Interactive Effects Of Salinity Research Articles

Interactive effects of salinity and straw on the soil aggregate stability and organic carbon sequestration in saline soils in the Hetao area, China

AbstractSoil organic carbon (SOC) and aggregate stability are the critical factors in evaluate soil quality and carbon sinks in agricultural soils. Especially in complex saline soils containing larges amount of sodium and calcium ions. To quantitatively estimate the importance of salinity factors, SOC fractions, and soil aggregate fractions on SOC contents and the mean weight diameter (MWD), as well as to reveal the transformation mechanism of SOC under the interactions between salinity and straw, a laboratory experiment was conducted on three soils with different salinity, with and without straw addition. The results showed that straw and salinity interactions significantly increased the proportion of large macro‐aggregate fractions and the MWD, decreased micro‐aggregate fractions, but promoted the conversion of SOC fractions to mineral‐associated organic carbon (MAOC) of micro‐aggregates in moderately saline soils. The responses of SOC contents and MWD to electrical conductivity (EC1:5) were nonlinear. The exchangeable sodium to calcium ions ratio (E‐Na/E‐Ca) (%IncMSE = 11.4, p < 0.01), and MAOC contents (%IncMSE = 17.0, p < 0.01) provided the best explanations of SOC contents, while the MWD was more explained by calcium carbonate (CaCO3) contents (%IncMSE = 9.6, p < 0.01), and MAOC/SOC (%IncMSE = 10.5, p < 0.01). The proportion of micro‐aggregate fractions was significant drivers of both SOC contents and MWD. The increased MAOC contents was mainly caused by improving the binding sensitivity of aliphatic compounds to salt‐related compounds, and the contents of C–C/C–H and C=O functional groups. The findings offer new perspectives into the mechanism of SOC sequestration and sustainable development of moderately saline soils under straw returning in the Hetao area.

Interactive effects of salinity, temperature and food web configuration on performance and harmfulness of the raphidophyte Heterosigma akashiwo

The cosmopolitan raphidophyte Heterosigma akashiwo commonly forms harmful algal blooms (HABs) in diverse estuaries discharging into Algoa Bay, South Africa, potentially leading to hypoxia, fish kills and a decline in key primary consumers. Despite the high environmental variability in these estuaries, little is known about how abiotic factors such as temperature and salinity constrain bloom formation and harmfulness of H. akashiwo. The present study therefore investigates growth, competition, and grazing interactions of H. akashiwo in laboratory experiments in response to two naturally relevant levels of salinity (15, 30) and temperature (16, 22°C), respectively. Experiments were set up with the naturally co-occurring dinoflagellate competitor Heterocapsa rotundata and two estuarine microzooplankton consumers, i.e., nauplii of the copepod Acartia tonsa and the rotifer Brachionus plicatilis. In monoculture, H. akashiwo growth was promoted at high temperature – low salinity conditions, while H. rotundata thrived under low temperature – high salinity conditions. In polyculture, H. akashiwo dominated at high temperature irrespective of the salinity regime, while at low temperature, it only dominated at low salinity and was suppressed by H. rotundata at high salinity. Grazing assays revealed highly negative effects of H. akashiwo on copepod nauplii survival and growth as well as mucus-induced immobilization, especially at high temperatures in combination with low salinity, while the estuarine adapted rotifers showed highest mortalities at the higher salinity level. The presence of H. rotundata significantly alleviated the harmful effects of H. akashiwo on both grazers, and the selectively feeding copepod nauplii actively avoided H. akashiwo when non-harmful prey was present. Overall, this study demonstrates that population dynamics and harmful effects of H. akashiwo are interactively determined by both abiotic conditions and food web configuration, implying competitor and consumer specific tolerances to the abiotic environment and their susceptibility to the harmful alga H. akashiwo.

The cumulative impacts of anthropogenic stressors vary markedly along environmental gradients.

