Soil Water Distribution Research Articles

Amelioration of takyric solonetz using drip irrigation with soil‐water‐redistribution medium*

AbstractTakyric solonetz is a highly saline‐sodic soil with poor soil structure and a saturated hydraulic conductivity close to zero. Drip irrigation, soil‐water‐redistribution medium (RM), ridge planting and film mulching have been successfully used to ameliorate such soils. Here, we compared soil moisture and cation distribution during the amelioration with planting years of 1, 3, 4, 5 and 6. A suitable root zone with low electrical conductivity, pH and sodium absorption ratio was quickly and continuously formed in the arid area. An irrigation regime with a decreasing soil matric potential threshold of −5 to −20 kPa in improving years 1–4 and stabilized at −20 kPa was feasible. The wetting front kept moving downward with time, and the dry soil layer in the middle of the profile gradually disappeared after 4 years. In the initial 4 years, the Na+ in the root zone leached mainly to the top layer of ridge slope and furrow. And then the Na+ leached downward. The spatial distribution of soil water and Na+ indicated that soil permeability improved with time, and significant changes occurred after the fifth year.

Neutron computed laminography yields 3D root system architecture and complements investigations of spatiotemporal rhizosphere patterns

PurposeRoot growth, respiration, water uptake as well as root exudation induce biogeochemical patterns in the rhizosphere that can change dynamically over time. Our aim is to develop a method that provides complementary information on 3D root system architecture and biogeochemical gradients around the roots needed for the quantitative description of rhizosphere processes.MethodsWe captured for the first time the root system architecture of maize plants grown in rectangular rhizotrons in 3D using neutron computed laminography (NCL). Simultaneously, we measured pH and oxygen concentration using fluorescent optodes and the 2D soil water distribution by means of neutron radiography. We co-registered the 3D laminography data with the 2D oxygen and pH maps to analyze the sensor signal as a function of the distance between the roots and the optode.ResultsThe 3D root system architecture was successfully segmented from the laminographic data. We found that exudation of roots in up to 2 mm distance to the pH optode induced patterns of local acidification or alkalization. Over time, oxygen gradients in the rhizosphere emerged for roots up to a distance of 7.5 mm.ConclusionNeutron computed laminography allows for a three-dimensional investigation of root systems grown in laterally extended rhizotrons as the ones designed for 2D optode imaging studies. The 3D information on root position within the rhizotrons derived by NCL explained measured 2D oxygen and pH distribution. The presented new combination of 3D and 2D imaging methods facilitates systematical investigations of a wide range of dynamic processes in the rhizosphere.

Numerical Modeling of Soil Water–Heat Transport under Oxo-Biodegradable Film Mulch and the Optimal Mulching Period

Timely monitoring and regulation of the transport and distribution of soil water and heat are appropriate methods to ensure and improve crop yields. With the degradation of the oxo-biodegradable film, the upper boundary condition is a time-variable boundary, and soil water-heat transport is more complicated, comparing with conventional plastic film. Based on HYDRUS-2D version 2.02 and the characteristics of mulching films, a soil water-heat coupled transport mathematical model of drip irrigation was established, and the simulated soil water content and temperature were tested against three-year field observations for calibration and validation purposes. The model prediction demonstrated that the induction periods of oxo-biodegradable film mulching differed in different hydrological years. In normal flow years, an induction period of 50–80 days had higher water use efficiency. While the window would increase to 50–100 days in low flow years. As for temperature, comparing with conventional plastic film mulching, the decreasing trend of temperature started to slow down when the induction period increased to 70 days. Therefore, the optimal induction period of the oxo-biodegradable film is 50–70 days.

