Silt Clay Soil Research Articles

Deep-Learning-Based Approach for Estimation of Fractional Abundance of Nitrogen in Soil From Hyperspectral Data

One of the vital growth nutrient parameters of crops is soil Nitrogen (N) content. The ability to accurately grasp soil nutrient information is a prerequisite for scientific fertilization within the field of precision agriculture. Information pertaining to soil macronutrients, such as N, may be obtained quickly through hyperspectral imaging techniques. Objective of this research is to explore the use of a deep learning (DL) network to estimate the abundance of urea fertilizer mixed soils for spectroradiometer data. The proposed approach was tested for silt clay and loamy types of soils. Spectral regions of 1899.2 nm for urea and 2195.1 nm for soils were identified as optimum spectral absorption features. The accuracy evaluation was performed using a linear regression model between actual and estimated abundances. At 1899.2 nm, the coefficient of determination ( R 2) for mixed samples of urea and silt clay soil was found to be 0.945, while R 2 for urea mixed loamy soil were 0.954. Similarly, at 2195.1 nm, R 2 obtained 0.953 for urea mixed silt clay soil and 0.944 for urea mixed loamy soil. The results show that the estimated abundances obtained through the derivative analysis for spectral unmixing (DASU)-based DL network facilitated a greater accuracy in comparison to the sole use of DASU. These results were then verified through conventional chemical analysis methods. The outcome of this article determines the abundance of urea mixed soils. Therefore, it is inferred that the hyperspectral imaging technique may be utilized in-situ to assess the agricultural land's soil fertility status.

Kriteria Desain Dinding Penahan Pada Tanah Campuran

Retaining wall is one of the reinforcing techniques used to control soil movement. Reinforcement with retaining walls is relatively expensive so an efficient design is needed. Unfortunately, the guidelines for planning a retaining wall are limited. Analysis of design criteria was carried out on silt clay soil taken in the area of the Karang Joang Kalimantan Institute of Technology (ITK) area based on the dimension guide given by Hardiyatmo (2010) and Nakazawa, et al (1980) for safe slope height based on the type of retaining wall. The minimum criteria for cantilever type retaining walls with a slope height of 2-3 meters is the width of the TOE (A) = B / 3 meters, the base width retaining wall (B) = minimum of 0.7 H meters, the width of the upper wall (C) = 0.2 meters and wall thickness (D) = H / 10-H / 12 meters, while for slopes with a height of 4- 5 meters the safe dimension range is TOE (A) width = A / 3, slope width (B) is designed to be a minimum of 0.9 H meters, width of the wall (C) = minimum 0.2 meters and wall thickness (D) = H / 10-H / 12 meters. Gravity retaining wall has design criteria for slopes as high as 2-3 meters of A = D / 2-D meters, B is taken to a minimum of 0.7 H meters, a minimum C value of 0.3 m and D of H / 8 - H / 6 meters for slopes with a height of 2-3 meters, meanwhile for slopes with a height of 4-5 meters, B to a minimum of 0.9 H meters, with a value of A = D / 2-D meters, the C value is designed to be a minimum of 0.3 meters and D = H / 8 - H / 6 meters.

Response of Some Sugar Beet Varieties Grown under Different Saline Soils and Plant Populations