Understanding the cumulative effects of multiple stressors on biodiversity is key to managing their impacts. Stressor interactions are often studied using an additive/antagonistic/synergistic typology, aimed at identifying situations where individual stressor effects are reduced or amplified when they act in combination. Here, we analysed variation in the family richness of stream macroinvertebrates in the groups Ephemeroptera, Plecoptera and Trichoptera (EPT) at 4658 sites spanning a 32° latitudinal range in eastern Australia in relation to two largely human-induced stressors, salinity and turbidity, and two environmental gradients, temperature and slope. The cumulative and interactive effect of salinity and turbidity on EPT family richness varied across the landscape and by habitat (edge or riffle) such that we observed additive, antagonistic and synergistic outcomes depending on the environmental context. Our findings highlight the importance of understanding the consistency of multiple stressor impacts, which will involve higher-order interactions between multiple stressors and environmental factors.

Effect of Salinity and Temperature on the Seed Germination and Seedling Growth of Desert Forage Grass Lasiurus scindicus Henr.

Lasiurus scindicus Henr. is one of the most important forage grass species of the Arabian deserts. Temperature and soil salinity are well known to influence the germination and seedling development of various forage species. Therefore, in the current study, the effect of temperature and salinity and their interaction on the germination parameters, seedling growth, and physiological parameters of L. scindicus were evaluated. For this reason, L. scindicus seeds were treated with five salinity concentrations (i.e., 0, 50, 100, 150, and 200 mM NaCl) and incubated at two temperature levels (T1 = 25/20 °C, D/N and T2 = 35/30 °C, D/N). The results indicated that the salinity and temperature significantly affected the germination indices, seedling growth parameters, chlorophyll, and proline content. The highest germination percentage (GP; 90%) was recorded in the non-saline-treated seeds incubated at T1. The seeds at T2 under the non-saline treatment exhibited an increased germination rate (GR = 17.5%). The interactive effect of salinity and temperature on germination and growth parameters was significant, indicating that the germination response to salinity depends on temperature. The germination of seeds treated with 200 mM NaCl was completely inhibited at both temperatures T1 and T2. However, the ungerminated seeds at both T1 (85%) and T2 (78%) restored their germination abilities after they were transferred to distilled water. Also, the seed vigor index (SVI) constantly showed a decline with the increasing salinity levels especially at T2, which was lowest when seeds were treated with 150 mM salinity. Growth parameters (i.e., aRL, aSL, RDW, SDW, SB, and SLA) and the chlorophyll content showed a similar pattern as that of germination. However, the proline content (shoot proline and root proline) showed a progressive increase with increasing salinity and temperature. All of these characteristics indicate that L. scindicus seeds were not able to germinate under extreme salinity and temperature conditions but remained viable in a state of enforced dormancy. This is most likely an important adaptive strategy of this species for survival in the high-saline changing habitats of the arid region of Saudi Arabia, and thus, it can be an excellent choice for restoring degraded rangelands and salinity-inflicted abundant farmlands for forage agriculture.

Role of Signaling Molecules Sodium Nitroprusside and Arginine in Alleviating Salt-Induced Oxidative Stress in Wheat.

Nitric oxide (NO) is a well-accepted signaling molecule that has regulatory effects on plants under various stresses. Salinity is a major issue that adversely affects plant growth and productivity. The current study was carried out to investigate changes in the growth, biochemical parameters, and yield of wheat plants in response to NO donors, namely sodium nitroprusside (SNP) (2.5 and 5.0 mM) and arginine (10 and 20 mM), under two salinity levels (1.2 mM and 85.5 mM NaCl). Salinity stress significantly decreased the lengths and weights of plant parts (shoot, tiller, and root) and reduced the flag leaf area, photosynthetic pigments, indole acetic acid (IAA), and yield and its components. Moreover, salt stress induced a significant accumulation of some osmoprotectants (total soluble sugars (TSS) and amino acids, especially proline) and triggered the accumulation of hydrogen peroxide (H2O2) and lipid peroxidation in wheat leaves. In contrast, arginine and SNP treatments significantly mitigated the negative impacts of salinity on growth and productivity via enhancing photosynthetic pigments, nitrate reductase, phenolic compounds, IAA, TSS, free amino acids, and proline. In addition, SNP and arginine potentially reduced oxidative damage by decreasing H2O2 and lipid peroxidation through the induction of antioxidant enzymes. The individual amino acid composition of wheat grains under the interactive effect of salinity and NO sources has been scarcely documented until now. In this study, the NO sources restrained the reduction in essential amino acids (isoleucine and lysine) of wheat grains under salinity stress and further stimulated the contents of non-essential and total aromatic amino acids. Interestingly, the applied protectants recovered the decrease in arginine and serine induced by salinity stress. Thus, SNP or arginine at the levels of 5.0 and 20 mM, respectively, had a profound effect on modulating the salt stress of wheat throughout the life cycle.