Dynamics of interspecific water relationship in vertical and horizontal dimensions under a dryland apple-Brassica intercropping system: Quantifying by experiments and the 3D Hi-sAFe model

Separation of water absorption by roots between trees and crops is critical to intercropping in water-limited regions. The current knowledge about interspecific water relationship is in one dimension, i.e., the vertical direction, little is known in both vertical and horizontal directions under different rainfall conditions. Therefore, an experiment was carried out in an apple tree based intercropping system and an apple tree monoculture on China's Loess Plateau during one growing season which started with a high rainfall period followed by a low rainfall period. We investigated the spatial distribution of soil water and plant root, and simulated their water use strategies using the 3D Hi-sAFe model. The root growth of apple trees in the top 60 cm was restricted by intercropping in the cropped area but increased in the top 40 cm in the uncropped area compared with monoculture. In the high rainfall period, compared with the control, the apple trees' water absorption from the uncropped area (0–60 cm) increased by 44.43%, but the water utilization from the cropped area (0–60 cm) decreased by 32.59%. More than 90% of the soil water absorbed by B. napus came from the 0–60 cm soil layer in the cropped area. During the low rainfall period, intercropping promoted an increase of 14.79% in apple trees' water absorption from the 60–100 cm soil layer in the cropped area. The soil water in the 20–60 cm layer became the main source for B. napus and its contribution was 63.51%, but only 20.56% of the water absorbed by apple trees came from here. It can be concluded that, to alleviate water competition, water absorption between species was segregated horizontally during the wet period due to the roots "niche differentiation", while water use complementarity occurred along the vertical axis during the dry period.

Changes in soil-water content and heat transport under different simulated systems of drip irrigation in gravel-mulched fields

Abstract Gravel mulching is an ancient mulching system with a history of more than 300 years in China. To explore the changes of soil-water content (SWC) and heat transport in watermelon gravel-mulched fields under drip irrigation, we simulated three irrigation quotas (W1, 180 m3/hm2; W2, 270 m3/hm2; and W3, 360 m3/hm2) and three irrigation frequencies (F1, three times; F2, six times; and F3, nine times) based on HYDRUS-2D. The results indicated that peak SWC increased with irrigation quota. The range of fluctuation of SWC decreased as irrigation frequency increased. The temperature of the 0–40 cm soil layer varied with air temperature, but the range of fluctuation decreased with depth. Irrigation affected the distribution of soil water, increased soil heat capacity, and reduced the impact of air temperature on soil temperature, thus delaying the impact of air temperature on soil temperature. High-frequency drip irrigation could therefore effectively improve SWC, reduce water stress during the period of watermelon growth, and effectively delay the effect of air temperature on soil temperature, providing a theoretical basis for developing reasonable irrigation strategies and regulating soil water and heat in gravel-mulched fields.

Spatial soil water and nutrient distribution affecting the water productivity of winter wheat

Understanding the effects of the spatial distributions of soil water and nutrients on crop growth and yields is important for optimizing their management to achieve high water productivity (WP) under water deficit conditions. In this study, three spatial distributions of irrigation and nutrients were set up to winter wheat (Triticum aestivum L.) grown in 1 m deep tubes (19.2 cm inner diameter) in 2017/18 and 1.4 m deep tubes in 2018/19 buried in the field. The three treatments included: both irrigation water and nutrients applied to the surface soil layer (NS+WS); nutrients in the surface soil layer and irrigation applied to deep soil layer (60 cm below soil surface) (NS+WD); and nutrients and water both applied to the deep soil layer (ND+WD). For the three main treatments, each was supplied with two irrigation levels, i.e., deficit irrigation and full irrigation at 160 mm and 240 mm, respectively, divided into four applications at different growing stages of winter wheat. The results showed that the wheat grain yield and WP at grain yield level (WPg) under NS+WD were the highest under deficit irrigation, with yields 7.7% and 20.9% higher, and WPg 9.2% and 20.4% higher than those of NS+WS and ND+WD averagely for the two seasons, respectively. The NS+WS treatment resulted in the highest grain yield and WP at both grain and biomass levels (WPb) under full irrigation, with yields 17.7% and 31.8% higher, and WPg 23.4% and 38.0% higher than those of NS+WD and ND+WD averagely for the two seasons, respectively. Treatments with nutrients located in deep soil layer produced the lowest yield and WP under both irrigation levels. Therefore, nutrients should be located in the top soil layer to increase their availability for crop use anytime during the growing season. Water applied in the deep soil layer could benefit grain production and WPg under deficit irrigation, possibly related to the increase in the proportion of the water use during reproductive growing stage to achieve higher harvest index (HI). Under full irrigation, water and nutrients matched in the topsoil layer, where the roots were mostly distributed, increased the availability of water and nutrients for root uptake and reduced the dry-matter allocation to root growth in acquiring resources, which resulted in a lower root/shoot ratio, higher biomass production and higher WPb. The spatial soil water and nutrient distribution affected their availability for crop use during different growing stages, and influenced the allocation of dry matter to above- and below-ground parts. Optimizing the spatial distribution of nutrients and water based on water availability would benefit crop production and water productivity.