Two field experiments were conducted in Senouris; Tamya Res. Station, Fayoum Governorate, Egypt (latitude of 30.82 o N and longitude of 29.40o E) during the two successive seasons of 2017/2018 and 2018/2019, to evaluate the performance of three sugar beet varieties (Alauda, Nefirtitis and Carnuta), sown using three spaces between hills (15, 20 and 25 cm) under conditions of loamy (saline soil) and silt-clay soils, in two separate field experiments on yield and quality. Under each soil condition; the experimental design was a split-plot with three replications. Collected data were analyzed combined over the two locations in each season. Hill spaces were allocated in the main plots, whereas, varieties were randomly distributed in the sub–plots.Results showed a positive statistical response in root length and diameter, as well as, root fresh weight/plant, root and sugar yields/fad, when sugar beet plants were sown under silt-clay soil, compared to saline soil (loamy texture) conditions. Meanwhile, the highest K and Na contents and sucrose% were obtained under saline soil conditions, in both seasons. Root dimensions, root fresh weight/plant, root and sugar yields/fad positively and continuously responded to increasing hill spaces up to 25 cm. However, the insignificant differences among sowing hills were found in K, Na and alpha-amino N contents, sucrose% and purity%, in both seasons. The examined varieties differed significantly in root diameter and root fresh weight/plant, in both seasons, as well as, root length only in the 1st season, and root yield/fad in the 2nd one. The heaviest roots were obtained from Carnuta variety and superiority over the other tested varieties. The significant differences among sugar beet varieties in sugar yield/fad were showed only in the 2nd season, meantime, the differences among varieties were insignificant in K, Na, alpha-amino N contents, sucrose% and purity%, in both seasons. The highest sugar yield/fad was obtained from Carnuta variety, followed by Alauda, while the least sugar yield/fad resulted from Nefirtitis variety, in the 2nd season.The interaction between soil types and hill spaces showed significant effects on root diameter in both seasons and sugar yield/fad only in the 2nd season. Carnuta variety recorded the highest. Significant values of root length under silt-clay soil conditions, in the 1st season. The significant interaction between hill spaces and varieties was reflected in purity% in the 2nd season. Alauda achieved the highest purity% at 15 and 25 cm between hills, meantime, Nefirtitis gave the best purity% at 20cm between hills. The 2nd order interaction, among the three factors under study had a significant influence on sucrose% only in the 2nd season. The highest sucrose% was attained from the interaction between varieties and distances between hills under saline soil (loamy texture) than silt-clay soil conditions.Based upon the obtained results, it was found that sowing Carnuta variety at 25cm between hills might be recommended to achieved the highest root and sugar yields/fad under silt-clay and/or saline soil (loamy texture) conditions.

Saline water irrigation in semiarid region: II – effects on growth and nutritional status of onions

The use of saline waters for the irrigation of crops such as onion is a common practice in the Brazilian semiarid region. However, the effect of the use of these waters on onion nutrition and growth has been underappreciated. This work aims to evaluate Ca2+, Mg2+, Na+, K+ and Cl- levels and onion growth in two Fluvisols under irrigation with waters of variable electrical conductivity and increasing values of sodium adsorption ratio. A greenhouse experiment was conducted in two Fluvisols cultivated with onion. After transplanting each plant was irrigated with saline waters, in a factorial arrangement 2 x 3 x 6, corresponding to two soils (sandy loam and silt clay loam), three values of electrical conductivity (EC - 200, 700 and 2,000 μS cm-1) and six levels of sodium adsorption ratio (SAR - 0, 5, 10, 15, 20 and 25 (mmolc L-1)0.5). Plants were collected at 90 days after transplanting and onion growth parameters as well Ca, Mg, K, Na and Cl levels were each measured. The SAR of the irrigation waters and the soil did not show any significant influence on the onion growth variables or on the levels of the evaluated elements. The increase in salinity of the irrigation water promoted a reduction in the growth variables of the evaluated onion cultivar. Increases in the levels of Ca, Na and Cl as well as a reduction in the level of K in the onion plant dry matter were all observed with increasing salinity of the irrigation water; however, the Mg content level was not affected. As the salinity of the irrigation water was the main factor affecting onion growth, an EC of 200 µS cm-1 is the limit to promote the best onion growth cultivated in both sandy and silt clay soils.