The Structuring Effects of Salinity and Nutrient Status on Zooplankton Communities and Trophic Structure in Siberian Lakes

Many continental saline lakes are under the effects of salinity increase and anthropogenic eutrophication exacerbated by global change. The response of the food web to these drivers of change is not straightforward. To understand the consequences of salinity and eutrophication interactive effects on the food web, we studied the seasonal dynamics of zooplankton and phytoplankton and water quality parameters in 20 lakes of different salinity (from freshwater to hypersaline) and nutrient status (from oligotrophic to eutrophic) located in southern Siberia. We observed a pronounced bottom-up effect of nutrients, which induced an increase in the biomass of phytoplankton and zooplankton and a decline in water quality. A significant decrease in the species abundance of zooplankton was observed at a threshold salinity of 3 g L−1 and the disappearance of fish at 10 g L−1. The top-down effect induced by salinity manifested itself in an increase in the biomass of zooplankton with the disappearance of fish, and in the change of the size distribution of phytoplankton particles with an increase in the proportion of cladocerans in the zooplankton. Even though we observed that with the salinity increase the food web in saline lakes transformed from three-trophic to two-trophic without fish, we conclude that in the salinity range from 10 to 20–30 g L−1 this transition in most cases will not increase the ability of zooplankton to control phytoplankton. Interactive effects of salinity and eutrophication strongly depend on the size and depth of the lake, as deep stratified lakes tend to have a better water quality with lower biomasses of both phyto- and zooplankton. Thus, the salinity per se is not the driver of the decline in water clarity or the uncontrolled development of phytoplankton. Moreover, for deep lakes, salinity may be a factor affecting the stability of stratification, which mitigates the consequences of eutrophication. Thus, small shallow lakes will be the most vulnerable to the joint effect of salinity increase and eutrophication with the degradation of ecosystem functioning and water quality at moderate salinities of 3–20 g L−1.

Interactive effects of salinity and plant density on the growth of Cyperus arenarius, a sand dune stabilizer

Competition and environmental stress are crucial factors for structuring plant population in natural habitats. Cyperus arenarius, a sedge of coastal sand dunes habitat, is a suitable species for coastal restoration and dune stabilization, but how salinity and plant density interact in affecting its growth is still unknown. Here, growth, survival, and physiological responses of C. arenarius to salinity (sea-salt) and plant density were investigated. A set of growth experiments in which combinations of 4 salinity levels (0, 2, 4, and 6 S m-1 sea-salt) and 3 planting densities (2, 5, 8 plants pot-1) were tested under controlled greenhouse conditions. Plant biomass and height were optimal in 2 S m-1 sea-salt while biomass decreased considerably at 6 S m-1. The inhibitory effect of high salinity was more severe in shoot dry mass relative to that of root dry mass, which resulted in increasing root/shoot dry mass ratio. Tissue succulence declined while the accumulation of Na and Cl increased with the increment of salinity, especially in root. Plant nutrient (K+, Ca2+, and Mg2+) contents decreased under salinity. Plant height was more sensitive with increasing plant density than biomass. High plant density (8 plants pot-1) lowered tissue biomass and water content in non-saline conditions to the similar levels observed under the 6 S m-1 seasalt salinity. Moreover, the combined effect of high salinity and increasing plant density had highly negative effects on plant growth attributes and water relations than their individual effect.