Mitigating global warming potential while coordinating economic benefits by optimizing irrigation managements in maize production

China is the second largest irrigated country in the world. Increasing irrigation intensity costs more water and energy, and produces more greenhouse gas (GHG). In the present study, the responses of maize economic and environmental benefits to different irrigation managements were analyzed in a 2-year field study. A purposely designed tube–study was conducted to explore mechanism underlying effects of irrigation managements in detail. Three treatments, rainfed (RF), flood irrigation (FI), and drip irrigation (DI) were included in the field. Five treatments, no irrigation, flood irrigation, irrigation in 0–30, 30–60, and 0–90 cm depth were conducted in the tube study. Compared to RF, grain yields of FI and DI significantly increased by 22.1 % and 35.7 %, respectively, the net ecosystem economic budget significantly increased by 34.2 % and 35.6 %, and carbon footprint decreased by 7.0 % and 12.7 % in the field study. The irrigation treatments in the tube study increased the global warming potential by 12.0–32.8 % and grain yield by 44.5–203.9 %, and reduced GHG intensity by 24.3–57.4 %, compared with no irrigation treatment. Water content at the top soil layer had the greatest impact on GHG emissions. In conclusion, the differences in grain yield and GHG emissions among irrigation managements are mainly due to the soil water content in space and time. Drip irrigation decreases GHG intensity by producing more grain yield due to the optimized soil water distribution in the root zone. Irrigation management with appropriate amount and frequency can increase economic benefit and reduce environmental cost in maize production.

Use of the stable oxygen isotope method to evaluate the difference in water consumption and utilization strategy between alfalfa and maize fields in an arid shallow groundwater area

Returning farmland to grasslands (RFG)to restore soil fertility and prevent land degradation in overused agricultural lands is an important measure. However, the hydrological processes, water consumption and utilization in field systems are undoubtedly changed in shallow groundwater areas owing to RFG. Experiments in the Hetao irrigation district, Inner Mongolia, China, during 2017 (2-yr for alfalfa) and 2018 (3-yr for alfalfa) were conducted to evaluate the difference in soil water distribution, percolation, groundwater recharge, water consumption and water productivity between alfalfa (Medicago sativa L.) and maize (Zea mays L.) fields. The stable oxygen isotope method was used to reveal a strategy to utilize different water sources for alfalfa and maize in an arid shallow groundwater area. Compared with maize, the increase in water consumption by alfalfa increased the soil water consumption of the 0–100 cm soil layer and the groundwater recharge, which led to an increase of 9.44 mm and 65.32 mm, respectively. However, the leakage below 100 cm layer decreased by 44.91% compared with those of the maize field. The yield and WPc of alfalfa were 29.27% and 6.28% greater than that of maize in 2018, respectively. Percentages of 75.43%, 18.73% and 5.84% of irrigation water, groundwater and precipitation were taken up by alfalfa during the irrigation period, respectively, while it was 81.27%, 12.90% and 5.83% in the maize field, respectively. After irrigation, the crops primarily absorbed water from upper soil layer (0–40 cm), comprising 72.93% (alfalfa) and 69.8% (maize). However, more water from the deeper layers was used by alfalfa before irrigation, and the average contribution of 40–100 cm soil layer was 63.0%, an increase of 11.2% compared with maize. In addition, even though maize absorbed water by roots that could reach a soil depth of 80 cm, it primarily drew water from the 40–60 cm soil layer.

