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In the acid paddy soil in Xiangtan, Hunan Province, rhizosphere chamber culture experiments were conducted to explore the remediation effects of sepiolite on cadmium (Cd) -contaminated soil using different depth treatments of the cultivated soil. The aim was to investigate the effects of sepiolite application depth on Cd bioavailability in soil, plant Cd absorption, and rhizosphere environment. The results showed that, compared with the control without sepiolite, the pH value of rhizosphere and non-rhizosphere soil increased by 1.00~ 1.16 and 0.59~1.21 units using treatments at depths of 20, 10, and 5 cm; further, the available Cd content in the rhizosphere and five nonrhizosphere soil layers decreased by 0.02%~3.40% and 1.00%~7.80%, respectively. In addition, when the sepiolite application depth was 5 cm (T2), the available Cd content of the rhizosphere and non-rhizosphere soil showed the largest decreases of 3.40% and 7.80%, respectively. Moreover, the Cd content of each part of the rice decreased after sepiolite treatments were applied at different depths, and the Cd content of each part of the rice had the biggest drop when the sepiolite was applied to the soil at a depth of 5 cm, preventing the root from reaching the unpassivated soil (T4) . Furthermore, compared to the control, the Cd content of the root decreased significantly (P<0.05) . At the same time, the plant height and yield of rice increased with treatments at different depths; the biggest rise was with treatments of T2 and T4, with significant differences (P<0.05) . Overall, it could be seen that the application of sepiolite in shallow tillage (a treatment applied under the 5 cm plow layer) resulted in the best effect in reducing soil Cd bioavailability, and it also reduced the Cd content in rice and significantly increased rice yield. [ABSTRACT FROM AUTHOR]

An experiment was conducted to determine the depth of urea supergranule (USG) application that reduces ammonia (NH3) volatilization and improves nitrogen use efficiency of rice. Canne, Voudou, Akuse, and Bumbi series were used. Treatments involved surface application of prilled urea (PU), USG applied at 0, 4, 8, 12 and 16 cm depths and a control. Rice variety IR-841 was grown up to maturity. Closed chamber device was used to trap NH3. Results indicated that the highest mean NH3 loss occurred in Bumbi series (13.67%) while the lowest was Canne series (8.16%). USG applied at 0 cm resulted in the highest NH3 loss (37.2%). NH3 volatilization decreased with increasing depth of USG application. The highest grain yields were obtained when USG was applied at 4 and 8 cm. In Canne series, the highest agronomic use efficiency (AE) of N (57 g g−1) was obtained with USG applied either at 8 or 12 cm while the highest recovery efficiency (RE) (84%) occurred at 8 cm. In Akuse series, the highest AE (55 g g−1) and RE (78%) were obtained when USG was placed at 8 cm. In Voudou and Bumbi series, the highest AE (45 and 48 g g−1 respectively) and RE (64%) were obtained with USG deep placed at 4 cm. The results therefore suggested different specific depths of USG application to reduce ammonia loss and improve nitrogen use efficiency. [ABSTRACT FROM AUTHOR]

This study investigated the effect of the digestate application depth on soil nitrogen volatilization and vertical distribution in black loam soil and sandy loam column. The contents of soil moisture, TKN (total Kjeldahl nitrogen), ammonium nitrogen, nitrate nitrogen, and the extent of ammonia volatilization were tested by applying digestate at depths of 0 cm, 2 cm, 6 cm, 10 cm, 15 cm and 20 cm, respectively. The experimental results showed that ammonia volatilization mainly occurred in the first 10 days and reduced significantly when the application depth was deeper than 10 cm. At the same application depth, compared with the black loam, the nitrogen loss in sandy loam through ammonia volatilization was less, and the penetration depth of nitrate nitrogen and ammonium nitrogen were all deeper. In the same soil, nitrate nitrogen penetrated deeper than ammonium nitrogen at all application depths. [ABSTRACT FROM AUTHOR]

