Irrigation Water Salinity Research Articles

Successive addition of rice straw biochar enhances carbon accumulation in soil irrigated with saline or non-saline water

Biochar has been evaluated globally to improve soil fertility and mitigate climate change. However, the long-term effects of successive biochar application on carbon (C) accumulation in soil irrigated with saline versus non-saline water (canal water) has not been investigated. A field experiment was conducted to study the effects of rice straw biochar addition rates (0, 2, 4, 8 Mg ha−1) on C storage in soil irrigated with water of different electrical conductivity [EC, dS m−1]; 0.3 (non-saline canal irrigation water; CIW), 5 (saline irrigation water; SIW5), 10 (SIW10), and 15 (SIW15) in a cotton-wheat system. Long-term irrigation with saline water of variable EC levels adversely affected soil functions, reducing above-ground biomass in cotton (12–48%) and wheat (5–27%). In contrast, plots irrigated with saline water but amended with rice straw biochar showed significant improvement in aboveground biomass (both in cotton and wheat), possibly due to its beneficial effects on soil properties such as soil EC, organic carbon, microbial population, water and nutrient availability, bulk density, soil aggregation, and proliferation of roots. Interestingly, the change in total organic C (TOC) stocks (8.5, 17, and 27.5 Mg C ha−1) after 5 years were found to be almost double the amount of biochar C added (4.3, 8.6, 17.2 Mg ha−1), indicating stabilization of belowground C inputs from the root biomass by the applied biochar and also possibly through its physical interaction with aggregates and minerals. Even though biochar application to saline water irrigated plots increased the contribution of plant-derived C to overall soil TOC stocks, it was still lower compared with canal water irrigated plots. The study conclusively established that the long-term stabilization of biogenic C through biochar has essential implications for mitigating climate change by accumulating additional C beyond the recalcitrant C contained in biochar.

Plant Growth Promoting Rhizobacteria and Silica Nanoparticles Stimulate Sugar Beet Resilience to Irrigation with Saline Water in Salt-Affected Soils.

Combined stressors (high soil salinity and saline water irrigation) severely reduce plant growth and sugar beet yield. Seed inoculation with plant growth-promoting rhizobacteria (PGPR) and/or foliar spraying with silica nanoparticles (Si-NP) is deemed one of the most promising new strategies that have the potential to inhibit abiotic stress. Herein, sugar beet (Beta vulgaris) plants were treated with two PGPR (Pseudomonas koreensis MG209738 and Bacillus coagulans NCAIM B.01123) and/or Si-NP, during two successive seasons 2019/2020 and 2020/2021 to examine the vital role of PGPR, Si-NP, and their combination in improving growth characteristics, and production in sugar beet plants exposed to two watering treatments (fresh water and saline water) in salt-affected soil. The results revealed that combined stressors (high soil salinity and saline water irrigation) increased ion imbalance (K+/Na+ ratio; from 1.54 ± 0.11 to 1.00 ± 0.15) and declined the relative water content (RWC; from 86.76 ± 4.70 to 74.30 ± 3.20%), relative membrane stability index (RMSI), stomatal conductance (gs), and chlorophyll content, which negatively affected on the crop productivity. Nevertheless, the application of combined PGPR and Si-NP decreased oxidative stress indicators (hydrogen peroxide and lipid peroxidation) and sodium ions while increasing activities of superoxide dismutase (SOD; up to 1.9-folds), catalase (CAT; up to 1.4-folds), and peroxidase (POX; up to 2.5-folds) enzymes, and potassium ions resulting in physiological processes, root yield, and sugar yield compared to non-treated controls under combined stressors (high soil salinity and saline water irrigation). It is worth mentioning that the singular application of PGPR improved root length, diameter, and yield greater than Si-NP alone and it was comparable to the combined treatment (PGPR+Si-NP). It was concluded that the combined application of PGPR and Si-NP has valuable impacts on the growth and yield of sugar beet growing under combined stressors of high soil salinity and saline water irrigation.

