Application Of Superabsorbent Polymers Research Articles

Using the AquaCrop model to simulate sesame performance in response to superabsorbent polymer and humic acid application under limited irrigation conditions.

Quantification of the effects of water consumption technologies on sesame performance has not been evaluated by any model yet. Field experiments were conducted to assess the sesame (Sesamum indicum L.) response to limited irrigation in an arid region. Experimental factors were irrigation levels (deficit and full irrigation; DI, FI respectively), application of superabsorbent polymer (SAP) (80 kg ha-1), foliar application of humic acid (HA) (6 kg ha-1), and control which were arranged in the split strip plot design. Sensitivity analysis demonstrated the robustness of the AquaCrop model for simulation of soil water content, sesame canopy cover, and final production. Satisfactory results were obtained for the simulation of biomass (B) (R2 = 0.92, EF = 0.87) and seed yield (SY) (R2 = 0.88, EF = 0.85). NRMSE (%) values for the simulated B (7.3%) and SY (6.9%) along with other model evaluation statistics confirmed the potential of the model for the study application. Model accuracy in simulating water use efficiency (WUE) (R2 = 0.70) and harvest index (HI) (R2 = 0.61) was slightly lower than SY and B. Comparison of the measured and simulated B, HI and WUE obtained for DI+SAP treatments revealed that the application of SAP under DI condition was an efficient approach and a useful alternative to FI at water scarcity conditions. Slight differences between the measured and simulated values of SY, B, HI, and WUE under conditions of application of SAP and HA as eco-friendly inputs and the results' consistency with other studies indicate the benefits of these inputs in arid regions for enhancing the performance of sesame crop.

Effect of Superabsorbent Polymer on Seedling Emergence and Growth of Cotton under Water Stress Conditions

Water availability is one of the major limiting factors of cotton productivity. The soil application of superabsorbent polymers (SAPs) may increase water use efficiency, improve soil physical properties, enhance seed germination and emergence, crop growth and yield and reduce the irrigation requirements of plants. The objective of this study was to investigate the effect of Zeba®, a polymer based on corn starch, on seedling emergence and growth of cotton under water stress. A set of pot experiments was conducted under completely randomized design with four replications of 25 seeds. Treatments included application rates of 5, 10, 15, 20 kg/ha and an untreated control, all under three levels of irrigation (adequate, moderate and deficit). The emergence performance was evaluated by final emergence percentage and mean emergence time. Root and shoot growth were measured for length and weight. The application of Zeba® promoted seedling emergence (higher emergence percentage from 17.9 to 22.6% and lower mean emergence time from 36 to 46% compared to control). Higher values for root and shoot traits were observed under Z10 and Z15 rates regardless of irrigation treatments. The adoption of the proposed SAP could represent a promising solution and thus increase moisture conservation in cotton.

Application of Super Absorbent Polymer and Plant Mucilage Improved Essential Oil Quantity and Quality of Ocimum basilicum var. Keshkeni Luvelou.

One of the major factors limiting the production of medicinal plants in arid and semi-arid areas is water deficit or drought stress. One-third of the land in the world is arid and semi-arid and is inhabited by nearly 4 × 108 people. Ocimum basilicum (sweet basil) is a valuable medicinal plant that is sensitive to water deficit, and water shortage negatively affects sweet basil yield and quality. Water availability in the root zone of basil could ameliorate the negative effects of water shortage. To the best of our knowledge, although the effects of hydrophilic polymers (HPs) have been studied in different agricultural crops, the effects of HP application in medicinal plants have not been previously investigated. This investigation was conducted to explore the effects on water use efficiency when using Stockosorb® (STS) and psyllium seed mucilage (PSM) as hydrophilic polymers (HPs) and the effects of these HPs on essential oil quality, quantity, and yield. The research was set up in a factorial experiment on the basis of completely randomized block design with three replications. We used two HPs, STS (industrial) and PSM (herbal), with two methods of application (mixed with soil, mixed with soil + root) at four concentrations (0%, 0.1%, 0.2%, and 0.3% (w/w)). Results showed that the STS and PSM significantly increased the dry herb yield (both shoot and root) in comparison to the control, and the improving effect was higher when these HPs were mixed with soil + root. The highest dry herb yield (6.74 and 3.68 g/plant for shoot and root, respectively) was detected in the PSM at 0.1% mixed with soil + root. There was not any significant difference in dry herb yield among PSM (0.1%), PSM (0.2%), and STS (0.2%) when mixed with soil + root. Soil application of PSM and soil + root application of STS at a concentration of 0.3% increased the Essential Oil (EO) content almost three-fold in comparison to the control (0.5% and 0.52% to 0.18% v/w, respectively). The maximum essential oil yield was recorded in plants treated with STS (0.2% in) or PSM (0.1%) by soil + root application (0.21 and 0.19 mL/plant, respectively). PSM at concentrations of 0.1% and 0.2% (mixed with soil + root) showed the highest water use efficiency (1.91 and 1.82 g dry weight (DW)/L H2O, respectively). STS mixed with soil also significantly improved water use efficiency (WUE) in comparison to the control. The application of these HPs improved the quality of sweet basil essential oil by increasing the linalool and decreasing the eugenol, epi-α-cadinol, and trans-α-bergamotene content.

