Estimation of Hydraulic Properties of Growing Media from Numerical Inversion of Mini Disk Infiltrometer Data

Accurately determining the hydraulic properties of soilless growing media is essential for optimizing water management in container-based horticulture and agriculture. The very rapid estimation of hydraulic properties using a Mini Disk Infiltrometer has great potential for practical use compared to the very time-consuming standard methods. The objectives of this study were (1) to calibrate simulated cumulative stepwise infiltration under different suctions with the measured data from Mini Disk Infiltrometer, (2) to evaluate the efficiency of the Hydrus-2D inverse model to predict water dynamics through substrates, (3) to compare the substrate hydraulic parameters obtained through the numerical inversion model to those obtained via laboratory methods, and (4) to provide recommendations on how to effectively use the MDI-based method for practical applications. This study employs numerical inversion of Mini Disk Infiltrometer (MDI) data to estimate the hydraulic parameters of three different growing media, namely white peat, thermally treated wood fibre (WF4), and Seedling substrate. Infiltration experiments were conducted under suction-controlled conditions using varying initial moisture contents, followed by numerical simulations using the Hydrus-2D model and the Van Genuchten equation to describe the hydraulic parameters. The results demonstrated strong agreement between observed and simulated infiltration data, particularly under moistened conditions, with high R2 > 0.9 values indicating the model’s effectiveness. However, discrepancies were observed for substrates in their initial dry state, suggesting limitations in capturing early-stage infiltration dynamics. The findings highlighted the potential of numerical inversion methods for estimating substrate hydraulic properties but also revealed the need for methodological refinements. Modifying the Van Genuchten model or exploring alternative approaches such as the Brooks and Corey model may enhance accuracy. Extending the suction range of measurement techniques is also recommended to improve parameter estimation. This study provides important evidence that the inverse method based on MDI is an effective tool for rapidly determining the hydraulic functions of substrates, which are important in promoting sustainable horticultural practices. Future research should focus on refining parameter estimation methods and addressing model limitations to enhance the reliability of hydraulic property assessments in soilless growing media

Two-dimensional modeling of water distribution under capillary wick irrigation system

Competition for limited available water for crop production is an ever-increasing issue for farmers due to increasing demand of irrigation water worldwide. Due to high energy cost in operating pressurized irrigation systems, energy-efficient low-pressure wick irrigation systems can play important roles for smallholder greenhouse crop production by ensuring higher water use efficiency than most traditional approaches. The objectives of this study were to investigate HYDRUS 2D-simulated water distribution patterns in soil and soilless growing media, and to evaluate water balance in these media under capillary wick irrigation system. To accomplish these objectives, eggplants (Solanum melongena L.) were grown in potted peatgro and sandy clay loam in a greenhouse experiment, water distribution was simulated by using HYDRUS 2D software package and compared with the measured values, and water uptake by the plant roots was determined for water balance calculation. The wetting pattern was found axially symmetric in both growing media (peatgro and soil) under the wick emitters. The simulated water distribution in both growing media revealed dependency of spatial extent of the wetted zone on water application period and hydraulic properties of the media. The mean absolute error (MAE) in water content over depth varied from 0.04 to 0.10 m3 m-3 and the root mean square error (RMSE) varied from 0.04 to 0.11 m3 m-3. Deviations between the measured and simulated water contents in the peatgro medium were larger over depth than over lateral distance. In contrast, the model criteria matched well for the sandy clay loam and provided MAE of 0.01 to 0.02 m3 m-3 and RMSE of 0.01 to 0.03 m3 m-3, indicating good agreement between the measured and simulated water contents

