Control Soil Salinity Research Articles

Laboratory Calibration of TDR Probes for Simultaneous of Measurements Soil Water Content and Electrical Conductivity

ABSTRACTAccurate measurement of water content (θ), apparent electrical conductivity (ECa) of soils, and soil solution electrical conductivity (ECw) is critical for a better management of irrigation water and the effective monitoring and control of soil salinity. In this paper, we demonstrate the design and validation of an identical time domain reflectometry (TDRWO) probe for accurate and non-destructive measurements of ECw. Two calibration functions were used to determine the soil-water content by TDR. Theses relations were verified by laboratory experiment over a wide range of θ and bulk density (BD) for dune sand. The exact length and the impedance of all TDR-probes were calibrated using the WinTDR procedure. Estimates of ECw were based on θ and the bulk ECa using a special modeling approach which applies long-time TDR waveform analysis. The geometrical disposition of the matrix phase factors (τ and β) was calculated by immersing the TDR probe in sodium chloride (NaCl) solutions of different electrical conductivities in pressure cells wetted and drained with each of these NaCl solutions. The reliability of the TDRWO was validated/proven under laboratory conditions. The laboratory experiment consisted in inserting the TDR probe into a pressure cell packed with mixed sand and 2-mm sieved loam soil that was subsequently wetted and drained with different NaCl solutions at various pressure heads. The ECw estimated by TDRWO was compared to the ECw measured in the draining solutions after they stabilized in the soil porous system. The τ and β factors calculated for the ceramic disks sets were 1.991 and 4.312, respectively. In the laboratory experiments, high and therefore significant correlations (R2 = 0.986; P < .001) were found between the ECw estimated by the TDRWO and the corresponding ECw values measured in the column-drainage. These results demonstrate that the TDRWO is an instrument which allows researchers to accurately estimate soil solution salinity independently of the soil water content and the porous medium in which the TDR probe is installed. Test results showed that the TDR method has high accuracy for monitoring soil water content but is less accurate in monitoring soil electrical conductivity across a water content range of about ≤0.03cm3/cm3. Regression analysis between TDR-Volumetric water content (ϴv) and weighing method – ϴv showed good correlation with an R2 of 0.97 and 0.98 during two laboratory experiments.

Site-specific management of salt affected soils: A case study from Egypt

In Egypt all agricultural practices are generally applied uniformly without taking spatial variability into consideration, which is not efficient and may be more expensive than site-specific management approach. This is based on accurate assessment of within-field variation and on field delineation into homogeneous zones to be submitted to differential management. Multivariate geostatistics allows to assess and model the spatial variation of a set of soil attributes influencing management. The objective of this paper was to propose an approach for determining spatially variable rate application (VRA) of leaching water, to control soil salinity, and of fertilizer to improve productivity while reducing environmental impact. The research was conducted in an experimental 3.1-ha field in Egypt and the following soil attributes were measured: electrical conductivity (ECe), available nitrogen (N), available phosphorus (P), available potassium (K) and organic matter content (OM). Ordinary cokriging was applied to produce thematic maps of soil attributes and the appropriateness of the linear model of coregionalization was evaluated with cross-validation. Spatial maps of the five soil variables were classified into three isofrequencies classes and the mean values were calculated for each class. These values were then compared with critical reference values to assess the local soil requirements for reducing soil salinity and/or improving soil fertility. The results showed that the estimations of soil attributes were unbiased and accurate. Only for ECe and available nitrogen site-specific management would be preferable because it would reduce the agricultural costs for both soil reclamation (saving water used to leach salts) and improvement of soil N fertility in comparison with the traditional uniform methods.The proposed approach, though producing encouraging results, would require improvements in the determination of the threshold values used to plan salt leaching and soil fertilization.

