Irrigation Events Research Articles

The Effect of Salinity on the Growth and Nutrient Status of Zinnia Grown Under Short- and Long-cycle Subirrigation Management

As water resources become limited, agricultural producers must resort to alternative sources for irrigation, including municipal reclaimed water which may contain impurities such as salts that can adversely impact irrigation management practices and crop yield. To test the effects of salinity on plant growth and nutrient composition under greenhouse conditions, zinnia (Zinnia elegans) was produced under two different subirrigation management regimes and exposed to various concentrations of NaCl to simulate the crop production challenges associated with poor water quality. Plants received either short- or long-cycle subirrigation to achieve differing levels of potting medium saturation at each irrigation event. Plants under these two irrigation management regimes were challenged with NaCl at concentrations up to 1.5 g·L−1 or 3 dS·m−1. Zinnia plants accumulated more Na in shoot tissues as salinity in the irrigation water increased from 0 to 1.5 g·L−1. The electrical conductivity (EC) in the potting medium also increased over time, and the rate of leaf area expansion decreased with increasing levels of salinity in the irrigation water. Short-cycle irrigation management has been shown to increase fertilizer and water use efficiency (WUE), thereby reducing the costs associated with these resources and also reducing the environmental impacts of agricultural crop production. In our study, the medium under short-cycle subirrigation management had lower gravimetric water content (GWC), both before and after irrigation, than the medium under long-cycle subirrigation, but the drier medium conditions did not increase susceptibility to salt injury. Furthermore, plants grown under short-cycle irrigation management for 4 to 6 weeks accumulated less Na in shoot tissue than plants grown under long-cycle irrigation management. Sodium accumulation in the shoot tissues was a product of both the amount of sodium in the irrigation solution and the amount of water used by the plant over time. Therefore, short-cycle subirrigation can be used as an effective water management technique even when raw water quality is poor as represented by elevated salinity. Our research indicates that zinnia can be irrigated with saline water up to 0.5 g·L−1 NaCl (an EC of 1 dS·m−1) in a 5-week production cycle without adverse effects on growth.

Modeling sprinkler irrigation infiltration based on a fuzzy-logic approach

In this study, the irrigation water infiltration rate (IR) is defined by input variables in linguistic terms using a fuzzy-logic approach. A fuzzy-logic model was developed using data collected from published data. The model was trained with three fuzzy membership functions: triangular (‘trimf’), trapezoid (trapmf), and pi (‘pimf’). The fuzzy system considered the number of irrigation events, applied water depth, polyacrylamide application rate, water application time, water electrical conductivity, soil surface slope, and soil texture components as input variables. The inputs were classified in terms of low, medium, and high levels. The output variable (i.e., IR) was rated in terms of five levels: very low, low, medium, high, and very high. Using statistical analysis, the values of IR resulting from the developed fuzzy-logic model were compared with the observations from the experiments. The results confirm that the agreement between the observations and predictive results was acceptable, except for fuzzy 'trimf'. The coefficient of determination provided the greatest value when using the 'trapmf' and 'pimf', with the value estimated for the 'pimf' slightly higher than that of 'trapmf'. Based on the results that were obtained, irrigation managers can use the fuzzy-logic approach to modify their field practices during the growing season to improve on-farm water management.

Comparing canopy temperature and leaf water potential as irrigation scheduling criteria of potato in water-saving irrigation strategies

Irrigation scheduling is important in irrigation water management. In this study, full (FI),deficit (DI) and partial root drying (PRD) irrigation strategies were applied in Agria and Ramospotato cultivars. Canopy temperature (CT) and leaf water potential (LWP) were assessed as thepotential tools for irrigation scheduling during the vegetative and productive growth stages.LWP varied between ca. -1.4 and -1.6 MPa and was not significantly different between FI, DIand PRD irrigation treatments. The LWP and CT values were not significant between the twopotato cultivars during the measurements, but CT was frequently significant between theirrigation treatments such that the PRD treatments were significantly 5 and 2 oC warmer than FIand DI treatments, respectively. Higher CT in PRD caused significant yield penalty such that DIand FI produced almost two times higher fresh tuber yield. Analysis revealed that CT hadsignificantly higher correlation (r=0.66) with water productivity (weight of fresh tuber yielddivided by volume of applied irrigation water) than LWP, which its correlation was notsignificant (r=0.40). This showed that crop water productivity could be better controlled by CT.Moreover, it was realized that the seven-day irrigation interval was far longer than required andpotatoes in all irrigation treatments were under water stress, especially in PRD, that mightpartially explain the 50% yield penalty of PRD compared to DI. The reason was that due to highatmospheric demand, soil water in the wet part of the root system would be completely depletedearlier by the time of next irrigation event. Conclusively, the CT is recommended as a morereliable crop water status and irrigation scheduling indicator than LWP in response to differentwater-saving irrigation managements.

