Arsenic Concentrations in Groundwater,Soils, and Irrigated Rice in Southwestern Bangladesh

Arsenic (As) poisoning of groundwater in Bangladesh has become a major environmental and health issue. The extensive use of groundwater in irrigation of rice has resulted in elevated As in soils and crops. A study was undertaken to determine As concentrations in groundwater, soils, and crops in 16 districts of southwestern Bangladesh. Groundwater samples were collected from shallow-tube and hand-tube wells (STW and HTW) used for irrigation and drinking water. Soil and rice plants were sampled from the command area of the tube wells. Arsenic concentrations were determined using an atomic absorption spectrometer equipped with flow injection hydride generator. Groundwater samples contained <10 to 552 μg As L^?1. Arsenic concentrations in 59% of STW samples exceeded 50 μg As L^?1, the national standard for As in drinking water. Unlike groundwater, most of the surface water samples contained <10 μg As L^?1. Concentrations of As in the soils from the command area of the tube wells ranged from 4.5 to 68 mg kg^?1. More than 85% of the soils contained <20 mg As kg^?1. The mean As concentration in the rice grain samples was 0.23 mg kg^?1, which is much less than the maximum food hygiene standard. A positive relationship was observed between groundwater and soil As, implying that soil As level increases as a result of irrigation with contaminated water. However, irrigation water As did not show any relation with rice grain As. The findings suggest that surface water bodies are a safe source of irrigation water in the As-contaminated areas.     

Potential of Carbon Dioxide Biosequestration of Saline–Sodic Soils during Amelioration under Rice–Wheat Land Use

Potential for carbon dioxide (CO₂) biosequestration was determined during the reclamation of highly saline–sodic soils (Aridisols) after rice (2003) and wheat (2003–2004) crops at two sites in District Faisalabad, Pakistan. Two treatments were assessed: T₁, tube-well brackish water only; and T₂, soil-applied gypsum at 25% soil gypsum requirement?+?tube-well brackish water. The irrigation water used at both sites had different levels of salinity (EC 3.9–4.5 dS m^?1), sodicity (SAR 21.7–28.8), and residual sodium carbonate (14.9 mmol_c L^?1). Composite soil samples were collected from soil depths of 0–15 and 15–30 cm at presowing and postharvest stages and analyzed for pH, EC_e, and sodium adsorption ratio (SAR). After rice harvest, there was no significant effect of gypsum application on EC_e, pH, and SAR at both sites, except pH at 0–15 cm depth decreased significantly with gypsum at site 1. After wheat harvest, EC_e, pH, and SAR decreased significantly with gypsum at site 1, whereas the effect of gypsum on these parameters was not significant at site 2. Compared to initial soil, EC_e and SAR in soil decreased considerably after rice or wheat cultivation, particularly at site 1, whereas pH increased slightly due to cultivation of these crops. For rice, the total CO₂ sequestration was significantly increased with gypsum application at both sites and ranged from 1499 to 2801 kg ha^?1. The total sequestration of CO₂ was also significantly increased with gypsum application in wheat at both sites and ranged from 2230 to 3646 kg ha^?1. The amounts of CO₂ sequestered by crops due to gypsum application were related to seed and straw yield responses of rice and wheat to gypsum, which were greater at site 1 than site 2. Also, the yield response to applied gypsum was greater for rice than wheat at site 1, whereas the opposite was true at site 2. Overall, the combined application of gypsum with brackish water reduced soil EC_e and SAR compared to brackish water alone, particularly at site 1. Our findings also suggest that the reclamation strategies should be site specific, depending on soil type and quality of brackish water used for irrigation of crops. In conclusion, the use of gypsum is recommended on brackish water–irrigated salt-prone soils to improve their quality, and for enhancing C biosequestration and crop production for efficient resource management.     

