Amelioration of calcareous saline sodic soils through phytoremediation and chemical strategies

Abstract. The worldwide occurrence of saline sodic and sodic soils on more than half a billion hectares warrants attention for their efficient, inexpensive and environmentally acceptable management. These soils can be ameliorated by providing a source of calcium (Ca²⁺) to replace excess sodium (Na⁺) from the cation exchange sites. Although chemical amendments have long been used to ameliorate such soils, the chemical process has become costly during the last two decades in several developing countries. As a low‐cost and environmentally acceptable strategy, the cultivation of certain salt tolerant forage species on calcareous sodic and saline sodic soils, i.e. phytoremediation, has gained interest among scientists and farmers in recent years. In a field study conducted at three calcareous saline sodic sites (pH_s=8.1–8.8, EC_e=7.8–12.5 dS m^–1, SAR=30.6–76.1) in the Indus Plains of Pakistan, we compared chemical and phytoremediation methods. There were four treatments; two involved plants: Kallar grass (Leptochloa fusca (L.) Kunth), and sesbania (Sesbania bispinosa (Jacq.) W. Wight). The other two treatments were uncropped: soil application of gypsum and an untreated control. All treatments were irrigated with canal water (EC=0.22–0.28 dS m^–1). The plant species were grown for one season (5–6 months). Sesbania produced more forage yield (34 t ha^–1) than Kallar grass (23 t ha^–1). Phytoremediation and chemical treatments resulted in similar decreases in soil salinity and sodicity, indicating that phytoremediation may replace or supplement the more costly chemical approach. The soil amelioration potential of sesbania was similar to that of the Kallar grass, which suggests that moderately saline sodic calcareous soils can be improved by growing a forage legume with market value.     

Annual warm-season grasses vary for forage yield,quality, and competitiveness with weeds

Warm-season annual grasses may be suitable as forage crops in integrated weed management systems with reduced herbicide use. A 2-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three warm-season grasses, and seed production by associated weeds. Tillage systems were zero tillage and conventional tillage with a field cultivator. The N fertilization methods were urea broadcast or banded near seed rows at planting. Warm-season grasses seeded were foxtail (Setaria italica L.) and proso (Panicum mileaceum L.) millets, and sorghum–sudangrass (Sorghum bicolor (L.) Moench × Sorghum sudenense Stapf.). Density of early emerging weeds was similar among treatments, averaging 51 m^?2. Millets exhibited higher weed density and weed biomass than sorghum–sudangrass. At harvest, sorghum–sudangrass produced significantly greater biomass and N accumulation than either millet. Water use (157 mm) and WUE (25.1 kg mm^-1 ha^?1) of total biomass did not vary among treatments or grass entries. Weed seed production by redroot pigweed and green foxtail was respectively 93 and 73% less in sorghum–sudangrass than proso millet. Warm-season grasses offer an excellent fit in semiarid cropping systems.     

Effect of salinity and nitrogen on growth,sodium, potassium accumulation,and osmotic adjustment of halophyte Suaeda aegyptiaca (Hasselq.) Zoh

Suaeda aegyptiaca is an important native annual halophyte in salt-affected soils around coastal areas of the Persian Gulf. In order to study the effects of different levels of saturation paste soil salinity (10, 20, 40, 60, and 80 dS m^?1) and nitrogen supply (25, 50, and 75 mg kg^?1 N as urea) on growth and physiological characteristic of S. aegyptiaca, a greenhouse factorial experiment in completely randomized design was conducted with three replications. Salinity treatments were established after early growth of plants and nitrogen was applied in two steps. Results showed that increasing salinity up to 20 dS m^?1 led to increase in dry weight (DW) of plants and this decreased by increasing salinity. Also, DW of plants was significantly increased by application of 75 mg kg^?1 nitrogen. Increasing salinity significantly decreased plant height, chlorophyll index, and total nitrogen content; while proline content and total soluble solids (TSS) were significantly increased. The electrolyte leakage (EL) and sodium concentration were increased under salinity stress. However, further increase in salinity decreased these two parameters. By increasing the nitrogen levels, relative water content (RWC), chlorophyll index, proline, and total nitrogen contents were increased, whereas EL was decreased.     