3D soil water nowcasting using electromagnetic conductivity imaging and the ensemble Kalman filter

Mapping and immediate forecasting of soil water content (θ) and its movement can be challenging. Although inversion of apparent electrical conductivity (ECa) measured by electromagnetic induction to calculate depth-specific electrical conductivity (σ) has been used, it is difficult to apply it across a field. In this paper we use a calibration established along a transect, across a 3.94-ha field with varying soil texture, using an ensemble Kalman filter (EnKF) to monitor and nowcast the 3-dimensional θ dynamics on 16 separate days over a period of 38days. The EnKF combined a physical model fitted with θ measured by soil moisture sensors and an Artificial Neural Network model comprising σ generated by quasi-3d inversions of DUALEM-421S ECa data. Results showed that the distribution of θ was controlled by soil texture, topography, and vegetation. Soil water dried fastest at the beginning after the initial irrigation event and decreased with time and soil depth, which was consistent with classical soil drying theory and experiments. It was also found that the soil dried fastest in the loamy and duplex soils present in the field, which was attributable to deep drainage and preferential flow. It was concluded that the EnKF approach can be used to improve the irrigation efficiency by applying variable irrigation rates across the field. In addition, soil water status can be nowcasted across large spatial extents using this method with weather forecast information, which will provide guidance to farmers for real-time irrigation management.

Simulated Summer Rainfall Variability Effects on Loblolly Pine (Pinus taeda) Seedling Physiology and Susceptibility to Root-Infecting Ophiostomatoid Fungi

Seedlings from four families of loblolly pine (Pinus taeda L.) were grown in capped open-top chambers and exposed to three different weekly moisture regimes for 13 weeks. Moisture regimes varied in intensity and frequency of simulated rainfall (irrigation) events; however, the total amounts were comparable. These simulated treatments were chosen to simulate expected changes in rainfall variability associated with climate change. Seedlings were inoculated with two root-infecting ophiostomatoid fungi associated with Southern Pine Decline. We found susceptibility of loblolly pine was not affected by water stress; however, one family that was most sensitive to inoculation was also most sensitive to changes in moisture availability. Many studies have examined the effects of drought (well-watered vs. dry conditions) on pine physiology and host-pathogen interactions but little is known about variability in moisture supply. This study aimed to elucidate the effects of variability in water availability, pathogen inoculation and their interaction on physiology of loblolly pine seedlings.

Optimizing preplant irrigation for maize under limited water in the High Plains

Due to inadequate irrigation capacity, some farmers in the United States High Plains apply preplant irrigation to buffer the crop between irrigation events during the cropping season. The purpose of the study was to determine preplant irrigation amount and irrigation capacity combinations that optimize yield, water productivity, and precipitation use efficiency (PUE) and minimize soil water evaporation losses prior to planting. The CERES-Maize model embedded in the RZWQM2 model in combination with long-term climatic data from 1986 to 2014 for southwest Kansas were used for this research.Experimental data from 2006 to 2009 was used to calibrate and validate the model. Model performance was satisfactory with high index of agreement (IA>0.88). Relative root mean square error (RRMSE) ranged between 4.5% and 27%. Under very limited irrigation capacity (2.5mm/day), applying 75–100mm of preplant irrigation produced median yields that were 10–17% higher than not applying preplant irrigation. However, even at limited irrigation capacity the benefit of preplant irrigation were only realized if the seasonal yield potential was in the range of 6000 to 10,000kg/ha corresponding to years with normal seasonal rainfall. Irrigation capacity had a stronger effect on maize grain yield compared to preplant irrigation amount. Preplant irrigation increased ET and transpiration under 2.5mm/day irrigation capacity. Preplant irrigation amount did not have a substantial impact on water productivity at high and moderate irrigation capacity but had second order dominant effect under limited irrigation capacity. At low irrigation capacity (2.5mm/day) increasing preplant irrigation increased median PUE up to 18% although the effect was second order dominant. Negligible water losses through deep percolation from 2.4m soil profile were simulated. Increasing preplant irrigation resulted in significantly higher soil water evaporation losses prior to planting at all irrigation capacities. Overall preplant irrigation is beneficial under very limited irrigation capacity but is not necessary under sufficient irrigation capacity in most years. The decision to apply preplant irrigation should be evaluated and implemented carefully in combination with other agricultural water management technologies and strategies such as soil water monitoring, drip irrigation, and residue management.