HYDRUS-1D simulation of nitrogen dynamics in rainfed sweet corn production

Nitrogen loss from agricultural fields results in contamination of ground and surface water resources due to leaching and runoff, respectively. Nitrogen transport dynamics vary significantly among agricultural fields of different climates, especially in the tropical climate. This study intended to evaluate the rainfall impact on nitrogen distribution and losses under tropical rain-fed conditions. The study was carried out in a sweet corn field for two growing seasons at the Malaysian Agricultural Research and Development Institute (MARDI) research field. The HYDRUS-1D numerical model was used to simulate nitrogen transport dynamics in this study. The observed nitrogen concentrations were used for calibration and validation of the model. Total nitrogen input to sweet corn was 120 kg/ha for both seasons. Nitrogen losses through surface runoff and leaching were dominating pathways. Surface runoff accounted for 35.3% and 22.2% of total nitrogen input during the first and second seasons, respectively. The leaching loss at 60 cm depth accounted for 4.0% (first season) and 18.5% (second season). The crop N uptake was 37.5% and 24.9% during the first and second seasons, respectively. Nitrate was the dominant form of N uptake by the crop that accounted for 83.6% (first season) and 78.5% (second season). The HYDRUS-1D simulation results of nitrogen concentrations and fluxes were found in good agreement with observed data. The overall results of simulation justified the HYDRUS-1D for improved fertilizer use in the tropical climate

Assessment of nutrient leaching in flooded paddy rice field experiment using Hydrus-1D

Solute runoff and leaching are two direct pathways of nutrient pollution from paddy fields into water systems. Due to the dynamic nature of paddy fields, solute transport and transformation processes are complex and difficult to understand. Therefore, in this study, nitrogen (N) transport in flooded paddy rice fields with conventional irrigation (flooding irrigation) in the Tanjung Karang Rice Irrigation Scheme (TAKRIS), Sawah Sempadan, were observed and modelled using the Hydrus-1D numerical model during two consecutive rice growing seasons. Based on solute transport analysis results, it was observed that 50.3% to 48% of percolated N was accumulated in the top 40-cm soil layer, while 49.7% to 52% of leachate N was lost below the 40-cm soil layer (40–100 cm) during the off and main seasons, respectively. About 85% of N leaching loss was in the form of NO3−. NO3− was absorbed by rice roots within 0–40 cm and the denitrified root zone; however, there was still a large quantity of NO3− which remained below the root zone, which was quickly transported downward along with the leachate water. The NH4+ concentration in subsurface water was lower than the NO3− concentration due to various processes that removed NH4+ from the topsoil layer (0–40 cm), such as ammonium volatilisation, nitrification, and plant uptake. The total leaching loss of N was 34.9 and 27.9 kg/ha during the off and main seasons, respectively. The simulated and observed water flow and nutrient leaching were in a good agreement (R2 = 0.98, RMSE = 0.24). The results showed that Hydrus-1D successfully simulated the solute movement under different soil depths during the study period

Modeling of capillary wick irrigation system for potted plant and small scale plantation