An operational-scale transfer of salvaged forest floor material (FFM) containing trembling aspen ( Populus tremuloides Michx.) roots was done to explore its feasibility for aspen forest restoration on heavily disturbed lands. This technique takes advantage of aspen's ability of regenerate vegetatively from root fragments. Surface soils from an intact 4 ha aspen forest were salvaged at two depths (15 cm and 40 cm) and immediately placed onto a reclamation site of the same size and at the same two depths. Over the next two growing seasons, aspen sucker density, mortality, and height growth were assessed in relation to root fragment density, burial depth, and root fragment size. Sucker density, height growth, and survival increased with salvage and placement depth, likely related to the fact that deeper salvage depths allowed for more roots to be in good mineral soil contact and proportionately fewer roots to be placed close to the surface (0-5 cm), decreasing their risk of exposure. Large-diameter root fragments buried deeper than 20 cm did not produce viable suckers, so placement of FFM thicker than 20 cm cannot be recommended for the vegetative regeneration of aspen. However, if possible, a deeper salvage of the FFM that contains the aspen root system could allow the material containing the roots to be spread over a larger area and still achieve vegetative regeneration of aspen from suckering, although the overall root propagule density is lower. [ABSTRACT FROM AUTHOR]

Application uniformity coefficient is an important parameter to quantify the quality of water distributions. When applying variable rate irrigation through a center pivot sprinkler system, the uniformity of water application both in the direction of pivot travel and along the pivot lateral within each management zone is greatly concerned. In this study, a variable rate irrigation (VRI) system was retrofitted from one three-span (140 m) conventional center pivot system outfitted with 34 rotating sprinklers spaced at 4.2 m through installing solenoid valve, pressure regulator, frequency transformer and control software. The performance of the constructed VRI system was evaluated under 3 typical operating conditions: all sprinklers on, partial sprinklers off, and sprinklers regulated by "on/off" pulsing of the solenoid valves. Catch-cans were arranged in transect, arc-wise, and grid patterns to test the accuracy of application depth in the direction of pivot travel and along the pivot lateral. The results indicated that the modified Heermann and Hein uniformity coefficient (CUHH) and the lower quarter distribution uniformity (DUlq) along the pivot lateral ranged from 92% to 94% and from 87% to 89% under condition of all sprinklers on, respectively, when the pivot rotation speed was changed between 20% and 100% of the full speed. This suggested a minor influence of moving speed of center pivot on application uniformity along the pivot lateral. In the direction of pivot travel, a uniform water distribution was observed with CUHH 95% and DUlq 93% regardless of pivot rotation speeds and measuring locations. A target water application depth could be obtained accurately through setting a specific rotation speed of the pivot. Under the conditions of variable rate irrigation, uniform water distributions in the direction of pivot travel were received with the uniformities similar to the values under all sprinklers on. However, the CUHH and DUlq values along the pivot lateral were reduced by 10 and 19 percentiles for partial sprinklers off, respectively, decreasing with an increasing number of sprinkler banks. The CUHH and DUlq values were reduced by 9 and 12 percentiles when sprinklers were regulated by "on/off" pulsing of the hydraulic valves. This reduction was positively related to the difference in application depth between the adjacent management zones. Application uniformity was impacted at the border of adjacent irrigation zones along the pivot lateral when the zones were applying different irrigation depths. To guarantee CUHH=85% within each management zone along the pivot lateral, a 0 to 3 m wide buffer zone should be implemented between adjacent irrigation zones when partial sprinklers were turned off, and a 0 to 4 m wide buffer zone should be used when sprinklers were regulated by "on/off" pulsing of the hydraulic valves. The accuracy of application depth obtained through regulating moving speed of variable rate center pivot irrigation system was related to pivot speed and duty cycle of solenoid valve. Overall, the actual application depth was 0.48 mm and 1.46 mm underestimated when variable rate irrigations were achieved by partial sprinklers off and by sprinklers regulated by "on/off" pulsing of the hydraulic valves, respectively. [ABSTRACT FROM AUTHOR]

EM-MWD systems transmit downhole data via an information channel composed of drill string and formation, and the formation has a strong attenuation effect on the signal. Signal attenuation in EM wave transmission in the formation limits the application well depth. This paper discusses several commonly used methods to improve the depth of EM-MWD applications, including turbine power supplies, adaptive power outputs, transmitting antenna extensions, and repeater transceivers. Based on both theory and practice, the characteristics of these methods are analyzed. An EM-MWD system in which signals are received from an adjacent well is proposed, and a formula for calculating the receiving voltage for an adjacent well is derived based on a model of this system. According to this formula, the proposed EM-MWD system can greatly increase the receiving voltage, where deeper adjacent wells provide a greater increase in the receiving voltage and a greater maximum transmission depth for the EM-MWD system. In-hole experiments of this EM-MWD system based on signals received from an adjacent well demonstrate that this method can effectively increase the voltage of the received signals on the ground, in agreement with theoretical results. • This paper discusses several methods to improve the depth of EM-MWD applications. • An EM-MWD system in which signals are received from an adjacent well is proposed. • A formula for calculating the receiving voltage of the system is derived. • Experiments demonstrate that this method can effectively increase received voltage. [ABSTRACT FROM AUTHOR]