Changes in growth and essential oil composition of sweet basil in response of salinity stress and superabsorbents application

To evaluate the effect of superabsorbent polymers (SAPs) on the growth, some physiological traits, essential oil (EO) content and composition of sweet basil (Ocimum basilicum cv. Keshkeni luvelu) under salinity stress, a pot factorial experiment in randomized complete design with three replications was done. Treatments included salinity stress levels (0, 40, 80, and 120 mM NaCl) and superabsorbents (Ackoasorb, Terracottem, Stockosorb, and control). The results showed that the growth characteristics, SPAD, K+, and K+/Na+ ratio were decreased by severity of NaCl stress, whereas the application of SAPs have increased them. On the other hand, EO content, membrane permeability, MDA, proline, and Na+ contents were increased under severity of NaCl stress and SAPs application were decreased them, except EO content. At the highest salinity level (120 mM NaCl), the application of the Terracottem reduced membrane permeability and Na+, however, shoot dry weight, shoot to root weight ratio, leaf dry matter and the EO content increased by the Terracottem application. In addition, the Stockosorb application decreased MDA and proline contents, but the percentages of oxygenated monoterpenes, especially linalool and tau-muurolol increased under Stockosorb application. In conclusion, the application of SAPs can alleviate the harmful effects of salt stress on quantity and quality yields of sweet basil.

Can Superabsorbent Polymers Improve Plants Production in Arid Regions?

Superabsorbent polymers (SAPs) have shown to be quite effective and useful in acting as a reservoir for water and some nutrients in arid and semiarid regions. There are many studies in Iran that have been performed in relation to SAPs and their useful application in agriculture; however, there is still a lack of its applied definition in arid regions. Therefore, this study was conducted with the aim of doing a meta-analysis of the results of studies conducted in Iran and answering a general question about whether the application of SAPs has been effective in enhancing the production or not, and if so, how much of SAP is recommended. To conduct this research, articles published during 2006–2016 on the subject of the effects of different rates of SAP application on yield and yield components of crops (including cereals, legumes, and medicinal and grassland plants) were investigated. The results of the meta-analysis showed that the mean consumption rate of SAPs for cereals, legumes, and medicinal and grassland plants was 83, 322, 1031, and 210 kg ha−1, respectively, and that, at these SAP application rates, the mean seed yield in cereals, medicinal plants, and legumes increased by 15.2, 12.6, and 38% (equivalent to 1059, 345, and 452 kg ha−1), respectively, compared with the control. Dry matter response to superabsorbent application was slower compared with the seed yield response. The mean consumption of 83 kg ha−1 of superabsorbent for cereals increased seed yield by 15.2% on average. According to the results, it seems that the application of 100 kg SAP ha−1 is the most appropriate rate for increasing seed and dry matter yields and satisfying economic aspects. These study findings may shed light on the environment and socioeconomic concerns and improve efficacy and reduction of costs.

