber cap and incubated at 25°C. In the first experiment, nitrapyrin (1 µg g^?1 dry soil) and dicyandiamide (10 µg g^?1 dry soil) were applied to samples of a water-saturated Andosol and a Gray Lowland soil to which ammonium sulfate had been applied at a rate of 0.1 mg N g^?1 dry soil. Nitrapyrin decreased N₂O emissions from the Andosol and the Gray Lowland soil by 71% and 24%, respectively. Dicyandiamide decreased N₂O emissions from the Andosol and Gray Lowland soil by 31% and 18%, respectively. In the second experiment, nitrapyrin (1 µg g^?1 dry soil) was applied to samples of an Andosol at 51% water-filled pore space to which ammonium sulfate had been applied at rates of 0.01, 0.1 and 0.5 mg N g^?1 dry soil. Nitrapyrin decreased N₂O emissions by 62%, 83% and 74%, respectively. Changes in the NH⁺ ₄ and NO^? ₂ + NO^? ₃ concentrations in soil showed that nitrapyrin and dicyandiamide slowed down the nitrification process, but did not completely stop the process at any time. The results reveal the potential of nitrification inhibitors to decrease N₂O emission from fertilized soil in a wide range of moisture conditions and nitrogen levels.     

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.     

Comparison of N2O and CO2 concentrations and fluxes in the soil profile between a Gray Lowland soil and an Andosol

Abstract

We measured nitrous oxide (N₂O) and carbon dioxide (CO₂) fluxes from the soil surface and in the soil through to a depth of 0.3?m, and their concentration profiles through to a depth of 0.6?m in both a Gray Lowland soil with macropores and cracks and an Andosol with undeveloped soil structure in central Hokkaido, Japan. The objective of the present study was to elucidate any differences in N₂O production and flux in the soil profile between these two soil types. In the Gray Lowland soil, the N₂O concentration above 0.4?m increased with an increase in soil depth. In the Andosol, there were no distinctive N₂O concentration gradients in the topsoil when the N₂O flux did not increase. However, the N₂O concentration at a depth of 0.1?m significantly increased and this concentration was higher than the concentration below 0.2?m when the N₂O flux greatly increased. Thus, the N₂O concentration profiles were different between these two soils. The contribution ratios of the N₂O produced in the top soil (0–0.3?m depth) to the total N₂O emitted from the soil to the atmosphere in the Gray Lowland soil and the Andosol were 0.86 and 1.00, respectively, indicating that the N₂O emitted from the soil to the atmosphere was mainly produced in the top soil. However, the contribution ratio of the subsoil to the N₂O emitted from the Gray Lowland soil was higher than that of the Andosol. There was a significant positive correlation between the N₂O flux through to a 0.3?m depth and the flux from the soil to the atmosphere in the Gray Lowland soil only. These results suggest that N₂O production in the subsoil of the Gray Lowland soil could have been activated by NO₃ ^? leaching through macropores and cracks, and subsequently the N₂O produced in the subsoil could have been rapidly emitted to the atmosphere through the macropores and cracks.     

Varietal difference in radiocesium uptake and transfer from radiocesium deposited soils in the genus Amaranthus

Abstract

Within Amaranthaceae, 33 different varieties, including local varieties from Japan, were grown in 2012 in a field in the town of Iino in the Fukushima prefecture, which is located approximately 51 km north of Tokyo Electric Power Company, Fukushima Daiichi Nuclear Power Plant (FDNPP). The contamination level of the soil was 2770 ± 140 Bq kg^?1 dry weight (¹³⁴Cesium (Cs) + ¹³⁷Cs, average ± SE), and the field was also cultivated in 2011. There was a significant varietal difference in the dry weight production, radiocesium accumulation and transfer factor (TF) of radiocesium from the soil to the plant. The ratio of the lowest TF to the highest TF was approximately 3. Because the ratio of ¹³⁷Cs to ¹³³Cs was significantly positive, radiocesium seems to be absorbed in a manner similar to that of ¹³³Cs. It is suggested that the varietal difference in the behavior of radiocesium uptake mainly depends on its genetic background rather than on environmental factors.     