Impact of changes in water management on hydrology and environment: A case study in North China

Irrigation projects often result in many far-reaching environmental changes. This paper considers the case of the Hetao Irrigation District, the largest irrigation project along the Yellow River in China, and studies the impacts of agricultural water management on the hydrology and the environment. Long-term data (1954–2013) concerning irrigation, drainage, soil salinity, groundwater, and the environment of Wuliangsuhai Wetland, the lake that receives the drainage water, were collected and analyzed. The findings show that uncontrolled irrigation and the absence of effective drainage initially resulted in a rising groundwater table, worsening soil salinization, and the expansion of the lake, which is an important internationally recognized wetland. The completion of an artificial drainage system and the implementation of water-saving practices have had promising effects on lowering the groundwater table and controlling soil salinity. However, the risk of soil salinity is still threatening the irrigation system because salt is continuously accumulating within it and the total dissolved salts (TDS) in the groundwater are increasing. For better soil salinity control, more effective drainage is necessary to drain more salt and lower the water table, but this may harm the natural vegetation and the eco-environment of the Wuliangsuhai Lake because the non-point-source pollution from agricultural drainage has resulted in a serious eco-crisis in the Wuliangsuhai Lake. The results show that it is important to ensure there is a certain amount of low-TDS drainage water to protect the Wuliangsuhai Lake environment. Therefore, a balance must be achieved among soil salinity control, groundwater quality, favorable conditions for natural vegetation, and wetland protection. Further research is needed to develop optimal agricultural water management strategies, especially in the context of the ongoing water-saving renovation program.

Actual Evapotranspiration and Tree Performance of Mature Micro-Irrigated Pistachio Orchards Grown on Saline-Sodic Soils in the San Joaquin Valley of California

In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and tree performance, and understanding the mechanisms regulating water-use reduction under saline and saline-sodic conditions. Pistachio ETa was measured with the residual of energy balance method using a combination of surface renewal and eddy covariance equipment. Saline and saline-sodic conditions in the soil adversely affected tree performance with different intensity. The analysis of field data showed that ETa, light interception by the tree canopy, and nut yield were highly and linearly related (r2 &gt; 0.9). Moving from non-saline to saline and saline-sodic conditions, the canopy light interception decreased from 75% (non-saline) to around 50% (saline) and 30% (saline-sodic), and ETa decreased by 32% to 46% relative to the non-saline orchard. In saline-sodic soils, the nut yield resulted around 50% lower than that of non-saline orchard. A statistical analysis performed on the correlations between soil physical-chemical parameters and selected tree performance indicators (ETa, light interception, and nut yield) revealed that the sodium adsorption ratio (SAR) adversely affected tree performance more than the soil electrical conductivity (ECe). Results suggest that secondary effects of sodicity (i.e., degradation of soil structure, possibly leading to poor soil aeration and root hypoxia) might have had a stronger impact on pistachio performance than did salinity in the long term. The information presented in this paper can help pistachio growers and farm managers better tailor irrigation water allocation and management to site-specific orchard conditions (e.g., canopy features and soil-water salinity/sodicity), and potentially lead to water and energy savings through improved irrigation management practices.

Five-Year Experimental Study on Effectiveness and Sustainability of a Dry Drainage System for Controlling Soil Salinity

The dry drainage system (DDS) is an alternative technique for controlling salinization. To quantify its role in soil salinity control, a five-year field observation from 2007 to 2011 was completed in a 2900 ha experimental plot in Yonglian Experimental Station, Hetao Irrigation District, China. Results showed that the groundwater table depth in the fallow areas quickly responded to the lateral recharge from the surrounding croplands during irrigation events. The groundwater electrical conductivity (GEC) of fallow areas increased from 5 mS·cm−1 to 15 mS·cm−1, whereas the GEC below croplands produced small fluctuations. The analysis of water and salt balance showed that the excess water that moved to fallow was roughly four times that moved by an artificial drainage system and with 7.7 times the corresponding salt. The fallow areas act as a drainage repository to receive excess water and salt from surrounding irrigated croplands. Slight salt accumulation occurred in irrigated croplands and salts accumulated, with an accelerating trend over the final two years. The evaporation capability weakened, partly due to the salt crust in the topsoil, and the decrease in soil permeability in the soil column, which was almost impermeable to water. Using halophytes may be an effective method to remove salts that have accumulated in fallow areas, having great economic and ecological value. A DDS may be effective and sustainable in situations where the fallow areas can sustain an upward capillary flux from planted halophytes.