Mulched drip irrigation increases cotton yield and water use efficiency via improving fine root plasticity

The morphological characteristics of crop roots, especially the plasticity of fine roots, are directly related to the crop’s ability to obtain soil water. Mulched drip irrigation can effectively regulate soil water distribution to achieve high cotton yield with reduced water consumption. In the previous study, from the perspective of root-shoot coordination, we found that mulched drip irrigation reduced the growth redundancy of roots and improved the root productivity of cotton, thus achieving the goal of water-saving and increased yield. However, it is unclear if and how mulched drip irrigation enhances absorptive capacity of roots via regulating dry and wet soil areas and optimizing fine root morphology and distribution compared with traditional flood irrigation. To achieve this, the effects of fine root plasticity on the absorptive capacity of roots were studied in a two-year field experiment. Mulched drip irrigation (conventional drip irrigation and excessive drip irrigation) and traditional flood irrigation (reduced flood irrigation and conventional flood irrigation) were used, and soil water distribution and root distribution were determined. The results showed that compared with traditional flood irrigation, mulched drip irrigation significantly increased the soil water content (SWC) in the 0–60 cm soil layer and reduced the fluctuation amplitude of SWC at the flowering and boll stage of cotton. Mulched drip irrigation formed different dry and wet areas in the root zone, i.e., the SWC was higher in the shallow layer (0–40 cm) at 0–20 cm on both sides of the drip line, and most of the cotton roots were in the wet area. The higher SWC increased the distribution of fine roots in this area and shaped the shallow fine root system, which enhanced the cotton plant’s ability to absorb soil water. Statistical analysis showed that the higher fine root biomass in the 0–40 cm soil layer at the late full boll stage of cotton under mulched drip irrigation was beneficial to increase aboveground biomass, thus increasing total bolls and seed cotton yield. However, compared with the irrigation amount of field production (390 mm), an excessive amount of irrigation (600 mm) reduced the seed cotton yield of mulched drip irrigation, resulting in the decrease of irrigation water use efficiency (IWUE). Therefore, mulched drip irrigation optimizes the distribution of fine roots and enhances water uptake by effectively regulating the water–root relationship, and thus improves seed cotton yield and IWUE.

Comparison of the root–soil water relationship of two typical revegetation species along a precipitation gradient on the Loess Plateau

Soil water and root distribution following revegetation are key research topics in water-limited ecosystems. However, little is known about the interaction between soil water and root distribution in deep soils under different precipitation conditions. Knowledge of the root–soil water relationship of revegetated land and its response to precipitation is crucial for the management of water resources and ecological restoration worldwide, including on the Chinese Loess Plateau. In this study, we investigated soil water and root distribution under apple orchard and black locust down a 10 m soil profile and exposed to different amounts of annual precipitation on the Loess Plateau. The results showed that soil water content (SWC) under two typical planted forests both significantly decreased as the mean annual precipitation (MAP) decreased. SWC spatial variation is demarcated by a 500–550 mm precipitation threshold, being relatively high when MAP > 550 mm but extremely low when MAP < 500 mm. In apple orchards, the depth above which 50% of the roots were present increased with increasing precipitation, but in black locust it became shallower. The results of a linear mixed model revealed a significant relationship between fine root length density and SWC depletion degree for black locust irrespective of the amount of precipitation, but it was only found in the 200–1000 cm soil layers with MAP > 550 mm and the 0–200 cm soil layers with MAP < 550 mm for apple orchards. The MAP × depth interaction was significant with respect to SWC depletion degree for MAP > 550 mm, but not for MAP < 550 mm in both vegetation types. These findings add to our current understanding of the root–soil water relationship of species used for revegetation and highlight the need to assess the long-term effect of revegetation on soil water consumption in water-limited ecosystems.

Remediating the Adverse Effects of Treated Wastewater Irrigation by Repeated On‐Surface Surfactant Application

AbstractThe use of treated wastewater (TWW) has gained recognition as an alternative source for freshwater irrigation, and is steadily expanding worldwide. Despite the benefits of freshwater conservation and nutrient richness, there is mounting evidence of TWW adverse effects on soil, yield, and the environment. Irrigation using TWW has resulted in soil water repellency, in which preferential flow pathways and uneven soil water and chemical distribution occur. These increase deep water percolation and chemical leaching, which can lead to soil and groundwater pollution. This study was conducted in a commercial citrus orchard grown on sandy‐loam soil in central Israel and irrigated with TWW, with the aim of investigating the remediation of these adverse effects, by repeatedly spraying a nonionic surfactant on the soil surface. The surfactant application succeeded to turn the soil wettable, diminishing the preferential flow pathways, and rendering the soil water and dissolved chemicals uniformly distributed. The overall water content in the 0–40 cm layer increased, and deep percolation and chemical leaching substantially decreased. The grapefruit yield increase during the two‐year study period increased the water use efficiency. Electrical resistance tomography scans executed during and after irrigation events for two subsequent years revealed that a “soil memory” phenomenon has been developed for water repellent soils, where water flow takes place through previously developed preferential flow pathways in such soils. This study demonstrates that recurrent surfactant application enables a continuous use of TWW, while eliminating most of its prejudicial effects.