Interactive effect of salinity and Ca to Mg ratio of irrigation water on pistachio growth parameters and its ionic composition in a calcareous soil

ABSTRACT This study investigated the effect of different salinity (EC≈6 and 9 dS/m) and Ca/Mg ratios (≈0.95,0.50, and 0.25) in irrigation water on the chemical composition of soil solution and growth of pistachio (Pistacia vera L.). The physiological, biochemical, and yield-related responses of pistachio seedlings were measured within ≈30 weeks in a greenhouse pot experiment. The EC of the soil solutions rapidly approached the one in the irrigation waters while the Ca/Mg ratios slowly altered, as such the final ratios were ≈50-100% larger than the one in the irrigation waters. The slower change in the Ca/Mg ratio is due to the fact that Ca concentration is dominantly controlled by the calcite solubility but the Mg concentration by the ion-exchange reaction. With increasing EC of the soil solution from 5.8–10.4 dS/m, we found 4-fold reduction in shoot dry weight and 62% increase in electrolyte leakage. In each salinity level, the highest yield and membrane stability were achieved at the Ca/Mg ratio of ≈1 in the soil solution. Overall, a Ca/Mg ratio < 1 in the irrigation water shifted the ionic composition of the soil solution, even in calcareous soil, towards a ratio < 1 and negatively affected pistachio growth.

Interactive effects of salinity and SOM on the ecoenzymatic activities across coastal soils subjected to a saline gradient

Salinity and soil organic matter (SOM) are key edaphic factors that exert substantial influence on soil microbial activity. To understand the interactive effects of both factors on microbial activity, nine ecoenzymes involved in C, N, P and S cycling were assayed across a saline gradient (coastal areas of the Bohai Gulf, CN). The electrical conductivity (EC) of the soils ranged from 0.14 to 13.65 dS m−1. The response of the ecoenzymatic activities (EEAs) to salinity followed a nonlinear relationship due to the interaction of SOM and salinity on EEAs. The nonlinear response demonstrated divergent patterns below and above an EC of 2 dS m−1. Specifically, when EC < 2 dS m−1, no correlation between EEAs and conductivity was observed and EEAs had a positive correlation with SOM; when EC > 2 dS m−1, the EEAs were negatively correlated with conductivity and no correlation with SOM was observed. Substrate amendment at EC < 2 dS m−1 significantly improved EEAs that reached the levels similar to those of non-saline soils, while EEAs remained unrecovered when EC > 2 dS m−1. This EC value may stand as critical (threshold) salinity. Under higher EC conditions, EEAs are mainly affected by salinity while SOM has no critical role. This becomes reversed when salinity (as EC) drops below the critical value. This study provides with a numerical salinity reference for the potential of the land ‘to be reclaimed by organic matter addition’ and assists in defining strategies for soil reclamation based on the proposed salinity threshold.

Interactive effects of salinity and copper toxicity on the growth and photosynthetic efficiency of germlings and adult brown alga Fucus ceranoides (Fucales, Phaeophyceae)

Laboratory experiments were conducted to investigate the effect of copper enrichment (0.6, 2, 4, 8, 18 and 36 μg L−1) and salinity (8.5, 17 and 24%) on growth, photosynthetic efficiency “PE” (expressed as chlorophyll fluorescence) and copper accumulation in germlings and adult brown alga Fucus ceranoides. The PE for the algae exposed to 17% salinity was markedly stable throughout the experiment, while it was significantly (0.01 ˂ p ˂ 0.05) reduced in algae exposed to 8.5% salinity in the presence of 36 μg L−1 Cu by 20% when compared to those exposed to 0.6 μg L−1 Cu. Moreover, the maximum electron transport rate (ETRmax) was decreased significantly with increasing concentrations of Cu (p ˂ 0.001) and level of salinity (p ˂ 0.01); moreover, there was a significant interaction between Cu and salinity. The combination of copper and reduced salinity gave synergistic effects, as a consequence, this could limit the population growth of seaweeds in coastal areas. More research is needed to understand the basic requirements and stress tolerance in seaweeds for reef restoration and other management actions to be successful for sustainable development.The results of the present study suggest that any change in the environment will directly and significantly affect algal physiology, and thus it could be used for biomonitoring in situ. Moreover, the assessment of the physiological status of algae in combination with the analysis of thallus metal content will improve the trustworthiness of the biomonitoring process.