引黄灌区次生盐碱地速生杨光谱与光合特性对不同秸秆层的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 引黄灌区次生盐碱地速生杨光谱与光合特性对不同秸秆层的响应 DOI: 10.5846/stxb201809051893 作者: 作者单位: 北京林业大学,宁夏大学新技术应用研究开发中心,北京林业大学理学院,宁夏大学新技术应用研究开发中心 作者简介: 通讯作者: 中图分类号: 基金项目: “宁夏（中阿）旱区资源评价与环境调控重点实验室”建设项目与宁夏科技支撑项目“银川国家农业园区盐渍化改良技术的研究与示范” Response of spectral reflectance and photosynthetic characteristics of fast-growing poplar (Populus) to different straw layers in secondary saline-alkali land in the Yellow River irrigation area Author: Affiliation: Beijing Forestry University,Development Center of New Technique Application and Research, Ningxia University,College of Science, Beijing Forestry University,Development Center of New Technique Application and Research, Ningxia University Fund Project: Ningxia(China-Arab) key laboratory of Resource Assessment and Environmental Regulation in Arid Region & Research and Demonstration on the Improvement Technology of Salinization in Yinchuan National Agricultural Park 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在宁夏引黄灌区次生盐碱地，设置了填埋秸秆层（B）、覆盖秸秆层（M）、填埋配合覆盖秸秆层（B+M）和无任何处理（空白对照，CK）共4种处理，通过随机区组试验，在土壤水盐变化的基础上，通过分析速生杨光谱及光合特性对秸秆层响应，探究不同秸秆层的植物光合速率、色素含量、营养状况以及受胁迫等情况，以期更准确的反应出各处理的改良效果及植被恢复情况。研究结果表明：（1）秸秆层有助于提升灌区次生盐碱地速生杨的光谱与光合等生理状况。B、M和B+M均能显著提升速生杨叶片的最大净光合速率与饱和光强，其中，B和B+M还能够明显降低速生杨叶片的光补偿点和暗呼吸速率，M则不能。B和B+M均显著提高速生杨叶片的净光合速率、蒸腾速率、气孔导度等光合参数。另外，B+M的速生杨叶片光合色素含量最高，营养状况最好，其他光谱参数结果与CK相比都有显著提高。处理B和M也可以显著提高速生杨叶片光合色素含量和营养状况，但效果均不如B+M。（2）B与B+M均能降低不同时期的土壤盐分含量，但B+M在不同时期提高土壤含水量的效果均高于B。M也能降低土壤盐分和提升土壤含水量，但不同时期的效果均不如处理B+M。综合试验结果，在引黄灌区次生盐碱地，不同秸秆层均能不同程度的调节土壤水盐变化，缓解水盐胁迫，提升速生杨光合与光谱特性，其中B+M作为秸秆层效果最佳。 Abstract:Soil secondary salinization an escalating problem worldwide, especially in arid and semi-arid regions. Plants growing in salt-affected soils may suffer from physiological drought stress, ion toxicity, and mineral deficiency that lead to reduced growth and biomass. At present, in the study of secondary salinization soil amelioration, more attention is focused on the influence of soil salt ions, and soil physical and chemical properties than on the evaluation of amelioration and vegetation restoration. However, this assessment does not simultaneously consider the effects on the growth and physiological conditions of vegetation. Utilization of the straw layer in soil is a widely used and effective measure for soil salinity control. To study the response of the spectral reflectance and photosynthetic characteristics of fast-growing poplar (Populus) to different straw interlayers, a field experiment was conducted in the typical secondary salinized land of the northwestern salinized and ecologically fragile area of Ningxia. The experiment was established with four treatments: straw interlayer (B), straw mulching (M), straw interlayer plus straw mulching (B+M), and no addition of straw interlayer (CK). All treatments were arranged in a randomized complete block design with four blocks. Based on the change of soil salt and water in the background, the response of the straw layer was studied by analyzing the spectrum and photosynthetic characteristics of the fast-growing poplar. The photosynthetic rate, pigment content, nutritional status, and stress of the above-ground plants under different straw layer conditions were measured to more accurately reflect the effect of each treatment on saline soil improvement and above-ground vegetation restoration. It is of great significance to further study the physiological indexes, such as reflectance spectra and photosynthetic characteristics of plants. The results showed that: (1) different straw layers had different effects on water and salt regulation, resulting in different soil conditions among different treatments, which caused changes in pigment content, nutritional status, and physiological and biochemical conditions of the plants; (2) by detecting the plant reflection spectrum and photosynthetic characteristics, changes in plant growth and physiological conditions could be reflected. Based on this, we could use the reflectance spectrum and photosynthetic characteristics of fast-growing poplar to respond to different straw layers and more accurately assess improvement measures. The maximum net photosynthetic rate and saturation light intensity of B, M, and B+M treatment were significantly increased, and the B and B+M treatment light compensation points and dark respiration rates were significantly reduced. B and B+M treatment significantly increased the leaf photosynthetic rate (Pn), transpiration rate (Tr), stomata conductance (Gs), and intercellular CO2 concentration (Ci). The spectral reflectance of plant leaves, chlorophyll content of the B+M treatment was highest, and photosynthetic and nutrition performed best. Compared with that of the control group, other spectral reflectance indices significantly improved. The B and M treatments also significantly improved chlorophyll content and photosynthetic characteristics, but were less effective than B+M; (3) the experimental study showed that the reflectance spectrum and photosynthetic characteristics of fast-growing poplar responded differently to different straw layers. The straw layer helped to improve the physiological condition of fast-growing poplar. Based on the results of comprehensive reflection spectrum and photosynthetic characteristics, B+M was the most suitable straw layer model for the improvement of secondary saline-alkaline land in the Northwest Yellow River irrigation area. 参考文献 相似文献 引证文献

