Physio-chemical properties and dynamic of the surface sediment in riparian mangroves along the Tien river, Tien Giang province

This study was conducted to investigate the physio-chemical properties and vertical dynamic of the surface sediment (0–5 cm) in riparian mangroves along the Tien river, Tien Giang province. The distribution of riparian mangroves located from the polyhaline zone (transect S1 and S2) to the mesohaline zone (transect S3 and S4) and the oligohaline zone (transect S5). Three plots (10x10 m) per transect were set based on the elevation of the mangrove floor (cm + mean sea level) and dominant plants. A total of 28 sediment samples were collected in December 2016 and April 2017. Seasonal variation of pH, redox potential (Eh), electrical conductivity of saturated extract (ECse), bulk density, sediment organic matter (SOM) and total sulfur (TS) were measured in accordance with the standard protocols. Seasonal trends of vertical erosion and accumulation were tested by the tracer stick method. The ECse values and TS concentrations were higher in the dry season and in transects closed to the estuary (S1, S2 and S3) but these trends weren’t found for pH, Eh, and SOM. In most of the riparian mangroves along the Tiền river, low elevation (0–50 cm) was one of important factors affecting the Eh and ECse. In the rainy season, major changes in vertical erosion and acumulation have occurred in the transects near the mouth of the river.

Diffused Reflectance Spectroscopy for Characterization of Salt-Affected Soil (SAS) Attributes

Identification of soil salinity based on traditional methods (measurement in saturation extract) required time, labour and capital, whereas, ground based non-imaging hyperspectral remote sensing estimates the soil salinity and alkalinity parameters within limited resources and can be used for real time monitoring purpose. Laboratory experiment was conducted to study the spectral properties using VNIR spectroscopy in silt loam and silty clay loam soil saturated with different levels of chloride, sulphate and carbonate of sodium salts. Salinity absorption features were more pronounced around 1900 nm, followed by 1400 and 2200 nm. The salt concentration was inversely related to reflectance values in saline soils. Wavelength was shifted from 1900 nm to higher wavelength value and this shifting feature was also correlated with the increase in salt concentration. Relatively high correlation coefficients of ECe, saturated extract Na+ and Cl- with soil reflectance values were found in between 1420 to 2020 nm than other soil properties. Increased use and application of VNIR for salt-affected soil would help establish a detailed spectral library through captured signature in sodium salt saturated soil.

Diffused Reflectance Spectroscopy for Characterization of Salt-Affected Soil (SAS) Attributes

Identification of soil salinity based on traditional methods (measurement in saturation extract) required time, labour and capital, whereas, ground based non-imaging hyperspectral remote sensing estimates the soil salinity and alkalinity parameters within limited resources and can be used for real time monitoring purpose. Laboratory experiment was conducted to study the spectral properties using VNIR spectroscopy in silt loam and silty clay loam soil saturated with different levels of chloride, sulphate and carbonate of sodium salts. Salinity absorption features were more pronounced around 1900 nm, followed by 1400 and 2200 nm. The salt concentration was inversely related to reflectance values in saline soils. Wavelength was shifted from 1900 nm to higher wavelength value and this shifting feature was also correlated with the increase in salt concentration. Relatively high correlation coefficients of ECe, saturated extract Na+ and Cl- with soil reflectance values were found in between 1420 to 2020 nm than other soil properties. Increased use and application of VNIR for salt-affected soil would help establish a detailed spectral library through captured signature in sodium salt saturated soil.

Evidence of nitrogen and potassium losses in soil columns cultivated with maize under salt stress

ABSTRACT The aim of this study was to evaluate the accumulation of salts in the soil from irrigation water and of N and K from fertilization. The experiment was conducted in PVC columns (20 cm in diameter and 100 cm in height), filled with non-saline soil, and cultivated with maize. A completely randomized block design in a 4 x 4 factorial was used, with four levels of salinity (0.5, 2.5, 5.0 and 7.5 dS m-1), four N rates, and five replicates. Nitrogen was applied as urea and potassium nitrate at the following rates: N1: N recommendation for maize (2.6 g column-1); N2: 0.3 times (0.78 g column-1) the recommended N1 dose; N3 and N4 with N based on N1 and N2 doses, respectively, reduced proportionally based on the evapotranspiration reduction caused by salinity. After 74 days from sowing, root and soil samples were collected at different soil depths. The electrical conductivity of the saturated extract (ECe) and the concentration of ions (Ca2+, Na+, and Cl-) increased as a function of salinity and soil depth. The opposite was observed for the root system. The increase in salinity also resulted in K+ and NO3- accumulation in the soil column, mainly in treatments with higher N rates (N1 and N3). At the end of the experiment, 88% of the NO3- applied at the highest salinity treatment (7.5 dS m-1) and the highest N rate (N1) was below 20 cm soil depth, evidencing a N loss process caused by leaching.

