Functional relationships between wastewater-induced predictors (e.g., organic carbon, OC) and amended soil properties are needed to develop pedo-transfer functions for wastewater-amended/-irrigated soils. The objective of this study was to determine the impacts of municipal wastewater on soil health and develop functional relationships between wastewater-amended soil hydro-physico-chemical properties. The objectives were realized by conducting laboratory experiments on repacked columns of four typical agricultural soils. The soil columns, after primary settlement over 7 months, were conditioned by applying tap water over 6 months and then a typical quality wastewater in nine irrigations (total 90 cm, equivalent to irrigation requirement for three wheat seasons) over the next 8 months with an irrigation interval of 25 days. Each irrigation amounting 10 cm wastewater was applied in 5 days (2 cm d −1). Wastewater significantly (p < 0.05) elevated OC (13.85%) but reduced bulk density (3.73%) of the soils; bulk density decreased linearly with OC with a strong correlation (r 2 = 0.90). The negative correlation between poresize distribution index and clay content of the soils became significant (p < 0.05) after wastewater treatment. Plant available soilwater content increased linearly (r 2 = 0.71) with increasing micro-porosity. The magnitudes of soil-properties change are however soil-and wastewater-type dependent functions. Municipal wastewater can be used to improve hydro-physico-chemical properties of soils and the strong functional relationships between wastewater-amended predictors (e.g., OC) and predictands (e.g., bulk density) can be used for designing and managing soil amendment and irrigation with wastewater.

The transport parameters of soluble chemicals through soils are needed to assess the pollution risks of soil and groundwater resources. The transport parameters of seven heavy metal/metalloid compounds (NaAsO2, Cd(NO3)2, Pb(NO3)2, Ni(NO3)2, ZnCl2, CuSO4 and Co(NO3)2), two pesticides (cartap and carbendazim) and an inert salt (CaCl2) were determined in repacked columns of eight agricultural soils of Bangladesh. The relationships between physicochemical properties of the soils and solutes and the solute-transport parameters were investigated by time-domain reflectometry (TDR) using bulk soil electrical conductivity as a proxy. The transport velocity (V) of the solutes decreased linearly with the increasing clay content of the soils. Of the nine reactive solutes, cartap and As moved with the largest and smallest V values, respectively. Dispersivity of the solutes decreased with increasing clay content linearly but following power law with increasing median grain diameter of the soils. It also increased significantly (P<0.05) with the increasing length of travel path. The solute retardation factor (R) increased with increasing clay content following power law, implying that clay content is a determining factor for heavy metal retention in soils. Parameter R increased non-linearly with increasing travel length except for cadmium, for which the increase was linear. Based on R, the general adsorption affinity of the solutes in the soils was As>Co>Cd>carbendazim>Pb>Cu>cartap>Zn>Ni>Ca. In some soils, however, Cd and carbendazim showed a lower adsorption than Pb and Co, and Zn and cartap were more strongly adsorbed than Ni. The relationships between physicochemical properties of the soils and solutes and the solute transport parameters contribute to the improved interpretation of TDR data as a preliminary assessment of pollutant mobility in soils with different textures.

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Solute-transport parameters are needed to assess the pollution risks of soil and groundwater resources. A reliable estimate of these parameters from easily measurable soil properties is therefore important. So, the correlations of the transport parameters for one metalloid compound (NaAsO2), six heavy metal compounds (Cd(NO3)2, Pb(NO3)2, Ni(NO3)2, ZnCl2, CuSO4 and Co(NO3)2), two pesticides (cartap and carbendazim) and one inert salt (CaCl2) with some basic properties of eight agricultural soils of Bangladesh were investigated. The purpose of this study was to generate information for development of non-parametric pedo-transfer functions for reactive solute transport through soils. The transport experiments with the solutes were done in repacked soil columns under unsaturated steady-state water flow conditions. The major solute-transport parametersvelocity of transport (V), dispersion coefficient (D), dispersivity (), retardation factor (R) and Peclet number (P)-were determined by analysing solute breakthrough curves (BTCs). The basic soil properties pertinent to solute transport: clay content, median grain diameter (D50), pore-size distribution index (n), bulk density (), organic carbon content (C) and pH were determined. The associations of the solute-transport parameters with these soil properties were investigated and evaluated. Both the solute dispersivity and retardation factor increased significantly (p<0.05) ( linearly and R following power law) with the increase in soil clay content. Dispersivity significantly decreased with the increase in median grain diameter following power law. The V, D,  and P values were weakly and negatively correlated with the soil bulk density. Retardation factor, R, was moderately and positively correlated with the ratio of clay content to organic carbon content. Dispersivity decreased but P increased, both significantly, with increasing poresize distribution index, n. V, D and P were positively correlated with soil pH, while R and  were negatively correlated with it. The correlation of the solute-transport parameters with soil properties being significant (p < 0.05), in most cases, provides strong possibility of predicting solute-transport parameters from the basic soil properties through the development of pedo-transfer functions.

Strengthening the early warning system to forecast extreme weather and provide action-oriented advisories may increase rice yield as well as enhance the income of the farmers through minimizing risks and losses, if proper use of the generated advisory is ensured. This study assessed the importance and impact of weather forecast based advisory service (WFBAS) in Bangladesh. Literature review and field experimental data were used in a sensitivity analysis to show the impact of WFBAS on rice production. Available literatures suggested that the weather based advisory service would enhance rice yield by around 6.7-10%, but the experimental findings revealed that yield advantage could be 21.48%. Besides, the adoption of this technology would reduce the cost of cultivation by 12%, whereas the aggregate impact would increase the farmers’ profit by 25%. In the sensitivity study, we considered the production and price of Aman and Boro seasons (actual and government procured prices for 2018-19) and assumed only 6.70% yield increase with 5% farmers adopting of WFBAS. As such, additional 0.172 million tons will be added to the national rough rice production and thus the nation will be benefited by 3143 million Bangladeshi taka (BDT) at the actual farmgate price and it would be 4478 million BDT at the government procured price. The return on one BDT investment in this technology would be 51-73 BDT based on actual and procured prices. The projection showed enhenced production of the rough rice at 0.119 million tons and 0.214 million tons by 2025 and 2030, on which the additional return would be BDT 2441 and BDT 5223 million at the projected actual farmgate price and BDT 3522 and BDT 6979 million at the projected Government procured price, respectively. Hence, the successful implementation of the WFBAS will help to develop resilient rice farming communities, minimize livelihood risk, reduce the cost of production, utilize resources efficienty, and enable the farmers to take maximum benefit from favorable weather conditions through improved agricultural extension services. Finally, the enhanced yield and loss reduction will help to achieve the target of Sustainable Development Goal (SDG) by 2030 through sustaining rice production in Bangladesh under changing climate. Bangladesh Rice J. 25 (1) : 51-74, 2021