Identifying Soil and Plant Nutrition Factors Affecting Yield in Irrigated Mature Pistachio Orchards

The main objective of this study was to evaluate the potential use of a hybrid Genetic Algorithm-Artificial Neural Network (GA–ANN) method for predicting pistachio yield and for identifying the determinant factors affecting pistachio yield in Rafsanjan region, Iran. A total of 142 pistachio orchards were selected randomly and soil samples were taken at three depths. Besides, water samples and leaves from branches without fruit were taken in each sampling point. Management information and pistachio yields were achieved by completing a questionnaire. Primarily, 58 variables affecting pistachio yield were measured, and then 26 out of them were selected by minimizing mean square error (MSE) using a feature selection (FS) method. The results showed that the accuracy of the method was acceptable. Furthermore, the sensitivity analysis showed that the main determinant features affecting the pistachio yield were the irrigation water amount, leaf phosphorus, soil soluble magnesium, electrical conductivity (EC), and leaf nitrogen.     

Evaluation of Rice and Wheat Cultivars for Tolerance to Salinity and Sodicity in Soil

The large genotypic variation for salt tolerance in rice and wheat is the driving force behind efforts to identify appropriate cultivars for salt‐prone environments where large variations in salinity (electrical conductivity, EC) and sodicity (sodium adsorption ratio, SAR) levels exist. An evaluation of the commonly grown rice and wheat cultivars at different EC/SAR ratios may thus help in coping with the crop failures on salt‐affected soils. Accordingly, we evaluated some salt‐tolerant cultivars of rice and wheat for growth and yield at different soil salinity and sodicity levels in a sandy clay loam soil. Among the cultivars tested, rice ‘SSRI‐8’ produced the highest productive tillers and paddy yield, and wheat cultivar ‘SIS‐32’ produced the highest tillers and grain and straw yields. The high EC/SAR ratios proved more hazardous for rice than for wheat. Irrespective of the varieties tested, the highest levels of EC and SAR (T₅ and T₆) caused significant reduction in paddy yield, whereas at the lowest levels of EC and SAR (T₁ and T₂), paddy yield was not affected significantly when compared with the control. However, in case of wheat crop, all the levels [i.e., the lowest (T₁ and T₂), medium (T₃ and T₄), and the highest (T₅ and T₆) of EC and SAR tested] affected wheat yield adversely with significant differences. For both the crops, there were little or no differences in yield between the two ratios tested (i.e., 1:2 and 1:4) at all the levels of EC and SAR.     

Evaluation of On-site Wastewater Disposal Systems in Mississippi Coastal Areas

Groundwater and surface water contamination have been linked to inadequate or failing on-site residential wastewater treatment and disposal systems. The potential for groundwater contamination in coastal areas with shallow water tables is higher; subsequently the ability of soil, microorganisms, and vegetation to mitigate pollutants may be reduced. This study evaluated the performance of the four types of on-site wastewater treatment and disposal systems predominantly used on the Mississippi Gulf Coast. One type of system was deemed inappropriate for this region as none of the dozens of installations examined were functioning acceptably. Of the remaining three types, subsurface water samples were collected from representative sites using lysimeters and monitoring wells. Apart from general performance evaluation of these systems, seasonal changes translating into possible variation in disposal efficiencies and groundwater contamination were investigated. Statistical analysis of variations in organics (COD and BOD₅), nitrogen (TKN and NH ₄ ⁺ ?CN), and fecal coliform concentrations was used to identify probable deficiencies in systems tested and to recommend changes to governing standards.     