Response of soil microbial community and diversity to increasing water salinity and nitrogen fertilization rate in an arid soil

The scarcity of fresh water has forced farmers to use saline water (SW) for irrigation. It is important to understand the response of the soil microbial community and diversity to saline irrigation water. The objective of this study was to determine the effects of irrigation water salinity and nitrogen fertilization rates on soil physicochemical properties, microbial activity, microbial biomass, and microbial functional diversity. The field experiment consisted of a factorial design with three levels of irrigation water salinity (electrical conductivities (ECs) of 0.35, 4.61 or 8.04?dS?m^?1) and two nitrogen rates (0 and 360?kg?N?ha^?1). The results showed that the 4.61 and 8.04?dS?m^?1 treatments both reduced soil microbial biomass C (MBC), microbial biomass N (MBN), basal respiration, total phospholipid fatty acid (PLFA), bacterial PLFA, fungal PLFA, and fungal:bacterial ratios. In contrast, the SW treatments increased the MBC:MBN ratio. Nitrogen fertilization increased soil MBC, MBN, basal respiration, total PLFA, bacterial PLFA, and gram-negative bacterial PLFA. In contrast, N fertilization decreased gram-positive bacterial PLFA, fungal PLFA, and fungal:bacterial ratios. Average well color development, Richness, and Shannon's Index were always lowest in the 8.04?dS?m^?1 treatment. Carbon utilization patterns in the 8.04?dS?m^?1 treatment were different from those in the 0.35?dS?m^?1 treatment. In conclusion, five years of irrigation with brackish or SW reduced the soil microbial biomass, activity, and functional diversity, which may cause the deterioration of soil quality. Thus, the high-salinity water (EC?>?4.61?dS?m^?1) is not appropriate as a single irrigation water resource. Proper N fertilizer input may overcome some of the negative effects of salinity on soil microbial.     

Ensiling properties of sweet sorghum

Abstract

Sweet sorghum [Sorghum bicolor (L.) Moench] cultivars have been bred for high sugar content; with accompanying adequate forage yield, the crop may offer potential for ensiling. “Wray”; sweet sorghum, a good sugar producer, was grown under field conditions to determine nutritional quality and subsequent animal performance of silage from the yield. In one experiment, “Wray”; was compared to “FS‐5”;, medium‐tall forage sorghum, at four reproductive stages of growth, in regard to agronomic characteristics and chemical composition. In another study, the “Wray”; sweet sorghum was harvested in early and late reproductive stages and stored in experimental silos. Ensiling losses were measured; in addition, the silages were offered to sheep to determine in vivo digestibility (IVODMD) and intake. In the first experiment, dry matter yields of both sweet and forage sorghum increased during the reproductive period, from 6.2 to 11.9 and 7.7 to 13.9 Mg/ha, respectively; at maturity, grain yields were 651 and 3,526 kg/ha, respectively. Total available carbohydrates tended to be higher in the forage type (23.4%) than in the sweet sorghum (19.9%). Average in vitro dry matter disappearance (IVDMD) was similar for both sorghums at 60.2%, but sweet sorghum IVDMD tended to be higher than forage sorghum at the hard‐dough stage (61.4 versus 55.1%) . In the second experiment, intake was greater when lambs were offered hard‐dough stage silage (1,240 g/lamb/day) versus bloom‐stage silage (878 g/lamb/day), even though IVODMD was similar (average 60.6%) at both harvest stages. The silages appeared to be properly ensiled, as silage pH was less than 4.0; however, effluent and dry matter losses were greater with bloom‐stage silage. These differences probably were due to the slight dry matter differential between the two <22.3 and 26.6%, respectively). To maximize yield, sweet sorghum should be ensiled at the hard‐dough stage. Resulting silage may be higher in digestible dry matter than that of medium‐tall forage sorghums, which produce grain.     