Nitrogen Dynamics of Strawberry Cultivation in Vermicompost-Amended Systems

ABSTRACTThe use of vermicompost as a soil amendment is suggested as a method to reduce nitrogen (N) losses in crop production; however, it is unclear whether and how vermicompost can affect water quality after a significant irrigation or rainfall event. Bare-root strawberry plugs were grown in 1-gallon plastic pots. The treatments consisted of two media: (1) a peat:perlite soil-less mix and (2) a fine sand soil. Each media was amended with three levels of dairy manure vermicompost: 0, 10, and 25% by weight, and a biweekly synthetic fertilizer treatment of 150 mg N-P-K L−1 evaluated in a full factorial randomized block design. Drainage water from each plant was collected each week for 18 weeks and analyzed for NO3− concentration. In the first 2 weeks, high (1000–5000 mg L−1) amounts of NO3− leaching occurred in all vermicompost-amended media relative to non vermicompost-amended media, but this leaching significantly (p < 0.01) decreased over time across all vermicompost treatments. Strawberry growth response to 10% vermicompost was similar to synthetic fertilizer only treatments. Plants grown with vermicompost at 25% with synthetic fertilizer had the highest above-ground vegetative biomass (15.3 g) relative to plants with synthetic fertilizer only (5.3 g). These data suggest vermicompost addition rates of 10 and 25% by weight promote high vegetative biomass in greenhouse strawberry but may facilitate high initial nitrate leaching, which can negatively affect water quality and environmental health.

Development of a new method for determination of infiltration coefficients in furrow irrigation with natural non-uniformity of slope

In this study, a new method was developed to calculate the infiltration coefficients in furrow irrigation with natural non-uniformity of longitudinal slope. For this purpose, 12 usual tilled furrows with 42 m length and 60 cm width were selected. Then, five irrigation events were carried out and the advance-recession and inflow-outflow data were collected. The parameters of the infiltration equation in power-polynomial form (Kostiakov–Lewis) were calculated using the volume-balance (VB) method and based on a power model as advance equation. The non-uniform longitudinal slope in furrows was purposefully made, so that the advance function should not to follow a usual power function, and the power of function to be more than one in some cases. Besides, in some irrigation events, the negative infiltration equation was obtained. Accordingly, from analysis of VB equation components, several modifications were incorporated in procedure of parameter estimation. Some of these modifications include fitting a quadratic function for advance data and calculating the flow cross-sectional area from maximum surface storage value. Volume of infiltrated water was calculated using this method in each irrigation, and compared with the measured volume based on the inflow and outflow hydrographs as a control. The results showed that using the presented method, the average error in computed infiltrated volumes was reduced to about 4%, which validates the application of the new method.

Surface Water and Groundwater Interactions in Traditionally Irrigated Fields in Northern New Mexico, U.S.A.

Better understanding of surface water (SW) and groundwater (GW) interactions and water balances has become indispensable for water management decisions. This study sought to characterize SW-GW interactions in three crop fields located in three different irrigated valleys in northern New Mexico by (1) estimating deep percolation (DP) below the root zone in flood-irrigated crop fields; and (2) characterizing shallow aquifer response to inputs from DP associated with irrigation. Detailed measurements of irrigation water application, soil water content fluctuations, crop field runoff, and weather data were used in the water budget calculations for each field. Shallow wells were used to monitor groundwater level response to DP inputs. The amount of DP was positively and significantly related to the total amount of irrigation water applied for the Rio Hondo and Alcalde sites, but not for the El Rito site. The average irrigation event DP using data for the complete irrigation season at each of the three sites was 77.0 mm at El Rito, 54.5 mm at Alcalde and 53.1 mm at Rio Hondo. Groundwater level rise compared to pre-irrigation event water levels ranged from 3 to 1870 mm, and was influenced by differences in irrigation practices between sites. Crop evapotranspiration estimates averaged across irrigation events were highest in Rio Hondo (22.9 mm), followed by El Rito (14.4 mm) and Alcalde (10.4 mm). Results from this study indicate there are strong surface water-groundwater connections in traditionally irrigated systems of northern New Mexico, connections that may be employed to better manage groundwater recharge and river flow.