RETRACTED: Biochar and compost amendment impacts on soil water and pore size distribution of a loamy sand soil

AbstractSoil structure, which refers to aggregates and pore characteristics, reflects the spatial arrangement of soil particles and is a key component for crop yield and soil health. Well‐formed soil structure has favorable pore size distribution, which supports soil water flow and retention and healthy plant growth. Compost and biochar, important organic amendments, have a potential to influence soil structure, but their effects on specific soil types and soil properties have not been fully investigated. The main objective of this study was to investigate the impact of the additions of compost and/or date palm biochar on selected soil water indicators and pore size distribution of a loamy sand soil using disturbed soil samples. Statistical parameters of pore size distribution properties such as SD, kurtosis, skewness, modal diameter (dmode), median diameter (dmedian), and mean diameter (dmean) as well as plant available water capacity (PAWC), available soil water capacity (ASWC), saturated soil water content, and measured saturated hydraulic conductivity (Ksat) were measured and evaluated. The results showed that the dmode, dmedian, dmean, SD, skewness, and kurtosis values for untreated soil (control) were 31.6 μm, 25.8 μm, 23.5 μm, 3.3, −0.16, and 1.14, respectively. Biochar, compost, and a mixture of biochar–compost additions to a loamy sand soil significantly reduced dmode, dmedian, and dmean values in comparison with nonamended soil. Application of these amendments increased PAWC and ASWC and reduced Ksat of the loamy sand soil, significantly. Biochar–compost mixture has the most significant effect on improving soil water retention and PAWC.

Statistical studies on the pore characteristic of Qinghai-Tibet Plateau silty clay modified by nano-silica

Abstract Nano-particles as additive materials have been widely used in geotechnical engineering, which can significantly improve the strength and suppress cracks formation of geo-materials. Nano-particle modified geo-materials consist of a ruleless distribution of soil particles, nano-particles, water, and gas. Thus, the micro-pore properties of modified geo-materials are uncertain and variable. In addition, the variability phenomenon is intensified by the strong water absorption and adhesive aggregation of nano-silica. However, the micro-pore characteristics of nano-material modified soil and the statistical properties are very limited in literature. To address those, large samples tests on Qinghai-Tibet Plateau silty clay ( ≥ 50 specimens) were conducted, and the median pore diameters and cumulative volume of pore diameters smaller than 0.1 μ m at four nano-silica contents (0, 0.75%, 2%, and 5%) were measured by the mercury intrusion porosimetry. The experimental data show that the two micro-pore parameters of fifty silty clay specimens with nano-silica additive show noticeable variability. To quantify these variablities, we assume the micro-pore diameter follows one of four probability distributions (normal, lognormal, Weibull, and gamma). The experimental curves were compared with four selected potential probability distributions and it was found that all distributions agreed well with the experimental data, approximatively. Nevertheless, only three distributions (normal, lognormal, and gamma) satisfy the Hypothesis testing. The results of chi-square test indicate that the normal distribution had the smallest effect evaluation index, and it could well describe the micro-pore parameters of nano-silica modified silty clay. The results will benefit a better understanding of the changeability of micro-pore characteristics of nano-particle modified geomaterials. Besides, these results are significant for interpreting the micromechanical mechanism of modified soils, and are helpful to guide the selection of additive materials for modified porous media.

Three-dimensional in vivo analysis of water uptake and translocation in maize roots by fast neutron tomography

Root water uptake is an essential process for terrestrial plants that strongly affects the spatiotemporal distribution of water in vegetated soil. Fast neutron tomography is a recently established non-invasive imaging technique capable to capture the 3D architecture of root systems in situ and even allows for tracking of three-dimensional water flow in soil and roots. We present an in vivo analysis of local water uptake and transport by roots of soil-grown maize plants—for the first time measured in a three-dimensional time-resolved manner. Using deuterated water as tracer in infiltration experiments, we visualized soil imbibition, local root uptake, and tracked the transport of deuterated water throughout the fibrous root system for a day and night situation. This revealed significant differences in water transport between different root types. The primary root was the preferred water transport path in the 13-days-old plants while seminal roots of comparable size and length contributed little to plant water supply. The results underline the unique potential of fast neutron tomography to provide time-resolved 3D in vivo information on the water uptake and transport dynamics of plant root systems, thus contributing to a better understanding of the complex interactions of plant, soil and water.