Effects of coalbed methane‐produced water on sorghum‐sudangrass growth and soil chemical properties

Abstract

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resulting from irrigation with coalbed methane‐produced water. The soil was a Montevallo (Typic Dystrochrepts)‐Nauvoo (Typic Hapludults) association located in northern Alabama. Two irrigation methods used in the initial greenhouse test were 1) continuous, irrigation 24 h d^‐1 and 2) intermittent, irrigation for 12 h and off for 24 h. In a second greenhouse test, three irrigation methods were used: 1) continuous, irrigation for 24 h d^‐1, 2) intermittent, irrigation for 12 h and off for 48 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and intermittent irrigation treatments was 3.75 mm h^‐1. In each greenhouse test, 5 levels of salinity were generated by mixing well‐produced water with deionized water to give solutions containing 0, 10, 20, 40, and 100% well‐produced water (specific conductance (second greenhouse test) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m^‐1, respectively). Corresponding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respectively. Sorghum‐sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14–30 days after initiation of irrigation treatments. Results from these preliminary short term, greenhouse studies show that coalbed methane produced water that is typical for Alabama (total dissolved solids ≤2000 mg L^‐1) can be applied to highly weathered soils. The results indicate that plant growth of summer annual grasses will be optimized if an irrigation system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.     

Effects of Electric-Arc Furnace Dust Application on Soil Properties,Sorghum Growth,and Heavy-Metal Accumulation

This study investigated the possibility of using electric-arc furnace dust (EAFD) as an acidic soil amendment. The experiments were conducted using incubation and pot experiments. In the incubation experiment, various rates of EAFD were added to an acidic soil and properties such as pH; electrical conductivity of the saturation extract (EC_se); and available phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), lead (Pb), and cadmium (Cd) were determined. In the pot experiment rates of EAFD incorporated with soil were 0.25%, 0.5%, 1%, and 2%. The results showed that with increasing the rate of EAFD application, soil pH, EC, and available P and K were enhanced. However, addition of EAFD more than 2% caused high salinity and alkalinity; hence, it is not recommended for reclamation of this acidic soil. A pot experiment was carried out to determine its effects on sorghum (Sorghum bicolor L.) dry matter and heavy-metal accumulation. Plant dry matter was enhanced with increase the EAFD rates. The concentrations of Fe, Zn, Cu, Cd, and Pb were enhanced with the increasing rate of applied EAFD in root and shoot. However, content of these elements in plant shoot were in the normal range.     

Natural Biostimulants Improve Saline Soil Characteristics and Salt Stressed-Sorghum Performance

Humus substances (HM) and Moringa oleifera leaf extract (MLE) are considered as biostimulants used for plant growing under normal and salt stress conditions. Therefore, effects of soil HM and foliar MLE applications on soil characteristics and on sorghum growth, physio-biochemical properties, and antioxidant defense system activity were investigated under salt stress using pot experiments. The experimental design was a split-split plot with three soil salinities (S₁, S₂, and S₃) as main-plots, two HM levels (0 and 0.1 g kg^?1 soil) as subplots, and two MLE levels (0% and 3%) as sub-subplots, and each one of the 12 treatments was replicated 20 times. Saline soil properties were improved by HM. Under saline conditions, either HM or MLE increased growth characteristics, photochemical activity, contents of RNA, DNA, phytohormones, osmoprotectants and non-enzymatic antioxidants, and activities of antioxidant enzymes in sorghum plants compared to those in the untreated control plants. The interactive HM×MLE application was most effective at overcoming the harmful effects of soil salinity stress and further increased the abovementioned criteria. This study, therefore, recommends using the integrative HM+MLE treatment for growing sorghum plants in saline soils up to more than 6.12 dS m^?1 without loss in growth characteristics.     

Germination,growth and ions uptake of moringa (Moringa oleifera L.) grown under saline condition

Salinity is the major environmental stress that affects the growth and productivity of plants. The present study was conducted to determine the effect of salinity on growth and ions uptake by moringa (Moringa oleifera L.) plant. The experiment was carried out in two phases. Initially, a germination test was conducted in the laboratory under the different salinity levels (control, 5, 10, 15, and 20 dS m^?1) and found that moringa seeds were germinated only at 5 and 10 dS m^?1 salinity levels, and no germination occurred at higher salinity levels (15 and 20 dS m^?1). The experiment was laid out in a completely randomized design (CRD) with five replications. In the second phase, three-week old nursery grown plants of moringa were shifted in pots under the five salinity levels (control, 5, 10, 15, and 20 dS m^?1). The experiment was laid out in CRD and replicated four times. In pot experiment, the root, shoot length, and dry weights were significantly affected by increasing the salinity levels. The uptake of K⁺ and Ca²⁺ was highly affected at different salinity levels as compared to control and Na⁺ ions accumulation was higher in roots rather than shoot. The results reveal that moringa plant can germinate, survive, and can be cultivated in areas with moderate saline condition.     

