Significant advances in unsaturated soils testing have been gained through the development of high suction tensiometers allowing direct measurement of suction beyond 100kPa. This has allowed the ...implementation of techniques that measure and control suction directly, where the soil is tested in the same conditions as in nature. Previously, much reliance had been placed on indirect measurements of suction and on control of suction using the axis translation technique. It is argued that this technique should be avoided as the use of an elevated air pressure does not replicate natural conditions. This paper presents advances resulting from the use of high suction tensiometers for laboratory testing and field measurements. It also describes an automated suction control system using the air circulation method that can impose controlled cycles of drying and wetting.
► Development of high suction tensiometers. ► Identification of saturation and calibration procedures. ► An alternative to the axis translation technique for testing unsaturated soils. ► Determination of soil water retention curves with high suction tensiometers. ► An automated suction control system using air circulation.
•Sunflowers are becoming a popular potted greenhouse crop.•Tensiometers were set at −5, −10, and −15 kPA to control irrigation levels.•Controlled-release fertilizer (15N-3.9P-10K) was applied at ...either 6, 12, or 18 g per pot.•Increased fertilizer levels accelerated photosynthesis, flower bud differentiation, and inflorescence development at −15 kPA.•‘Choco Sun’ should be grown at −10 kPA and at least 12 g of fertilizer to maintain adequate size and flower characteristics.
This study was conducted to analyze the effect of varying levels of irrigation and fertilizer on the growth and development of potted sunflower (Helianthus annuus L. ‘Choco Sun’). Irrigation was applied automatically to maintain targeted rootzone water potentials representing excess (−5 kPa), normal (−10 kPa), or limited (−15 kPa) irrigation. Controlled-release fertilizer (15N-3.9P-10K) was applied at a rate of 6, 12, or 18 g per pot. The two factors were randomized in a factorial design resulting in nine treatment combinations. Five growth parameters and six photosynthesis indices were used to evaluate the growth and development differences within treatments. There were no significant interactions for photosynthetic parameters except intercellular CO2 concentration. Irrigation and fertilizer main effects did not affect the final plant height, although −15 kPa/18 g treatment increased plant height during the vegetative phase. For −5 kPa, stem diameter was thickened, varying from 1.26 to 1.30 cm. Higher fertilizer rates accelerated flower bud differentiation and inflorescence development within −15 kPa treatments. These plants also demonstrated increased net photosynthetic rate (Pn), stomatal conductance (Gs) chlorophyll concentration (SPAD). Water use efficiency (WUE) was greatly improved with −15 kPa although this generally restricted the biomass accumulation despite higher photosynthetic activity. In conclusion, ‘Choco Sun’ sunflower should be grown at −10 kPa and at least 12 g of fertilizer to maintain adequate size.
Water productivity enhancement in farming systems is one of the most critical challenges facing the agricultural sector in the twenty-first century. Precision irrigation based on soil matric ...potential (SMP) measurements effectively enhances water productivity. However, the temporal effect of an SMP-based comfort zone on potato crops is lacking. This paper evaluates the temporal effect of a range of soil matric potential thresholds (namely, −7, −10, −15, −18, −21, −24, −30, and −45 kPa) in a sandy soil on the marketable yield and irrigation water productivity (WP) of potato grown in containers in a greenhouse with the Partial Least Square algorithm (PLS) and a mixed model. The results of this study suggest that a comfort zone maximizing potato yield is located between − 10 and − 24 kPa. The − 24 kPa threshold generated the highest yield while reducing the irrigation water use up to 47% and generating the highest WP. The average yield in the comfort zone reached 496.4 g per plant, an increase of 88% over the lowest yield achieved at an SMP of –45 kPa. In addition, the leaf expansion and tuber initiation physiological stages are the most important periods where the daily SMP had the most influence on the marketable yield. This information will assist potato growers in maintaining high yields while optimizing their use of irrigation water.
•Both SMP threshold and irrigation temporal distribution affect potato yield and WP.•The PLS is a suitable method to explore the temporal effect of SMP on yields.•The SMP-based comfort zone the potato was identified between − 10 and − 24 kPa.•The SMP threshold that optimizes both yield and water productivity is − 24 kPa.•The SMP threshold temporal effect begins in the leaf expansion stage and is maintained until maturity.
•A new vacuum saturation device for high-suction tensiometers was proposed.•The new device significantly improved the measured range of suction.•We analyzed the response characteristics of an ...insertion tensiometer.•The developmental stages of the tensiometer response curve were suggested.
