Field leaching and degradation of atrazine in a gradationally textured alkaline soil

1997 ◽  
Vol 48 (3) ◽  
pp. 371 ◽  
Author(s):  
P. R. Stork
Keyword(s):  
Soil Temperature ◽  
Soil Water ◽  
Sandy Loam ◽  
Soil Layer ◽  
Residue Level ◽  
Late Winter ◽  
Alkaline Soil ◽  
Response Curves ◽  
Water Contents ◽  
Soil Water Contents

The leaching and degradation of atrazine to 40 cm was monitored over a 1-year period, following a spray application in May 1991, at a field site on a highly alkaline sandy loam cropping soil with a soil pH ≥8·5. To account for gradational changes in soil texture and pH with depth, separate dose response curves of an oat bioassay for each 10-cm soil-sampling interval were used, to quantify the soil concentrations of the herbicide. Throughout the trial the movement of atrazine was not observed to exceed beyond 40 cm with total rainfall of 386 mm. The only significant leaching of the herbicide was detected in late winter 1991, when approximately 30·5% of the applied amount leached from the 0–10 cm to 10–20 cm soil layer, with trace amounts detected at greater depths. This leaching occurred during a period of rainfall of 50 mm when soil water contents in the 0–10 cm to 10–20 cm soil layers were at an optimum, and it was deduced that the extent of the leaching, when evaluated with other studies, was influenced by the pH of the soil. Atrazine recovery decreased exponentially with sampling time. The data fitted a first-order exponential function (R2 = 0·99), with a half-life time for degradation of 62 days. The good fit of the data to this function also indicated that the rate of degradation was apparently independent of seasonal changes in water content and soil temperature. From this, it was inferred that any lowering to the rate of degradation, owing to decreasing soil water contents in spring–summer, was offset with compensating rises in soil temperature. Edaphic conditions in this spring–summer period approximate those in other studies where chemical hydrolysis was an important process of breakdown of atrazine. The degradation of the herbicide was almost complete by the end of the trial in late May 1992. An applied amount of 2·7% remained in the 10–20 cm soil layer, which corresponded to a residue level of 0·02 µg atrazine/g soil. This residue level is well below the recorded phytotoxic threshold of select cultivars of wheat, barley, and lucerne.

scholarly journals Development of a Shallow-Depth Soil Temperature Estimation Model Based on Air Temperatures and Soil Water Contents in a Permafrost Area

2020 ◽  
Vol 10 (3) ◽  
pp. 1058
Author(s):  
Keunbo Park ◽  
Yongwon Kim ◽  
Kichoel Lee ◽  
Dongwook Kim
Keyword(s):  
Soil Temperature ◽  
Soil Water ◽  
Air Temperature ◽  
Thermal Response ◽  
Shallow Depth ◽  
Estimation Model ◽  
Temperature Estimation ◽  
Layer Development ◽  
Water Contents ◽  
Soil Water Contents

A model for predicting shallow depth soil temperatures is important and effective to assess the changes in soil conditions related to global climate change and local disturbances. Shallow-depth soil temperature estimation model in cold region in Alaska is developed based on thermal response using air temperature and shallow-depth soil water content during active layer development period of 160 days from May to October. Among the seven soil temperature measurement sites, data from four sites were used for model development, and the remaining three sites were used for model validation. Near the middle of the seven measurement sites, air temperature is monitored at one location. The proposed model implemented concepts of thermal response and cumulative temperature. Temperatures and soil water contents were measured using automated remote sensing technology. Consequently, it was confirmed that the developed model enables fast and accurate assessment of shallow-depth soil temperature during active soil layer development period.

scholarly journals Simultaneous measurement of net nitrogen mineralization and denitrification rates in soil using nitrification inhibitor 3,5-dimethylpyrazole

2020 ◽  
Vol 100 (1) ◽  
pp. 1-10
Author(s):  
B.J. Zebarth ◽  
D.L. Burton ◽  
J. Spence ◽  
M.K. Khosa
Keyword(s):  
Soil Water ◽  
Soil Texture ◽  
N Mineralization ◽  
Sandy Loam ◽  
Pore Space ◽  
Nitrification Inhibitor ◽  
Net N Mineralization ◽  
Wide Range ◽  
Water Contents ◽  
Soil Water Contents

