Wind erosion control using crop residue I. Effects on soil flux and soil properties

Effects of millet stover residue (0, 500, and 2000 kg ha⁻¹) on wind erosion and surface soil properties were determined from 1991 to 1993 at the ICRISAT Sahelian Center in Niger, West Africa. Soil flux 0.1 m above the ground was significantly reduced with 2000 kg ha⁻¹ residue but not with 500 kg ha⁻¹. Topographic measurements indicated that soil removed from the soil surface was less with either residue level than in the control. After 2 y, the soil surface (0–0.01 m) of both residue treatments had less coarse sand than the control, but more fine sand and clay, more organic carbon and an increased cation exchange capacity. The organic-C content of blown material was greater than that of surface soil. An amount of 500 kg ha⁻¹ residue can be considered useful for soil conservation, but 2000 kg ha⁻¹ are required for a significant reduction of soil flux caused during severe wind erosion events.     

Effect of biochar on CH4 and N2O emission from soils vegetated with paddy

Biochar is believed to have positive impact on soil properties and plant yield. Due to the presence of C, it can also enhance CH₄ emission in paddy soils. On the other hand, ammonium sulphate can decrease CH₄ emission due to negative impacts on methanogenesis. Keeping these points in view, a pot experiment was conducted to determine the effect of biochar along with ammonium sulphate on CH₄ and N₂O emission from paddy soil. Analysis revealed that biochar treated soils released more CH₄ compared to untreated. Ammonium sulphate treated soil emitted the highest N₂O whereas biochar addition decreased its emission significantly. Further, total emission was found to be higher for CH₄ (16.9–34.7 g/m²) in comparison to N₂O (?0.05 to 0.02 g/m²) for all treatments. Biochar application has positive impact on plant variables such as panicle number and weight of panicles. This study suggests that biochar application significantly decrease N₂O emission and increase CH₄ emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH₄ emission by following biochar could be attributed to the increase in plant biomass.     

Convective velocity of ponded water in the vegetated paddy lysimeter

Ponded water convection kinetics should be altered by growth stages of rice plants. We investigated the convective velocity of ponded water in a vegetated paddy field. The convective velocity was measured using the equipment through use of the principle of a hot-wire anemometer, and the temperature profile of the ponded water was measured using lysimeters with and without paddy rice vegetation. The maximum convective velocity in a vegetated plot was 0.7 mm s⁻¹, slower than the maximum velocity in an unvegetated plot, which was 1.6 mm s⁻¹. The convective velocity in a vegetated plot increased slightly when the temperature of the surface water was higher than that near the soil, between 09:00 and 17:00.     

Mechanical insights into the effect of fluctuation in soil moisture on nitrous oxide emissions from paddy soil

Paddy fields are subjected to fluctuating water regimes as a result of the alternate drying and wetting water management, which often incurs a sensitive change in N₂O emissions from paddy soils. However, how the soil moisture regulates the emission of N₂O from paddy soil remains uncertain. In this study, three incubation experiments were designed to study the effects of constant and fluctuating soil moisture on N₂O emission and the sources of N₂O emission from paddy soil. Results showed that the N₂O emission from paddy soil at 100 % WHC (water-holding capacity) was higher than that at 40, 65, 80, 120, and 160 % WHC, indicating that 100 % WHC was the optimum soil moisture content for N₂O emission under the incubation experiment. Small peak of N₂O flux appeared when the soil moisture content from 250 % WHC decreased near to 100 % WHC, lower than that triggered by nitrogen (N) fertilization, which was mainly owing to the low NH₄ ⁺ concentration at this period. Nitrification dominated the emissions of N₂O from paddy soil at 250 % WHC (54.96 %), higher than that of nitrification-coupled denitrification (6.74 %) and denitrification (38.3 %). The contribution of denitrification to N₂O emissions (44.10 %) was equivalent to that of nitrification (44.45 %) in soil at 100 % WHC, which was higher than that of 250 % WHC treatment. In conclusion, the finding suggested that the peak of N₂O in paddy soils during midseason aeration could be attributed to the occurrence of optimum soil moisture under sufficient N availability, favorable for the production and accumulation of N₂O.     

Monitoring of soil radiation doses from contaminated soil buried in a paddy field in Iitate Village,Fukushima

Paddy and Water Environment - Radiocesium released from Fukushima Daiichi nuclear power plant in March 2011 was accumulated in paddy fields within 5 cm of the surface soil layer. In order...     