Cesium uptake of field-grown Amaranthus species in Fukushima focusing on Cs concentration in xylem exudate and root distribution

ABSTRACT

Radiocesium (RCs) discharged by the Fukushima Daiichi Nuclear Power Plant (Tokyo Electric Power Co., Inc.) accident has extensively contaminated agricultural land in Fukushima Prefecture and its neighboring areas. Many studies have demonstrated that Cs (RCs and ¹³³Cs) uptake of plants is affected by the exchangeable K (Ex-K) concentration in soil. However, the precise plant–soil interaction in relation to Cs uptake is still unclear. The aim of this study was to investigate Cs uptake of plant in field by focusing on xylem exudate and roots because nutrients in xylem exudate reflect medium (soil) conditions and affect nutrient accumulation in shoots. Two varieties of amaranth, K4 (Amaranthus caudatus L.) and Mexico type (A. hypochondriacus L.), which have different Cs uptake abilities, were grown in four fields and in pots (750 to 3440 Bq kg^?1 of RCs) in Fukushima Prefecture. Cs concentrations in xylem exudate, shoot, and soil; Ex-K concentration in soil; and root distribution in soil were determined. RCs concentration in xylem exudate varied from 0.04 to 164 Bq kg^?1 and ¹³³Cs concentration in xylem exudate ranged from 0.01 to 33.7 μg kg^?1. The Cs concentrations were decreased by the high Ex-K concentration and the large amount of 2:1 type clay minerals in soil. The average of the ratios of Cs concentration in shoot to Cs concentration in xylem exudate for all samples was 127 ± 112 (mean ± standard deviation), although no clear correlation was found between them. The correlations betwee\n RCs and ¹³³Cs concentrations in xylem exudate and shoot were strong in pot and in the field with low Ex-K concentration. Eighty-five percent of the total root length was distributed in the topsoil (0–20 cm soil layer). The positions where roots take up Cs were estimated from the differences in the vertical distribution of RCs and ¹³³Cs concentrations in soil. The estimated Cs uptake ratios of topsoil to total soil layer ranged from 7% to 91% and varied with the concentration and the vertical distribution of Ex-K in soil.     

Copper induced iron deficiency in wheat (Triticum aestivum L)

Abstract

A pot experiment was conducted to study the interaction effects of phosphorus and copper on wheat. The soils used were calcareous loamy sand (ls) and non calcareous sandy loam (sl). Four levels of Cu (0, 5, 10 and 20?mg Cu kg^?1 soil) and six levels of P (0, 25, 50, 100, 200 and 400?mg P kg^?1 soil) were applied in all possible combinations with three replications. Soil pH decreased with Cu application while Olsen P increased with P application in both soils. Growth and yield of wheat improved significantly with graded levels of applied P. However, when any level of P was combined with 20?mg Cu kg^?1 soil, severe iron chlorosis of leaves, a drastic reduction in growth and chlorophyll content was observed in calcareous ls only. The results indicated that it was Cu and not P that induced Fe deficiency in wheat grown in alkaline calcareous soil and the Cu requirement of the crop seemed to be much lower in the calcareous ls. Root dry matter, grain and straw yield decreased with increasing levels of applied Cu in ls but in sl maximum increase of 62.5, 74.3 and 63.7 per cent in root, grain and straw yield was observed with a combined application of 400?mg P and 5?mg Cu kg^?1 soil over control. Accumulation of Cu in roots decreased the Fe absorption by roots which indicated that Fe chlorosis of wheat leaves is expected when Cu: Fe concentration ratio in root is > 0.30.     