A practical means to quantify the response of the rates of net N mineralization and denitrification over a wide range of soil water contents is generally lacking. This study examined the potential to use a nitrification inhibitor (NI) assay system to simultaneously estimate the rates of net N mineralization and denitrification, and applied the NI assay to assess the effect of water content on net N mineralization and denitrification rates in two soils with contrasting soil texture. The compound 3,5-dimethylpyrazole (DMP) applied at a rate of 200 mg kg−1 was found to provide essentially complete inhibition of nitrification over the duration of the soil incubation for two soils with contrasting soil texture (clay loam vs. sandy loam) and over a range of soil water contents (35%, 55%, and 85% water-filled pore space). This allowed net N mineralization to be estimated as the accumulation of soil ammonium ([Formula: see text]) and of denitrification as the disappearance of added nitrate ([Formula: see text]). Addition of DMP resulted in a small increase in soil respiration rate but did not appear to influence the rate of net soil N mineralization. The NI assay provides a practical means to quantify the rates of net N mineralization and denitrification simultaneously over a wide range of soil water contents. The assay can be readily scaled up to routinely test multiple soils in an efficient manner, has limited material costs, and is also relatively simple to perform.

scholarly journals ANALYSIS THE WETTED AREA FOR SUBSURFACE DRIP IRRIGATION IN DIFFERENT SOILS TEXTURE

2020 ◽  
Vol 51 (2) ◽  
pp. 712-722
Author(s):  
Z. K. Rasheed
Keyword(s):  
Soil Water ◽  
Drip Irrigation ◽  
Sandy Loam ◽  
Irrigation System ◽  
Subsurface Drip Irrigation ◽  
Wetted Area ◽  
Subsurface Drip ◽  
Water Contents ◽  
Soil Water Contents ◽  
Volumetric Soil Water

Subsurface drip irrigation is one of the most efficient systems for management of water.  This study is aimed to analysis the wetted area for subsurface drip irrigation system.  Several models are developed for predicting the wetted widths and the wetted depths which are very important for designing an optimal irrigation system. HYDRUS/2D is used for predicting the dimensions of wetting patterns numerically by using the two dimensional transient flow of water from a subsurface drip irrigation through sandy loam and loamy sand soils.   The wetting patterns from a subsurface drip source are simulated by using the system of United States Department of Agriculture, USDA, the wetting patterns are simulated at different values of applied heads, different diameters of drip, and different values of initial volumetric soil water contents which selected as initial conditions.  In this work, greater spreading occurs in loamy sand than sandy loam in vertical and horizontal directions. Moreover, the results showed that the empirical formulas which can be used for estimating the wetting dimensions of wetted width and wetted depth in terms of initial volumetric soil water contents, applied heads, diameters of the drip and times of operation, are good with an average relative error not exceed 3%, so it can be used to assist the designers in irrigation field.

FLOW OF WATER INTO CERAMIC TUBES SIMULATING ROOT SYSTEMS

1972 ◽  
Vol 52 (1) ◽  
pp. 59-65
Author(s):  
D. S. STEVENSON
Keyword(s):  
Soil Water ◽  
Radial Flow ◽  
Sandy Loam ◽  
Porous Ceramic ◽  
Root Systems ◽  
Plant Roots ◽  
Silt Loam ◽  
Water Contents ◽  
Soil Water Contents

In model root systems constructed of porous ceramic tubing, accumulated outflow volumes of water from four inner tubes, simulating plant roots, surrounded by 12 outer tubes was reduced when spacings narrowed below 2.0 mm in both sandy loam and silt soils. Soil water contents and, simultaneously, capillary conductivity decreased faster at close tube spacings than at wider ones in the order of the decrease at 1.0 mm > at 1.5 mm > at 2.0 mm = that at 3.0 mm = that at 6.0 mm. The ratio of outflow from 12 tubes to that from four, surrounded by the 12, is 3 and constant if all tubes receive water from discrete equal-sized cylinders of soil. At less than 2.0 mm between tubes, the ratio increased with time to maximum of about 9 and 5 for sandy loam and silt loam, respectively, indicating soil cylinder overlap for the particular suction of −0.9 bar imposed on the tubes. At 2.0 mm spacing or greater, the ratio was relatively constant and reasonably close to 3. Radial flow of water may be quickly restricted at root spacings below some limiting distance that is probably dependent upon the demand potential at the soil–root interface.

scholarly journals The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

2021 ◽  
Vol 13 (4) ◽  
pp. 1759
Author(s):  
Said A. Hamido ◽  
Kelly T. Morgan
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Salinity ◽  
Planting Density ◽  
Stem Water Potential ◽  
Irrigation Rate ◽  
Biological Stress ◽  
Stem Water ◽  
Water Contents ◽  
Soil Water Contents

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

Soil aggregate breakdown in a field experiment with different rainfall intensities and initial soil water contents