Uncertainty Analysis of HYDRUS-1D Model to Simulate Soil Salinity Dynamics under Saline Irrigation Water Conditions Using Markov Chain Monte Carlo Algorithm

Utilizing degraded quality waters such as saline water as irrigation water with proper management methods such as leaching application is a potential answer to water scarcity in agricultural systems. Leaching application requires understanding the relationship between the amount of irrigation water and its quality with the dynamic of salts in the soil. The HYDRUS-1D model can simulate the dynamic of soil salinity under saline water irrigation conditions. However, these simulations are subject to uncertainty. A study was conducted to assess the uncertainty of the HYDRUS-1D model parameters and outputs to simulate the dynamic of salts under saline water irrigation conditions using the Markov Chain Monte Carlo (MCMC) based Metropolis-Hastings algorithm in the R-Studio environment. Results indicated a low level of uncertainty in parameters related to the advection term (water movement simulation) and water stress reduction function for root water uptake in the solute transport process. However, a higher level of uncertainty was detected for dispersivity and diffusivity parameters, possibly because of the study’s scale or some error in initial or boundary conditions. The model output (predictive) uncertainty showed a high uncertainty in dry periods compared to wet periods (under irrigation or rainfall). The uncertainty in model parameters was the primary source of total uncertainty in model predictions. The implementation of the Metropolis-Hastings algorithm for the HYDRUS-1D was able to conveniently estimate the residual water content (θr) value for the water simulation processes. The model’s performance in simulating soil water content and soil water electrical conductivity (ECsw) was good when tested with the 50% quantile of the posterior distribution of the parameters. Uncertainty assessment in this study revealed the effectiveness of the Metropolis-Hastings algorithm in exploring uncertainty aspects of the HYDRUS-1D model for reproducing soil salinity dynamics under saline water irrigation at a field scale.

Potassium Humate and Plant Growth-Promoting Microbes Jointly Mitigate Water Deficit Stress in Soybean Cultivated in Salt-Affected Soil.

Lack of high-quality irrigation water and soil salinity are two main environmental factors that affect plant development. When both stressors are combined, the soil becomes sterile and constrains plant productivity. Consequently, two field trials were designed to assess whether plant growth-promoting microbes (PGPMs; Bradyrhizobium japonicum (USDA 110) and Trichoderma harzianum) and potassium humate (K-humate) can stimulate soybean growth, productivity, and seed quality under two different watering regimes as follows: (i) well-watered (WW), where plants were irrigated at 12-day intervals (recommended), and (ii) water stress (WS), where plants were irrigated at the 18-day intervals in salt-affected soil during 2020 and 2021 seasons. Results revealed that coupled application of PGPMs and K-humate resulted in a substantial improvement in K+ levels in the leaves compared to Na+ levels, which has a direct positive impact on an enhancement in the antioxidants defense system (CAT, POX, SOD), which caused the decline of the oxidative stress indicators (H2O2, MDA, and EL%) as well as proline content under water stress in salt-affected soil. Hence, a significant increase in root length, nodule weight, soybean relative water content (RWC), stomatal conductance, photosynthetic pigments, net photosynthetic rate, soluble protein, seed carbohydrate content as well as the number of pods plant-1 and seed yield was reported. In conclusion, the combined application of PGPMs and K-humate might be recommended to maximize the soybean growth and productivity under harsh growth conditions (e.g., water stress and soil salinity).

NaCl Accumulation, Shoot Biomass, Antioxidant Capacity, and Gene Expression of Passiflora edulis f. Flavicarpa Deg. in Response to Irrigation Waters of Moderate to High Salinity

Passiflora edulis f. flavicarpa (yellow passion fruit) is a high-value tropical crop explored for both fruit and nutraceutical markets. As the fruit production in the US rises, the crop must be investigated for the effects of salinity under semi-arid climates. We assessed the effects of irrigation-water salinity, leaf age, and drying method on leaf antioxidant capacity (LAC) and plant genetic responses. Plants were grown in outdoor lysimeter tanks for three years, with waters of electrical conductivities of 3.0, 6.0, and 12.0 dS m−1. Both Na and Cl significantly increased with salinity; leaf biomass at 3.0 and 6.0 dS m−1 were similar but reduced significantly at 12.0 dS m−1. Salinity had no effect on LAC, but new leaves had the highest LAC compared to older leaves. Low-temperature oven-dried (LTO) and freeze-dried (FD) leaves had the same LAC. The analyses of twelve transporter genes, six involved in Na+ transport and six in Cl− transport, showed higher expressions in roots than in leaves, indicating a critical role of roots in ion transport and the control of leaf salt concentration. Passion fruit’s moderate tolerance to salinity and its high leaf antioxidant capacity make it a potential new fruit crop for California, as well as a rich source of flavonoids for the nutraceutical market. Low-temperature oven drying is a potential alternative to lyophilization in preparation for Oxygen Radical Absorbance Capacity (ORAC) analysis of passion fruit leaves.