Development and application of long-term root zone salt balance model for predicting soil salinity in arid shallow water table area

A simple root zone salt balance model was developed for long-term soil salt prediction. A groundwater balance module was integrated to obtain the water flux at the bottom of the root zone, since groundwater level is easily and reliably measured data. An assumption that the net percolation at the bottom of root zone equals to the net recharge from root zone to unconfined groundwater system was used, which makes capillary rise and infiltration water leaching of root zone obtainable. The model accuracy and limitation were evaluated by comparing the simulation results with those from HYDRUS-1D under various soil texture and bottom boundary conditions. The mean relative error (MRE) of soil salt content ranged from −6.25% to 9.95%, and the root mean square error (RMSE) from 0.02 kg/100 kg to 0.05 kg/100 kg, which suggest the model accuracy. The determination coefficient (R2) of the cumulative percolation at the bottom of root zone and recharge to groundwater at the end of each calculation period was 0.99, which validates the model assumption. The model was then applied to predict soil salinity in the Longsheng irrigation district of Hetao Irrigation District, China. The soil salinity and water table depth data from 1999 to 2016 were used to calibrate and validate the model parameters. The MRE values of water table depth and average soil salt content were 10.08% and 10.84%, and RMSE values 0.37 m and 0.04 kg/100 kg in the validation period. Subsequently, the validated model was used to simulate the soil salinity in future 100 years under various water saving conditions. Water table depth and autumn irrigation for salt leaching were the two major factors to control soil salinity. The required autumn irrigation to keep root zone in mild salinity level (0.3 kg/100 kg) can decrease by 25.1 mm with 0.1 m water table depth increase, while it should increase by 64 mm with 1.0 kg/m3 groundwater salinity increase in the crop growing season. Moderate groundwater exploitation to increase water table depth is recommended to save autumn irrigation water and control soil salinity.

Improving Irrigation Scheduling of Wheat to Increase Water Productivity in Shallow Groundwater Conditions Using Aquacrop

AbstractIrrigation scheduling plays a key role in increasing crop production and controlling soil salinity in arid and semi‐arid regions. Inappropriate irrigation scheduling is considered an effective factor in low water productivity and soil salinization in central and southern parts of Khuzestan. Therefore, the aim of this research was to improve irrigation scheduling in order to increase water productivity and maintain the water and salt balance in a district in central Khuzestan. AquaCrop was selected as the research model, and the effects of the scenarios on wheat grain yield, water productivity, salt and water content in an effective root zone, and salt content moved upward from the groundwater table by capillary rise were compared with each other. Various scenarios of irrigation scheduling were simulated for a 12‐year period (2003–2014). To collect the required data for calibration and validation of the model, a field experiment was carried out during the wheat growing season (2014–2015). The results of the model evaluation indicated that it was an appropriate one for simulating the water and salt balance in the soil and wheat grain yield under different irrigation scheduling scenarios in experimental conditions. Finally, the recommended irrigation scheduling for wheat was seven times of irrigation with 550 mm water consumption. © 2018 John Wiley &amp; Sons, Ltd.