Impacts on soil quality from long-term irrigation with treated greywater

Drought condition in many places leads to the imperative use of greywater for irrigation. There is a serious concern on the impact of such prolonged uses on soil sustainability. The objective of this study was to evaluate the long-term impacts of greywater irrigation on soil electrical conductivity (EC) and other soil quality parameters in field conditions. Six locations were monitored in this study where home gardens have been irrigated with treated greywater for 2 years. Results showed a general reduction in EC levels of soil samples along all depth intervals at all locations. The average soil EC before greywater irrigation was 0.97 dS/m and decreased to 0.41 dS/m, which may be due to the use of greywater as well as the rainwater effect. The reduction in soil EC and irrigation water quantity shows positive correlation (correlation coefficient r = 0.64). Calcium precipitation might also have a major role in soil EC reduction. Soil calcium content was 81 mg L^?1 before using treated greywater and decreased to 43 mg L^?1 after 2 years of treated greywater usage, which might have been caused by calcium carbonates (CaCO₃) precipitation. The results of other soil chemical analyses clearly show that using treated greywater for irrigation has reduced the concentration of organic matters, K, Cd, Pb, P, Mg, Cl, Na, exchangeable sodium percentage, and sodium adsorption ratio after 2 years of application. Zn concentration increased from 11 to 15 mg L^?1, and soil pH became slightly higher from 7.6 to 7.8.     

Nitrogen transport and transformation in packed soil columns from paddy fields

Our understanding of nitrogen transformation in paddy fields or wetlands is limited due to the complex interactions between soil, water, and biomass. Therefore, we studied transformation patterns resulting from the oxic level in the soil, and studied saturated (anoxic) and unsaturated (oxic) flow conditions. We present a model designed to predict concentrations of nitrate and ammonium at several soil depths resulting from the processes of nitrification, denitrification, and ammonification. Model equations were obtained that describe NO₃-N and NH₄-N concentrations in terms of position, rate constant, and average flow velocity. Although many parameters were included in the model equations, some were determined from the literature and others were derived from experiments. A sensitivity analysis of the rate coefficients for NO₃-N and NH₄-N revealed that they are extremely sensitive to denitrification and ammonification respectively. Experimental results show that there were large differences in the transformations of NO₃-N and NH₄-N, the water pressure distributions, and the oxygen reduction potentials (ORP) between saturated and unsaturated pore water flow conditions. The performance of the model for sequential transformations during the transport of NO₃-N is well documented under both saturated and unsaturated flow conditions.     

甘蔗根际土壤产木聚糖酶菌株的筛选及鉴定

以木聚糖为唯一碳源,从甘蔗根际土壤中筛选木聚糖酶产量较高的菌株。根据筛选培养基上水解圈的大小和摇瓶培养后木聚糖酶的酶活力筛选到产酶量高的菌株Xw2,其水解圈与菌落的直径比为2.3及初筛酶活力达113.8205 IU.mL-1。并利用形态学及基于核糖体DNA ITS序列构建进化树分析鉴定Xw2菌株为一株木霉。     

借鉴日本的土壤培肥管理成果提高大豆品质和产量

本文通过借鉴日本大豆氮元素、磷元素、钾元素,矿物质元素等化学肥料,农家肥以及土壤的pH值调整等的培肥管理技术,阐述了重视土壤的培肥管理,对提高我国大豆品质和产量的重要性。     

Fumigant persistence and emission from soil under multiple field application scenarios

Chemical fumigants are routinely used for soil disinfestation of high value crops. Good agricultural practices (GAPs) are needed to reduce their human health risks, environmental impacts, and improve their cost-effectiveness. This study investigated the effect of fumigant application methods on soil persistence and emission of 1,3-dichloropropene (1,3-D) and chloropicrin (CP). Field experiments were conducted to measure the individual and combined effects of pre-application tillage practices, fumigant application technology, and plastic films on 1,3-D soil concentrations to obtain a numerical index (CT value) to estimate their potential for pest control efficacy and to compare soil persistence, atmospheric flux rate, and cumulative emission of CP and 1,3-D under two diverse application scenarios. Greater 1,3-D soil vapor concentrations were observed by combining a pre-application soil seal with low soil disturbance application technology when compared to pre-application soil tillage and the use of back-swept application shanks. Under high density polyethylene plastic, the low disturbance scenario resulted in time weighted exposure concentration (CT) values ranging from 6.8 to 12.2 μg h cm⁻³ of soil as compared to CT values ranging from 2.9 to 5.4 μg h cm⁻³ under the conventional application scenario. Cumulative atmospheric emission of 1,3-D was decreased by 18% under the low disturbance scenario and atmospheric emission of CP by 21% when compared to a conventional application scenario. This study identified GAPs that can be readily implemented in the field to reduce the human and environmental impacts of soil fumigants and improve their cost-effectiveness under solid-tarp (broadcast) applications.     

Ammonia volatilization from Vietnamese acid sulfate paddy soil following application of digested slurry from biogas digester

Paddy and Water Environment - In some areas of Vietnam, digested slurry from biogas digesters is discharged into canals without wastewater treatment. In order to reduce environmental pollution,...     