An optimum combination of irrigation amount, irrigation water salinity and nitrogen application rate can improve cotton (for fiber) nitrogen uptake and final yield

In some arid regions, the complex planting environment creates higher requirements in terms of cotton planting field management. In order to make a reasonable strategy to utilize underground saltwater resources, save irrigation water and reduce the excessive application of nitrogen fertilizer , we carried out a field experiment in Xinjiang. This study is conducted to explore the effects of irrigation water quantity, irrigation water salinity , and nitrogen application rate on nitrogen fertilizer absorption and cotton yield. Here, three experimental factors and four levels were used in the experiment. Irrigation amounts: 0.7, 1.0, 1.3 and 1.6 ETc; irrigation water salinity: 10.9, 7.8, 4.7, 1.5 dS m −1 ; nitrogen application: 100, 200, 300 and 400 kg N ha −1 were set in the experiment. The experiment was designed according to orthogonal table L 16 (4 3 ). The results showed that the salinity of irrigation water had no effect on soil nitrogen transport, and the soil nitrogen content increased with the increase in nitrogen application. A low level of irrigation increased the lateral migration of nitrogen, whereas excessive irrigation increased the migration of nitrogen to deep soil. When the ratio of irrigation amount (mm) and nitrogen application (kg N ha −1 ) was 2.77, it could ensure the uniform distribution of nitrate nitrogen, and made nitrogen accumulate in the soil layer around the crop root zone . High irrigation increased the nitrogen uptake of the whole cotton plant; however, excessive irrigation would cause the apical dominance of cotton, such that the accumulation of dry matter and nitrogen migration were mainly concentrated in cotton roots and stems, which was not conducive to the migration of nitrogen to the boll (boll shell, seed and fiber). The combination of 675 mm, 7.8 dS m −1 , and 400 kg N ha −1 was more conducive to the migration of nitrogen to the cotton boll. Through principal component analysis, 675 mm irrigation amount, 1.5dS m −1 , and 200 kg N ha −1 is the most recommended irrigation and fertilization strategy. When the irrigation water salinity drops to 7.8 dS m −1 , salt stress can be alleviated by increasing the nitrogen application to 400 kg N ha −1 . • The interaction of irrigation amount and nitrogen application rate greatly affected the soil nitrate nitrogen content. • The ratio of irrigation amount (mm) and N application (kg N ha −1 ) of 2.77 can ensure the uniform distribution of nitrate-N. • Excessive irrigation will cause the apical dominance of cotton and also can decrease productivity. • A combination of 675 mm, 7.8 dS m −1 , and 400 kg N ha −1 was found more favorable for the migration of N to the cotton boll.

Fisiologia e crescimento do milho sob salinidade da água e aplicação de peróxido de hidrogênio

ABSTRACT The salinity of irrigation water or soil is the abiotic factor that most negatively impacts the yield of crops, including green maize, so it is necessary to find alternatives to ensure production. In this context, this study aimed to evaluate gas exchange, photosynthetic pigments, and growth of maize under salinity of irrigation water and application of hydrogen peroxide. The experiment was conducted at the Center of Sciences and Agrifood Technology, Pombal, PB, belonging to the Federal University of Campina Grande, in the period from January to February 2015, using the maize hybrid ‘AG 1051’. The treatments consisted of two salinity levels of irrigation water (0.3 and 2.0 dS m-1) and five concentrations of hydrogen peroxide (0, 40, 80, 160, and 320 µmol L-1) applied via irrigation water. The experimental design was completely randomized, in a 2 × 5 factorial scheme, with four replicates. ECw of 2.0 dS m-1 reduces transpiration, stomatal conductance, total chlorophyll, carotenoids, and initial growth, but does not affect the dry mass accumulation of maize plants. Application of H2O2 via soil varying from 0 to 320 µmol L-1 causes reductions in the CO2 assimilation rate and transpiration, as well as at concentrations from 0 to 160 µmol L-1 for stomatal conductance of plants irrigated with ECw of 2.0 dS m-1. Application of H2O2 via soil up to a concentration of 320 µmol L-1 increases the plant height, but reduces culm diameter of maize.