Strengths and weaknesses of temporal stability analysis for monitoring and estimating grid‐mean soil moisture in a high‐intensity irrigated agricultural landscape

AbstractMonitoring and estimating grid‐mean soil moisture is very important for assessing many hydrological, biological, and biogeochemical processes and for validating remotely sensed surface soil moisture products. Temporal stability analysis (TSA) is a valuable tool for identifying a small number of representative sampling points to estimate the grid‐mean soil moisture content. This analysis was evaluated and improved using high‐quality surface soil moisture data that were acquired by a wireless sensor network in a high‐intensity irrigated agricultural landscape in an arid region of northwestern China. The performance of the TSA was limited in areas where the representative error was dominated by random events, such as irrigation events. This shortcoming can be effectively mitigated by using a stratified TSA (STSA) method, proposed in this paper. In addition, the following methods were proposed for rapidly and efficiently identifying representative sampling points when using TSA. (1) Instantaneous measurements can be used to identify representative sampling points to some extent; however, the error resulting from this method is significant when validating remotely sensed soil moisture products. Thus, additional representative sampling points should be considered to reduce this error. (2) The calibration period can be determined from the time span of the full range of the grid‐mean soil moisture content during the monitoring period. (3) The representative error is sensitive to the number of calibration sampling points, especially when only a few representative sampling points are used. Multiple sampling points are recommended to reduce data loss and improve the likelihood of representativeness at two scales.

Impact of Substrate Volumetric Water on Pythium aphanidermatum Infection in Petunia ×hybrida: A Case Study on the Use of Automated Irrigation in Phytopathology Studies

Real-time irrigation monitoring and control afforded by dielectric soil moisture sensors allows for precise substrate volumetric water content (VWC) to be maintained under dynamic experimental conditions. A case study was conducted with Petunia ×hybrida ‘Dreams Red’ grown using a sensor-based irrigation system with half of the plants infected with Pythium aphanidermatum. Four soilless substrate moisture profiles were maintained postinoculation, with VWCs set at 0.2, 0.3, and 0.4 m3/m3, as well as a cyclic soil moisture profile that underwent a 0.25-m3/m3 change in VWC (0.18 to 0.43 m3/m3) between irrigation events. Once established, half of the plants in each trial were inoculated and grown out for one month under the defined irrigation regimes. The probability of root infection was lowered when VWC was maintained at 0.2 m3/m3 compared with 0.4 m3/m3 and cyclic (0.18 to 0.43 m3/m3) VWC. Mortality and biomass were unaffected by irrigation regime in both uninoculated and inoculated treatments. The soil moisture-sensor-based automated irrigation system was successfully able to maintain programmed irrigation profiles throughout the trial, under dynamic greenhouse conditions, increasing trust in the data and resulting conclusions of the study.

Implementing Standardized Reference Evapotranspiration and Dual Crop Coefficient Approach in the DSSAT Cropping System Model

Abstract. While methods for estimating reference evapotranspiration (ETo or ETr) and subsequent crop ET (ETc) via crop coefficient (Kc) and dual crop coefficient (Kcb, Ke) methods have been standardized since 2005 and 1998, respectively, the current version of the DSSAT cropping system model (CSM) has not been updated to fully implement these methods. In this study, two major enhancements to the model’s ET routines were evaluated: (1) addition of the ASCE Standardized Reference Evapotranspiration Equation so that both grass and alfalfa reference ET were properly calculated using the most recent reference ET standard and (2) addition of the FAO-56 dual crop coefficient approach to determine potential ET, which combined an evaporative coefficient (Ke) for potential evaporation with a dynamic basal crop coefficient (Kcb) for potential transpiration as a function of simulated leaf area index. Previously published data sets for maize in Colorado (five years) and cotton in Arizona (seven years) were used to parameterize the model. Simulations of ETo were compared to outputs from Ref-ET software, and simulated crop coefficients were contrasted among three crop coefficient methods: the current approach (Kcs), a previously published adjustment to the model’s Kc equation (Kcd), and a new dual Kc approach that follows FAO-56 explicitly (Kcb). Results showed that crop coefficient simulations with the new ETo-Kcb method better mimicked theoretical behavior, including spikes in the soil evaporation coefficient (Ke) due to irrigation and rainfall events and basal crop coefficient response as associated with simulated crop growth. Simulated ETc and yield with the new ETo-Kcb method were up to 4% higher and 28% lower for cotton and up to 13% higher and 26% lower for maize, respectively, than that with the current ETo-Kcs method, indicating that the seasonal ETc effects were minimal while yield effects were more substantial. Use of FAO-56 concepts and current ET standards in DSSAT-CSM demonstrated a well-accepted ET benchmark to guide assessment of other ET methods in the model and made the model much more conceptually relevant to irrigation and ET specialists. Keywords: Cotton, DSSAT, Evaporation, Evapotranspiration, FAO-56, Maize, Reference crop ET, Standardization, Transpiration.