Water productivity of irrigated maize production systems in Northern China: A meta-analysis

Understanding water productivity (WP) on a regional scale is useful for identifying and managing inefficiencies in irrigated crop production systems. However, relevant WP analyses are not available for maize production systems in China. A meta-analysis was conducted of maize WP in Northern China that included 2354 observations from 282 articles published between January 2000 and March 2018. Our goal was to quantify the current WP and its constraining factors, and estimate the boundary function for WP in the different maize agro-ecological zones of Northern China. The Northern China average WP across the large set of field experiments was 22.3 kg ha–1 mm–1, with Northeast China (NE, 25.8 kg ha–1 mm–1) > North China Plain (NCP, 22.3 kg ha–1 mm–1) ≈ Northwest China (NW, 21.6 kg ha–1 mm–1). The boundary function for WP had slopes of 42.5, 36.8 and 40.4 kg ha−1 mm−1 for NW, NCP and NE, respectively. The WP was significantly correlated with latitude, vapor pressure deficit, N application rate, seasonal average temperature, experimental regions and years. WP was increased by optimal irrigation, soil surface with plastic mulch, deep tillage, straw incorporation into the soil, ridge planting, and the application of super absorbent polymer. In this study, we provided both reference WP values, recommendations to achieve higher WP and identification of regions with opportunities for improvement.

高吸水性高分子樹脂（SAP）の植林への利用:SAP の特徴と現場における土壌水分の変化

高吸水性高分子樹脂（SAP）の植林への利用:SAP の特徴と現場における土壌水分の変化

Effects of drought stress and superabsorbent polymer on morpho-physiological and biochemical traits of Caper (Capparis spinosa L.)

Capparis spinosa, commonly known as caper bush, is native to certain hostile growing conditions including sandy or gravelly soils, rocky hillsides, cliffs, stone walls and rock crevices in Mediterranean coastal regions. Caper plant is used for the prevention of soil erosion in sloppy areas. Synthetic superabsorbent polymer was developed as a soil conditioner to heighten plant establishment and growth in drought-prone growing area. During growing seasons of 2016-2017, the effects of soil amendment with the superabsorbent Polymer A200 in four levels (S1= 0, S2= 75, S3= 150 and S4= 225 g) were investigated for each caper plant, considering three levels of irrigation (I1=0, I2= One irrigation per month and I3= one irrigation every two months) on the physical properties of the soil as well as their physiological parameters (chlorophyll a, b and total chlorophyll, carotenoid, Tss, electrolyte leakage) and plant height, yield per hectare, WUE, Soil moister, RWC and leaf area of an established caper plant under drying conditions. Analyses of variance showed that the interaction effects of treatments were significant (p<0.01) in all the studied traits. The results showed that water stress significantly decreased the height of a plant, yield per hectare, WUE, Soil moister, RWC, leaf area, total Chlorophylla, Carotenoid and electrolyte leakage, whereas the application of superabsorbent polymer compensated for the negative effect of drought stress, especially in high rates of polymer application (150 g), where the maximum effect was attained for all the studied traits. These findings strongly suggested that the irrigation intervals of caper can lead to an increase in the application of the superabsorbent polymer.

Swelling kinetic behavior of biochar-graft superabsorbent polymer composites

Superabsorbent polymers (SAPs) are crosslinked three dimensional structures that poses high swelling capacity in aqueous medium. Its application in agriculture beneficial as it is able to retain moisture in soil. SAPs incorporated with bio-char have been prepared via solution polymerization of polyacrylic acid with co-monomer of polyacrylamide in the presence of bio-char using methylenebisacryalmide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. In this research, the swelling kinetic behavior of SAP with biochar was studied on the effect of biochar percentage loading from 0-0.8wt. SEM imaging of sap icorporated biochar shows a porous structure which influences water absorbency. The maximum of water absorbency capacity reached an optimum value of 129.89 g/g at 0.4 % before decreasing with increasing bio-char loading. Mathematical model of kinetic diffusivity also revealed that the SAP-biochar incorporated follows a second order kinetic. The presence of bio-char could enhance physical properties by increasing the water-holding capacity, enhancing its water absorbency ability. Application of SAP incorporated biochar not only able to retain water, it could also help to fertilize agriculture.