Interactive effects of waterlogging and salinity on perennial ryegrass and alkaligrass

AbstractA lot of salt‐affected soils in the world are also affected by compaction and waterlogging due to shallow water tables or decreased infiltration of water due to sodicity. Waterlogging and compaction cause reduced oxygen exchange (hypoxia). Research on the combined impacts of salinity and hypoxia on turfgrass growth is limited. The interactive effects of salinity and oxygen availability on nine perennial ryegrass entries (Lolium perenne L.) and one alkaligrass [Puccinellia tenuiflora (Jacq.) Parl.] cultivar were studied. In a controlled greenhouse, grasses were subjected to 4 treatments: control, salinity, hypoxia, and salinity + hypoxia for 12 weeks. All entries exhibited decreased clipping yield in both salinity and hypoxia + salinity treatments except ‘Fults’ alkaligrass. With or without hypoxia treatment, ‘Fults’ alkaligrass was the most salt tolerant grass among all entries. In general, all perennial ryegrass entries had better turf quality in control and hypoxia treatments than in salinity and salinity with hypoxia treatments. All perennial ryegrass entries were more severely affected (quality and yields) under combined hypoxia and salinity treatment compared to salinity or hypoxia only. Plant Na+ and Cl− concentrations increased under salinity and salinity + waterlogging treatments. The experimental entries (‘10.0824’ and ‘10.0825’) were able to maintain better turf quality than other perennial ryegrass cultivars under salinity and the combination of hypoxia + salinity treatments.

Interactive effects of salinity and drought stress on photosynthetic characteristics and physiology of tomato (Lycopersicon esculentum L.) seedlings

Sufficient quantity and quality of water are essential for vegetable production.Evaluating the individual and combined effects of drought and salt stress on plant establishment may help inform management of plant production in terms of stabilizing yield. This study investigates the effects of drought and salt stress on plant growth, nutrition elements, and select physiological parameters of tomato (Lycopersicon esculentum L. cv. H2274) through a pot experiment under greenhouse conditions. Drought stress was applied to tomato seedlings at 3 different levels of irrigation: D0 (control), D1, and D2 at 100%, 75%, and 50% field capacity, respectively. Salinity stress was applied at 3 different doses S0, S1, and S2 at 0 mM, 100 mM, and 150 mM NaCl, respectively. The effects of salinity, drought and their co-occurring stresses on growth, physiological and photosynthetic properties of tomato seedlings were statistically significant. Photosynthetic rate (Pn), stomatal conductance (gs), chlorophyll reading value (CRV), and plant dry weight (DW) decreased with salt and drought treatments. However, electrolyte leakage (EL) of the leaves increased with increasing salt and drought treatments. Fresh weight (FW) of the tomato seedlings decreased 67% under the 150 mM NaCl treatment (S-2), and decreased 69% under severe drought (D2); however, the interactive effects of these two treatments together (S2D2) resulted in an 80% decrease in FW. Furthermore, dry weight (DW) decreased 80% in the S2D2 treatment compared to the control. In general, both drought and salinity altered the mineral nutrient composition by decreasing N, P, K, Fe, Ca and Z content of the tomato seedlings, but Na, B and Cl content increased. These results show that effects of salinity and drought on tomato seedlings were less detrimental for plant establishment than the combined effects of the two stresses together.