Effect of the Operating Depth and the Lateral Inclination Angle on the Draft Force Requirements and the Lateral Force of the Vertical and Laterally Inclined Mole Plows in Silt Clay Soil

Effect of the Operating Depth and the Lateral Inclination Angle on the Draft Force Requirements and the Lateral Force of the Vertical and Laterally Inclined Mole Plows in Silt Clay Soil - written by Shaker H. Aday , Sadiq J. Muhsin published on 2019/05/23 download full article with reference data and citations

Responses of soil water dynamic processes and groundwater recharge to irrigation intensity and antecedent moisture in the vadose zone

AbstractIn this study, a field experiment was conducted to investigate the soil water dynamics and water percolation through the deep vadose zone. A calibrated HYDRUS‐1D model was used to simulate the process of soil water movement and the water budget. Based on the measured volumetric soil water contents, the model was well calibrated and validated. Then, we conducted scenario analyses to determine the combined effects of irrigation amount (IA), antecedent soil moisture (AM), crop evapotranspiration, and deep percolation (DP) in an irrigation event. Four IAs (5, 10, 15, and 20 cm) and three AM conditions (AM‐1, AM‐2, and AM‐3) were controlled in the scenario analyses. The results indicate that according to the Se's (effective saturation) values status and the observed or simulated depth, there could be different conclusions on the influence of DP. Under different IAs in dry (AM‐1) and medium (AM‐2) AM status, DP changed slightly; it was 0.39 and 2.47 cm in AM‐1 and 0.40 and 2.48 cm in AM‐2 for the summer maize and winter wheat crop, respectively; the AM had a crucial contribution to DP. While under the condition of wet AM (AM‐3) or small observation depth, the water inputs could have a significant effect on DP. According to increasing irrigation intensity, the higher values of Se (>0.6) in the whole profile were only displayed between 70 and 300 cm at AM‐1, 70–500 cm at AM‐2, and 70‐below 600 cm at AM‐3, which were gradually extended and moved down with increasing AM. Hence, the IA significantly affected the water percolation at a depth of 200 cm, whereas there was a weak influence at 600 cm except in AM‐3. Furthermore, in the higher values of the Se (>0.65) domain, the correlation between IA and DP was an exponential function and significantly under P < 0.05. In addition, DP began to occur when the soil water content was equal to or greater than 0.75 times that of the field water capacity or the Se > 0.65. When the coarse silt layer became embedded in the silt clay soil profile, it lagged the process of water transport but did not affect permeability in the end.

The impact of residential septic tanks on soil water infiltration and groundwater contamination in Duhok city

This study was conducted to assess the impact of septic water on soil water infiltration in Duhok city potentiallycontaminating regional groundwater through designing a large-scaled laboratory physical model of vertical flowdirection packed homogenously with silt-Clay soil. The designed model was supplied with newly collected septicwater. With steady-state flow condition, the model was run, water samples were collected and analyzed weekly.Various parameters and constituents that may influence soil structure and water infiltration were examined including : Electrical conductivity, sodium, calcium, magnesium, carbonate, bicarbonate, residual sodium carbonate (RSC), pHc and adjusted sodium absorption ratio (adj. SAR). For assessing groundwater quality, bacteriological analysis were conducted. Analytical results were used to estimate the examined parameters and predict their future trends. Results revealed that electrical conductivity (EC) was accumulating until it reaches the carrying capacity. Sever hazard of (RSC) was detected within 25 meter depth. Average pHc was 6.74 indicating the tendency of lime (CaCO3) to precipitate from applied septic water. adj. SAR for port A and port B were 11.1 and 8.65 respectively which, caused severe soil deterioration, but on the other hand helped in decreasing the rate of contaminants transport for treatment within the soil before reaching the groundwater. Results of bacteriological analysis indicated that groundwater shallower than 31 meter was contaminated by fecal and total coliform bacteria. This study helped local authorities in establishing precaution strategies of groundwater management to protect public health.

Global meta-analysis reveals agro-grassland productivity varies based on species diversity over time.