The Characteristics of Absorbency Under Load (AUL) for Superabsorbent and Soil Mixtures

Various applications of superabsorbent polymers (SAP) include the use of these materials in agriculture and environmental engineering to increase soil water retention. Under such conditions, there is water absorption of the SAP in soil under load. This paper presents the results of absorbency under load (AUL) of a cross-linked copolymer of acrylamide and potassium acrylate mixed at ratios of 0.3%, 0.5% and 1.0% with coarse sand and sandy loam. The mixtures were subjected to loads equivalent to 10, 20 and 40 cm of soil. The highest differences in AUL values for both soils, compared to the control sample, were obtained after 24 hours and at a maximum load of 5.9 kPa, which corresponds to a load of a 40 cm thick topsoil layer. The AUL was 71.4 g∙g−1 for coarse sand and 52.7 g∙g−1 for sandy loam with a 1.0% SAP addition, which corresponded to 24.0% and 18.0%, respectively, of the absorption in the control sample. All the conducted tests revealed a significantly low rate of water absorbency, which is especially important for capturing the water that infiltrates into the soil profile. The results demonstrate that water absorption by SAPs decreased with the increase in SAP addition.

Effect of organic coats with superabsorbent polymers on improving the germination and early vigor Milk thistle (Silybum marianum L.) seeds under salinity stress

Salinity is a major environmental stress negatively influencing germination and seedling establishment in a wide variety of crops. The objective of this study was to use the organic materials with superabsorbents to improve the emergence rate and seedling traits of Milk thistle (Silybum marianum L.) under salinity stress. A factorial experiment in a completely randomized design with three replications was conducted in outdoor pots. Treatments included: organic coats at two levels (C1= peat moss and C2= vermicompost), superabsorbent polymers at seven levels (A1= without superabsorbent, A2-A4= coats with 2, 4, and 6 g superabsorbent of A200 per kg organic material, and A5-A7= coats with 2, 4, and 6 g superabsorbent of F1 per kg organic material), and salinity (S) stress at five levels (0, -2, -4, -6, and -8 bar). Results showed that organic material and the type and amount of superabsorbent significantly (p ≤ 0.05) affected emergence, emergence rate, plant vigor index, shoot dry weight, leaf area, specific leaf area, relative water content, and total chlorophyll. Application of superabsorbent polymers with organic material reduced salinity stress in the primary growth stage of Milk thistle. Generally superabsorbent A200 is more effective than superabsorbent F1 and vermicompost coats better are than peat moss coats.

Responses of Native Plants and Downy Brome to a Water-Conserving Soil Amendment

Restoring native plants in rangelands threatened by downy brome (Bromus tectorum L.) presents a serious challenge to land managers. Higher, more consistent soil moisture, as well as slightly compacted soils, may reduce the competitive abilities of downy brome. We manipulated these factors with three treatments: superabsorbent polymer (SAP), a soil-binding agent, and roller compaction at two restoration sites, Wagon Road Ridge (WRR) and Sagebrush (SGE), in northwestern Colorado. SAPs absorb water when soils are wet and then gradually release it, often reducing plant water stress. The binding agent we used is purported to increase water infiltration while reducing soil movement. In Experiment 1, we crossed an SAP, a binding agent, and rolling and found that SAP benefitted perennial grass establishment at the WRR site only. SAP also decreased downy brome cover and biomass at WRR. The binding agent increased soil moisture at both sites, and the highest level of binding agent reduced downy brome cover in the absence of SAP at the SGE site. In Experiment 2, we examined only SAP, with larger plots and a more complex seed mix. Again, SAP benefitted perennial grass establishment at WRR only. SAP reduced initial perennial forb density at both sites but did not affect forb cover in subsequent years. SAP effects on downy brome were site-specific. There was a trend for reduced downy brome cover with SAP at WRR, but SAP caused a large increase in downy brome cover in yr 3 at SGE. Granulated SAP can be applied easily along with drill seeding, making it potentially applicable for dryland restoration. However, site specific factors may influence whether perennial grasses or downy brome most benefit from SAP application.