Moment Analysis for Modeling Soil Water Distribution in Furrow Irrigation: Variable vs. Constant Ponding Depths

Despite increasing use of pressurized irrigation methods, most irrigation projects worldwide still involve surface systems. Accurate estimation of the amount of infiltrating water and its spatial distribution in the soil is of great importance in the design and management of furrow irrigation systems. Moment analysis has previously been applied to describe the subsurface water distribution using input data from numerical simulations rather than field measured data, and assuming a constant ponding depth in the furrow. A field experiment was conducted in a blocked-end level furrow at Maricopa Agricultural Center, Arizona, USA, to study the effect of time-variable ponding depths on soil water distribution and the resulting wetting bulb under real conditions in the field using moment analysis. The simulated volumetric soil water contents run with variable and constant (average) ponding depths using HYDRUS 2D/3D were almost identical, and both compared favorably with the field data. Hence, only the simulated soil water contents with variable ponding depths were used to calculate the moments. It was concluded that the fluctuating flow depth had no significant influence on the resulting time-evolving ellipses. This was related to the negligible 10-cm variation in ponding depths compared to the high negative matric potential of the unsaturated soil.

Effects of Crop and Grass Intercropping on the Soil Environment in the Karst Area

The karst area in Southwest China is facing the challenges of environmental degradation and agricultural safety. Intercropping is a green and efficient planting mode that can make full use of the differences in crops’ physiological and ecological characteristics and land and climate resources while considering the environmental and yield benefits. This study selected five treatments: Salvia miltiorrhiza monoculture, Dactylis glomerata intercropped with S. miltiorrhiza, Cichorium intybus intercropped with S.miltiorrhiza, Trifolium repens intercropped with S.miltiorrhiza, and Lolium perenne intercropped with S.miltiorrhiza. Using one-way ANOVA, principle component analysis (PCA), and linear correlation analysis, we analyzed the changes in the soil physicochemical factors and the coupling relationship between them in the intercropping mode. The results showed that at different soil depths, the soil bulk density in the intercropping mode was significantly lower than that in the single cropping mode (p &lt; 0.05), and the soil water content and total porosity were significantly increased (p &lt; 0.05). There were no significant differences in soil pH among the five models (p &gt; 0.05), the content of soil organic matter was significantly higher than that in the single cropping mode (p &lt; 0.05), and the content of nitrogen and phosphorus also showed different changes. The correlation analysis showed that there was no significant correlation between the pH and soil physical properties (p &gt; 0.05); bulk density and chemical properties were negatively correlated, while the soil water content, field water-holding capacity, and total porosity were significantly positively correlated with the chemical properties (p &gt; 0.05). Therefore, it is suggested to strengthen the management of agricultural grass intercropping, improve soil pore structure, regulate the distribution of soil water and fertilizer, and improve the resilience of agricultural systems in the karst area of southwest China.

Distribution of soil water and nitrate in furrow irrigation under different plastic mulch placement conditions for a maize crop: Field and modelling study

1. Abbasi F., Feyen J., and Van Genuchten M.T., 2004. Two-dimensional simulation of water flow and solute transport below furrows: model calibration and validation. J. Hydrol., 290(1-2), 63-79. https://doi.org/10.1016/j.jhyd.... CrossRef Google Scholar

Evaluation of Moisture Content of Soil at Different Stages of Plant Growth under Different Irrigation Treatments

Drip irrigation is artificial technique of providing water to the roots of the plant at very low rates (2-20 litres/hour) from a system of small diameter plastic pipes fitted with emitters or drippers. A few low cost automation systems were developed and evaluated their performance with drip irrigation on sweet corn on the sandy soils of College of Agricultural Engineering, Bapatla. It was observed that single row drip irrigation showed better results compared to flood irrigation and paired row drip irrigation. The results indicated that the soil water distribution pattern showed the highest water content near the drip line for all scheduling techniques.As increase in time of operation Wetting diameter and Penetration depth increased in relative to time. With comparison of different irrigation systems, the soil moisture content value of before irrigation and after irrigation is better in single row drip system.