Ecological research suggests increased diversity may improve ecosystem services, as well as yield stability; however, such theories are sometimes disproven by agronomic research, particularly at higher diversity levels. We conducted a meta-analysis on 2,753 studies in 48 articles published over the last 53 years to test: if biological N2 fixation (BNF) supplies adequate nitrogen (N) for plant growth relative to synthetic fertilizers; how crop physiological traits affect legume-grass symbiosis; and, how cultural practices affect BNF over a range of soils and climates overtime (in polycultures versus sole grasslands). Globally, net primary productivity (NPP; total aboveground production response of grass and legume in higher-diversity treatments) increased 44% via legume associations relative to sole grass controls (including both with and without N fertilizer). Several moderating variables affected NPP including: (i) plant photosynthetic pathway (mixtures of C3 grasses resulted in a 57% increase in NPP, whereas mixtures of C4 grasses resulted in a 31% increase; similarly cool-season legumes increased NPP 52% compared to a 27% increase for warm-season legumes relative to grasslands without diversity); (ii) legume life cycle [NPP response for perennial legume mixtures was 50% greater than sole grass controls, followed by a 28% increase for biennial, and a 0% increase for annual legumes)]; and, (iii) species richness (one leguminous species in a grassland agroecosystem resulted in 52% increase in NPP, whereas >2 legumes resulted in only 6% increases). Temporal and spatial effect sizes also influenced facilitation, considering facilitation was greatest (114% change) in Mediterranean climates followed by oceanic (84%), and tropical savanna (65%) environments; conversely, semiarid and subarctic systems had lowest Rhizobium-induced changes (5 and 0% change, respectively). Facilitation of grass production by legumes was also affected by soil texture. For example, a 122% NPP increase was observed in silt clay soils compared to 14% for silt loam soils. Niche complementarity effects were greatest prior to 1971 (61% change), compared to recent studies (2011–2016; -7% change), likely owing to reduced global sulfur deposition and increased ambient temperatures overtime. These historical trends suggest potential for legume intercrops to displace inorganic-N fertilizer and sustainably intensify global NPP. Results herein provide a framework for ecologists and agronomists to improve crop diversification systems, refine research goals, and heighten BNF capacities in agro-grasslands.

Positive effects of apple branch biochar on wheat yield only appear at a low application rate, regardless of nitrogen and water conditions

The agriculture industry is under intense pressure to produce more food with a lower environmental impact, while also mitigating climate change. Biochar has the potential to improve food security while improving soil fertility and sequestering carbon. The aim of our research was to evaluate the effects of apple branch biochar on wheat yield and soil nutrients under different nitrogen (N) and water conditions. Durum wheat was grown for nearly 6 months in pots with silt clay soil supplemented with apple branch biochar. The biochar was applied at five rates (0, 1, 2, 4, and 6% w/w; B0, B1, B2, B3, and B4), and N fertilizer was applied at three rates (0, 0.2, and 0.4 g kg−1; N0, N1, and N2). From the jointing to maturation stages, the soil water content was controlled at two rates to simulate sufficient water and drought conditions (75 and 45% of field capacity; W1 and W2). After harvest, we investigated grain yield and soil nutrient status. The application of biochar alone had a positive effect on wheat production and soil nutrients, especially under sufficient water conditions. Compared with the addition of N fertilizer alone, the addition of biochar at B1 and B2 combined with N fertilizer under sufficient water conditions increased the crop yield by 7.40 to 12.00%, whereas this was not the case under drought stress. Furthermore, regardless of water conditions, compared with N fertilizer application alone, a high rate of biochar application (B3 and B4) led to a significant decrease in the grain yield of approximately 6.25–21.83%. Biochar had strong effects on soil nutrients, with NO3− and available phosphorus contents and the C:N ratio exerting the greatest effects on wheat yield. The effects of biochar on wheat production and soil nutrients varied with the biochar application rate, N fertilizer application rate, and water conditions. Drought stress weakened or offset the positive effect of biochar on crop production, especially under the high-N level (N2) conditions. The optimum application combination was 1% (or possibly even less) apple branch biochar (B1) and moderate N fertilizer (N1).