Influence of Super Absorbent Polymers (Saps) on Irrigation Interval and Growth of Black Pepper (<i>Piper Nigrum</i> L.) in Nursery Management

Drought stress is one of the most adverse limitations of local black pepper production in Dry and Intermediate zones of Sri Lanka. Application of Super Absorbent Polymers (SAPs) is hypothesized to result in the optimised use of water resources in these regions. A study was undertaken to examine the effect of different levels of irrigation intervals and different level of SAPs and then to find out the best treatment combination for growth of black pepper plants under nursery management. The experiment was conducted at Intercropping and Betel Research Station, Narammala. GK49 was the selected variety and Zeba (commercial name) was the selected SAP type. The experiment was carried out following a factorial layout based on Complete Random Design (CRD) with three replicates. The factors were three levels of irrigation intervals as 4, 8 and 10 days (T1 to T3) and four levels of SAPs as no Zeba, 1g, 1.5g and 2g of Zeba (L1 to L4). Plant growth parameters were measured at two weeks interval and all the parameters were analysed by anova using SAS software. Statistical analysis had shown that there were significant effects (P<0.05) of main factors and their interactions on plant parameters. Plant parameters were decreased with decreased Zeba amount and increased irrigation interval. In this study 2g of Zeba with 4 and 8 days irrigation interval (L4T1, L4T2) and 1.5g of Zeba with 4 days of irrigation interval (L3T1) treatments were the better treatments. However, considering the cost effectiveness 2g of Zeba with 8 days irrigation interval (L4T2) treatment is recommended as the best treatment for increasing plant performances and decreasing water stress conditions to the plant. Therefore, the results of this study showed that SAPs can store and absorb a considerable amount of water and reduce unfavourable effects of water shortage on black pepper plants in nursery management.

Recommendations of RILEM TC 260-RSC for using superabsorbent polymers (SAP) for improving freeze–thaw resistance of cement-based materials

This recommendation is focused on application of superabsorbent polymers (SAP) for the improvement of the resistance of cement-based materials to freeze–thaw attack with or without deicing salts. A simple approach to the determination of the amount and properties of SAP as well as methods to verify SAP effectiveness for frost resistance protection are presented.

Effects of insecticides applied in-furrow with superabsorbent polymer on peanut cultivars infected with Tomato spotted wilt virus

ABSTRACT Spotted wilt of peanut (SWP) (Arachis hypogaea L.) caused by Tomato spotted wilt virus (TSWV; family Tospoviridae, genus Orthotospovirus) is a common disease that causes severe economic losses in peanut producing regions of the world. The causal agent is transmitted by thrips (Thysanoptera: Thripidae). Field experiments were conducted in 2017 and 2018 to determine if management of spotted wilt and subsequent productivity of peanut, including economic value, could benefit from applying a superabsorbent polymer (SAP) with standard in-furrow insecticides at planting. To determine this, two individual experiments were performed. In the first study, phorate and imidacloprid were individually applied with (2.24 kg/ha) or without SAP across cultivars susceptible (FloRun 157 or TUFRunner 511), moderately susceptible (Georgia 06G), and resistant (Sullivan or TifNV-High O/L) to TSWV. Nontreated controls were included in all experiments. The second study sought to determine the efficacy of different rates of SAP (0, 2.24, 5.6, and 8.97 kg/ha). The initial study was conducted in three locations across South Carolina and Georgia, while the second was conducted at Blackville, SC. In the first study, incidence of SWP was reduced (P = 0.0547) in multiple location-year analysis with a reduction of 9.4% observed in susceptible cultivars treated with phorate compared to untreated checks and those with imidacloprid. SAP did not affect final SWP incidence or economic value (P &amp;gt; 0.05) and was not consistently significant for yield. From the SAP rate study, a linear relationship of decreasing SWP incidence was observed with increasing SAP application rates for both imidacloprid and phorate in 2017 and 2018. On a means comparison basis, SWP was lower than the no-SAP check at SAP rates of 5.56 and 8.97 kg/ha, but this did not necessarily translate into increased yield. Additional experiments are needed to elucidate the relationship superabsorbent polymer may have to susceptible cultivars and phorate.

Salt-Tolerant Superabsorbent Polymer with High Capacity of Water-Nutrient Retention Derived from Sulfamic Acid-Modified Starch.