Cesium-137 concentration of forage corn and Italian ryegrass in a double cropping system under different rates of cattle farmyard manure application after the Fukushima Daiichi Nuclear Power Station accident in 2011

Abstract

Radioactive ¹³⁷Cs concentrations of forage corn (Zea mays L.) and Italian ryegrass (Lolium multiflorum Lam.) in a double cropping system under continuous cattle farmyard manure (FYM) application were observed for more than 2 years after the Fukushima Daiichi Nuclear Power Station accident in 2011. The experiment field is located 110 km southwest of the Fukushima Daiichi Nuclear Power Station, and the soil contains ¹³⁷Cs of 920 Bq kg^?1 on average. For crop cultivation, nitrogen fertilizer was applied in addition to FYM. The ¹³⁷Cs concentrations in corn decreased significantly between 2011 and 2012, but only differed significantly between 2012 and 2013 for the plot with no FYM application. For Italian ryegrass, no significant differences were observed between the harvest in 2012 and 2013 despite the FYM application rate. To minimize corn ¹³⁷Cs concentrations, the FYM application rate should be more than and equal to 30 Mg ha^?1 when FYM is used as the major nutrient source. Exchangeable potassium oxide (K₂O) greater than around 0.3 g kg^?1 was mostly maintained with the FYM application rates. Corn ¹³⁷Cs concentration appeared to increase at exchangeable K₂O levels below 0.15 g kg^?1. These results suggest that continuous FYM application can maintain soil nutrients including K₂O and thereby control radioactive Cs transfer from the soil. FYM application rate of 30 Mg ha^?1 is within the levels recommended by the prefectural governments around Fukushima Prefecture for crop production before the accident. These levels are sufficient to decrease the radioactive Cs concentrations for corn. However, unlike corn, differences in soil chemical properties by FYM application did not affect ¹³⁷Cs concentrations in Italian ryegrass in this study, although low exchangeable K₂O seemed to increase concentrations of stable ¹³³Cs. Further experiments should be conducted to understand the observed differences between corn and Italian ryegrass.     

Accumulation of radioactive cesium in sorghum (Sorghum bicolor (L.) Moench) accessions cultivated in Fukushima in 2011 and 2012

ABSTRACT

The accident at Fukushima 1 Nuclear Power Plant in 2011 caused contamination by radioactive cesium (¹³⁴Cs and ¹³⁷Cs) in surrounding areas. After this accident, concerns about Cs contamination, including food safety, have limited industrial activities and reconstruction in Fukushima. Sorghum (Sorghum bicolor (L.) Moench) is an annual C₄ crop that can be used as biofuel feedstock due to its high biomass. Use of Cs-contaminated fields to produce biofuel feedstock would be more acceptable than use for food or feed crops due to the lower risk of human internal exposure to radioactive Cs. In addition, high-biomass sorghum might be suitable for removal of Cs from fields (phytoremediation). For both applications, it is important to use accessions showing the appropriate level of accumulation of radioactive Cs (low for biofuel feedstock, high for phytoremediation). Here, we examined the accumulation of radioactive Cs in the aerial parts of 56 sorghum accessions grown in Fukushima. Accessions were cultivated in a low-level-contaminated field in 2011 and in a highly contaminated field in a planned evacuation zone in 2012. After cultivation, activity concentrations from ¹³⁴Cs and ¹³⁷Cs were measured in the aerial plant parts. In 2011, the activity concentrations of ¹³⁴Cs and ¹³⁷Cs were 58.2–350 and 58.6–450 Bq kg^?1 dry weight, respectively. In 2012, the concentrations of ¹³⁴Cs and ¹³⁷Cs were 54.2–1320 and 57.1–1960 Bq kg^?1 dry weight, respectively. Relative to the median values of the accessions grown each year, 3 showed lower activity concentrations and 2 showed higher activity concentrations of radioactive Cs under both cultivation conditions. In contrast to a previous report, there was no significant correlation between biomass and Cs activity concentration. Because both biomass and Cs concentration are important in classifying accessions for use in phytoremediation, we also calculated the Cs accumulation index (single-plant biomass × Cs activity concentration) for each accession. The accession AKLMOI WHITE showed the highest values in both years, suggesting that this accession has the high per-plant accumulation capacity for radioactive Cs. Our data collected from actual contaminated fields is irreplaceable for choosing sorghum accessions for cultivation in Cs-polluted sites such as Fukushima.     