ASSESSMENT OF SELECTED PHYSICO-CHEMICAL PARAMETERS OF GROUND WATER IN DIRECT CONTACT WITH SEPTIC TANKS: EXPERIMENTAL MODELING

Improper use of septic systems has shown to contribute in ground water contamination by heavy metals, toxic chemicals, and organic chemicals typically found in septic tank cleaning products. Therefore, it suggested evaluating the implication of heavy metals on shallow ground water contamination with direct contact of failed septic tanks. In conducting this research, a laboratory physical vadose model with a vertical flow direction was designed and packed with Silt-Clay soil, which was modified by replacing (20% by weight) of fine sand to satisfy the desired hydraulic conductivity to collect water samples, using a new packing technique other than the ordinary compaction procedure. The model was then fully saturated, well-drained, and run using raw filtered septic water. The model was run for three months and water samples were collected on daily basis at 12.5cms from top of model representing 6.25m underground (model scale was 1:50). Collected samples were analyzed weekly for any pollution occurrence in ground water quality with reference to heavy metals including Fe, Pb, Cu, Cd, Zn, Cr, Al, and Mn. Analytical results used to identify trends of contamination and predict future trends. Results revealed that Fe and Mn were much higher than the permissible limits of world health organization (WHO, 2008) then Al and Cd. Cr fluctuated around the permissible level, Zn precipitated and disappeared within the soil while both of Pb and Cu were safe and at very low level. This study helps the local government in establishing precaution strategies for ground water management to protect public health.

Modeling the Movement of Septic Water Chloride through a Soil Profile

The purpose of this study was to investigate the movement of chloride through a vadose zone located under failed and non-regulated septic tanks of Duhok city, Kurdistan of Iraq, potentially contaminating its groundwater. A physical vadose model (PVM) of a vertical flow direction was built in the laboratory to represent the city soil profile. The size of the PVM was 210 × 122 × 9.7 cm (height, width, and depth). Preliminary soil tests were conducted to better represent the lithology of study area. The PVM was then packed with regional silt clay soil, after modifying its texture, using an innovative packing procedure to preserve natural soil density and porosity. The model was run for a period of three months with newly collected septic water (black water from a septic tank) as an exclusive source of contaminants. Water samples from eight vertically arranged portals representing 12.5, 37.5, 62.5, 87.5, 112.5, 137.5, 162.5, and 187.5 cm levels in the subsurface soil profile were collected on a daily basis and analyzed weekly. Logistic regression and logarithmic models were developed to spatially predict the movement of chloride ions at different sampling depths in the soil profile until the system had reached the equivalent chloride concentration of the septic water or had stabilized. There was a good agreement between the physical model and the statistical models, however each model had its strengths and weaknesses. This study demonstrated that there is a potential for septic water to reach the water table within a 2–3 weeks period. Dilution and dispersion appear to play important roles in the fate and transport of septic water. This study has the potential to help the local authorities predict percolation rates and establish strategies for groundwater management in order to protect the public health.

Modeling the relationship of soil water repellency with soil moisture for Pinus massoniana and Schima superb secondary forests

In China, secondary forests occupy a large area of forested lands. However, the relationship of soil water repellency with soil moisture, and the threshold value of soil moisture at which soil water repellency disappears in the forest soils are unknown. In this study, the relationship between soil water repellency and soil moisture was investigated and analyzed by water drop penetration time with soil samples. The soil samples were collected in 10 kinds of stands that were three pure <i>Pinus massoniana</i> stands (PPM [P1 to P3]); three pure <i>Schima superb</i> stands (PSS [S1 to S3]); and four mixed forest stands (PSM [M1 to M4]) with sandy clay, silt clay, and clay soil, respectively, from the state-owned forest farm of Qingshigang, Hunan, China. The obtained relationships could be characterized by nonlinear curves with one peak and a long tail to the right for all the stands. Three nonlinear models, including Gaussian, Lorentzian, and Lognormal models, were applied to fit the data with regression analysis. The results showed that (1) at the beginning, soil water repellency increased with the increasing soil moisture until reaching to its maximum value, then decreased and gradually became zero at which the threshold value of soil moisture was yielded for each of the stands. However, the maximum value of soil water repellency and the threshold value of soil moisture varied depending on the soil types, soil properties, and forest types. (2) The smaller the initial soil moisture contents, the smaller the peak values of the water repellency. (3) The Lorentzian model more accurately modeled the relationship than the Gaussian and Lognormal models and thus could be used to simulate the response of soil water repellency to soil moisture and to predict the maximum water repellency. It is expected that this study can provide useful information and guidelines for improvement of soils and comparison of different repellent soils in the secondary forests. This study can also offer corresponding suggestions for other secondary forests.