Dynamic heat flux measurement for advanced insulation materials

Odour formation in the textile is a serious and embarrassing problem for an individual. The axilla born bacterial species are noted as the main reason for odour formation in axilla. In this research an attempt has been made to identify the odour generating compounds on the textile material after wear trial using gas chromatography and mass spectrum (GC-MS). The result indicates that the worn textile material consisted steroidal fractions of 5a-androst-16-ene-3-one and cholesterol, the major odour forming source from axilla. The results also identified the other important odour forming fatty acids and alcohols like lauric acids, diethyl esters of 1,2-benzenedicarboxylic acid, methyl esters of tetradecanoic acid, 3- methylhexanoic acid, Tetradecanol and acetic acid in axilla worn textile. These components were the derivatives of axilla specific odourous components like phthalic acid, myristic acid, isobutric acid and alcohols. The effect of Terminalia chebula extract finish on the odour formation also analysed and the results shows a considerable reduction in odour causing short chain volatile fatty acids (VFAs) in the worn textile compare to the untreated textile. The analysis also identified more amounts of active components of Terminalia chebula on the fabric surface instead of the odourous components from axilla.     

Isolation and identification of a lipase producing Bacillus sp. from soil

Lipase production in an indigenous lipolytic Bacillus sp. was detected in media containing Tributyrin-Tween 80 and Rhodamine B-Olive oil. The statistical Taguchi model was used to predict the optimum experimental conditions for bacterial growth and lipase production. Partial optimization was carried out for selection of salt base, oil, glucose, NH4Cl and yeast extract concentrations, inoculum density, pH and agitation. Maximum lipase activity was detected in the cell free supernatants of cultures grown in a medium containing 10 g L(-1) yeast extract, 15 g L(-1) NH4Cl, 3 g L(-1) K2HPO4, 1 g L(-1) KH2PO4, 0.1 g L(-1) MgSO4 x 7H2O, 2 g L(-1) glucose, 0.6 mM MgCl2 and 15 ml L(-1) olive oil, pH 8.5 at 30 degrees C for 24 h and low agitation. The amount oflipase produced in the designed medium was in agreement with the predicted values by the statistical method. 16S rRNA cloning and sequencing identified the test organism as Bacillus pumilus.     

Influence of irrigation frequency on greenhouse gases emission from a paddy soil

Water management is known to be a key factor on methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) emissions from paddy soils. A field experiment was conducted to study the effect of continuous irrigation (CI) and intermittent irrigation (II) on these emissions. Methane, CO₂, and N₂O emissions from a paddy soil were sampled weekly using a semi-static closed chamber and quantified with the photoacoustic technique from May to November 2011 in Amposta (Ebro Delta, NE Spain). Intermittent irrigation of rice paddies significantly stimulated (N₂O + N₂)–N emission, whereas no substantial N₂O emission was observed when the soil was re-wetted after the dry phase. The cumulative emission of (N₂O + N₂)–N was significantly larger from the II plots (0.73 kg N₂O–N ha^?1 season^–1, P < 0.05) than from the CI plots (?1.40 kg N₂O–N ha^?1 season^?1). Draining prior to harvesting increased N₂O emissions. Draining and flooding cycles controlled CO₂ emission. The cumulative CO₂ emission from II was 8416.35 kg CO₂ ha^?1 season^?1, significantly larger than that from CI (6045.26 kg CO₂ ha^?1 season^?1, P < 0.05). Lower CH₄ emission due to water drainage increased CO₂ emissions. The soil acted as a sink of CH₄ for both types of irrigation. Neither N₂O–N nor CH₄ emissions were affected by soil temperature. Global warming potential was the highest in II (4738.39 kg CO₂ ha^?1) and the lowest in CI (3463.41 kg CO₂ ha^?1). These findings suggest that CI can significantly mitigate the integrative greenhouse effect caused by CH₄ and N₂O from paddy fields while ensuring the highest rice yield.     

从土壤中分离微生物转化人参皂苷Rb_1为Rg_3

选用从土壤中分离出的148种微生物来进行人参皂苷Rb1微生物转化,HPLC分析显示能转化人参皂苷Rb1为Rg3的菌株11种。其中菌株YS-22和YS-38使人参皂苷Rb1有效地转化为Rg3。通过显微镜观察,YS-22属于杆菌,YS-38属于球菌。     

Estimating tuber dry matter concentration from accumulated thermal time and soil moisture

Summary The tuber dry matter concentration, [DM], of crops of potato (Solanum tuberosum L.) was related using regression analysis, to time, thermal time, incident radiation accumulated from plant emergence, and soil moisture deficit (SMD). Variation in [DM] was best accounted for by the regression model that was a function of thermal time above a base of 0 °C accumulated from plant emergence, and SMD. When validated against an independent data set, there was good agreement between observed and estimated [DM] with a linear relation accounting for 79.3% of the variance.     