Estimate of the source of soil protease in upland fields

Selective inhibition of bacterial or fungal growth in remoistened, oven-dried, inoculated Andosols indicated that bacteria were a more important source of benzyloxycarbonyl-l-phenylalanyl-l-leucine hydrolyzing activity (z-FLase) and casein-hydrolyzing activity (caseinase) than fungi. The same test indicated that bacteria were also a more important source of soil caseinase under upland conditions in a Gray Lowland soil. Most of the proteolytic bacteria isolated from the three upland fields by azocoll agar plates (Andosol upland field, 100%; Andosol uncultivated field, 96.4%; Gray Lowland upland field, 70.0%) wereBacillus spp. Most (100%, 97.1%, and 84.0%, respectively) of the gelatin liquefiers selected from the azocoll degraders, as those with high extracellular z-FLase and caseinase, were alsoBacillus spp. We conclude thatBacillus spp. are the major source of soil protease in the three upland fields studied.     

Effect of Salinity on the Transformation of Wheat Straw and Microbial Communities in a Saline Soil

Currently, straw transformation in saline soil is largely unknown. The effect of soil salinity on wheat straw transformation and the roles of nitrogen (N) and phosphorus (P) were evaluated in a greenhouse experiment. By sodium chloride (NaCl) addition, straw was applied at the rate of 30 g kg^?1 in various saline soils (2.0–4.0 g kg^?1). N or combined N and P added in straw amended saline soil (3.0 g kg^?1). Three replications of each treatment were sampled to determine straw residues at 30, 60, and 90 d. Results showed straw application significantly increased microbial biomass, especially fungal biomass. Soil salinity increased by 1.0 g kg^?1, which decreased straw decomposed rate by 6.3 ~ 11.1%. N application significantly increased straw decomposed rate (p < 0.05), and high salinity obviously inhibited the humidification process of straw. We suggested that straw carbon transformation regulation and little straw residue accumulation in saline soil should arouse more attentions in future studies.     

Influence of nitrogen fertilizer forms and crop straw biochars on soil exchange properties and maize growth on an acidic Ultisol

Effects of repeated application of urea (UN) and calcium nitrate (CN) singly and together with crop straw biochars on soil acidity and maize growth were investigated with greenhouse pot experiments for two consecutive seasons. Canola straw biochar (CB), peanut straw biochar (PB) and wheat straw biochar (WB) were applied at 1% of dried soil weight in the first season. N fertilizers were applied at 200 mg N kg^?1. In UN treatments, an initial rise in pH was subjected to proton consumption through urea hydrolysis, afterwards nitrification of NH₄⁺ caused drastic reductions in pH as single UN had soil pH of 3.70, even lower than control (4.27) after the 2nd crop season. Post-harvest soil analyses indicated that soil pH, soil exchangeable acidity, NH₄⁺, NO₃^? and total base cations showed highly significant variation under N and biochar types (P < 0.05). Articulated growth of plants under combined application with biochars was expressed by 22.7%, 22.5%, and 35.7% higher root and 25.6%, 23.8%, and 35.9% higher shoot biomass by CB, PB and WB combined with CN over UN, respectively. Therefore, CN combined with biochars is a better choice to correct soil acidity and improve maize growth than UN combined with biochars.     