Nitrogen application effects on forage sorghum production and nitrate concentration

Abstract

Forage sorghum (Sorghum bicolor (L.) Moench) is an important annual forage crop but prone to high nitrate concentration which can cause toxicity when fed to cattle (Bos taurus and Bos indicus). Two field experiments were conducted over six site-years across Kansas to determine the optimum nitrogen (N) rate for no-till forage sorghum dry matter (DM) yield and investigate the effect of N fertilization on sorghum forage nitrate content. A quadratic model described the relationship between sorghum DM and N rate across the combined site-years. Maximum DM yield of 6530?kg ha^?1 was produced with N application rate of 100?kg N ha^?1. The economic optimum N rate ranged from 55 to 70?kg N ha^?1 depending on sorghum hay price and N fertilizer costs. Crude protein concentration increased with N fertilizer application but N rates beyond 70?kg N ha^?1 resulted in forage nitrate concentrations greater than safe limit of 3000?mg kg^?1. Nitrogen uptake increased with N fertilizer application but nitrogen use efficiency and N recovery decreased with increasing N fertilizer rates. In conclusion, forage sorghum required 55–70?kg N ha^?1 to produce an economic optimum DM yields with safe nitrate concentration.     

Combined Effect of Poultry Manure and Soil Mulching on Soil Properties,Physiological Responses,Yields and Water-use Efficiencies of Sorghum Plants under Water Stress

ABSTRACT

The present investigation was planned to determine the effect of deficit irrigation, mulching and poultry manure application on sorghum grain, forage yield and water-use efficiencies. Two field experiments were conducted during 2016 and 2017 growing seasons at Demo farm, Fayoum, Egypt. Eighteen treatments comprising of two rates of rice straw as soil mulching (SM; zero and 10 ton per hectare), three irrigation treatments (I_100% = 100%, I_85% = 85% and I_70% = 70% of crop evapotranspiration (ETc) and three poultry manure (PM) levels (0, 24 and 36 ton per hectare) were studied under controlled surface irrigation system. Sorghum growth attributes (plant height, stem diameter, leave area), grain and forage yield, water-use efficiencies (G-WUE and F-WUE) were significantly (p < .05) affected by irrigation quantity and both soil mulch and poultry manure application. Poultry manure resulted in a significant decrease in soil bulk density, electrical conductivity (ECe), soil pH, hydraulic conductivity and total porosity, useful pores, and water holding pores were increased. The results showed that underwater scarcity, application of (I₈₅ × PM₃₆× SM₁₀) treatment was found to be favorable to save 15% of the applied irrigation water as compared to I₁₀₀, at the time produced the same sorghum yields.     

Fodder production and soil health with conjunctive use of saline and good quality water in ustipsamments of a semi‐arid region