Abstract: The study was carried out at the experimental station of the Japan International Research Center for Agricultural Sciences to investigate gas fluxes from a Japanese Andisol under different N fertilizer managements: CD, a deep application (8cm) of the controlled release urea; UD, a deep application (8cm) of the conventional urea; US, a surface application of the conventional urea; and a control, without any N application. NO, N2O, CH4 and CO2 fluxes were measured simultaneously in a winter barley field under the maize/barley rotation. The fluxes of NO and N2O from the control were very low, and N fertilization increased the emissions of NO and N2O. NO and N2O from N fertilization treatments showed different emission patterns: significant NO emissions but low N2O emissions in the winter season, and low NO emissions but significant N2O emissions during the short period of barley growth in the spring season. The controlled release of the N fertilizer decreased the total NO emissions, while a deep application increased the total N2O emissions. Fertilizer-derived NO–N and N2O–N from the treatments CD, UD and US accounted for 0.20±0.07%, 0.71±0.15%, 0.62±0.04%, and 0.52±0.04%, 0.50±0.09%, 0.35±0.03%, of the applied N, respectively, during the barley season. CH4 fluxes from the control were negative on most sampling dates, and its net soil uptake was 33±7.1mgm−2 during the barley season. The application of the N fertilizer decreased the uptake of atmospheric CH4 and resulted in positive emissions from the soil. CO2 fluxes were very low in the early period of crop growth while higher emissions were observed in the spring season. The N fertilization generally increased the direct CO2 emissions from the soil. N2O, CH4 and CO2 fluxes were positively correlated (P<0.01) with each other, whereas NO and CO2 fluxes were negatively correlated (P<0.05). The N fertilization increased soil-derived global warming potential (GWP) significantly in the barley season. The net GWP was calculated by subtracting the plant-fixed atmospheric CO2 stored in its aboveground parts from the soil-derived GWP in CO2 equivalent. The net GWP from the CD, UD, US and the control were all negative at −243±30.7, −257±28.4, −227±6.6 and −143±9.7gCm−2 in CO2 equivalent, respectively, in the barley season. [Copyright &y& Elsevier]

To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N2O, CH4 and CO2 from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004. Trace gas flux measurements were made 2–3 times per week, in zero-N fertilizer plots that were cropped continuously to corn ( Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0, 5 and 10 cm in Exp. 2, respectively) were used. Liquid urea–ammonium nitrate (UAN, 224 kg N ha−1) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N2O, CH4 and CO2 ranged from 3.9 to 5.2 μg N m−2 h−1, 60.5 to 92.4 μg N m−2 h−1, −0.8 to 0.5 μg C m−2 h−1, and 42.1 to 81.7 mg C m−2 h−1 in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N2O emissions compared with shallow N placement (0 and 5 cm) while CH4 and CO2 emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged N2O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission and CH4 oxidation but increased N2O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N2O, CH4 and CO2 was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT- and NT-soils. [ABSTRACT FROM AUTHOR]

This study presents the results of a four-year field experiment assessing the effectiveness of phosphorus application in maize cultivation according to the depth of two-component fertilizer (NP) placement in the soil layer, type of nitrogen fertilizer and date of application. Nitrogen utilization from mineral fertilizer was low—on average, 37.1% during the four years of research. The nitrogen metabolism index, measuring the agricultural and physiological efficiency of nitrogen use, confirmed the significant impact of NP fertilizer placement at 10 and 5 cm as optimal in maize fertilization. The use of nitrogen in maize cultivation before sowing, compared to the application of this component at the phase of 5-6 leaves BBCH 15/16 stage (stage of leaf development with five–six leaves unfolded), significantly increased the agricultural and physiological effectiveness of nitrogen applied in mineral fertilizer. Ammonium nitrate application before sowing the maize, compared to top dressing at the BBCH 15/16 stage, significantly increased nitrogen uptake and utilization from mineral fertilizer. Date of urea fertilizer application to the soil did not have a significant impact on these indicators in maize cultivation. [ABSTRACT FROM AUTHOR]