Biochar, an environmentally friendly soil conditioner, is produced using several thermochemical processes. It has unique characteristics like high surface area, porosity, and surface charges. This paper reviews the fertilizer value of biochar, and its effects on soil properties, and nutrient use efficiency of crops. Biochar serves as an important source of plant nutrients, especially nitrogen in biochar produced from manures and wastes at low temperature (≤ 400 °C). The phosphorus, potassium, and other nutrient contents are higher in manure/waste biochars than those in crop residues and woody biochars. The nutrient contents and pH of biochar are positively correlated with pyrolysis temperature, except for nitrogen content. Biochar improves the nutrient retention capacity of soil, which depends on porosity and surface charge of biochar. Biochar increases nitrogen retention in soil by reducing leaching and gaseous loss, and also increases phosphorus availability by decreasing the leaching process in soil. However, for potassium and other nutrients, biochar shows inconsistent (positive and negative) impacts on soil. After addition of biochar, porosity, aggregate stability, and amount of water held in soil increase and bulk density decreases. Mostly, biochar increases soil pH and, thus, influences nutrient availability for plants. Biochar also alters soil biological properties by increasing microbial populations, enzyme activity, soil respiration, and microbial biomass. Finally, nutrient use efficiency and nutrient uptake improve with the application of biochar to soil. Thus, biochar can be a potential nutrient reservoir for plants and a good amendment to improve soil properties.

In this study, the hydrochemical characteristics of shallow groundwater in a coastal region (Khulna) of southwest Bangladesh have been evaluated based on different indices for drinking and irrigation uses. Water samples were collected from 26 boreholes and analyzed for major cations and anions. Other physico-chemical parameters like pH, electrical conductivity (EC), and total dissolved solids were also measured. Most groundwater is slightly alkaline and largely varies in chemical composition, e.g. EC ranges from 962 to 9,370 ls/cm. The abundance of the major ions is as follows:Interpretation of analytical data shows two major hydrochemical facies (Na ? -K ? -Cl --SO 4 2-and Na ? -K ? -HCO 3 -) in the study area. Salinity, total hardness, and sodium percentage (Na%) indicate that most of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standard. Results suggest that the brackish nature in most of the groundwaters is due to the seawater influence and hydrogeochemical processes.

No abstract

In this study, the relationship between water quality (as represented by major inorganic ion concentrations) and land use characteristics is examined for a small river basin which runs through the urbanizing area of central Japan. Water samples were taken from 24 sites at base flow and analyzed, and the proportions of the various land uses associated with the respective drainage basins were calculated using a digital land-use map (scale: 1:25000). The electrical conductivity (EC) of the water ranged from 84.5 to 600 lS cm -1 . Ca 2+ and Na + were the major cations, accounting for 77% of all cations. Among the anions, HCO 3 -was dominant (56%), followed by Cl -(24%), SO 4 2-(13%) and NO 3 -(7%). Applying principal component analysis to land use in the drainage basin yielded three principal components. The first principal component expressed the degree of occupation by residential areas, the second indicated the degree of urban developing area (i.e., fast-developing and industrial areas), and the third showed the degree of coverage with farmland and green space. The residential area showed significant positive correlations with K + , Mg 2+ , Ca 2+ , NO 3 -, HCO 3 -, EC and TMI (total major ions). Urban developing area showed significant positive correlations with Ca 2+ , Cl -, HCO 3 -, EC and TMI as well as weak negative correlations with NO 3 -and SO 4 2-. Industrial area showed weak positive correlations with Na + and Cl -and a moderate negative correlation with NO 3 -. Farmland showed significant positive correlations with NO 3 -and SO 4 2-; these ions are present due to fertilizers and the biological activity of plants.Forest area is inversely related to almost all ions, indicating the need for this form of land use in order to maintain river water quality.

No abstract