Food and fodder shortage in arid and semi‐arid regions force farmers to use marginal quality water for meeting the water requirement of crops which result in low quality, reduced production and an adverse impact on soil properties. A field study on loamy‐sand (Hyperthermic Typic Ustipsamments) saline soil was conducted during 1999–2001 at Central Institute for Research on Buffaloes, Hisar. This involved assessment of effects of conjunctive use of saline water, EC = 4·6–7·4 dSm⁻¹, SAR = 14–22 ((mmol⁻¹)^½ with good quality water on five fodder crop rotations: oat‐sorghum (Avena sativa‐–Sorghum bicolor), rye grass–sorghum (Loleum rigidum—Sorghum bicolor), Egyptian clover—sorghum (Trifoleum alexandrinum—Sorghum bicolor), Persian clover—sorghum (Trifoleum resupinatum—Sorghum bicolor) and Indian clover–sorghum (Melilotus indica—Sorghum bicolor) and certain soil properties associated with it. Leguminous winter fodder crops were more sensitive to poor quality water use. Reductions in fodder yield with use of saline water alone throughout season were 85, 68, 54, 42, 36 and 26 per cent in Indian clover, Egyptian clover, Persian clover, oat, rye grass and sorghum respectively as compared to good quality water. Leguminous fodder crops produced protein rich (12–14 per cent) and low fibre (18–20 per cent) fodder as compared to poor quality grassy fodder under good quality water irrigation but their quality deteriorated when saline water was used. These leguminous crops accumulated proportionately higher Na⁺ (1·58 per cent) resulting in adverse impact on their growth as compared to grassy fodder crops. Higher soil salinity (12·2 dSm⁻¹), SAR = 20 (mmol⁻¹)^½ was recorded with saline water irrigation; and slight adverse impact was noticed on infiltration rate and contents of water dispersible clay. Alternate cyclic use of canal and saline water could be an option for fodder production under such conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of Magnesium Chloride–Induced Salinity on Carbon Dioxide Evolution and Nitrogen Mineralization in a Silty Clay Loam Soil

A laboratory incubation experiment was conducted to evaluate the effect of magnesium chloride–induced salinity on carbon dioxide (CO₂) evolution and nitrogen (N) mineralization in a silty loam nonsaline alkaline soil. Magnesium chloride (MgCl₂) salinity was induced at 0, 4, 8, 12, 16, 20, 30, and 40.0 dS m^?1 and measured CO₂ evolution and N mineralization during 30 days of incubation. Both CO₂ evolution and N mineralization decreased significantly with increasing salinity. The cumulative CO₂ evolution decreased from 235 mg kg^?1 soil at electrical conductivity (EC) 0.65 dS m^?1 to 11.9 mg kg^?1 soil at 40 dS m^?1 during 30 days of incubation. Similarly, N mineralization decreased from 185.4 mg kg^?1 at EC 0.65 dS m^?1 to 34.45 mg kg^?1 at EC 40.0 dS m^?1 during the same period. These results suggested that increasing magnesium chloride salinity from 4 dS m^?1 adversely affect microbial activity in terms of carbon dioxide evolution and N mineralization.     

Influence of Salinity on Nitrogen Transformations in Soil

Laboratory experiments were carried out to study the influence of various salinity levels [1 (control), 9 (medium), 17 (high), and 27 dS m^–1(strong)] on nitrogen (N) transformations in soil fertilized with urea and ammonium sulfate. Generally, soil salinization affected the normal pathway of N transformations. The results showed that salinity (medium to high) inhibited the second step of nitrification, causing nitrite (NO₂ ^?) accumulation in soil. The inhibition was more severe in cases of high level of salinity. The greatest salinity level caused inhibition of even the first step of nitrification, leaving more ammonium (NH₄)-N accumulation in soil. Severity in nitrification inhibition was observed with increase in salinity and rate of N application, which declined with time. Ammonium accumulation with increased salinity caused N losses in the form of ammonia (NH₃) volatilization. After 14 days, the NH₃ losses were 1.4-, 2-, and 5-fold greater at 9, 17, and 27 dS m^–1 than that of the control (1 dS m^–1). After 42 days, the losses reached up to 6-fold more than the control at the greatest salinity level. Initially (up to 14 days), NH₃ losses were more from urea than from ammonium sulfate, whereas at the later stages (42 days), the losses were almost equal from both the fertilizers. The overall results revealed significant adverse effects of salinity on N transformations in soil.     