Soil Properties under Major Halophytic Vegetation Communities in Arid Regions

Soil physical, chemical, and biological properties of seven desert halophytes (Kalidium foliatum, Achnatherum splendens, Leymus secalinus, Phragmites australis, Karelinia caspia, Tamarix ramosissima, Atriplex tatarica) were investigated in saline-sodic badlands of the Hexi Corridor, Gansu Province, China. The results showed that sampled soils were generally infertile and characterized by low levels of organic matter, available nitrogen, phosphorus, copper, manganese, and zinc as well as microbial communities with dominant bacteria supporting native desert halophytes. Available potassium and iron were sufficient in the study sites. With increasing soil layer depth, the concentrations of organic matter, available nitrogen, potassium, manganese, copper, bacteria, and actinomyces in the soil decreased significantly (P<0.05), while the concentrations of moisture, available iron, and zinc in the soil increased significantly (P<0.05). The contents of moisture, total salt, organic matter, available nitrogen, potassium, iron, manganese, zinc, copper, bacteria, and actinomyces showed significant seasonal variations (P<0.05). All these variables except bacteria and actinomyces were the greatest in summer and the lowest in spring. The redundancy analysis revealed that total salt, organic matter, available potassium, and copper were positively correlated with vegetation coverage. K. foliatum community was the constructive or dominant species in the desert community for the biological control of soil salinization.

Potassium Fertilization Role in Tomato Tolerance of Water Salinity and Stress under Drip Irrigation System

A study was carried out on a field scale during two successive growth seasons (2009/2010 and 2010/2011) on tomato plants irrigated with saline ground water (2.24 and 3.86 dS m-1) using drip irrigation system, subjected to water stress (irrigation every 3, 4, and 5 days), and were grown under application of potassium fertilization (96, 120, and 144 kg K2O/feddan) in newly reclaimed lands at the Agricultural Experiments and Research Center, Faculty of Agriculture, Minia University, El-Minia Governorate, Egypt. The current study aims to investigate the effects of irrigation water salinity and water stress on tomato growth, tomato yield, and tomato fruit quality under application of a salinity and water stress alleviated amendment (potassium fertilization) using drip irrigation system. The obtained results of the current study showed that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 decreased tomato plant height, tomato shoots fresh weight, average tomato fruit weight, fresh tomato fruit yield, and tomato fruit dry weight, while, it increased tomato shoots dry weight, number of tomato fruits per plant, total soluble solids of tomato, and tomato fruits marketability (shelf life) in growth seasons. Increasing irrigation interval from 3 up to 5 days decreased tomato shoots fresh weight in both growth seasons, however, it increased tomato shoots dry weight, total soluble solids, and tomato fruits marketability in the two growth seasons. Increasing the potassium fertilization level from 96 up to 144 kg K2O/feddan increased the tomato plant height, tomato shoots dry weight, average tomato fruit weight, total soluble solids of tomato, and tomato fruits marketability. Increasing the potassium fertilization level from 96 to 120 or 144 kg K2O/feddan increased the tomato shoots fresh weight, number of tomato fruits per plant, fresh tomato fruit yield, and tomato fruit dry weight in the two growth seasons. The increase in the tomato plant height, tomato shoots fresh weight, tomato shoots dry weight, number of tomato fruits per plant, average tomato fruit weight, fresh tomato fruit yield, total soluble solids of tomato, tomato fruits marketability, and tomato fruit dry weight implies that application of potassium fertilization to soil alleviated adverse effects of salinity stress and water stress on tomato growth, tomato yield, and tomato fruit quality. The results of the current research indicated that it can be recommended that to alleviate and manage adverse effects of salinity stress and water stress on tomato growth, tomato yield, and tomato fruit quality, good cultural practices management to be followed are: (1) irrigate tomato plants every 4 days, (2) apply appropriate and optimized requirements of potassium fertilization to soils (120 kg K2O/feddan), and (3) use drip irrigation system as an irrigation management which might control soil salinity build-up and soil water content since it can keep a high soil water content and low salt concentration in the root zone.