Optimization of an automatic irrigation system for precision irrigation of blueberries grown in sandy soil

An experiment was carried out to assess the performance of an automatic irrigation system based on remotely-sensed soil moisture measurements in blueberries grown in sandy soil under plastic tunnels. The system uses the information provided by soil moisture sensors installed at three soil depths (10, 20 and 30 cm) and user-defined irrigation set-points to trigger automatic irrigation events. An Optimized irrigation treatment in which irrigation set-points and duration of irrigation have been determined from soil hydraulic properties analysis and soil water modelling is compared to the irrigation scheduling criteria established by the grower (Control treatment). The results showed that the Optimized treatment applied 30% of the water applied by the Control treatment, led to mild to moderate crop water stress conditions and had no impact on berry yield and quality.

Automatic Irrigation Control System for Soilless Culture Based on Feedback from Drainage Hydrograph

Abstract. In a soilless culture, water and nutrients must be frequently and precisely applied due to the reduced volume and low water holding capacity of the substrate. We describe a low-cost and efficient control system for the irrigation management of soilless culture based on an irrigation tray. Both irrigation and drainage volumes from the irrigation control tray are measured automatically. The proposed irrigation scheduling options were based on applying both variable timing and amounts. A Proportional Integral Derivative (PID) algorithm was used to establish the irrigation timing option while two different irrigation application options, based on measurements from the drainage hydrograph, were developed and tested. A field test performed on a tomato crop was carried out to assess the performance of the two irrigation application options. Both irrigation algorithms performed well as they fitted the leaching fraction for every irrigation event to the target value. The fruit yield and quality were comparable to results obtained from the control treatment of the tomato crop. The designed low-cost irrigation control system, if implemented on commercial farms, could prove to be economically very beneficial. Keywords: Automation, Drainage hydrograph, Irrigation control tray, Irrigation scheduling, Proportional-Integral-Derivative (PID) controller, Substrate culture.

Field Assessment of Basin Irrigation Performance in Hetao, Inner Mongolia

Hetao irrigation district (Hetao) is located in the upper reaches of Yellow River basin. Surface irrigation is used because there is a high charge of sediments in the irrigation water and is appropriate to leach salts. Basin irrigation is the most used irrigation method. Traditional practices are inadequate for saving water and surface irrigation modernization is needed. A better knowledge of the performance of irrigation systems is required to base that modernization. An experimental research work was developed at Dengkou Experimental Station to assess the irrigation performance in laser land leveled fields. It is located on an irrigation sector supplied in agreement with a rotational delivery scheme managed by the Water Users Association (WUA), which usually practices a total of 7 events and the autumn irrigation. The typical field length is 50 m, with a width between 10 and 50 m, with a silt loamy soil. The irrigation performance was assess from field measurements carried out in several fields, cropped with the main irrigated crops, wheat, maize and sunflower. The irrigation field evaluation was based on observations of advance and recession times, soil moisture, inflow discharges, application time, topographic survey and crop development data. In addition, infiltration curves for typical and seasonal irrigation events were developed, and the Kostiakov infiltration parameters were estimated from field observations using the inverse method with the SIRMOD model. The irrigation operative parameters and the performance indicators were obtained, concluding that the distribution uniformity is very high, between 90 and 96%, and that the cutoff time has a very sensitive effect on beneficial water use fraction. Finally, the results of this study allowed the appropriate knowledge, including the crop irrigation scheduling data, for the irrigation design models aimed at developing irrigation alternatives.