Transfer factor of radioactive cesium to forage corn (Zea mays L.) from soil to which contaminated farmyard manure had been applied

Abstract

Radioactive cesium (Cs) deposited after the Fukushima Daiichi Nuclear Power Station accident contaminated farmyard manure (FYM) in the wide area surrounding the plant. We conducted a field trial to determine the transfer factor of radioactive Cs to forage corn (Zea mays L.) from soil to which the contaminated FYM had been applied. The main purpose of this experiment was to examine the behavior of the radioactive Cs from contaminated FYM that was incorporated in agricultural fields. Application of FYM containing 3900 Bq kg^?1 dry matter (DM) of cesium-137 (¹³⁷Cs) at a rate of 4.3 kg m^?2 increased the ¹³⁷Cs concentration in the soil by 64 Bq kg^?1 dry soil, and in the forage corn by 9.2 Bq kg^?1 DM. Therefore, we calculated the transfer factor to corn plants from the soil after application of contaminated FYM to be 0.14. This value is lower than that observed for soil to which uncontaminated FYM had been applied as a control, and it is within the range of reported soil-to-plant transfer factors of 0.003–0.49 listed in the recent parameter handbook by International Atomic Energy Agency. The increase in the radioactive Cs concentration in the corn plants, expressed as the sum of ¹³⁷Cs and cesium-134 (¹³⁴Cs), was only 3% of the 2012 provisional tolerance level for cattle roughage in Japan. Even though the application of contaminated FYM did not cause a large change in the radioactive Cs concentration in the corn plants in this trial, such application should be carefully controlled because it increased radioactive Cs concentrations in both soil and forage corn.     

Effect of soil application of nickel on growth,micronutrient concentration and uptake in barley (Hordeum vulgare L.) grown in Inceptisols of Varanasi

A pot experiment was conducted in a glass house on low nickel containing alluvial soil in the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, during 2012–13 and 2013–14, to study the response of barley to soil application of nickel (Ni). There were ten treatments of Ni (0, 2.5, 5, 10, 15, 20, 30, 40, 50 and 60 mg kg^?1) studied with recommended dose of fertilizers nitrogen, phosphorus, potassium and sulfur (N:P:K:S :: 40:30:30:20 mg kg^?1).The results showed a significant increase in plant height, number of tillers, chlorophyll content, straw and grain yield, and 1,000 grains weight with application of 10 mg Ni kg^?1 soil during both years of study. The micronutrient concentration and uptake in straw and grain increased with application of <15 mg Ni kg^?1 soil and beyond that declined significantly. Diethylenetriaminepentaacetic acid-extractable micronutrient iron, manganese, copper, zinc and nickel (Fe, Mn, Cu, Zn and Ni) content in soil increased with increasing level of Ni. The maximum urease activity in post-harvest soil was noticed with application of 40 mg Ni kg^?1 soil. The microbial population viz. bacteria, fungi and actinomycetes were higher with 5, 30 and 10 mg Ni kg^?1 soil, respectively.     

Comparison of Conventional and Polymer Coated Urea as Nitrogen Sources for Lowland Rice Production

Nitrogen (N) is one of the most yield limiting nutrients in lowland rice production. Improving N use efficiency is essential to reduce cost of crop production and environmental pollution. A greenhouse experiment was conducted with the objective to compare conventional and polymer coated urea for lowland rice production. Grain yield, straw yield, panicle density, maximum root length, and root dry weight were significantly increased in a quadratic fashion with the increase of N rate from 0 to 400 mg kg^?1 soil. Nitrogen source X N rate interactions for most of these traits were not significant, indicating that lowland rice responded similarly to change in N rates of two N sources. Based on regression equations, maximum grain yield was obtained with the application of 258 mg N kg^?1 soil and maximum straw yield was obtained with the addition of 309 mg N kg^?1 soil. Nitrogen use efficiency (grain yield per unit of N applied) was maximum for polymer coated urea compared to conventional urea. Root length and root dry weight improved at an adequate N rate, indicating importance of N fertilization in the absorption of water and nutrients and consequently yield. Polymer coated urea had higher soil exchangeable calcium (Ca) and magnesium (Mg), Ca saturation, Mg saturation, base saturation, and effective cation exchange capacity compared to conventional urea. There was a highly significant decrease in soil exchangeable potassium (K) with increasing N rates at harvest of rice plants.     