Hidrogel como mitigador do estresse salino durante o estabelecimento de mudas de Tagetes patula L.

ABSTRACT Hydrogels favor moisture retention in the substrate and can attenuate the effects of salt stress on the production of potted plants. In this context, this research sought to evaluate the use of hydrogel to mitigate the damage caused by the salinity of irrigation water on the emergence, growth, and thermal index of Tagetes patula L. seedlings. The research was carried out in a greenhouse, in September 2020, in the municipality of Fortaleza, Ceará State, Brazil. The design used was randomized blocks in a split plot. The plots corresponded to seven levels of electrical conductivity of the irrigation water - ECw (0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 dS m-1) and the subplots corresponded to four hydrogel concentrations (0, 1.0, 2.0, and 3.0 g L-1), with five replicates and each subplot consisted of 27 seeds. The application of 3.0 g hydrogel L-1 of substrate favored the production of leaves and reduced the thermal index in plants associated with the increase in the salinity of the substrate up to 6.0 dS m-1. The use of 3.0 g L-1 hydrogel increases seedling height, leaf dry mass, and total dry mass compared to treatments without water-retaining polymer, even at moderate (2.0 to 3.0 dS m-1) and high (4.0 to 6.0 dS m-1) salinity levels, thus indicating a possible effect of mitigation of damage caused by the salinity of the irrigation water. However, the intensity of this mitigating effect decreases at higher levels of salt stress.

Adubação orgânica e estresse salino no desempenho agronômico da cultura do milho

ABSTRACT Irrigation water salinity can cause serious problems in crop production, while organic fertilizer sources potentially mitigate saline stress. Thus, this study aimed to evaluate the productivity of maize crops under irrigation with saline water and organic fertilization. The study was conducted in the field from August to November 2020 at the experimental farm of the Universidade da Integração Internacional da Lusofonia Afro-Brasileira (UNILAB), Redenção-CE. A randomized block design was used, in subdivided plots, in which the plots consisted of two levels of irrigation water salinity (0.8 and 3.0 dS m-1). Four combinations of organic fertilizer sources were applied in the subplots, composed of 10 plants each, with four replications: C1, cattle manure + poultry biofertilizer + goat biofertilizer; C2, cattle manure + goat biofertilizer; C3, cattle manure + poultry biofertilizer; and C4, control treatment. The combination of organic fertilizer sources did not influence the accumulation of assimilates and productivity of maize crops under the irrigation water salinity of 3.0 dS m-1, except for C3, which attenuated the saline effect.

Sugarcane (Saccharum officinarum L.) under saline stress: Growth, productivity, technological quality, and industrial yield

Water scarcity is one of the main factors that contribute to the reduction of productivity in crops, and irrigation with lower water quality is an option to minimize water stress. The objective of this work was to evaluate the growth, productivity, technological quality, and industrial yield of the plant sugarcane and the first ratoon irrigated with brackish water and leaching conditions and the productivity of the second ratoon under the rainfed regime. The research was carried out at the Federal Rural University of Pernambuco, Recife-PE, in drainage lysimeters using a completely randomized design, in a 5 × 2 factorial scheme: five levels of irrigation water salinity (ECw: 0.5, 2.0, 4.0, 6.0, and 8.0 dS m −1 ) obtained by adding NaCl and CaCl 2 to the local distribution water (0.5 dS m −1 ) and conditions without leaching fraction (LF1 = 0) and with leaching fraction (LF2 = 0.17), corresponding to 100 % and 120 % of the crop evapotranspiration , with four replications. The growth, productivity, and technological quality were measured in the plant and first ratoon cane and the productivity of the second ratoon. The salinity of the irrigation water reduced the growth, productivity, technological quality, and industrial yield in the plant sugarcane and first ratoon; this effect is minimized by the leaching fraction of 0.17. The salinity of irrigation water from plant sugarcane and the first ratoon promoted a residual effect , negatively affecting the agronomic performance of the second ratoon. • Salinity reduces growth, yield, technological quality, and industrial yield in sugarcane plants. • Salinity of 8 dS m −1 promotes an average yield reduction of up to 43 % in the condition without leaching fraction. • The use of the leaching fraction (0.17) promotes a yield greater than 25 % compared to the condition without leaching. • Sugarcane is classified as moderately salinity tolerant when the leaching fraction (0.17) is adopted.