KINETIC OF COPPER ADSORPTION IN CALCAREOUS SOIL

Laboratory experiment was carried out to study kinetic of copper adsorption using silt clay loam calcareous Iraqi soil. 5ml of copper nitrate solutions (0,25,100 and500 mg Cu L-1)that were prepared from Cu(NO3)2.3H2O Added to (soil) and (soil+compost) treatments. Compost (0.05gm) was added to (soil+compost) treatment that equal 10g kg-1 soil. The soil samples were incubated at 293±2 K for four incubation periods 24,168,336 and 672 h using Batch equilibrium technique. At each incubation period the soluble copper was determined and kinetic equations were tested. The results showed that the soil had high fixation capacity to copper at all concentrations and treatment. The percentage of copper adsorption was 99.72% at first incubation period followed by gradual increase till the pseudo equilibrium at 336h at all concentration (25,100 and 500 mg Cu L-1 solution). Compost application increased the copper fixation capacity and the copper adsorption curves showed the continuation of adsorption from 24 h. to 336 h. incubation period followed by little release of copper at 672 h. at all concentration and treatments. The power function equation was best described the adsorption of copper and copper adsorption constant (Ka) ranged from 3x10-4 to 5.5x10-3 mg Cu kg-1 h-1, which indicate to the high adsorption capacity of such alkaline soil to adsorb Cu and this will be related to Cu fertilizer management.

Laboratory study of a novel marsh shoreline protection structure: Wave reduction, silt-clay soil collection, and mathematical modeling

Shoreline erosion along open water bodies and waterways is a major cause in the conversion of wetlands and uplands to open water habitat. Conventional shoreline protective structures are expensive to construct in these environments, and may impede environmental exchanges essential for connectivity and functionality. The structure, Wave Suppression and Sediment Collection (WSSC) System that contains multiple Wave Robber™ units, is an alternative for shoreline protection that maintains environmental connectivity. The primary goals of this study are to evaluate the wave reduction and sediment collection performance of the unit as well as optimize its design. This study showed that the unit reduces 84 to 90% of the wave energy while collecting and retaining fine-grained sediment. A mathematical model fits the sediment collection data reasonably well with average correlation coefficients of about 0.87. Modeling results show that the sediment collection efficiency of the unit for fine-grained sediment is about 14%. Total area of flow through the unit was determined to be more important than the area distributed among the number and size of pipes. The sensitivity study shows that wave height and initial concentration are the most important factors effecting sediment collection.

Experimental Heat Transfer Study on Green Roofs in a Semiarid Climate during Summer

An experimental study was conducted on green roofs under the semiarid summer climatic conditions of West Texas to investigate the effect of soil type, moisture content, and the presence of a top soil grass layer on the conductive heat transfer through the roof. Two soil types were investigated: uniform sand and local silt clay. Tests were also conducted on a control roof. A dual-needle heat-pulse sensor was used to conduct thermal property tests on the soils. The tests reveal that unlike sand, the thermal conductivity of silt clay did not increase continuously with soil moisture. Better heat transfer conditions were achieved when the sand and silt clay roofs were watered to a water depth of 10 mm per day rather than double the amount of 20 mm per day. The roof with silt clay soil had the lowest fluctuation in inner temperature between daytime and nighttime. Green roofs with silt clay soil required more than twice the amount of soil moisture than green roofs with sand to achieve similar roof heat transfer rates. The best net heat flux gains for vegetated green roofs were 4.7 W/m2 for the sand roof and 7.8 W/m2 for the silt clay roof.