A large-scale lysimeter study of stormwater biofiltration under cold climatic conditions

Stormwater biofiltration was studied at a large-scale lysimeter facility in southern Finland. Biofiltration systems, constructed within eight lysimeters, consisted of an organic topsoil, a sand layer and three gravel layers of varying gravel size underneath. Six of the lysimeter systems were vegetated with Phalaris arundinacea, Salix glauca var. callicarpaea and Lythrum salicaria, and two systems were left unplanted. The effect of vegetation on the functioning of the systems was studied by comparing the vegetated with the non-vegetated systems. The systems were irrigated during three seasons with artificial stormwater containing nitrate, phosphate, zinc, copper and aluminium to study pollutant retention and water infiltration during warm and cold temperatures. Half of the systems also received road salt (NaCl) to study its effect on the functioning of the systems. Phosphate, zinc and copper were well retained (81–98%) during each season in each system. Nitrate retention improved (from 0 to 47%) with time in the vegetated system but negative retention was also observed during some irrigation events, indicating that nitrate also leached from the parent soil. The retention of aluminium in the unsalted biofilters decreased (from ca. 80 to 0%) during the snowmelt season in spring and was highly negative in the salted systems during spring and summer. Salt also slightly diminished (ca. 8%) the retention of Cu. Vegetation only improved the retention of nitrate. However, the non-vegetated systems infiltrated water poorly while the vegetated systems infiltrated large volumes and intensities of water one year after biofilter establishment. Hence, vegetation was necessary for operational infiltration. The study showed positive results for stormwater biofiltration in cold climates. Nonetheless, long-term studies with varying soil types and pollutants are recommended.

Improvements of soil salt characteristics and nutrient status in an impermeable saline–sodic soil reclaimed with an improved drip irrigation while ridge planting Lycium barbarum L.

Takyric solonetz is spread widely across the arid area of northwest China. The extremely poor soil structure and low hydraulic conductivity (Ks < 0.1 mm day−1) hinder its amelioration. The purpose of this study was to investigate the soil salt leaching characteristics, nutrient contents, and distributions in the impermeable saline–sodic soil reclaimed with an improved drip irrigation method, and to explore the impacting mechanisms of agronomic practices involved on the amelioration. A 3-year field experiment was conducted to investigate the success of planting Lycium barbarum L. in the highly saline–sodic wasteland of takyric solonetz using drip irrigation. The soil beneath the drip emitters near the plants was replaced with sand in niches that were 0.2 m in ground diameter and 0.2 m deep. Five treatments based on soil matric potential (SMP) were designed to find the optimal irrigation schedule: −5 kPa (S1), −10 kPa (S2), −15 kPa (S3), −20 kPa (S4), and −25 kPa (S5). A significant improvement was found in soil infiltration capability, which was demonstrated by the increasingly enlarged wetted area beneath the drip emitter. This improvement was resulting from the combined affects of all the agronomic practices involved, including drip irrigation, sand-filled niches, film mulching. After 3 years, soil salt leaching rates in S1–S5 root zones were 68.16 , 39.45 , 26.56 , 25.14 and 10.40%, respectively, indicating that the higher SMP improved soil salt leaching. The increased soil ECe/SAR ratio reflected the amelioration of soil physical properties. After planting, the soil nutrient status considerably improved. N fertilizer, which often was leached away, should be applied in the latter half of an irrigation event. Available P content in the soil was relatively low and it was necessary to apply adequate P fertilizer to meet crop growth needs, while the studied soil was rich in K and moderate supplement of K fertilizer was proposed. After 3 years, S2, S3, and S4 produced the significantly higher dry fruit yields (∼900 kg ha−1), which were close to those produced by local farmland. Our findings indicated that an improved drip irrigation made the reclamation of an impermeable saline–sodic soil possible. The key operations included drip irrigation, sand-filled niches beneath drip emitters, ridge tillage, film mulching, and the use of thresholds to control SMP.