Manejo da irrigação para o cultivo de sorgo granífero com água salina

ABSTRACT In order to obtain an efficient cultivation of grain sorghum in production systems that use saline water, an adequate management becomes necessary for maximizing its production. The present study aimed to evaluate the effect of the application of leaching fractions in the saline water irrigation management on the production of sorghum varieties and on the distribution of water and salts in the soil profile, under semiarid conditions. The study was carried out in the municipality of Petrolina, semiarid region of Brazil. The experimental design was randomized blocks, with four replicates, in split-split plots; four leaching fractions (LF): 0, 5, 10, and 15% with saline water from artesian well in the plots, three varieties of grain sorghum: 1011-IPA, 2502-IPA and Ponta Negra in the subplots, and two crop cycles (1st and 2nd cut) in the sub-subplots. The evaluated variables were distribution of water and salts in the soil profile, biometric variables, fresh biomass, dry biomass, and grain yield. Application of leaching fractions of up 15% in saline water irrigation promotes better distribution of salts in the soil profile, with increments of up to 60% in the grain yield of the sorghum varieties evaluated. The production of the varieties 1011-IPA and Ponta Negra is a feasible alternative in systems irrigated with saline water with average electrical conductivity of 4.19 dS m-1, in Ultisol, under semiarid conditions.

Long-term saline water drip irrigation alters soil physicochemical properties, bacterial community structure, and nitrogen transformations in cotton

Saline water irrigation has become important in alleviating shortages of freshwater resources in arid areas. However, long-term saline irrigation increases soil salinity with resulting effects on soil nutrient transformations. Although soil nitrogen (N) transformations are key processes in terrestrial ecosystems, how irrigation with saline water affects N transformations is not fully understood. Therefore, we used metagenomics to investigate effects of 11 years saline water drip irrigation on soil bacterial community structure and N transformations in a cotton field. In a field experiment, there were two irrigation water salinity (ECw) treatments, 0.35 dS·m−1 [freshwater (FW)] and 8.04 dS·m−1 [saline water (SW)], and two N application rates, 0 (N0) and 360 kg N ha−1 (N360). Compared with FW irrigation, SW irrigation significantly increased soil water content, salinity, organic carbon, total N, and ammonium N, but significantly decreased pH, nitrate N, and potential nitrification rate (PNR). PNR was significantly positively correlated with soil nitrate N and total N but negatively correlated with soil water content. In the bacterial community, SW irrigation significantly increased relative abundances of the phyla Actinobacteria, Chloroflexi, and Gemmatimonadetes but decreased those of Proteobacteria and Acidobacteria. Saline water irrigation increased relative abundance of genes associated with N fixation (M00175), denitrification (M00529), and dissimilated nitrate reduction (M00530) but decreased that of Nitrate/nitrite transport system (M00438). Saline water irrigation significantly increased relative abundances of nirK, nirS, norC, nifD, nifK, nifH, gdhA, GDH2, GLUD1_2, nasB, narI, narG, narH, nxrA, and nxrB genes but decreased those of amoC nirA, nirB, nirD, narB, norB, gudB, GLU, napA, and nasA. Saline water irrigation also affected enzymes associated with N transformations, with increases in relative abundance of enzyme genes associated with nitrite reductase (NO formation), N fixation enzymes, and glutamate dehydrogenase and decreases in that of glutamate synthase. According to redundancy analysis, soil water content, electrical conductivity, and bulk density were the main soil physicochemical drivers of functional genes affecting N transformations. Thus, SW irrigation changes bacterial community composition by affecting soil physicochemical properties and therefore affects N cycling by promoting denitrification and N fixation and inhibiting nitrification.

Silicon improves the effect of phosphate-solubilizing bacterium and arbuscular mycorrhizal fungus on phosphorus concentration of salinity-stressed alfalfa (Medicago sativa L.)