Gaseous emissions from soil biodisinfestation by animal manure on a greenhouse pepper crop

Soil solarisation together with the application of animal manure has been described as an alternative process for control of Phytophthora capsici root rot in pepper crops. A mixture of fresh sheep manure and dry chicken litter (SCM) and a semi-composted mixture of horse manure and chicken litter (HCM) were applied at 5.1 kg m⁻² (dry weight) under plastic sheets to reduce Phytophthora inoculum survival rate and disease incidence. Non-solarised (C) and solarised (S) soils were used as control treatments. Mean NH₃ concentration increased in SCM during biodisinfestation process (14.8 mg NH₃ m⁻³) compared with HCM (9.1 mg NH₃ m⁻³), accounted for the higher organic N content and potential N mineralisation. The higher NH₃ concentration in SCM could have contributed to reduce the inoculum survival rate (30.6% and 75.0% in SCM and HCM plots, respectively). Inoculum survival rate was not reduced in S (94.4%) as temperature was below 33 °C throughout the experimental period. After biodisinfestation treatment, N₂O and CO₂ emissions tended to be higher in SCM, despite high spatial variability. Cumulative N₂O emissions were 1.31 and 0.42 g N₂O-N m⁻² in SCM and HCM after 43 days. The larger N application and organic N mineralisation rate on fresh manure amended soils might have contributed to higher N₂O emissions during and after soil biodisinfestation by denitrification and nitrification, respectively. Cumulative CO₂ emission averaged 211.0 and 159.9 g CO₂-C m⁻² in SCM and HCM, respectively. The soluble organic C, more abundant in fresh manure, might have favoured soil respiration in SCM. Disease incidence decreased in SCM and HCM plots (disease incidence, 2%-8%) in relation to solarised soils (42%) after 4 months. Microbial suppressiveness might have contributed to minimise Phytophthora disease incidence in SCM and HCM plots. Pepper fruit yield increased with manure amendment in SCM and HCM, which averaged 4.6 and 4.3 kg m⁻², respectively. Further research will be necessary to guarantee an effective Phytophthora biodisinfestation by fitting manure N and organic matter applications, improving crop yield and reducing greenhouse gas pollution.     

The influence of soil wetness on utilized output from grassland on commercial farms

Records of grassland productivity have been used for 93 farms in 1975–76 (a dry year) and 117 farms in 1977–78 (a wetter year). The samples were selected to contrast well-drained and poorly/ badly drained farms and were further subdivided into dairy and beef. The number of farms in each of the four subsamples for each year was between 19 and 32. In addition the number of days on which the soil was at meteorological field capacity (field capacity days) on each farm was calculated.
The mean utilized metabolizable energy (UME) output within the dairy sample was 45 GJ ha⁻¹ on both well-drained and poorly/badly drained farms. Within the beef sample the output was 41 GJ ha⁻¹ on well-drained farms and 37 GJ ha⁻¹ on the poorly/badly drained farms.
The correlation between fertilizer N and UME output was stronger on well-drained farms than on the poorly/badly drained farms in the wetter year (r = 0.69 v. 0.16 on dairy farms; r = 0.56 v. − 0.12 on beef farms). In the drier year the converse was found (r=0.15 v . 0.49 on dairy farms; 0.13 v. 0.44 on beef farms). The effect of field capacity days on output was inconsistent; only within the dairy sample in the wetter year did increased wetness appear to reduce output.
It is suggested that soil wetness may have only a small effect on utilized output from grassland on a whole-farm basis because (i) most farms have at least some well-drained land, (ii) much of the utilization damage occurs in relatively short periods in spring and autumn and (iii) despite having utilization problems, badly drained land is capable of growing large quantities of grass.     

Maximum surface temperature model to evaluate evaporation from a saline soil in arid area

In order to estimate soil evaporation from saline soil in arid area, a maximum surface temperature (MST) model was applied to Hetao Irrigation District (HID). The model was developed based on energy balance and sinusoidal function of surface soil temperature. Evaporation and surface temperature of drying soil columns and surface temperature of natural field were observed in each 1-h interval in daytime (from September 10 to 19, 2010) in a saline land in HID. The results indicated that the estimated evaporation shows a similar trend and in good agreement with the observed values. To quantitatively evaluate the performance of the model, some statistic parameters were calculated as well. These statistics could also indicate that the observed values perform similar trend to the estimated values. It is concluded that the MST model could be applied to estimate soil evaporation from saline land. The proposed method is hopeful to estimate soil evaporation over large scale area using only surface temperature available from the satellite image while assigning an effective exchange coefficient (c _h ).