混合施用微咸水和氮肥对甜高粱生物量和产糖量的影响

Soil salinization and non-point source pollution are among the most important and widespread environmental problems in European Mediterranean regions. Sweet sorghum (Sorghum bicolor (L.) Moench var. saccharatum) is a moderate to high salinity tolerant crop with low water and nutrient needs, seen as an alternative to grow in the water scarce regions. A three-year multifactorial study was conducted in southern Portugal to evaluate the combined effects of saline water and nitrogen application on the dry biomass (total, stems, and leaves), sugar content (total reducing sugars and sucrose contents), and sugar yield (here defined as the product of total reducing sugars and stems dry biomass) functions of sweet sorghum. Sorghum dry biomass and sugar yield showed diminishing returns for each incremental change of nitrogen. The use of saline irrigation waters also led to yield reduction. Exception was sucrose content which increased with increasing levels of sodium in the soil. Nitrogen need decreased as the amount of sodium applied increased. Stem dry biomass, sucrose content, and sugar yield progressively increased with progress in the experiment. The effect could be attributed to the increase of the amount of irrigation applied throughout the years, thus increasing the leaching fraction which promoted salt leaching from the root zone, reduced the salinity stress, increased plant transpiration, nitrogen uptake and biomass yield.     

Amelioration of a calcareous saline-sodic soil by gypsum and forage plants

A field experiment was carried out at the University of Agriculture, Faisalabad (Pakistan) during 1988–90 to evaluate the comparative efficiency of chemical and biological methods for the reclamation of a calcareous saline-sodic soil (pHs

1 pHs = pH of saturated soil paste

= 8.2–8.6; ECe

2 ECe = Electrical conductivity of the saturation extract

= 7.4–9.0 dS m⁻¹; SAR

3 SAR = Sodium adsorption ratio

= 55.6–73.0 for upper 30 cm layer). Five treatments were assessed, three involved cropping: sesbania (Sesbania aculeata), sordan (Sorghum bicolor x Sorghum sudanese), and kallar grass (Leptochola fusca) and two were non-cropped (control and gypsum at 100.0 per cent GR-15·0 cm) were employed. Water of low electrolyte concentration (EC = 0.27 dS m⁻¹) was used for irrigation and leaching. Sesbania and kallar grass were found to be effective biotic materials for soil reclamation. These plant species produced substantial biomass and also improved the soil environment by lowering the EC and SAR of the soil. Sordan was relatively less-effective due to its sensitivity to high temperature and sodicity during germination and early seedling stages. After two cropping seasons, wheat (cultivar LU 26S) was sown as a test crop. Efficiency of treatments as indicated by wheat grain yield was in the order: sesbania = gypsum > kallar grass > sordan > control.     

Effect of Salinization of Soil on Growth and Nutrient Accumulation in Seedlings of Prosopis cineraria

ABSTRACT

Greenhouse experiments were conducted to assess the effects of salinization of soil on emergence, seedling growth, and mineral accumulation of Prosopis cineraria (Linn.) Druce (Mimosaceae). A mixture of chlorides and sulfates of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) was added to the soil and salinity was maintained at 5.1, 7.2, 9.3, 11.5, and 13.3 dS m^?1. A negative relationship between seedling emergence and salt concentration was obtained. Seedlings did not emerge when soil salinity exceeded 11.5 dS m^?1. Results suggested that this tree species is salt tolerant at seed germination and seedling stages. Elongation of stem and root was retarded by increasing salt stress. Young roots and stem were most tolerant to salt stress, followed by old roots and leaves. Leaf tissue exhibited maximum reduction in dry-mass production in response to increasing salt stress. However, production of young roots and death of old roots were found to be continuous and plants apparently use this process as an avoidance mechanism to remove excess ions and delay onset of ion accumulation in this tissue. Plants accumulated Na in roots and were able to regulate transfer of Na ions to leaves. Stem tissues were a barrier for translocation of Na from root to leaf. Moreover, K decreased in root tissues with increased salinization. Nitrogen (N) content significantly (P < 0.01) decreased in all tissues (leaf, stem, and root) in response to low water treatment and salinization of soil. Phosphorus (P) content significantly (P < 0.01) decreased while Ca increased in leaves as soil salinity increased. Changes in elements-accumulation patterns and the possible mechanisms for avoidance of Na toxicity in tissues and organism level are discussed.     