外来调水对华北低平原区地表水和地下水 水化学特征的影响* ——以河北省南皮县为例

华北低平原区有着巨大的粮食增产潜力,同时也是粮食生产和农业水资源矛盾突出的地区。外来调水与浅层微咸水的联合利用是解决区域水资源问题的有效途径之一,同时也将引起区域水循环和水环境的改变。为明确外来调水对华北低平原区地表水和地下水水化学特征的影响,本研究在华北低平原区河北省南皮县域内对调水后不同季节地表水和地下水进行调查和采样,利用水文地球化学和氢氧(d~2H、d~(18)O)稳定同位素相结合的方法,研究外来调水对地表水和地下水转化及其水化学特征的影响。研究结果表明,11月至翌年7月,受蒸发作用的影响,地表水电导率(EC)和钠吸附比(SAR)增加,d2H、d18O同位素不断富集;由于地表水和周围土壤的交换吸附作用使其水化学类型向Na~+、Cl~-和SO_4~(2-)增加、HCO_3~-减少的咸水转变。调水改变了地表水和浅层地下水之间的补给关系,11月至翌年3月,沟渠附近浅层地下水受外来调水直接或者灌溉补给,使得3月浅层地下水EC降低,埋深变浅,部分采样点分布在外来调水的SAR-EC区域。受调水影响,3月沟渠附近浅层地下水水化学类型为Na·Mg·Ca-Cl·SO_4、Na·Mg-Cl·SO_4·HCO_3、Na·Mg-SO_4·Cl·HCO_3等,是11月调水(Na·Mg·CaSO_4·HCO_3·Cl)和浅层地下水(Na·Mg-Cl·SO_4)的过渡类型。3月至7月浅层地下水补给沟渠水,地下水埋深变深,7月浅层地下水水化学类型与3月相似。调水可以季节性地改善区域内沟渠水及其附近的浅层地下水水质,而对深层地下水和坑塘水的水质无改善作用。调水对沟渠水水质的改善体现在调水季节,对浅层地下水水质的改善存在滞后性,2014年11月调水之后,2015年3月浅层地下水的水质得到改善。因此,采用调水和浅层地下水、坑塘水混合灌溉,对合理开发利用区域咸淡水资源以及深层地下水压采,恢复地下水位意义重大。     

Spatial and Temporal Variability of Groundwater Nitrate Concentrations in Irrigated Mediterranean Agriculture

As nitrogen (N) fertilizer-use efficiency rarely exceeds 50% in most agricultural systems, the potential leaching of N to the groundwater, particularly under irrigated conditions, has economic, health, and environmental implications. Research in the Akarsu irrigation district in the Lower Seyhan Plain in southern Turkey sought to determine spatial and temporal variability of groundwater (GW) nitrate (NO₃) concentrations in 2007–2008. Shallow groundwater observation wells 3 m deep were installed at different locations to represent the whole irrigation district. Groundwater samples were collected (February, April, July, October) and analyzed for ammonium (NH₄) and NO₃ concentrations. Because NH₄ values were negligible, only NO₃ data were processed to determine spatial and temporal variability and then used to develop regional NO₃ maps using geographic information systems. Groundwater NO₃ concentrations ranged between 0.17 and 55.96 mg L^–1 during the 2 years, only exceeding the critical 50 mg L^–1 concentration in 1% of the area sampled. The areal mean of NO₃ concentration was greatest in February, indicating a potential N leaching of unused N from the early season with intensive rainfall, especially in wheat-growing areas. Groundwater NO₃ concentrations decreased after February; however, during the peak irrigation season in July, NO₃ was relatively low because of crop uptake during spring and summer. In about half the area, groundwater NO₃ concentrations ranged between 20 and 50 mg L^–1 and were thus marginal relative to the critical pollution level. As N fertilizer use will continue to increase, especially with the expanded irrigation that is now occurring in the Mediterranean region, regular monitoring of groundwater NO₃ is advisable under such conditions.     