Phytochemical and Quality Attributes of Strawberry Fruit under Osmotic Stress of Nutrient Solution and Foliar Application of Putrescine and Salicylic Acid

The moderating role of salicylic acid (SA) and putrescine (PUS) as plant growth regulators (PGRs), on the growth parameters and phytochemical and qualitative characteristics of strawberry fruit 'Selva' under osmotic stress was investigated under soilless culture. The osmotic potential (salinity) of the nutrient solution containing different NaCl concentrations (0, 7.5, 15, 30 and 45 mM) and foliar application of PUS (0 and 1.5 mM) and SA (0 and 1.5 mM) were studied. The results showed a significant decrease in plant leaf area (79.6%), total chlorophyll content (48%), fruit yield (73.5%), leaf relative water content (33%), total protein (33.4%), total phenol (7.8%), and vitamin C content (24.5%) under osmotic stress. Moreover, peroxidase (POD) and superoxide dismutase (SOD) enzymes activity, leaf ion leakage, and soluble carbohydrate and proline content increased significantly under osmotic stress. Application of PGRs had a significant effect on all the studied traits (except for SOD activity). Interactive effects of salinity and PGRs were significant on all the traits except for leaf ion leakage, POD activity, soluble carbohydrates, and protein. The highest total phenol and vitamin C contents were obtained with 15 mM salinity along with foliar application of PGRs. In conclusion, foliar application of PUS and SA ameliorate negative effects of salt stress on growth, yield, and quality of strawberry fruit.

Anti-stress phytohormones impact on proteome profile of green gram (Vigna radiata) under salt toxicity

Anti-stress phytohormones impact on proteome profile of green gram (Vigna radiata) under salt toxicity

Interactive effects of salinity and silicon application on Solanum lycopersicum growth, physiology and shelf-life of fruit produced hydroponically.

Using water with high salinity for plant fertigation may have detrimental effects on plant development and total yield and on the quality of the crop produced. As a possible means to alleviate the negative effects of salinity, silicon (Si) can be incorporated in the nutrient solution supplied to plants. In the present study, hydroponically grown tomato (Solanum lycopersicum Mill.) plants were subjected to two different salinity levels (0 and 50 mmol L-1 NaCl) with and without the application of Si (0 and 2 mmol L-1 K2 SiO3 ) in order to evaluate its possible positive impact on mitigation of salinity stress-induced symptoms. An additional experiment was implemented with postharvest Si application (sodium silicate) to investigate effects on the shelf-life of tomato fruit. Salinity (50 mmol L-1 NaCl) decreased plant size, total yield and fresh fruit weight while a high percentage of blossom end rot symptoms of tomato fruit was also observed. The application of Si in the nutrient solution counteracted these detrimental effects, generating a higher yield and healthier fruit (lower blossom end rot incidence) compared to the untreated plants (no application of Si). Salinity improved several quality-related traits in tomato fruit, resulting in higher marketability, whereas the addition of Si (pre- and postharvest) maintained fruit firmness following storage thereby increasing the shelf-life of tomato fruit. These findings indicate that Si application (pre- and postharvest) could provide an effective means of alleviating the unfavorable effects of using low-quality water in plant fertigation on tomato plant development, fruit yield and post-harvest quality, through increased fruit firmness. © 2019 Society of Chemical Industry.

Interactive effects of salinity and inundation on native Spartina foliosa, invasive S. densiflora and their hybrid from San Francisco Estuary, California.

Sea level rise (SLR) associated with climate change is intensifying permanent submersion and salinity in salt marshes. In this scenario, hybridization between native and invasive species may result in hybrids having greater tolerance of abiotic stress factors than their parents. Thus, understanding the responses of native and invasive halophytes and their hybrids to interacting physiological stresses imposed by SLR is key to native species conservation. We analysed how salinity, inundation depth and their interaction impact the functional traits of native and invasive cordgrass species and their hybrid (genus Spartina; Poaceae). In a mesocosm experiment, we evaluated interactive stress effects of three inundation depths (4.5, 35.5 and 55 cm) and four aqueous salinities (0.5, 10, 20 and 40 ppt) on 27 functional traits of native Spartina foliosa, invasive S. densiflora and their hybrid S. densiflora × S. foliosa from San Francisco Estuary. The combined effect of salinity and inundation led to synergistic effects on leaf biochemical stress indicators. Spartina foliosa behaved as a stress-tolerant species, with high leaf sodium exudation rate and glycine betaine concentrations that also increased with stress. Spartina foliosa was less sensitive to salinity than S. densiflora and the hybrid but was highly growth-limited in response to increased inundation and salinity. Spartina densiflora was fast-growing in low-stress conditions and tolerated moderate interactive stresses. The hybrid produced more biomass, rhizome reserves and tillers than its parents, even under the most stressful conditions. Transgressivity improved the hybrid's capacity to deal with flooding stress more so than its response to increasing salinity. Based on our observations, we predict that established populations of both native and invasive cordgrasses will experience reduced vegetative and sexual fitness in response to SLR. In particular, the combined effects of high salinity and deep inundation may decrease floret production in S. densiflora, a key trait for the spread of its invasive populations. In contrast, the hybrid likely will be able to sustain its invasiveness under SLR based on its ability to maintain growth and biomass production under stressful conditions.