The influence of phosphate fertilizer application levels and cultivars on cadmium uptake by Komatsuna (Brassica rapa L. var. perviridis)

Cadmium (Cd) is a common impurity in phosphate fertilizers and application of phosphate fertilizer may contribute to soil Cd accumulation. Changes in Cd burdens to agricultural soils and the potential for plant Cd accumulation resulting from fertilizer input were investigated in this study. A field experiment was conducted on Haplaquept to investigate the influence of calcium superphosphate on extractable and total soil Cd and on growth and Cd uptake of different Komatsuna (Brassica rapa L. var. perviridis) cultivars. Four cultivars of Komatsuna were grown on the soil and harvested after 60 days. The superphosphate application increased total soil Cd from 2.51 to 2.75?mg?kg^?1, 0.1?mol?L^?1 hydrochloric acid (HCl) extractable Cd from 1.48 to 1.55?mg?kg^?1, 0.01?mol?L^?1 HCl extractable Cd from 0.043 to 0.046?mg?kg^?1 and water extractable Cd from 0.0057 to 0.0077?mg?kg^?1. Cd input reached 5.68?g?ha^–1 at a rate of 240?kg?ha^–1 superphosphate fertilizer application. Superphosphate affected dry-matter yield of leaves to different degrees in each cultivar. ‘Nakamachi’ produced the highest yield in 2008 and ‘Hamami No. 2’ in 2009. Compared with the control (no phosphate fertilizer), application of superphosphate at a rate of 240?kg?ha^–1 increased the Cd concentration in dry leaves by 0.14?mg?kg^?1 in ‘Maruha’, 1.03?mg?kg^?1 in ‘Nakamachi’, 0.63?mg?kg^?1 in ‘SC8-007’ in 2008, and by 0.19?mg?kg^?1 in Maruha’, 0.17?mg?kg^?1 in ‘Hamami No. 2’, while it decreased by 0.27?mg?kg^?1 in ‘Nakamachi’ in 2009. Field experiments in two years demonstrated that applications of different levels of calcium superphosphate did not influence Cd concentration in soil and Komatsuna significantly. However, there was a significant difference in Cd concentration of fresh and dry Komatsuna leaves among four cultivars in 2008 and 2009. The highest Cd concentration was found in the ‘Nakamachi’ cultivar (2.14?mg?kg^?1 in 2008 and 1.91?mg?kg^?1 in 2009). The lowest Cd concentration was observed in the ‘Maruha’ cultivar (1.51?mg?kg^?1?dry weight (DW)) in 2008 and in the ‘Hamami No. 2’ cultivar (1.56?mg?kg^?1?DW) in 2009. A decreasing trend in Cd concentration was found in ‘Nakamachi’, followed by ‘SC8-007’, ‘Hamami No. 2’ and ‘Maruha’ successively. It is necessary to consider a low-uptake cultivar for growing in a Cd polluted soil. In these two years’ results, ‘Maruha’ cultivar was the lowest Cd uptake cultivar compared to the others.     

Effectiveness of crop straws,and swine manure in ameliorating acidic red soils: a laboratory study

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg^?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH₄⁺) and nitrate plus nitrite (NO₃^??+?NO₂^?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg^?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol₍₊₎ kg^?1 compared to 2.82 and 4.19 cmol₍₊₎ kg^?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol₍₊₎ kg^?1 per pH unit increase for both straws compared to 6.25 cmol₍₊₎ kg^?1 per pH unit from the manure. The NO₃^??+?NO₂^? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.