EFFECTS OF WATER SALINITY ON GROWTH INDICES AND PHYSIOLOGICAL PARAMETERS IN SOME PISTACHIO ROOTSTOCKS

Pistachio is one of the most important horticultural crops in Iran. The majority of the pistachio producing regions is located in arid and semi-arid areas with saline conditions. Therefore, selection of suitable rootstocks is important for increasing yield efficiency of this important nut crop. In this study, the effect of four water salinity levels (0.75, 5, 10 and 15 ds m^?1) on growth indices and physiological parameters of four Pistacia vera L. rootstocks (Badami-e-Zarand A, Badami-e-Zarand B, Qazvini, and Sarakhs) were investigated under greenhouse conditions. After treatment for three months, leaf dry weight was reduced by about 30-50% at an irrigation water electrical conductivity (EC_w) of 10 ds m^?1. Badami-e-Zarand B was the most vigorous rootstock at the highest EC. Decreases in root and stem dry weight (average of all rootstocks combined) occurred at water salinity of 10 ds m^?1. Chemical analysis of shoot and root indicated that the salinity affected the concentration and distribution of sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺) in pistachio rootstocks. The concentrations of Na⁺ and K⁺ increased with a rise in water salinity levels. Comparison between Na⁺ concentration of shoot and root showed that all examined rootstocks limited the Na⁺ transportation to shoot tissue up-to 15 ds m^-1, and retained it in the roots. However, this ability was less in the Sarakhs rootstock. Based on measured parameters, Badami-e-Zarand B and Sarakhs could be considered as tolerant and sensitive pistachio rootstocks to water salinity, respectively.     

Reclamation and salt leaching efficiency for tile drained saline‐sodic soil using marginal quality water for irrigating rice and wheat crops

Due to increased population and urbanization, freshwater demand for domestic purposes has increased resulting in a smaller proportion for irrigation of crops. We carried out a 3‐year field experiment in the Indus Plains of Pakistan on salt‐affected soil (EC_e 15·67–23·96 dS m⁻¹, pH_s 8·35–8·93, SAR 70–120, infiltration rate 0·72–0·78 cm h⁻¹, ρ _b 1·70–1·80 Mg m⁻³) having tile drainage in place. The 3‐year cropping sequence consisted of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) crops in rotation. These crops were irrigated with groundwater having electrical conductivity (EC) 2·7 dS m⁻¹, sodium adsorption ratio (SAR) 8·0 (mmol L⁻¹)^1/2 and residual sodium carbonate (RSC) 1·3 mmol_c L⁻¹. Treatments were: (1) irrigation with brackish water without amendment (control); (2) Sesbania (Sesbania aculeata) green manure each year before rice (SM); (3) applied gypsum at 100 per cent soil gypsum requirement (SGR) and (4) applied gypsum as in treatment 3 plus sesbania green manure each year (GSM). A decrease in soil salinity and sodicity and favourable infiltration rate and bulk density over pre‐experiment levels are recorded. GSM resulted in the largest decrease in soil salinity and sodicity. There was a positive relationship between crop yield and economic benefits and improvement in soil physical and chemical properties. On the basis of six crops, the greatest net benefit was obtained from GSM. Based on this long‐term study, combined use of gypsum at 100 per cent soil gypsum requirement along with sesbania each year is recommended for soil amelioration and crop production. Copyright © 2010 John Wiley & Sons, Ltd.     

A Comparative Study of Different Amendments on Amelioration of Saline-Sodic Soils Irrigated with Water Having Different EC: SAR Ratios

Soil degradation affects soil properties such as structure, water retention, porosity, electrical conductivity (EC), sodium adsorption ratio (SAR), and soil flora and fauna. This study was conducted to evaluate the response of contrasting textured soils irrigated with water having different EC:SAR ratios along with amendments: gypsum (G), farm manure (FM), and mulch (M). Water of different qualities viz. EC 0.6 + SAR 6, EC 1.0 + SAR 12, EC 2.0 + SAR 18, and EC 4.0 + SAR 30 was used in different textured soils with G at 100% soil gypsum requirement, FM at 10 Mg ha^?1, and M as wheat straw was added on surface soil at 10 Mg ha^?1. Results revealed that the applied amendments in soils significantly decreased pH_s and electrical conductivity (EC_e) of saturated paste and SAR. Four pore volumes of applied water with leaching fraction 0.75, 0.77, and 0.78 removed salts 3008, 4965, and 5048 kg ha^?1 in loamy sand, silty clay loam, and sandy clay loam soils, respectively. First four irrigations with LF of 0.82, 0.79, 0.75, and 0.71, removed 5682, 5000, 3967, and 2941 kg ha^?1 salts, respectively. The decreasing order for salt removal with amendments was FM > G > M > C with LF = 0.85, 0.84, 0.71, and 0.68, respectively. This study highlights a potential role of soil textures to initiate any mega program for reclamation of saline-sodic soils in the perspective of national development strategies.     