Under salinity stress, the availability of soil nutrients to plants is reduced, leading to disruption of nutrition and the balance of plant nutrients, including phosphorus (P). The use of phosphate-solubilizing microorganisms (PSM) and silicon (Si) in alleviating salinity stress and improving the uptake of P by plants has become a global solution. However, there is limited information on the effect of phosphate-solubilizing bacteria and arbuscular mycorrhizal fungi in the combination with Si on improving the absorption of P by plants including legumes under salinity stress. In this study, the plant growth-promoting potential of an effective phosphate-solubilizing bacterial strain (R115), Microbacterium shaanxiense, and an arbuscular mycorrhizal fungus, Claroideoglomus etunicatum, alone or in the combination with Si to alleviate salinity stress in alfalfa inoculated with its rhizobial symbiosis, Ensifer meliloti N44, and improve the absorption of P by this plant was investigated by a pot-experiment in a completely randomized design with factorial arrangement in three repetitions. Experimental treatments included: Si factor at two levels of 0 and 4 mM Si from potassium silicate source, bacterial strain R115 factor at two levels of B0 (control), and strain R115 (B1), mycorrhizal fungus factor at two levels of F0 (control) and mycorrhizal fungus (F1), and salinity (saline water) factor at three levels of 0, 5, and 15 dS m−1. Salinity stress reduced plant biomass, the content of chlorophyll, the concentration of N, P and K of plant and increased the concentration of Na in shoot tissue and the activity of antioxidant enzymes (catalase and superoxide dismutase) in alfalfa plant. However, the use of PSM (M. shaanxiense R115 and C. etunicatum) and Si improved the morphological and physiological characteristics of the plant, reduced the plant Na concentration, and increased the concentration of N, P, and K of alfalfa plants. The highest improvement in plant growth indices (shoot P concentration) was recorded in plants inoculated with PSM in the presence of Si. The results of this study showed that Si fertilization can be suggested as a sustainable strategy for improving the plant growth promoting effects of PSM on the growth of alfalfa (e.g., increased shoot P concentration) and encouraging ecological adaptability of this plant under saline water irrigation.

Responses of Soil N2O and CO2 Emissions and Their Global Warming Potentials to Irrigation Water Salinity

Irrigation using marginal quality water (brackish, saline, or treated wastewater, with a salinity of 2–8 g L−1) instead of fresh water alters the soil carbon and nitrogen cycle, and thus, soil greenhouse gas emissions. To reveal the responses of soil nitrous oxide (N2O) and carbon dioxide (CO2) emissions and their global warming potentials (GWPs) to irrigation water salinity, a pot experiment was conducted at three levels (2, 5, and 8 g L−1, namely S2, S5, and S8). The results show that the cumulative soil CO2 emissions were reduced with increases in the irrigation water salinity and were 11.6–28.1% lower than those from the fresh water-irrigated treatment (CK). The cumulative N2O emissions from S2 and S8 decreased by 22.7% and 39.6% (p < 0.05), respectively, in comparison to CK, whereas those from S5 increased by 87.7% (p < 0.05). The cumulative GWPs from S2 and S8 were 19.6% and 44.1% lower than those from CK, while those from S5 were significantly higher (p < 0.05). These findings indicate that reducing the salinity of brackish water from 5 to 2 g L−1 before using it for irrigation is a potential strategy to mitigate soil GHGs and solve water resource scarcity. The response of soil greenhouse gas (GHG) emissions to salinity may be significantly different among irrigation water salinity ranges. The results have an important guiding significance for exploring greenhouse gas emission reduction measures, and sustainable utilization models of water and soil resources.

Effect of Salinity and Silicon Doses on Onion Post-Harvest Quality and Shelf Life.

Salt stress during pre-harvest limits the shelf life and post-harvest quality of produce; however, silicon nutrition can mitigate salt stress in plants. Thus, we evaluated the effects of salinity and fertilization with Si, in pre-harvest, on the morpho-physiological characteristics of onion bulbs during shelf life. The experiment was set up in randomized complete blocks, with treatments arranged in split-split plots. The plots had four levels of electrical conductivity of irrigation water (0.65, 1.7, 2.8, and 4.1 dS m−1). The subplots had five fertilization levels with Si (0, 41.6, 83.2, 124.8, and 166.4 kg ha−1). The sub-sub plots had four shelf times (0, 20, 40, and 60 days after harvest). Irrigation water salinity and shelf time reduced firmness and increased the mass loss of onion bulbs during shelf life. Salt stress reduced the contents of sugars and total soluble solids of onion bulbs during storage; however, Si supply improved the contents of these variables. Salinity, Si supply, and shelf time increased the concentrations of pyruvic and ascorbic acids in onion bulbs during shelf life. Si doses between 121.8 and 127.0 kg ha−1 attenuated the impacts caused by moderate salinity, increasing the synthesis of metabolites and prolonging the onion bulbs’ shelf life.