Use of Hppd-inhibiting Herbicides for Control of Troublesome Weeds in the Midsouthern United States

Transgenic crops provide cotton and soybean producers additional weed control options for many of the most problematic weeds in mid southern US. production systems. The expected commercialization of 4-hydroxyphenylpyruvate dioxygenase (HPPD)-resistant soybean in 2017 and cotton in 2020 will provide producers the option to apply HPPD-inhibiting herbicides that will offer an alternative mechanism of action for previously hardto- control weeds. Experiments were conducted in 2010 and 2011 to determine the efficacy of HPPD-inhibiting herbicides applied pre emergence (PRE) or post emergence (POST) for control of problematic weeds of cotton and soybean in the mid southern US. PRE experiments were conducted to understand the length and degree of control of Palmer amaranth and barn yard grass that could be expected with HPPD-inhibiting herbicides compared with current standards on silt loam and clay soil textures. The HPPD herbicides evaluated included mesotrione, tembotrione, and isoxaflutole compared to several standards currently labeled in soybean. In the POST experiment, applications of isoxaflutole, tembotrione, glyphosate, and two rates of glufosinate applied alone and both HPPD herbicides combined with glyphosate or glufosinate were evaluated for control of Palmer amaranth, barn yard grass, hemp sesbania, and yellow nutsedge. When herbicides were applied PRE, the HPPD-inhibiting herbicides and the current standard treatments all provided greater than 90% control of Palmer amaranth 4 weeks after treatment (WAT) on both soil textures. Barn yard grass control with HPPD-inhibitors was generally weaker than the current standards with the exception of mesotrione which proved to be comparable to the standards 4 WAT. In the POST experiment, all treatments, except for glyphosate alone, provided excellent (>85%) control of Palmer amaranth less than 10 cm in height. Barn yard grass, yellow nutsedge, and hemp sesbania were effectively controlled with HPPDinhibiting herbicides with and without glufosinate or glyphosate.

Dissipation Behavior of 14C-Deltamethrin in Egyptian Soil Columns in Absence and Presence of Chlorpyrifos under Subtropical Conditions

The dissipation of deltamethrin in silt clay under subtropical climate conditions was studied. 14 C- Deltamethrin labeled at gem–dimethyl groups of cyclopropane ring was used alone in one sets of columns and in presence of chloropyrifos in the other sets and kept under field conditions for eleven months. Radioactivity was concentrated in the upper zone of the columns 0-10 cm. The total dissipation of the insecticide amounted to 31%; 52% of the applied dose in silt clay soil in absence and presence of chlorpyrifos, respectively. The soil binding capacity increased with time whereby the extractable 14 C-residues simultaneously decreased. The nature of methanolic extract of soils was determined by chromatographic analysis. Deltamethrin was the main degradation product of the extractable residues in addition to 3-phenoxybenzaldehyde, 3-phenoxybenzoic acid and 3-phenoxybenzyl alcohol.

The nitrification inhibitor 3,4-dimethylpyrazole-phosphat (DMPP) - quantification and effects on soil metabolism