Effects of Various Quantities of Three Irrigation Water Types on Yield and Fruit Quality of ‘Succary’ Date Palm

A field experiment was conducted on date palm trees (Phoenix dactylifera ‘Succary’) cultivated on sandy loam soil from 2017 to 2018. This study investigated the effects of providing water of three different qualities, namely freshwater (FR) and two saline water sources: reclaimed wastewater (RW) and well-water (WE) applied through three irrigation levels representing 50% (I50), 100% (I100), and 150% (I150) of crop evapotranspiration (ETc), on the soil water and salt distribution patterns, yield, water productivity (WP), and fruit quality of the ′Succary′ date palm. The electrical conductivity (ECw) of FR, RW, and WE were 0.18, 2.06, and 3.94 dS m−1, respectively. Results showed that WE applied by the I150 treatment had the highest soil water content, followed by RW used in the I100 irrigation level and FR with I50, whereas the soil salt content was high for WE applied in the I50 level and low for FR applied by the I150 treatment. Deficit irrigation (I50) of date palms with either RW or WE reduced date yields on average 86 kg per tree, whereas the yield increased under over-irrigation (I150) with FR to 123.25 kg per tree. High WP values were observed in the I50 treatments with FR, RW, or WE (on average 1.82, 1.68, and 1.67 kg m−3, respectively), whereas the I150 treatment with each of the three water types showed the lowest WP values. Fruit weight and size were the lowest in the full irrigation (I100) with WE, whereas the I150 treatment with RW showed the highest values. There were no significant differences in either total soluble solids (TSS) or acidity values when the irrigation level decreased from 100% to 50% ETc. Compared with both I50 and I100 treatments, reduced values of both TSS and acidity were observed in the I150 treatment when ECw decreased from 3.94 to 0.18 dS m−1,. Fruit moisture content decreased with the application of saline irrigation water (i.e., RW or WE). Total sugar and non-reducing sugar contents in fruits were found to be decreased in the combination of RW and I150, whereas the 50% ETc irrigation level caused an increment in both parameters. These results suggest that the application of deficit irrigation to date palm trees grown in arid regions, either with FR or without it, can sufficiently maximize WP and improve the quality of fruits but negatively affects yield, especially when saline water is applied. The use of saline water for irrigation may negatively affect plants because of salt accumulation in the soil in the long run.

Field study and regression modeling on soil water distribution with mulching and surface or subsurface drip irrigation systems

The soil water status was investigated under soil surface mulching techniques and two drip line depths from the soil surface (DL). These techniques were black plastic film (BPF), palm tree waste (PTW), and no mulching (NM) as the control treatment. The DL were 15 cm and 25 cm, with surface drip irrigation used as the control. The results indicated that both the BPF and PTW mulching enhanced the soil water retention capacity and there was about 6% water saving in subsurface drip irrigation, compared with NM. Furthermore, the water savings at a DL of 25 cm were lower (15-20 mm) than those at a DL of 15 cm (19-24 mm), whereas surface drip irrigation consumed more water. The distribution of soil water content (θv) for BPF and PTW were more useful than for NM. Hence, mulching the soil with PTW is recommended due to the lower costs and using a DL of 15 cm. The θv values were derived using multiple linear regression (MLR) and multiple nonlinear regression (MNLR) models. Multiple regression analysis revealed the superiority of the MLR over the MNLR model, which in the training and testing processes had coefficients of correlation of 0.86 and 0.88, root mean square errors of 0.37 and 0.35, and indices of agreement of 0.99 and 0.93, respectively, over the MNLR model. Moreover, DL and spacing from the drip line had a significant effect on the estimation of θv. Keywords: palm tree waste mulching, plastic film mulching, soil water distribution, regression models DOI: 10.25165/j.ijabe.20211402.5200 Citation: Mattar M A, Al-Othman A A, Elansary H O, Elfeky A M, Alshami A K. Field study and regression modeling on soil water distribution with mulching and surface or subsurface drip irrigation systems. Int J Agric & Biol Eng, 2021; 14(2): 142–150.