Adopting adequate leaching requirement for practical response models of basil to salinity

Several mathematical models are being used for assessing plant response to salinity of the root zone. Objectives of this study included quantifying the yield salinity threshold value of basil plants to irrigation water salinity and investigating the possibilities of using irrigation water salinity instead of saturated extract salinity in the available mathematical models for estimating yield. To achieve the above objectives, an extensive greenhouse experiment was conducted with 13 irrigation water salinity levels, namely 1.175 dS m−1 (control treatment) and 1.8 to 10 dS m−1. The result indicated that, among these models, the modified discount model (one of the most famous root water uptake model which is based on statistics) produced more accurate results in simulating the basil yield reduction function using irrigation water salinities. Overall the statistical model of Steppuhn et al. on the modified discount model and the math-empirical model of van Genuchten and Hoffman provided the best results. In general, all of the statistical models produced very similar results and their results were better than math-empirical models. It was also concluded that if enough leaching was present, there was no significant difference between the soil salinity saturated extract models and the models using irrigation water salinity.

Managing Saline and Sodic Soils for Producing Horticultural Crops

About 33% of all irrigated lands worldwide are affected by varying degrees of salinity and sodicity. Soil with an electrical conductivity (EC) of the saturated extract >4 dS·m−1 is considered saline, but some horticultural crops are negatively affected if salt concentrations in the rooting zone exceed 2 dS·m−1. Salinity effects on plant growth are generally osmotic in nature, but specific toxicities and nutritional balances are known to occur. In addition to the direct toxic effects of Na salts, Na can negatively impact soil structure. Soil with exchangeable sodium percentages (ESPs) or saturated extract sodium absorption ratios (SARs) > 15 are considered sodic. Sodic soils tend to deflocculate, become impermeable to water and air, and puddle. Many horticultural crops are sensitive to the deterioration of soil physical properties associated with Na in soil and irrigation water. This review summarizes important considerations in managing saline and sodic soils for producing horticultural crops. Economically viable management practices may simply involve a minor, inexpensive modification of cultural practices under conditions of low to moderate salinity or a more costly reclamation under conditions of high Na.

1063 CONSIDERATIONS IN THE MANAGEMENT OF SALINE AND SODIC SOILS FOR THE PRODUCTION OF HORTICULTURAL CROPS

Approximately 33% of all irrigated lands worldwide are affected by varying degrees of salinity and sodicity. Soils with an electrical conductivity (EC) of, the saturated extract greater than 4 dS/m are considered saline, but some horticultural crops are negatively impacted if salt concentrations in the rooting zone exceed 2 dS/m. Salinity effects on plant growth are generally considered osmotic in nature, but specific ion toxicities and nutritional imbalances are also known to occur. In addition to direct toxic affects from Na salts, Na can negatively impact soil structure. Soils with exchangeable sodium percentages (ESPs) or saturated extract sodium absorption ratios (SARs) exceeding 15 are considered sodic. Sodic soils tend to deflocculate, become impermeable to water and air, and have a strong tendency to puddle. Some soils are both saline and sodic. This workshop presentation will summarize various considerations in the management of saline and sodic soils for the production of horticultural crops.

Les extraits de sols saturés à l’eau et le suivi des nutriments dans l’érablière dépérissante

The soil solution provides the majority of essential nutrients needed for plant growth. Obtaining this solution in situ presents logistic problems and therefore most results are obtained from air-dried soils, even though chemical properties of soils can be substantially modified by drying. Water-saturated extracts obtained from dried soils were tested for their efficiency to detect the effects of in situ fertilization with P-TSP, K-K2SO4 and Ca-Ca(OH)2 on the Ahe horizon of a maple stand. Results obtained with water-saturated extracts on dried soils were compared with those obtained from conventional (exchangeable) extraction on dried soils and to those obtained from extraction with a soil:water ratio of 1:5 on dried soils. A similar experiment comparing water-saturated extracts with the soil:water ratio of 1:5 was carried out using soils fertilized in vitro. The effects of fertilization were clearly evident with saturated extracts when these could be observed by conventional analysis. Furthermore, the saturated extract indicated potential toxicity of Al in relation to pH. For the same samples, the saturated extracts were more sensitive than the extracts with a soil:solution ratio of 1:5, especially with regard to element ratios not easily expressed by conventional analysis. The originality of this method rests on a combination of efficient centrifugation with a double bottom container, the convenience in the utilization of air-dried soils and the use of near water field capacity as a representative water content. Key words: Saturated extracts, fertilization, toxicity, maple stand

EVALUATION OF HORIBA CARDY COMPACT METERS FOR MONITORING GROWING MEDIA EXTRACT AND CELL SAP pH, E. C., NO3, NA AND K CONCENTRATION

Horiba Cardy compact pH, Electrical Conductivity (E.C.), Nitrate (NO3), Sodium (Na), and Potassium (K) meters were used to monitor the nutrient content of solutions extracted from five organic potting media. Solution extracts were collected using the Saturated Extract Method (SEM). Duplicate samples were sent to three analytical labs for comparative purposes. The meters proved to be quick and easy to use and there was good to excellent agreement with lab value for pH, E.C., Na and K. The NO3 meter did not provide good values below 80 ppm. For higher values there was a good relationship to lab values. The standard deviation for meter values was low, as were lab values for all parameter. Results of cell sap measurements as a method for evaluating the nutritional status of plants will be presented.