Sodicity Intensifies the Effect of Salinity on Grain Yield and Yield Components of Wheat

ABSTRACT

This study reports the relationship of the leaf ionic composition with the grain yield and yield components of wheat in response to salinity x sodicity and salinity alone. The study was conducted in soil culture in pots with three treatments including control (ECe 2.6 dS m^{? 1} and SAR 4.53), salinity (ECe 15 dS m^{? 1} and SAR 9.56), and salinity x sodicity (ECe 15 dS m^{? 1} and SAR 35). The soil was treated before being put in the pots and the pots were arranged in a completely randomized factorial arrangement with five replications. The seeds of three wheat genotypes were sown directly in the pots and the study was continued till the crop maturity. At booting stage, the leaf second to the flag leaf of each plant was collected and analyzed for sodium (Na⁺), potassium (K⁺), and chloride (Cl^?). At maturity, plants were harvested and data regarding grain yield and yield components were recorded. This study shows that salinity and sodicity in combination decreases the grain yield of wheat more than the salinity alone with a greater difference in the sensitive genotype. This study also shows that as for salinity, the maintenance of lower Na⁺ and higher K⁺ concentrations and higher K⁺: Na⁺ ratio in the leaves relates positively with the better development of different yield components and higher grain yield in saline sodic soil conditions. Although, the leaf Cl^? concentration was increased significantly by salinity as well as salinity x sodicity and would have affected the growth and yield, yet it does not seem to determine the genotypic tolerance or sensitivity to either salinity or salinity x sodicity.     

Effect of elemental sulphur and sulphur containing waste in a calcareous soil in Turkey

The effect of elemental sulphur (S) and S containing waste applications on soil pH treated with 0–2,000 kg ha^‐l elemental S, and 0–100 tons ha‐¹ of waste was determined in the field and the pots. Sorghum (Sorghum bicolor L.) was grown in a Lithic Xerorthent soil which was taken from where the field experiment was conducted in pots receiving 5 kg soil. Plants were harvested 20 weeks after planting or 30 weeks after the applications for determination of dry matter yield and phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) uptake by shoots. EC, NaHCO₃‐extractable P, and DTPA‐extractable Fe, Zn, Mn, Cu also were measured in pot soil at the 5th, 10th, and 30th weeks. All treatments led to a decrease in soil pH though pH tended to increase again during course of time in both field and pot experiments. The both elemental S and waste applications in pot experiment caused an increase in dry matter yield and P, Fe, zinc (Zn), Mn and Cu uptake (mg pot^‐1) by shoots in sorghum plant. There was also an increase in EC of soil due to both applications of S. The concentration of available P extracted by NaHCO₃ in the pot soil, though not significantly different, was slightly higher compared with the control. Waste applications increased DTPA‐extractable Fe content of the soil, DTPA‐extractable Mn and DTPA‐extractable Cu. DTPA‐extractable Zn content, however, was reduced by the same applications.     

利用15N揭示滴灌区盐旱胁迫对土壤氮素分布与棉花生长的影响

为了探究盐旱胁迫对土壤中氮素分布和棉花生长的影响,通过测坑试验研究滴灌区不同盐分、干旱条件下土壤全氮、硝氮、氨氮的分布和棉花生长情况。试验设置3种盐分梯度的土壤（电导率,EC）：3,6,9 dS/m,分别用T1、T2、T3表示;3个灌水量：2 700,3 600,4 500 m³/hm²,分别用W1、W2、W3表示（4 500 m³/hm²为当地推荐灌水量）。结果表明：当土壤盐分梯度> 3 dS/m时土壤全氮累积量显著高于低盐土壤（P<0.05）,且土壤盐分对棉花花期生长影响较大。土壤的氨氮挥发量和土壤盐分梯度成正比。土壤硝态氮的淋失与灌水量呈正比,与正常灌水量的硝态氮淋失相比,水分胁迫对棉花产量的影响更为严重（P<0.01）。随土层深度的增加,土壤碱解氮以每20 cm土层8%的速度减少。各处理土壤¹⁵N残留率为11%~40%,随土壤盐度增加而增加,随灌水量增加而减少,与土壤全氮含量呈正比,与棉花产量呈反比。综上所述,T1W3处理更有利于棉花对氮肥的利用和产量的提高,推荐滴灌区棉花土壤盐度<3 dS/m,灌水量4 500 m³/hm²,可在花期适当提高施肥量以稳定产量。