The application of superabsorbent polymers (SAPs) is hindered because their absorption capability is greatly affected by the electrolytes in a solution. A novel modified water-absorbent polymer was fabricated by solution polymerization of sulfamic acid-modified starch and acrylic acid; the swelling ratios of this absorbent polymer were 1026 g/g in deionized water and 145 g/g in 0.9% sodium chloride solution and increased by 99.5 and 13.4%, respectively, when compared with ordinary starch-grafted acrylic SAPs. The water absorption capacity was measured in water at different pH values, salt concentrations, and temperatures. In addition, water and fertilizer retentions were studied by simulated leaching tests in a soil column. The results showed that water absorption capacities of the modified SAP in salt solutions were improved due to the adsorption and transfer of water molecules by the sulfonic acid groups. Compared to the losses when there was no superabsorbent treatment, the water, nitrate, ammonium nitrogen, and water-soluble potassium losses during the salt-tolerant superabsorbent treatment were significantly reduced by 18.5, 22.8, 88.0, and 63.8%, respectively. The method introduced in this study could guide the development and wide application of salt-tolerant SAPs in agriculture and horticulture.

Nutrient content of fermented fertilizers and its efficacy in combination with hydrogel in Zea mays L.

PurposeThe nutritional content of fermented fertilizers was determined, and the effect of its application in combination with hydrogel was evaluated in a bioassay with maize plants.MethodsThe fertilizers were produced in artisanal biodigesters and the bioassay was carried out in pots with CP-569 maize. The nutritional content of the fermented fertilizers was evaluated, and in maize plants growth variables were measured, along with N–P–K contents in the aerial and root biomass.ResultsThe types of biol show different characteristics for organic matter, N, N–NH4, N–NO3, P, K, Ca, Mg, Fe, Cu, Zn, Mn and B, as well as physical characteristics. The terms of the bioassay, the treatments with super absorbent polymer (SAP), biol and biol + SAP, showed significant statistical differences in terms of plant height, stem diameter and number of leaves 30 days after emergence. In the dry weight of aerial and root biomass, no statistical differences were found. In terms of the contents of N–P–K in biomass, statistical differences were found for P in aerial biomass and K in both aerial and root biomass.ConclusionDue to their physical and chemical properties, biols are an alternative to fertilizers. With the application of biol and SAP, maize plants undergo significant increases in height, stem diameter and number of leaves. By applying biol and SAP, the contents of N–P–K were not increased significantly in the aerial and root biomasses in comparison to the control.

The effect of humic acid and water super absorbent polymer application on sesame in an ecological cropping system: a new employment of structural equation modeling in agriculture

BackgroundThe current knowledge does not prepare a precise scientific tool for quantifying the effects of inputs particularly ecofriendly inputs such as superabsorbent polymer (SAP) and humic acid (HA) are being used to increase soil fertility, improve crop performance and finally food production. This study was designed and conducted aimed to suggest an innovative approach not only to identify and quantify the effects of these inputs but also to determine the efficient path among underground/aboveground relationships associated with sesame oil production. Two experiments were conducted at the Research Farm of Ferdowsi University of Mashhad using randomized complete block design with split strip plot arrangement and three replications in two successive cropping years (2015–2016) to evaluate the effects of SAP and HA on Sesamum indicum L. growth characteristics and oil production under two different irrigation levels including: supplying 50 and 100% of the sesame water requirement were allocated to the main plots. Applying of SAP (80 kg ha−1) into the soil and control (no applying SAP) were allocated to the subplots. Foliar application of HA (6 kg ha−1) and control (not applying HA) were allocated to the strip plots. The analysis of variance revealed that the effects of HA and SAP on many sesame traits also soil properties were significant.ResultThe fitted structural equation model suggests a direct strong-positive effect of leaf area index (LAI), plant height (PlantH) and water-use efficiency (WUE) on plant architecture construct (PlantArchitecture), soil nitrogen content (SoilN), soil electrical conductivity (SoilEC), and on soil properties construct (SoilProperties), which finally increase the sesame qualitative yield production. The calculation of the standard regression coefficients of the model’s variables revealed that variables including: LAI, WUE and PlantPhysiology have had the most causal effect to defining the yield of sesame oil under the field condition of SAP and HA application. The findings in our study suggest that the direct advantages of SAP and HA application is to increase PlantPhysiology, PlantArchitecture and SoilProperties by 65, 50 and 17 percent, respectively, through contributing to the respective processes.ConclusionGenerally, the coefficient of determination of the suggested model (R2= 0.44) indicates that the model explains 44% of the variations in the sesame qualitative yield. The present study suggests employing the structural equation modeling could be best taken as a precise and practical quantitative modeling approach rather than a specific statistical technique, not only to quantify the effects of inputs and management operations but also helps to profound our understanding to identify the most efficient paths involved to certain process which in turn prepare options to reduce production costs beside to produce healthy food and products.