Crop-weed interactions in saline environments

Abstract Soil salinization is one of the most critical environmental factors affecting crop yield. It is estimated that 20% of cultivated land and 33% of irrigated agricultural land are affected by salinity. In the last decades, considerable effort to manage saline agro-ecosystems has focused on 1) controlling soil salinity to minimize/reduce the accumulation of salts in the root zone and 2) improving plants ability to cope with osmotic and ionic stress. Less attention has been given to other components of the agro-ecosystem including weed populations, which also react and adapt to soil salinization and indirectly affect plant growth and yield. Weeds represent an increasing challenge for crop systems since they have high genetic resilience and adaptation ability to adverse environmental conditions such as soil salinization. In this review, we assess current knowledge on salinity tolerance of weeds in agricultural contexts and discuss critical components of crop-weed interactions that may increase weeds competitiveness under salinity. Compared to crop species, weeds generally exhibit greater salt tolerance due to high intraspecific variability, associated with diverse physiological adaptation mechanisms (e.g. phenotipic plasticity, seed heteromorphism, allelopathy). Weed competitiveness in saline soils may be enhanced by their earlier emergence, faster growth rates and synergies occurring between soil salts and allelochemicals released by weeds. In the future, a better understanding of crop-weed relationships and molecular, physiological and agronomic stress responses under salinity is essential to design efficient strategies to achieve weed control under altered climatic and environmental conditions.

Sensor-Based Assessment of Soil Salinity during the First Years of Transition from Flood to Sprinkler Irrigation.

A key issue for agriculture in irrigated arid lands is the control of soil salinity, and this is one of the goals for irrigated districts when changing from flood to sprinkling irrigation. We combined soil sampling, proximal electromagnetic induction, and satellite data to appraise how soil salinity and its distribution along a previously flood-irrigated field evolved after its transformation to sprinkling. We also show that the relationship between NDVI (normalized difference vegetation index) and ECe (electrical conductivity of the soil saturation extracts) mimics the production function between yield and soil salinity. Under sprinkling, the field had a double crop of barley and then sunflower in 2009 and 2011. In both years, about 50% of the soil of the entire studied field—45 ha—had ECe < 8 dS m−1, i.e., allowing barley cultivation, while the percent of surface having ECe ≥ 16 dS m−1 increased from 8.4% in 2009 to 13.7% in 2011. Our methodology may help monitor the soil salinity oscillations associated with irrigation management. After quantifying and mapping the soil salinity in 2009 and 2011, we show that barley was stunted in places of the field where salinity was higher. Additionally, the areas of salinity persisted after the subsequent alfalfa cropping in 2013. Application of differential doses of water to the saline patches is a viable method to optimize irrigation water distribution and lessen soil salinity in sprinkler-irrigated agriculture.

Impact of using two different sources of water quality for simulation of salt and moisture content in unsaturated zone

Monitoring water quality and moisture content throughout the root zone become essential for proper management and for reduction of undesirable and diverse effects caused by using different water quality. In the field level, poor management of using different quality water can cause a huge reduction on the vegetation production. Two field plots were selected in Al-Khalis region in Diyala governorate as a case study. Four scenarios were applied for the data collected for a complete season from a local meteorological station and by using HYDRUS-3D V2.05 software package to simulate water and salt transport through a 1m depth of unsaturated zone. Irrigation scheduling was estimated using FAO method. The net water depth required for a season was 65 mm for 7 days irrigation interval and 21 irrigation events. For depths (20, 40, 60, 80, and100 cm) the salt concentration were simulated for the four scenarios and for the whole season. For the limit of controlling soil salinity at low level in initial and develop stage of plantation, it has been found that the Fourth scenario has to be chosen.