Tensiometers are devices that can be used to monitor suction variation in landslides and slopes. The soil suction that can be measured with a conventional tensiometer is limited to 85 ∼ 90 kPa due to water cavitation in the tensiometer. This low measurement range of suction may be insufficient to interpret and determine the hydraulic properties of unsaturated soil, especially in semihumid and semiarid climate regions. However, in most geotechnical engineering studies, conventional tensiometers are still utilized. Although several types of high-suction tensiometers have been developed in recent decades, high suction measurements are difficult in the field because the saturation procedures for these tensiometers are complex and time consuming. Hence, the development of a simple and rapid saturation method is necessary to support their application. The vacuum saturation technique is a simple and reliable technique for saturating the porous ceramic cup of a tensiometer. However, if a high-suction tensiometer is saturated via a vacuum syringe, the measurable maximum suction is usually<200 kPa, which limits the application of tensiometers in geotechnical engineering. In this paper, we proposed a simple saturation device and a saturation method (the vacuum cylinder saturation method, VCSM) to saturate high-suction tensiometers. Soil column experiments were conducted to investigate the advantages of the VCSM and the response characteristics of insertion tensiometers. The results indicated that high-suction tensiometers could easily and steadily measure a maximum suction of 350 kPa if saturated via the VCSM. The VCSM could effectively prevent or retard the occurrence of cavitation due to the high vacuum pressure and slow progress of water filling in the tensiometer shaft. In addition, the response curve of insertion tensiometers could be divided into three stages: installing disturbance stage, delayed response stage and equilibrium stage. The extent of the disturbance caused by insertion tensiometer installation is a key factor influencing the delayed response characteristics of the tensiometer response curve. This paper also provides greater insight into the saturation method of tensiometers and the application of insertion tensiometers.
The application of water-retention polymers with improved fertilizers is a better crop-growing technique, especially in soils where the water-retention capacity is low. In Pakistan, different types ...of fertilizers, such as urea, DAP, MOP or SOP, are used from sowing to harvesting of crops. The use of water-retention polymers in low water-retaining soils is very important to increase its retention time. The experiment was conducted on half an acre of land in FFC Research Center located in Dyyalgarh, Millat Rd., near Deputy Wala interchange M4, Faisalabad, Punjab, Pakistan. The seed variety used in this experiment is zincole and the seed rate is 50 kg/acre. This experiment contains four different treatments, and each treatment contains three replicates. In T1, no water-retention polymers were used, while T2 was treated with standard and neem-coated urea under no water-retention polymer application. While in T3 and T4 recommended doses of polymers were used with standard and neem-coated urea. Irrigation scheduling was determined using tensiometers.. The research is aimed to keep moisture available in the root zone for better growth. For proper moisture monitoring tensiometers were installed.
Globally, coal mining wastes (CMWs) are associated with significant environmental and economic costs. Processing CMW into an ingredient of foam concrete is a promising solution but the behaviour of ...this particular construction material has not been sufficiently evaluated, especially during the initial period of cement hydration. The purpose of this paper is to present novel laboratory set-up and experimental procedures designed to investigate the early age behaviour of hydrating foam concrete samples made with a CMW from Poland. Two types of tests were devised to simulate air-curing conditions and water-curing conditions, respectively. These tests were carried out in custom-built unsaturated oedometer cells, and the matric suction in the test samples was monitored for approximately 14 days, using Warwick high capacity tensiometers. Experimental results show that in both curing conditions, a higher matric suction during cement hydration corresponds to a denser sample at the end of the monitoring period. A comparison of water-cured and air-cured samples also reveals different responses to CMW inclusion in their mix designs. The responses can be convincingly explained based on complementary test data and idealised capillary tube models adapted for the hydrating foam concrete samples.
•A novel laboratory set-up, incorporating high capacity tensiometers (HCTs) into purpose-built unsaturated oedometer cells, is proposed to investigate the curing behaviour of foam concrete during early age hydration. The incorporation of the HCTs made it possible to directly monitor the matric suction evolution of the mix and the corresponding interplays depending on the foam concrete samples’ (water- or air-) curing conditions.•The influence of natural sand replacement by coal mining waste (CMW) in the foam concrete mix has been studies, together with the corresponding effects on the evolutions of matric suction and porosity during the early age hydration.•Two different types of tests were devised for measuring the impacts of different curing environments on foam concrete properties. The first type was adapted for a water-curing condition and is akin to a chemical shrinkage test. The second type was adapted for an air-curing condition where water inflow was not permitted into the hydrating foam concrete sample over the monitoring period. In both cases. The evolution and interplays of matric suction were studied in correspondence with formation/stabilisation of the pore networks.•Simplified capillary models are proposed that meaningfully describe the rather complex kinetics of foam concrete hydration associated to the matric suction variations.
•Mild water deficit stress (WDS) reduced water input by 43% while maintaining yield.•Changes in antioxidant metabolite content (AM) can reduce the yield loss under WDS.•Rice genotypes with higher AM ...can be used as donor for WDS varietal improvement.