Salt tolerance of Soft and Hard jackfruit varieties in the seedling stage

The formation of seedlings is an essential step in fruit plant development, playing a fundamental role in successful orchard implantations. This study aimed to evaluate the salinity tolerance through irrigation water in jackfruit varieties at the seedling stage. The study was carried out at the Centro de Ciências Agrárias of the Universidade Federal da Paraíba, Areia, Paraíba, Brazil. The treatments were distributed in randomized blocks, in a 5 × 2 factorial scheme with four replications and three plants per plot, totaling 40 experimental plots and 120 plants to be evaluated. At 85 days after sowing, the plants were collected and separated into root, stem, and leaves and dried to obtain dry matter. The leaf area was measured using the LAI-model 2200 equipment, from which the specific leaf area and leaf
 area ratio was calculated. Dickson's quality index was calculated with data on the root, shoot and total dry matter, seedling height, and stem diameter. The results of the study showed that the increase in water salinity reduced the leaf area and inhibited plant biomass formation, negatively affecting the quality of the seedlings, especially in the hard jackfruit variety. Seedlings of the Jackfruit soft variety were tolerant to the salinity level of 3.0 dS m-1, whereas the hard variety was tolerant until up to 2.0 dS m-1. In conclusion, the soft jackfruit variety is more tolerant to the salinity of irrigation water than the hard variety.

Effect of Climate Change on the Quality of Soil, Groundwater, and Pomegranate Fruit Production in Al-Baha Region, Saudi Arabia: A Modeling Study Using SALTMED

Groundwater depletion coupled with climate change, increasing temperature, and decreasing precipitation, has led to groundwater quality deterioration and diminishing groundwater quantity, subsequently affecting agricultural productivity in arid environments. The groundwater of the Al-Baha region, Saudi Arabia is located in unconfined shallow aquifers and responds quickly to climate change. The Al-Baha region is facing an increase in temperature and a substantial decrease in precipitation. Over the 24-year period from 1995 to 2019, average temperatures increased by 1.1 °C–1.6 °C, while rainfall decreased by 24–41%. Consequently, this study aimed at investigating the influence of climate change on soil salinity and pomegranate productivity. To achieve this goal, a hundred and fifteen samples of soil and groundwater were collected from different locations in the Al-Baha region. Furthermore, the SALTMED model was calibrated using the salinities of 50 groundwater samples, which are used as irrigation water, and climatic data from the year 2020. The model was then validated using 65 irrigation water salinities and climatic data from the year 2020. Pomegranate fruit yield was used as the main variable for calibration and validation. After successful calibration and validation, the SALTMED model was run using ‘what if’ scenarios for the years 2044, 2068, and 2092. It is assumed that the temperature will increase, while the annual rainfall will decrease in upcoming decades. Consequently, the groundwater salinities will reach 1.44, 2.59, and 4.67 dS m−1 for the years 2044, 2068, and 2092, respectively. The results revealed that the soil salinities will increase by 113%, 300%, and 675%, respectively, compared with the average soil salinity of the year 2020 (2.22 dS m−1). Furthermore, the pomegranate tree productivity in the Al-Baha region will decrease significantly (24.0%, 36.6%, and 41.6%) in the predicted three years due to deterioration of groundwater quality and increasing temperatures. Interventions by the regional authorities to minimize the impact of climate change on crop and fruit productivity and groundwater deterioration in the Al-Baha region should be planned and carried out as soon as possible. The method used in this investigation can be utilized in similar ecosystems worldwide.

Biochar Amendment Combined with Straw Mulching Increases Winter Wheat Yield by Optimizing Soil Water-Salt Condition under Saline Irrigation