Studying the effects of deficit irrigation as an on-farm strategy on carrot yield in arid environment

The deficit irrigation (DI) as an on-farm water management strategy was tested for 3-years to determine the water requirements and productivity, soil salinity and yield for carrot irrigated with saline water (3.6 dS/m) under actual farming conditions in southern Tunisia. The irrigation regimes were full (I100) and deficit (I80 and I60) irrigated with levels of 100, 80 and 60% of ETc when the readily available water, 35% of total available water (TAW), in the I100 treatment was depleted, and traditional farmer practice (Farmer). Regulated DI regime where 40% reduction is applied only during ripening stage (I60-ripening) was also used . Higher soil salinity is observed at harvest under I60 and Farmer treatments compared to I100. Carrot yield was highest over 3 years for the I100 scheduling technique, (29.5, 28.7 and 26.8 t/ha) although no significant differences were observed with the I60-ripening strategy . However, the I80 and I60 treatments caused significant reductions in carrot yields through a reduction in roots number and weight in comparison with I100. The farmer’s method not only caused significant reductions in yield but also resulted in using 43 to 57 % more water and increased soil salinity. For all treatments, carrot yields were higher in first than the two following years. Water productivity (WP) values reflected this difference and varied between absolute extremes of 3.3 and 9.7 kg/m 3 . WP was the greatest in the I60 treatment and the least in the Farmer's strategy. I100 irrigation strategy provides significant advantage on yield and WP compared to farmer’s method in carrot production. Therefore, for water-saving purposes, the I100 irrigation scheduling is recommended to optimize the use of saline water in carrot production and to control soil salinity. Nonetheless, under water scarcity, irrigation of carrot could be scheduled using I60-ripening and I80 deficit strategies, with some yield reductions (4-15%).

Effect of concentration and temperature on the interactions between saline soil salts and nitro phosphate fertilizer under atmospheric pressure: A thermo-acoustic approach

A decrease in the ability of the plants to absorb nutrients usually takes place in saline soils. Application of fertilizers corrects nutrients deficiencies and decreases the adverse effects of saline salts on the plants. The present work is aimed to study the interactions of fertilizer with saline salts in aqueous solutions to explore the role of fertilizer on soil fertility by controlling soil salinity in terms of fertilizer-salt interactions. Density and speed of sound of nitrophosphate in water and in saline salts solutions of different concentrations has been measured at different temperatures. Thermo acoustical parameters like apparent and partial molar volume, partial molar expansibility and Hepler's constant, compressibility factor and intermolecular free length have been calculated. Positive values of apparent molar volume (VФ) and negative values of apparent and partial molar compressibility (KФ and Kфo)of fertilizer in solutions showed strong intermolecular interactions in solutions. Positive values of Hepler's constant indicate the structure making behavior of fertilizer in water and in saline salt solutions.

Characteristics of soil salinity in the typical area of Yellow River Delta and its control measures

The Yellow River Delta is one of important ecological areas in eastern China, however sustainable development of the Yellow River Delta is seriously restricted because of severe soil salinization. The main sources of soil salinity are chloride, sodium and sulfate ions. The distribution of soil salinity in soil profiles showed that surface accumulation of soil salt was significant in the Yellow River Delta. Some control measures including soil improvement and regulation, reasonable combination of salt-fresh water irrigation in farmland, land cover and effective drainage were put forward for soil salinity control.

Soil vs. groundwater: The quality dilemma. Managing nitrogen leaching and salinity control under irrigated agriculture in Mediterranean conditions

A 3-year field trial was carried out in southern Italy on an agricultural farm close to the seacoast of Manfredonia Gulf (Apulia Region) where crop irrigation with saline water is standard practice. Seawater intrusion into the groundwater, and the consequent soil salinization represent a serious environmental threat. Each year, two crop cycles were applied, in spring-summer and autumn-winter seasons, respectively. The crop pairing over the three years was tomato and spinach; zucchini and broccoli; pepper and wheat. Cultivation was performed in a field-unit characterised by three adjacent plots. At the centre of each plot, a hydraulically insulated drainage basin was dug (0.70m depth) to collect the draining water. The crops were irrigated with saline water and leaching treatments were applied with saline or fresh water whenever soil salinity reached a predetermined electrical conductivity threshold. Since soil salinity control might increase nitrate leaching, operational criteria should optimize the trade-off between the application of higher water volumes to reduce soil salinity and lower water volumes to protect groundwater quality from nitrate leaching. The amount of nitrogen leached from the soil root-zone was considerable (on average, 156kgNha−1year−1) and higher in autumn-winter than spring-summer (72 vs. 28% of the average annual value). In autumn-winter season, nitrogen losses were mainly due to plentiful nitrogen fertilisation and high rainfall. In spring–summer, extra irrigations promoted salt leaching together with nitrogen losses. To manage both irrigation and nitrogen fertilisation a “decoupling” strategy is recommended. This strategy suggests applying leaching preferably at the end of the spring-summer growing season, soon after crop harvesting or at the beginning of the autumn-winter season, before second crop cycle starting. In autumn-winter season, proper nitrogen supplies and timely top-dressing applications, still allow salts to be discharged by rainfalls but prevent nitrogen losses, thus preserving groundwater quality.