2017 ◽  
Vol 68 (6) ◽  
pp. 853-863 ◽  
Author(s):  
P. Shi ◽  
S. Thorlacius ◽  
T. Keller ◽  
M. Keller ◽  
R. Schulin
Keyword(s):  
Field Experiment ◽  
Soil Water ◽  
Soil Aggregate ◽  
Aggregate Breakdown ◽  
Initial Soil ◽  
Water Contents ◽  
Soil Water Contents

MITIGATION YIELD SCALED METHANE EMISSION FROM RICE GROWN IN WATER STRESS CONDITIONS WITH BIOCHAR AND SILICATE AMENDMENTS

2021 ◽  
Author(s):  
MUHAMMAD ASLAM ALI ◽  
SANJIT CHANDRA BARMAN ◽  
MD. ASHRAFUL ISLAM KHAN ◽  
MD. BADIUZZAMAN KHAN ◽  
HAFSA JAHAN HIYA
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Field Capacity ◽  
Saturated Soil ◽  
Rice Grain ◽  
Standing Water ◽  
Water Contents ◽  
Soil Water Contents

Climate change and water scarcity may badly affect existing rice production system in Bangladesh. With a view to sustain rice productivity and mitigate yield scaled CH4 emission in the changing climatic conditions, a pot experiment was conducted under different soil water contents, biochar and silicate amendments with inorganic fertilization (NPKS). In this regard, 12 treatments combinations of biochar, silicate and NPKS fertilizer along with continuous standing water (CSW), soil saturation water content and field capacity (100% and 50%) moisture levels were arranged into rice planted potted soils. Gas samples were collected from rice planted pots through Closed Chamber technique and analyzed by Gas Chromatograph. This study revealed that seasonal CH4 emissions were suppressed through integrated biochar and silicate amendments with NPKS fertilizer (50–75% of the recommended doze), while increased rice yield significantly at different soil water contents. Biochar and silicate amendments with NPKS fertilizer (50% of the recommended doze) increased rice grain yield by 10.9%, 18.1%, 13.0% and 14.2%, while decreased seasonal CH4 emissions by 22.8%, 20.9%, 23.3% and 24.3% at continuous standing water level (CSW) (T9), at saturated soil water content (T10), at 100% field capacity soil water content (T11) and at 50% field capacity soil water content (T12), respectively. Soil porosity, soil redox status, SOC and free iron oxide contents were improved with biochar and silicate amendments. Furthermore, rice root oxidation activity (ROA) was found more dominant in water stress condition compared to flooded and saturated soil water contents, which ultimately reduced seasonal CH4 emissions as well as yield scaled CH4 emission. Conclusively, soil amendments with biochar and silicate fertilizer may be a rational practice to reduce the demand for inorganic fertilization and mitigate CH4 emissions during rice cultivation under water stress drought conditions.

scholarly journals Effect of Nano-Carbon on Water Holding Capacity in a Sandy Soil of the Loess Plateau

2017 ◽  
Vol 21 (4) ◽  
pp. 189-195 ◽  
Author(s):  
Beibei Zhou ◽  
Xiaopeng Chen
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Loess Plateau ◽  
Sandy Soil ◽  
Water Retention ◽  
Soil Mixture ◽  
Cumulative Infiltration ◽  
Nano Carbon ◽  
Water Contents ◽  
Soil Water Contents

The poor water retention capacity of sandy soils commonly aggregate soil erosion and ecological environment on the Chinese Loess Plateau. Due to its strong capacity for absorption and large specific surface area, the use of nanocarbon made of coconut shell as a soil amendment that could improve water retention was investigated. Soil column experiments were conducted in which a layer of nanocarbon mixed well with the soil was formed at a depth of 20 cm below the soil surface. Four different nanocarbon contents by weight (0%, 0.1%, 0.5%, and 1%) and five thicknesses of the nanocarbon- soil mixture layer ranging from 1 to 5 cm were considered. Cumulative infiltration and soil water content distributions were determined when water was added to soil columns. Soil Water Characteristic Curves (SWCC) were obtained using the centrifuge method. The principal results showed that the infiltration rate and cumulative infiltration increased with the increases of nanocarbon contents, to the thicknesses of the nano carbon-soil mixture layer. Soil water contents that below the soil-nano carbon layer decreased sharply. Both the Brooks-Corey and van Genuchten models could describe well the SWCC of the disturbed sandy soil with various nano carbon contents. Both the saturated water content (θs), residual water content (θr) and empirical parameter (α) increased with increasing nano carbon content, while the pore-size distribution parameter (n) decreased. The available soil water contents were efficiently increased with the increase in nanocarbon contents.

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