This study was conducted to investigate the effects of six irrigation regimes on grain yield, yield attributes, water use efficiency, plant water status and antioxidant metabolite content of four rice varieties. We conducted a two year (dry seasons of 2014 and 2015) field experiment with four rice varieties (Apo, Annada, Satabdi and Naveen) and six irrigation schedules based on tensiometric measurement of soil water potential (SWP) with irrigation thresholds of −20 (SWP 1), −30 (SWP 2), −40 (SWP 3), −50 (SWP 4) and −60kPa (SWP 5), in addition to the traditional practice of growing flooded rice (CF). Among the six irrigation treatments, both grain yield and water input were lowest at SWP 5 and highest at CF. There was no significant difference in grain yield upto SWP 3 for Apo and Annada, whereas for Naveen and Satabdi the yield difference was non-significant up to SWP 2 as compared to CF. Reduced electrolyte leakage, root bleeding rate and increased concentration of proline, catalase and peroxidase contributed to tolerate the water deficit stress and higher grain yield in Apo and Annada varieties. The results indicated that adoption of water deficit irrigation strategy with an appropriate irrigation threshold and tolerant varieties can save water and increase water productivity. Rice genotypes having inherent capacity to produce higher amount of antioxidant metabolites in response to water deficit stress should be a primary target of breeding high yielding rice varieties for water deficit environments.
Water is an important for plants growth, development and generating good crop yield. The rate of consumption of water by the crops depends on the type of crop, stage, soil characteristics and local ...climatic conditions. Irrigation scheduling takes care of when and how much water is to be applied to a crop during the entire the growing period. This calls for optimal water management, equipment, and labor in developing countries. An Electronic Wetting Front Detector was developed for irrigation scheduling by estimating the optimum soil moisture content present at the root-zone depth of the crops. The device measures the volumetric water content using electrical resistance of the soil and alarms the growers for the need of irrigation through its LED indicator installed in the device. The device was further calibrated and validated in the laboratory as well as in the farmer's field near Central University of Jharkhand, Ranchi, India. The device was tested and calibrated in the laboratory with the soil present in a container along with the Tensiometer fixed in the same container of soil and the data of the gravimetric soil moisture content was compared for accuracy by using regression analysis. Similarly, validation was also performed in the farmer's field and the result showed that it has a higher accuracy for measuring the soil water content. The developed device interprets readings from the sensors and alarms the farmer of overirrigation or underirrigation based on the sensors data. The EWFD developed is new intervention since the device could be easily used by farmer to understand the soil water content and schedule irrigation with respect to crop needs by alarming the farming. Therefore, the device may prove a valuable contribution to the list of other scientific instruments used for measuring the soil water content. The device can be used perfectly for scheduling irrigation.
•An Electronic Wetting Front Detector (EWFD) has been developed to schedule irrigation.•The proposed consists of soil moisture sensor, controller board, Arduino UNO circuit board, 9-V battery and 20 mm led bulb.•The EWFD could be used as a scientific instrument that can measure soil moisture content with greater accuracy.•The device may prove a valuable contribution to the list of other scientific instruments.
To investigate the effect of the changes of the soil suction on volume changes, laboratory experiments were conducted on pure bentonite and bentonite mixed with sand of proportion: 30, 40 and 50% at ...different initial water contents and dry unit weights that were chosen from the compaction curves. In addition, large-scale model with dimensions (700 × 700 × 650) mm was used for testing soils prepared at the same initial water content and dry unit weight to show the effect of water content changes on different relations (swelling potential, swelling pressure and soil suction). The soil water characteristic curve (SWCC) was measured by the tensiometer at depths 200 and 500 mm from the surface footing. The SWCC was obtained experimentally from the tensiometer method. Different curves were obtained due to different initial water contents and different soils. It was concluded that the suction tends to decrease steeply with increase of the initial water content. The increase in bentonite content shifts the SWCC slightly. The residual water content increases as the bentonite content increases when the residual water content decreases from 44 to 32% when adding 30% sand to pure bentonite due to that the samples with higher bentonite content had a higher volumetric change potential on wetting than samples with low bentonite content. The air-entry value (AEV) increases with increase of initial water content and clay content, where AEV for B1 (pure bentonite) soil sample is 10 kPa, while AEV is 25 kPa for B2 (pure bentonite) soil sample due to increase of initial water content from 25 to 34%; however, AEV for BS1 (70:30, bentonite/sand) soil sample is 8 kPa, on the other hand, AEV reaches 6 kPa for BS3 (60:40, bentonite/sand) soil sample due to decrease of the clay content in this sample.
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