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.     

Assessment of Contaminant Migration in Groundwaterfrom an Industrial Development Area,Medak District,Andhra Pradesh,India

Number of chemical and pharmaceutical industries have been established during 1977 in the PatancheruIndustrial Development Area near Hyderabad city in the Medak district, Andhra Pradesh, India. Thetreated and untreated effluents from the industriesare being discharged in two streams: Nakkavagu and Peddavagu. The Pamulavagu, a tributary of the Nakkavagu alsocarries effluents from the adjacent Bolaram Industrial Development area. The industrial effluents are being discharged into open channels and streams in the area. Groundwater contamination has been reported since 1985.Groundwater level and water quality monitoringwas carried out during 1997 and 1998 in Patancheru andits environs, covering an area of 120 km². Surface watersamples were also analyzed for the water quality. Thesurface water TDS (Total Dissolved Solids)concentration was found ranging between 3000–5000 mg L^-1. The groundwater in the alluvium ofthe Nakkavagu has shown TDS concentrations ranging from1000–3000 mg L^-1. The Nakkavagu is acting as adiffuse source of contaminants all along its course. Aquifer parameters were estimated by carrying outpumping tests at a number of wells. Groundwater flowand mass transport models were prepared using visualMODFLOW software. The extent of migration ofcontaminants from the Nakkavagu and other streams has beenassessed for 20 yr (1977–1997). The stream-aquifer interaction was found to be responsiblefor faster migration of contaminants in theover-exploited area east of the Nakkavagu.     

黄河三角洲土壤盐渍化与地下水特征关系研究

为研究黄河三角洲表层土壤盐分含量与地下水特征的关系,对研究区内土壤盐分含量及地下水进行原位监测,分析土壤盐渍化和地下水特征,并运用灰色关联分析法对地下水埋深、电导率、p H和主要离子含量的关系进行定量分析。结果表明:土壤表层盐分含量均值为3.90~6.31 g kg-1,表层以下土壤盐分含量均值为2.54~3.44 g kg-1,属于中度及以上盐渍化程度;地下水埋深平均值为1.16~1.71 m,普遍较浅;地下水阴离子以Cl-为主,阳离子以Na+为主,两者分别占阴、阳离子总量的比例约为65%。关联分析表明,不同地下水特征指标与土壤表层盐分含量的密切程度不同,同一特征指标与土壤表层盐分含量的密切程度在不同时期间差异显著,总体而言,土壤表层积盐与地下水电导率、Na+、Cl-的关系较为密切,与p H、CO32-和HCO3-之间的关系较弱。在防治土壤盐渍化中,应当加强对地下水电导率、Na+、Cl-的控制与管理。     

Selenium Behavior in Open Bulk Precipitation, Soil Solution and Groundwater in Alluvial Fan Area in Tsukui, Central Japan

A monitoring study was carried out in an alluvial fan area in Tsukui, Central Japan during the study period of 1999–2003, in order to explain selenium (Se) behaviors in ecosystem combined with air, soil and groundwater. Monthly Se concentrations in open bulk precipitation (rainfall+aerosol, gaseous deposition and etc.), soil solution (collected by porous ceramic-cup) and groundwater ranged from 0.1 to 1.4 μg L^?1 (volume-weighted average: 0.34 μg L^?1), 0.21 to 1.0 μg L^?1 (0.48 μg L^?1) and 1.6 to 2.4 μg L^?1 (2.2 μg L^?1), respectively. Se concentration in open bulk precipitation was negatively correlated with the rainfall amount. Se concentration in soil solution significantly increased with DOC concentration in soil solution. Besides, despite atmospheric Se input and rainfall to the grassland study area, Se concentration in soil solution and groundwater received no significant effect from the rainfall amount, pH, Se, DOC, SO₄ ^2?, NO₃ ^? and EC in rainfall. Even though Se concentrations in groundwater were significantly correlated with soil solution volume, Se, DOC and NO₃ ^? and groundwater level, the result of multiple regression analyses (MRA) indicated that the groundwater Se was negatively influenced by groundwater level, which depended on groundwater recharge. Se was transported into the groundwater through the groundwater recharge that largely increased in this alluvial fan study area after heavy rain.     