Nitrification inhibitors (NI) formulated on granulated ammonium sulphate nitrate (ASN) are an option to minimize nitrate leaching into ground waters and emissions of the greenhouse gas N2O. This paper focuses (a) on the development of an analytic enabling to extract and quantify the NI 3,4-dimethylpyrazolephosphate (DMPP), marketed since 1999. The efficiency of DMPP has been studied in laboratory and field soils. Here the DMPP analytic and the behaviour of a nitrifying bacterial consortium enriched from a field soil and exposed to zero, field applied and a 10 fold higher DMPP concentration than the recommended one for field application are in the focus. For extracting DMPP quantitatively from soils a method connected to a HPLC analytic has been developed by us and was standardized in laboratory experiment with a silt clay field soil (allochtone Vega). The method is detailed described here. Its reliability has been tested in a 3 years field trial under varying cropping systems and climatic conditions asides the influence of DMPP on CO2−, CH4− and N2O- emissions, measured by the closed chamber method. Parallel a nitrifying bacterial consortium of the silty clay field soil was enriched and subjected to 0, the recommended DMPP concentration for field applications and a 10 times higher one. In incubation experiments the conversion of ammonium to nitrite and nitrate in presence and absence of DMPP was spectrophotometer determined and pH-shifts with a scaled litmus paper. In sacrificed flasks at the end of incubation morphological changes of the bacteria involved were studied by transmission electron microscope (TEM). The ammonium, nitrite and nitrate determinations and the TEM pictures show that in presence of the field applied DMPP concentration the nitrifying activity returned around 30 days later than in the control and the cells were slightly enlarged. In presence of a 10 times higher DMPP concentration a recovery was prevented. DMPP prolongs, compared with dicyandiamide (DCD), the period of nitrifiers’ inhibition and reduced N2O− and CO2− the emissions (Weiske et al., Biol Fertil Soils 34:109–117, 2001a, Nutr Cycl Agroecosys 60:57–64, b). With the method developed by us the stability of DMPP in agricultural soils can be satisfyingly and reproducible studied down to a detection limit of 0.01 μg DMPP g−1 dry soil. The morphological changes in the nitrifying consortium due to DMPP concentrations are in agreement with the recovery rate found by nitrite and nitrate formation.

Stress-Strain and Strength Characteristics of Silt-Clay Transition Soils

AbstractThe influence of nonplastic silt content on the stress-strain, volume change, and strength characteristics of anisotropic silt-clay transition soils is investigated. A series of one-dimensional compression tests, isotropic compression tests, and undrained and drained triaxial tests on three soils of similar base clay but different nonplastic silt contents are performed on cross-anisotropic specimens prepared from consolidation of slurries. Tests with major loading directions both parallel and perpendicular to the specimens’ axis of deposition are performed. It is observed that the tested silt-clay soils are less compressible with increasing silt content during one-dimensional and isotropic compression tests. During drained and undrained triaxial tests, the normally consolidated soils at the same consolidation stress show larger values of stiffness and drained and undrained shear strengths with increasing silt content. The silt-clay soils also show larger pore pressure changes during undrained tria...

Estimation of the daily water consumption by maize under Atlantic climatic conditions (A Coruña, NW Spain) using Frequency Domain Reflectometry – a case study

Abstract. Climatic variables and soil present a high spatio-temporal variability. Evapotranspiration estimations based on climatic variables may be inadequate for assessing soil water content in the root-influenced zone and/or soil water consumption by plants. Other methods may provide better estimates of this water consumption. The aim of this study was to quantify the soil moisture dynamics in the root-influenced zone and to assess the daily water consumption by the crop using Frequency Domain Reflectometry (FDR). The studied site is located in A Coruña (Spain). The study was carried out from June to October in 2008 and 2009, in a maize (Zea mays, L.) field on a silt-clay textured soil. Evapotranspiration was estimated by the Penman-Monteith equation using meteorological data from a station located on the experimental site. Soil water content in the root-influenced zone (0–60 cm depth) was hourly monitored each 20 cm (0–20 cm, 20–40 cm, and 40–60 cm) using FDR. Evaluations were performed on days with slight or no rainfall. During the study period, the magnitude of the diurnal soil water loss was more evident in the first layer (0–20 cm depth) and less important in the subsequent soil layers. The greatest consumption occurred between 14 and 19 h, up to 53.64% of the total. Overall, daily water consumption increased significantly with soil water content (p-value &lt; 0.001). In general, water losses from the 0–20 cm soil layer were greater than in subsoil horizons due to maize water-uptake and evaporation. In contrast, water content in the deepest part of the soil profile was close to saturation, even on the driest days of the studied period. Evapotranspiration overestimate maize water requirements as its values were greater than those measured with the probe. In conclusion, FDR allows a more accurate estimation of the soil water balance. Therefore, monitoring soil water content would be useful in the assessment of saturation risks or water stress (drought), thus aiding in the decision making, for instance, in irrigation management. Results from this study may help to improve irrigation practices in humid zones.