Heavy metal elimination from industrial wastewater using natural substrate on pitcher irrigation

Combination of pitcher irrigation with drip irrigation system could be resulted in prolonging the secondary treatment period, as it could be an efficient system in which municipal and industrial wastewater can be treated and heavy metals can be reduced. For this purpose, an experiment was conducted with three treatments [clay pitcher included natural zeolite Clinoptilolite (NZ), perlite (P) and vermiculite (V)] which filled half of the volume of a clay pitcher with five replications for each treatments. Beside each tree, one pitcher was placed at 50 cm depth. The soil of each hole was initially sampled, sealed, and transported to the laboratory. The pitchers were irrigated with treated industrial wastewater (from steel factory) 60 times (1500 cc per each irrigation event) over a period of six months. At the end of experiment period, the pitchers were removed and samples were taken from the substrate inside each pitcher and from the soil near the walls and bottoms of the holes. The sealed samples were transported to the laboratory for analyzing heavy metals (Fe, Cd, Cr, Cu, Pb, Mn, and Zn) using an atomic absorption spectrophotometer. The results showed that the used substrates in this experiment have high ability to absorb some heavy metals, especially Pb and Zn which concentration were increased in final value 75 and 80 times compared with initial values, respectively. However, an increase of these two elements in the soil (Zn = 26 and Pb = 71 ppm) nearby the pitcher indicate that the used substrates have limitations in absorption capacity for the heavy metals in high concentration of them in the wastewater. As this is related to their surface area, application of a nano form of the substrates such as nano zeolite might remarkably increase their cation exchange capacity and surface area.

Influence of commercial formulation on the sorption and leaching behaviour of propyzamide in soil

Experiments compared sorption and leaching behaviour for the herbicide propyzamide when applied to two soils either as technical material or in the commercial formulation Kerb® Flo. Sorption was investigated in batch systems as well as using a centrifugation technique to investigate changes in pesticide concentration in soil pore water over incubation periods of up to 28days. Studies with small soil columns compared leaching of technical and formulated pesticide for irrigation events (6 pore volumes) 1, 7, 14, 21 and 28days after treatment. There were no differences in sorption of technical and formulated propyzamide when measured by batch systems. Sorption of technical material was significantly greater than that of formulated pesticide in sandy loam (p<0.05), but not in sandy silt loam when measured by centrifugation of soil incubated at field capacity. Partition coefficients measured by batch and centrifugation methods were similar after 1day and those measured by centrifugation increased by factors of 5.3 to 7.5 over the next 4weeks. The mass of propyzamide leached from soil columns ranged between 1.1±0.33% and 14.4±3.2% of the applied amount. For all time intervals and in both soils, the mass of propyzamide leached was significantly greater (two-sided t-tests, p<0.001) for the formulated product than for the technical material. Leached losses decreased consistently with time in the sandy loam soil (losses after 28days were 14–17% of those after 1day), but with less consistency in the sandy silt loam. There was a highly significant effect of formulation on the leaching of propyzamide through soil (two-way ANOVA, p<0.001) as well as highly significant effects of time and soil type (p<0.001). Results are consistent with modelling studies where leaching from commercial products in the field could only be simulated by reducing sorption coefficients relative to those measured with technical material in the laboratory.

Using tracer tests to estimate vertical recharge and evaluate influencing factors for irrigated agricultural systems

Accurate estimation of groundwater recharge is critical for (semi) arid regions, especially in places like the North China Plain (NCP) where recharge from irrigation and intermittent precipitation events comprises the largest portion of recharge. Tracer tests were used to estimate potential recharge beneath agricultural systems irrigated by groundwater, and to help delineate factors that influence recharge. A bromide solution was applied below root regions to trace infiltration in the vadose zone beneath irrigated agricultural fields and non-irrigated woodlands at both piedmont plain (Shijiazhuang) and alluvial and lacustrine plain areas (Hengshui) in the NCP. The tracer tests lasted for more than 2 years and were conducted at 37 subsites grouped in sets of two to four at 12 regionally distributed sites. For the piedmont plain sites, the potential recharge rate ranged between 37–466 mm/a (6–27% of precipitation plus irrigation, P + I) beneath wheat-maize, 110–564 mm/a (12–52% of P + I) beneath orchard, and 7–10 mm/a (1–2% of P + I) beneath woodlands. For the alluvial and lacustrine plain sites, the potential recharge rate ranged between 14–177 mm/a (2–20% of P + I) beneath wheat-maize, 6–57 mm/a (0.5–5% of P + I) beneath orchard, 87–279 mm/a (10–31% of P + I) beneath cotton, and 6–44 mm/a (1–8% of P + I) beneath woodlands. The potential recharge was impacted by various external factors, like lithology, crops, and irrigation. When an irrigation controlled experiment was conducted in the same field with the same crop cultivation, the results revealed that larger irrigation quantities led to larger potential recharge rates.