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.     

Leaching and reclamation of calcareous saline‐sodic soil by moderately saline and moderate‐SAR water using gypsum and calcium chloride

Lysimeter experiments were conducted with sandy‐clay‐loam soil to study the efficiency of two amendments in reclaiming saline‐sodic soil using moderately saline and SAR (sodium‐adsorption ratio) irrigation water. Gypsum obtained from industrial phosphate by‐products and reagent grade Ca chloride were applied to packed soil columns and irrigated with moderately saline (ECe = 2.16 dS m^–1), moderate‐SAR water (SAR = 4.8). Gypsum was mixed with soil prior to irrigation at application rates of 5, 10, 15, 20, 25, and 32 Mg ha^–1, and Ca chloride was dissolved directly in leaching water at application rates of 4.25, 8.5, 12.75, 17.0, and 21.25 Mg ha^–1, respectively. The highest application rate in both amendments resulted in 96% reduction of total Na in soil. The hydraulic conductivity (HC) of soils receiving gypsum increased in all treatments. The highest HC value of 6.8 mm h^–1 was obtained in the highest application rate (32 Mg ha^–1), whereas the lowest value of 5.2 mm h^–1 was observed with the control treatment. Both amendments were efficient in reducing soil salinity and sodicity (exchangeable‐sodium percentage, ESP); however, Ca chloride was more effective than gypsum as a reclaiming material. Exchangeable Na and soluble salts were reduced with gypsum application by 82% and 96%, and by 86% and 93% with Ca chloride application, respectively. Exchangeable Ca increased with increasing amendment rate. Results of this study revealed that sodium was removed during cation‐exchange reactions mostly when the SAR of effluent water was at maximum with subsequent passage of 3 to 4 pore volumes. Gypsum efficiently reduced soil ESP, soil EC, leaching water, and costs, therefore, an application rate of 20 Mg ha^–1 of gypsum with 3 to 4 pore volumes of leaching water is recommended for reclaiming the studied soil.     

Longtime effects of deep groundwater extraction management on water table levels in surface aquifers

Purpose

A longtime monitoring (2003–2013) of groundwater levels and soil moisture was done in a plain tract surrounded by deposits from the Saale glacial stage in northern Germany. The purpose was to document the changes in the soil water regime over time in relation to changes in management of groundwater extraction and to evaluate if the hitherto management has been suitable for plant water supply for the local grassland production.

Materials and methods

Groundwater wells in the surface aquifer were monitored at 11 survey sites, and soil matric potentials were measured with tensiometers at five depths per site. Soil analyses also were done. This report contains the results from three of the 11 survey sites, which best represent the variability of the soils in the area.

Results and discussion

The monitoring showed that groundwater extraction from deep aquifers via individual wells altered the groundwater levels in the surface aquifer, even though there was a distance of several meters depth and a geological parting between the two aquifers. The impact of the groundwater extraction was shown by significant correlations between groundwater levels in the surveyed soils and groundwater extraction rates of individual wells. Climatic factors only affected groundwater levels in individual years. The management of the groundwater extraction from 1977 to 2006 severely lowered the groundwater level in the surface aquifer. Due to a limitation of the groundwater extraction rates and a shift in the degree of capacity utilization of the individual wells from 2006 onward, groundwater levels in the area are recovering. Correspondingly, the contribution of capillary rise to plant water supply has increased within the monitoring period.

Conclusions

The monitoring proves that the present management of groundwater extraction is more suitable for the groundwater situation than past management. However, groundwater levels have not yet obtained a new equilibrium, so continual monitoring is needed.