The freshwater deficit is the major constraint to winter wheat production. Saline water irrigation could alleviate wheat water stress while increasing the risk of soil salinization, which would result in wheat yield reduction due to additional salt stress. The objective of the present study is to explore the effect of a straw-returning mode to promote winter wheat production under saline water irrigation. A field experiment was conducted during the winter wheat growing seasons of 2017–2018 and 2018–2019. Four returning modes were set, based on an equivalent carbon input: straw mulching (SM), biochar amendment (BA), straw mulching combined with biochar amendment (SM+BA), and the control without straw-returning (CK), along with three salinity levels of irrigation water: 0.47 dS m−1 (I0, freshwater), 3.25 dS m−1 (I1), and 6.75 dS m−1 (I2). Saline water irrigation alone triggered soil salt accumulation and reduced the wheat grain yield by 9.43––18.19%. Returning straw to fields increased soil organic carbon content by 16.41––52.21% and decreased soil bulk density by 0.69––1.46%. The highest increase in wheat grain yield (16.60––21.80%) was always obtained when using treatment SM+BA, due to the increased soil moisture content (3.15––12.31%) and lower salt levels (24.79––44.29%) compared to CK. The results of the present study established that SM+BA provided better soil water–salt conditions and nutrient environment for winter wheat growth than a single treatment. Thus, the combined application of SM and BA was shown to be a proper mitigating strategy to cope with the adverse effects of saline irrigation on winter wheat production and to promote the sustainable use of saline water irrigation.

Irrigation with desalinated and raw produced waters: Effects on soil properties, and germination and growth of five forages

Produced water is generated during oil and gas production in copious amounts daily in the United States. With increasing water shortfalls in arid and semi-arid regions, it could be a valuable source of water for irrigation purposes after treatment. The present study examined the effects of irrigation with produced waters on five perennials cool season forage, species western wheatgrass (Pascopyrum smithii), alfalfa (Medicago sativa), meadow bromegrass (Bromus biebersteinii), Russian wildrye (Psathyrostachys junceus), and tall fescue (Schedonorus arundinaceus). The forages were grown in a greenhouse, in loamy soil, and irrigated with desalinated reverse osmosis RO (231 mg/l), diluted RAW (1400 mg/l), RAW produced (8610 mg/l), and tap (427 mg/l) water. All forages were harvested three times at an interval of ≈ 90 days after 30 days germination period. Tall fescue germinated (100 %) and grew well under all four treatments. The higher biomass was with alfalfa, tall fescue, wheatgrass, bromegrass, and Russian wildrye, respectively. Evapotranspiration (ET) of the five species decreased with increasing soil and irrigation water salinity. Na, Cl, and B ions concentrations were 10.7, 13.6, and 42.3 mg/l, respectively in wheatgrass; 24.7, 17, and 14.5 mg/l, respectively in alfalfa; 27.7, 25.6, and 92.5 mg/l, respectively in bromegrass; 18, 14.6, and 59.6 mg/l, respectively in Russian wildrye; and 33, 35, and 207.5 mg/l, respectively in tall fescue, in plant tissues obtained after the second harvest. In soil, Na and B ions concentrations were 1173, 2.1 mg/l, respectively in wheatgrass pots; 1047, 1.7 mg/l, respectively in alfalfa pots; 874.6, 1.4 mg/l, respectively in bromegrass pots; 782, 1.6 mg/l, respectively in Russian wildrye pots; and 1974, 3.17 mg/l, respectively in tall fescue pots. Plant biomass decreased with increasing salinity; however, plants continued to grow even after the third harvest. Utilizing desalinated and diluted produced waters as a valuable source of water for irrigation after treatment could alleviate water demand in arid oil producing regions of the world.

ANÁLISE MULTIVARIADA DE GRAVIOLEIRA SOB ESTRESSE SALINO E APLICAÇÃO EXÓGENA DE PERÓXIDO DE HIDROGÊNIO

ABSTRACT The objective of this study was to evaluate, through multivariate data analysis, the effect of exogenous application of hydrogen peroxide on the photosynthetic pigments, gas exchange and growth of soursop seedlings under salt stress. The study was conducted in a greenhouse, at Federal University of Campina Grande - Paraíba. The assay was carried out from May to October 2018. The treatments were distributed in a randomized block design, in a 5 × 5 factorial arrangement, corresponding to five levels of irrigation water electrical conductivity - ECw (0.6-control, 1.2, 1.8, 2.4, and 3.0 dS m-1) and five concentrations of hydrogen peroxide - H2O2 (0, 10, 20, 30, and 40 μM), with two plants per plot and four replicates. Irrigation water salinity from 1.2 dS m-1 negatively affected the biosynthesis of photosynthetic pigments, gas exchange and growth of soursop. Application of hydrogen peroxide at the concentration of 20 μM resulted in attenuation of salt stress effects on the biosynthesis of photosynthetic pigments, gas exchange and growth of soursop. Hydrogen peroxide concentrations above 30 μM intensified the deleterious effect of irrigation water salinity on the photosynthetic pigments, gas exchange and growth of soursop.