Assessment of Reclamation Treatments of Abandoned Farmland in an Arid Region of China

Reclamation of abandoned farmland is crucial to a sustainable agriculture in arid regions. This study aims to evaluate the impact of different reclamation treatments on abandoned salinized farmland. We investigated four artificial reclamation treatments, continuous cotton (CC), continuous alfalfa (CA), tree-wheat intercropping (TW) and trees (TS), which were conducted in 2011–2012 in the Manasi River Basin of Xinjiang Province, China. Soil nutrient, microorganism and enzyme activity were examined in comparison with natural succession (CK) in an integrated analysis on soil fertility improvement and soil salinization control with these reclamations. Results indicate that the four artificial reclamation treatments are more effective approaches than natural restoration to reclaim abandoned farmland. TW and CA significantly increased soil nutrient content compared to CK. CC reduced soil salinity to the lowest level among all treatments. TW significantly enhanced soil enzyme activity. All four artificial reclamations increased soil microbial populations and soil microbial biomass carbon. TW and CA had the greatest overall optimal effects among the four treatments in terms of the ecological outcomes. If both economic benefits and ecological effects are considered, TW would be the best reclamation mode. The findings from this study will assist in selecting a feasible method for reclamation of abandoned farmland for sustainable agriculture in arid regions.

ADVANCES IN SOIL SALINITY DETECTION IN ARID AND SEMI- ARID REGIONS USING SALINITY AND VEGETATION INDICES

Soil salinization as a result of natural or of human-induces processes is a serious global-scale problem. Salinization is a major reason for soil resources degradation and declining of soil fertility. From an ecological and economic point of view it is extremely important to follow the occurrence and distribution of soil salinity as well as the intensity of the process. Several studies and efforts in assessing and controlling soil salinity have been made. Remote sensing techniques are widely used to detect and map the salt-affected areas. The indices used in this research are the normalized differential vegetation index (NDVI), normalized difference salinity index (NDSI) and modified soil adjust vegetation Index (MSAVI). MSAVI was found to be effective in discriminating the plants under severe and moderate conditions of soil salinity as well as under non-saline conditions. Temporal trend analysis technique was carried out to detect significant changes in the soil verses vegetation conditions. The obtained results showed that the studied area is mostly covered by field crops where, NDVI values were ranging between 0 and 0.82 and MSAVI ranging from 0.02 to 0.70. The NDSI values, however, showed the land salinity classes, as they were fluctuated from 0.01 to 0.89.

Leaching effect of rainfall on soil under four-year saline water irrigation

In the context of the overall competition for water resources it is important to understand the complex dynamics of crop water management including evapotranspiration, water quality, and leaching requirement, each of them depending on the site-specific conditions. The research started with grain maize and continued with sunflower, grain maize, and wheat, at the experimental field. On both grain maize and sunflower, 10 irrigation treatments were compared that resulted from the factorial combination of two types of water (fresh and brackish water) with five irrigation regimes; the scheduled treatments were applied by furrow irrigation. The amount of salts brought into the soil with the irrigation water during the three irrigation seasons of our trial increased shifting from the lowest to the highest irrigation regime and with the increase of salinity in the irrigation water. From the study of salt distribution in the soil it follows that at the end of the irrigation season the salt concentration increased by passing from the middle of the furrow, a zone more subject to leaching during irrigation, to the intermediate zone between the furrow and the ridge, and in the middle of the ridge between two contiguous furrows, an area of confluence of the wetting and salt accumulation fronts. The leaching water supplied during the irrigation season was poorly efficient in leaching the salts brought in through irrigation, whereas the rainfall water of the autumn-winter period after the irrigation season ensured a good control of soil salinity.