     

Nitrate Transformation and N2O Emission in a Typical Intensively Managed Calcareous Fluvaquent Soil: A 15-Nitrogen Tracer Incubation Study

A 56-day aerobic incubation experiment was performed with 15-nitrogen (N) tracer techniques after application of wheat straw to investigate nitrate-N (NO₃-N) immobilization in a typical intensively managed calcareous Fluvaquent soil. The dynamics of concentration and isotopic abundance of soil N pools and nitrous oxide (N₂O) emission were determined. As the amount of straw increased, the concentration and isotopic abundance of total soil organic N and newly formed labeled particulate organic matter (POM-N) increased while NO₃-N decreased. When ¹⁵NO₃-N was applied combined with a large amount of straw at 5000 mg carbon (C) kg^?1 only 1.1 ± 0.4 mg kg^?1 NO₃-N remained on day 56. The soil microbial biomass N (SMBN) concentration and newly formed labeled SMBN increased significantly (P < 0.05) with increasing amount of straw. Total N₂O-N emissions were at levels of only micrograms kg^?1 soil. The results indicate that application of straw can promote the immobilization of excessive nitrate with little emission of N₂O.     

Radiocesium transfer into the fruit of deciduous fruit trees contaminated during dormancy

Following the accident at the Tokyo Electric Power Company, Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium (¹³⁴Cs + ¹³⁷Cs) concentrations in deciduous mature fruits were determined in orchards in the northern area of Fukushima Prefecture. At the time of the nuclear accident, most deciduous fruit trees were in the dormant stage prior to bud burst. To evaluate the relationship between radiocesium deposition in the soil and fruit contamination, radiocesium concentrations were measured from the 5-cm topsoil and from six fruit species across 17 orchards in 2011. The vertical distribution of radiocesium in the topsoil (0–30 cm in depth) and its spatial distribution in the 5-cm topsoil underlying the tree canopy of a peach, Prunus persica (L.) Batsh, orchard (“Akatsuki” cultivar) were also investigated. Significant correlations between the radiocesium concentration in the mature fruit and that in the 5-cm topsoil layer were observed for the 17 orchards as well as for the trees of the peach orchard. However, 93% of the ¹³⁷Cs found in the 30-cm soil core was retained within the top 3 cm of the soil in the peach orchard. Considering the profile of the root of this deciduous fruit tree, we assumed a negligible level of radiocesium uptake via the roots. However, the possibility of inward migration via the bark was undeniable, because some radiocesium adhered to the tree canopy before bud burst while depositing on the soil surface. Additionally, transfer factors for peach and grape, hybrid of Vitis labrusca L. and Vitis vinifera L., from young, uncontaminated trees cultivated with contaminated soil were lower than those previously reported.     

Determining critical limit of boron in soil for wheat (Triticum aestivum L.)

Abstract

Critical values of boron (B) for wheat nutrition in soil and plant were determined through a pot experiment with twenty-one surface soils of Alluvial flood plain and Red-latertic belt comprising three major soil orders (Entisols, Alfisols, Inceptisols) with four levels of boron. Application of boron significantly increased the dry matter yield as well as uptake of B by plants. Critical concentration of hot calcium chloride (CaCl₂) extractable B in soil for wheat was found to be 0.53?mg?kg^?1. The critical plant B concentration varied with growth stages and values were 7.4?mg?kg^?1 at panicle initiation and 4.18?mg?kg^?1 at maturity, respectively. The findings of this investigation also recommend the application of 2?kg?B^?1?ha^?1 for ensuring B sufficiency to wheat in Indo-gangetic alluvial and Red-Lateritic soils.     

Determination of Natural and Artificial Radionuclide Levels in Soils of Western and Southern Coastal Area of Turkey

Soil samples were collected from western and southern region of Turkey in 1995 from 17 sampling stations of different depths. Natural and artificial radionuclide activity levels of soil samples of the western and southern sea in Turkey were previously reported about nine years after the Chernobyl accident. The aim of the study was to collect data for following up of the earlier study and to present result for distributions of radionuclides in soil samples of the western and southern regions of Turkey. ²²⁶Ra is in the range 19–276 Bq kg^?1, 7–173 Bq kg^?1 for ²³⁸U, 8–244 Bq kg^?1 for ²³²Th, 86–1162 Bq kg^?1 (dry wt.) for ⁴⁰K and ¹³⁷Cs activity result varies between 1.8–82 Bq kg^?1 (dry wt.).