     

Assessment of spatial and seasonal changes in groundwater nitrate pollution of agricultural lands through ordinary and indicator kriging techniques

Geostatistical approaches (ordinary kriging (OK) and indicator kriging (IK)) were used in this study to investigate the spatial and temporal variations in groundwater nitrate concentrations in Çar?amba plain of Turkey. Groundwater samples were taken in April 2012, July 2012, September 2012 and March 2013 from 78 groundwater wells. The experimental semivariograms were often fitted well by a Gauss model for April 2012 and September 2012, whereas a spherical model was fitted to experimental semivariograms for July 2012 and March 2013. Spatial distribution maps revealed that groundwater nitrate concentrations were above the threshold value of 50 mg L^?1 specified for drinking water in 4.3% of the study area in April 2012, 40.8% in July 2012, 32.8% in September 2012 and 19.1% in March 2013. Probability maps created with IK showed that 3.1% and 3.2% of the total area had very strong probability (0.8–1.0) of exceeding the threshold nitrate concentration in July 2012 and September 2012, respectively. Current findings revealed that groundwater nitrate concentrations changed seasonally and increased much more in summer. It was concluded that OK and IK may yield significant outcomes for groundwater management, identification of risky sites for potential pollution and identification of the sites with excessive fertilizer uses.     

Zinc Nutrition in ‘Nagpur’ Mandarin on Haplustert

ABSTRACT

Zinc (Zn) deficiency is the most prevalent nutritional disorder in citrus orchards world over. The management strategy of Zn deficiency today is still governed by the efficacy of two conventionally used methods of Zn supply to plants via soil or foliar fertilization. A field experiment with 12-yr-old ‘Nagpur’ mandarin (Citrus reticulata Blanco) orchard was, therefore, carried out during 2004–07 comparing soil application versus foliar application of Zn, each at three levels viz., 100, 200, and 300 g tree^?1 with constant doses of N (600 g tree^?1), P (200 g tree^?1), K (300 g tree^?1), and Fe(60 g tree^?1) on Haplustert soil type with reference to response on flowering intensity, fruit set, tree volume, fruit yield, changes in soil fertility/leaf nutrient status, fruit quality, and transformation of native soil Zn fractions. Soil application of Zn at all the three levels, produced significantly higher increase in tree volume over foliar application on equivalent rates viz., T₁ (2.53 m³) vs. T₄ (2.06 m³) and T₂(4.30 m³) vs. T₅ (2.23 m³). The yield-determining parameters like flowering and fruit set intensity (no. m^?1 shoot length) were, respectively, much higher with soil applied (135.74 and 21.90) than foliar applied Zn (31.20 and 11.6). These observations set the favorable conditions required for yield response, e.g., all the three treatments involving soil application of Zn, T₁ (32.1 kg tree^?1), T₂ (52.6 kg tree^?1), and T₃ (51.8 kg tree^?1) were correspondingly superior over T₄ (22.5 kg tree^?1), T₅ (34.3 kg tree^?1), and T₆ (42.1 kg tree^?1) as foliar application treatments. All the three major fruit quality parameters (juice, acidity, and TSS) were likewise more influenced by soil application than foliar application of Zn. Improvements in soil Zn fractions (mg kg^?1) viz., exchangeable Zn (0.25–0.60), complex-Zn (2.71 to 4.86), organically bound Zn (0.86 to 2.0), and Zn-bound to carbonates and acid soluble minerals (2.56–4.96) were observed in response to Zn fertilization with treatments T₁–T_3. On the other hand, foliar applied Zn treatments (T₄–T₆) produced no such changes in any of the soil Zn fractions.     

灌溉水质对土壤化学特征和作物生长的影响

本文以灌溉水矿化度和钠吸附比为两个主要指标，组合成１６个灌溉水质处理，研究了不同灌溉水质对土壤化学性质和作物生长的影响。初步提出了引起盐害和碱害的灌溉水矿化度和钠吸附比的临界值。研究结果表明，灌溉水带入土壤的盐分在土壤中累积与淋洗交替进行。