Interactive Effects of Salinity and Cadmium Pollution on Enzyme Activity in a Calcareous Soil Treated With Plant Residues

Interactive Effects of Salinity and Cadmium Pollution on Enzyme Activity in a Calcareous Soil Treated With Plant Residues

Effects of salinity and moisture on sediment net nitrogen mineralization in salt marshes of a Chinese estuary

The interactive effects of salinity and moisture on the net nitrogen mineralization were seldom studied in coastal wetlands. To reveal the phenomenons and mechanisms of salinity and moisture effects, we conducted a 30-days laboratory experiment with different salt addition levels (0, ppt, 5 ppt and 35 ppt) and moisture levels (10%, 50% and 100% of water holding capacity (WHC)), and the key N transformation rates and enzymes activities were measured. Our results showed that during the incubation, the rates of soil net nitrogen mineralization (Rmin) and nitrification (Rnit) under all treatments, increased during 0–1 day, decreased during 1–3 days, then increased and kept around zero. As incubation time increased, urease activities increased, arylamidase activities decreased and fluorescein diacetate activities increased first and then decreased. Increasing salinity under high moisture (100% WHC) treatments and increasing moisture under high salinity (35 ppt) treatments would promote Rmin and Rnit. Whereas, increasing salinity under low moisture (10% WHC) treatments, and increasing moisture under low salinity (0 ppt) treatments would suppress Rmin and Rnit. The responses of enzyme activities to salinity and moisture gradients almost correspond with Rmin, indicating salinity and moisture could affect N transformation by the regulation of related microbial enzyme activities.

Interactive effects of salinity and nitrogen forms on plant growth, photosynthesis and osmotic adjustment in maize

To enhance crop productivity and minimize the harmful effects of various environmental stresses, such as salinity and drought, farmers often use mineral fertilizers. However, inadequate or excessive fertilization can reduce plant growth and nutritive quality and contribute to soil degradation and environmental pollution. This study investigated the effects of salinity (0, 100 or 150 mM NaCl) and nitrogen form (sole NO3− or NH4+, or combined NO3−:NH4+ at 25:75 or 50:50) on growth, photosynthesis, and water and ion status of a commercial variety of maize (Zea mays SY Sincero). In the absence of NaCl, the media containing ammonium only or both nitrogen forms had higher aboveground growth rates than that containing nitrate only. Indeed, the maize growth, expressed as leaf dry matter, seen on NH4+ in the absence of salinity, was nearly double the biomass compared to that with NO3−treatment. Irrespective of N form, the presence of NaCl severely reduced leaf and roots growth; the presence of ammonium in the nutrient solution diminished these negative effects. Compared to the NH4+ only and combined treatments, the leaves of plants in the NO3−-only medium showed signs of nitrogen deficiency (general chlorosis), which was more pronounced in the lower than upper leaves, indicating that nitrate is partly replaced by chloride during root uptake. NH4+ favored maize growth more than NO3−, especially when exposed to saline conditions, and may improve the plant's capacity to osmotically adjust to salinity by accumulating inorganic solutes.

Interactive effects of salinity and drought stresses on the growth parameters and nitrogen content of three hedge shrubs

The effect of salinity and drought stresses on three hedge shrubs was studied in a factorial experiment based on a Randomized Complete Block Design with three replications. The studied treatments i...