Amelioration of drought effects in wheat and cucumber by the combined application of super absorbent polymer and potential biofertilizer.

Biofertilizer is a good substitute for chemical fertilizer in sustainable agriculture, but its effects are often hindered by drought stress. Super absorbent polymer (SAP), showing good capacity of water absorption and retention, can increase soil moisture. However, limited information is available about the efficiency of biofertilizer amended with SAP. This study was conducted to investigate the effects of synergistic application of SAP and biofertilizers (Paenibacillus beijingensis BJ-18 and Bacillus sp. L-56) on plant growth, including wheat and cucumber. Potted soil was treated with different fertilizer combinations (SAP, BJ-18 biofertilizer, L-56 biofertilizer, BJ-18 + SAP, L-56 + SAP), and pot experiment was carried out to explore its effects on viability of inoculants, seed germination rate, plant physiological and biochemical parameters, and expression pattern of stress-related genes under drought condition. At day 29 after sowing, the highest viability of strain P. beijingensis BJ-18 (264 copies ng−1 gDNA) was observed in BJ-18 + SAP treatment group of wheat rhizosphere soil, while that of strain Bacillus sp. L-56 (331 copies ng−1 gDNA) was observed in the L-56 + SAP treatment group of cucumber rhizosphere soil. In addition, both biofertilizers amended with SAP could promote germination rate of seeds (wheat and cucumber), plant growth, soil fertility (urease, sucrose, and dehydrogenase activities). Quantitative real-time PCR analysis showed that biofertilizer + SAP significantly down-regulated the expression levels of genes involved in ROS scavenging (TaCAT, CsCAT, TaAPX, and CsAPX2), ethylene biosynthesis (TaACO2, CsACO1, and CsACS1), stress response (TaDHN3, TaLEA, and CsLEA11), salicylic acid (TaPR1-1a and CsPR1-1a), and transcription activation (TaNAC2D and CsNAC35) in plants under drought stress. These results suggest that SAP addition in biofertilizer is a good tactic for enhancing the efficiency of biofertilizer, which is beneficial for plants in response to drought stress. To the best of our knowledge, this is the first report about the effect of synergistic use of biofertilizer and SAP on plant growth under drought stress.

THE USE OF SOIL HYDRAULIC PROPERTIES AS INDICATORS FOR ASSESSING THE IMPACT OF MANAGEMENT PRACTICES UNDER SEMI-ARID CLIMATES

Water retention capacity and hydraulic conductivity are major soil hydraulic properties that influence soil quality and the environment. The objective of this work was to assess major soil hydraulic characteristics in response to the effect of soil management and tillage practices. Eight soil treatments were considered: conventional tillage, reduced tillage, no-tillage, fallow no-tillage, abandoned soil, compacted soil, plough on compacted soil, and application of super absorbent polymers. The experiments were conducted at Koohin station, Iran. The equality of field saturated hydraulic conductivity (Kfs) and estimated Kfs was studied. Moreover, the contribution of the porosity to soil water flux was investigated and quantified. At the -1500 kPa potential, water content was influenced by the compacted treatment at soil depth of 0 to 25 cm. In this study, van Genuchten water retention curve parameters n, a, and .r values were not significantly different among treatments. The fit of the van Genuchten equation to the soil water retention data resulted in low sum of squared errors. No distinct trend was observed for estimated sorptivity in the studied area. The sorptivity values were not significantly different among soil management practices. Moreover, estimated Kfs values by DISC software were lower than measured Kfs. Soil treatments did not influence the soil water-conducting medium and macropores. Unsaturated hydraulic conductivity may partly be affected by soil texture and soil structure which were uniform under all treatments. Soil water retention and transmission may be manipulated with changes in pore size distribution under different tillage and management practices in long-term.