Limited availability of fresh water supplies worldwide demonstrates the urgent need to develop and adopt efficient irrigation methods and proper irrigation management strategies. The relatively high performance of drip irrigation is no doubt. It saves a substantial amount of water and labor, increases yields, and often also improves the quality of the produce. However, the higher investment and energy cost limit the development of the low-cost irrigation system for subsistence farmers. There has been an immense interest in developing and promoting the low-cost drip irrigation system appropriate for small-scale crop growers and greenhouse crop production. This study, by conducting laboratory experiments,investigated hydraulic characteristics and performance of cotton-bonded non-woven material to be used as the wick emitter. Furthermore, greenhouse experiments were carried out to simulate water movement and solute dynamics under root water uptake for potted eggplant crops. To determine proper water application strategies, three irrigation schedules were evaluated. The wick emitter provided the uniformity coefficient of 95.65% and distribution uniformity of 92.67% in applying irrigation in two growing media: peatgro (peat), coconut coir dust and sandy clay loam soil. The growing media and the soil were wetted in an axially symmetric pattern under the wick emitter; in traditional and modern watering methods,growing media are wetted in one-dimensional pattern. HYDRUS simulation of water distribution revealed the dependency of the spatial extent of the wetted zone in the growing media on water application period and hydraulic properties of the media. Furthermore, the results demonstrated that the solutes are transported very slowly, and most of the nutrient solution remains within the middle and bottom of the pots. The results from this study revealed that the eggplant growth showed insignificant differences for the three irrigation schedules when fresh water was used because all the three irrigation schedules provided with enough water content for the crop. In contrast, the eggplant growth showed differences between the treatments relatively when nutrient solutions were used. In terms of wick water application strategies, although 202 ml/day of nutrient solution was applied for the Management Allowed Deficit (MAD) treatment and 155 ml/day was applied for Evapotranspiration (ET) treatment. The total leaf area of the ET schedule (1252.9 cm2) was higher than the total leaf area of the MAD (1007.8 cm2). The result suggests that the ET schedule is the best under wick irrigation. Discharge of the wick emitter followed an inverse linear relation with a capillary height of water in the wick. This relation led to the development of an equation for compensating wick emitter discharge by replacing the pressure head of a drip emitter with capillary height of the wick emitter. The measured water volume found the close match with the simulated water and solute movement using HYDRUS 2D/3D in a container planted with brinjal plant and for various porous mediums. The findings from this study invoke opportunities to develop an effective Capillary Wick Irrigation System (CWS) for small-scale crop production. Further investigation would provide generalized broader evidence on CWS performance based on techno-economical performance of the wick under diverse conditions

Hydraulic characteristics of capillary wick irrigation system

Limited availability of freshwater supply worldwide demonstrates urgent need to develop and adopt efficient irrigation methods and effective irrigation management strategies. This study, by conducting laboratory experiments, investigated hydraulic characteristics and performance of cotton-bonded non-woven material to be used as wick emitter. The wick emitter provided uniformity coefficient of 95.65% and distribution uniformity of 92.67% in applying irrigation in two growing media - peatgro (peat) and coconut coir dust. The growing media were wetted in an axially symmetric pattern under the wick emitter; in traditional and modern watering methods, growing media are wetted in one-dimensional pattern. HYDRUS simulation of water distribution revealed dependency of spatial extent of the wetted zone in the growing media on water application period and hydraulic properties of the media. Discharge of the wick emitter followed an inverse linear relation with capillary height of water in the wick. This relation lead to development of an equation for compensating wick emitter discharge by replacing pressure head of drip emitter with capillary height in wick emitter. The findings of this study thus invoke opportunities to develop an effective Capillary Wick Irrigation System (CWS). Further investigation would provide a generalized broader evidence on CWS performance based on techno-economical performance of the wick under diverse conditions

The status of freshwater and reused treated wastewater for agricultural irrigation in the Occupied Palestinian Territories

Abstract Global freshwater scarcity is imposing the demand for using non-conventional water resources for irrigation and non-irrigation purposes. Direct reuse of treated wastewater for agricultural irrigation is a widespread practice in arid and semi-arid regions, because of water shortage and scarcity. Water scarcity and the need for ecological sustainability have led to the introduction of treated wastewater as an additional water resource in the national water resources' management plans of Mediterranean countries. The use of wastewater for irrigation is an important tool for water resources' supplement. However, the reuse of effluent in irrigation can have negative impacts on crop quality and soil conditions, as well as on public health and the environment. Furthermore, inappropriate management of agricultural irrigation with treated wastewater can also pose problems for plant production and the physical and chemical properties of soils. This paper presents some approaches to understand the impacts of reusing treated wastewater. It also presents a critical analysis of the treated wastewater's reuse for irrigation in the Occupied Palestinian Territories (OPT), while shedding light on the water status in the OPT. The paper investigates the wastewater treatment and reuse for agricultural irrigation, especially in the lack of control of Palestinians on their own freshwater resources in the OPT.</jats:p