Nitrate and Dissolved Organic Carbon Release in Sandy Soils at Different Liquid/Solid Ratios Amended with Graphene and Classical Soil Improvers

This study emphasizes the importance of employing parallel batch tests with different liquid/solid (L/S) ratios to assess their dissolution mechanisms. Changes in physicochemical parameters (electrical conductivity, pH, and oxidation-reduction potential), as well as the sorption/desorption of dissolved organic carbon (DOC) and nitrate (NO3-) due to graphene addition in a calcareous sandy soil (CS) and in a siliciclastic riverine sandy soil (SS) were assessed via batch experiments at different L/S ratios. Graphene's production is growing at a great pace, so it's important to test methods to reuse graphene wastes. The results of soil batch experiments mixed with graphene were compared with classical soil improvers (compost, biochar, and zeolites). The batches were performed using the saturation soil extraction method with deionized water as a proxy of rainwater. The contact time was 48 h. At the end of the experiment, water samples were collected to be analyzed for NO3-, DOC, DIC, Ca, and Mg. Graphene did not alter the physiochemical parameters of both soils. Moreover, its addition did not trigger any NO3- increase respect to control and to other improvers. Biochar increased EC and pH beyond recommended limits for most crops' growth in both soils. As expected, compost addition produced the highest NO3- release

Assessment of the Intrinsic Vulnerability of Agricultural Land to Water and Nitrogen Losses via Deterministic Approach and Regression Analysis

A set of indices was developed in order to classify the vulnerability of agricultural land to water and nitrogen losses (LOS), setting a basis for the integrated water resources management in agricultural systems. To calibrate the indices using multiple regression analysis, the simulation results of Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) model for combinations of different soil properties, topography, and climatic conditions of a reference field crop were used as "observed values." GLEAMS quantified (1) the annual losses of the percolated water beneath the root zone, (2) the annual losses of the surface runoff, (3) the annual losses of the nitrogen leaching beneath the root zone, and (4) the annual losses of nitrogen through the surface runoff, which were used to calibrate the following indices LOSW-P, LOSW-R, LOSN-PN, and LOSN-RN, respectively. All the simulations to gain the LOS indices were carried out for the same reference field crop, the same nitrogen fertilization, and the same irrigation practice, in order to obtain the intrinsic vulnerability of agricultural land to water and nitrogen losses. The LOS indices were also combined to derive nitrogen concentrations in the percolated and in the runoff water. Finally, the connection of LOS indices with the groundwater was performed using an additional equation, which determines the minimum transit time of the percolated water to reach the groundwater table. © Springer Science+Business Media B.V. 2011

Estimated Water Savings in an Agricultural Field Amended With Natural Zeolites

Agricultural practices can jeopardize soil and water quality, thus mitigation measures to reduce nutrient loss and to protect water resources have to be implemented in order to ensure a sound environmental quality and, at the same time, a high crop yield. Natural zeolites have been tested as soil conditioner to diminish nutrient leaching and increase irrigation efficiency. In this study, an experimental site of 6 ha was monitored for two years to assess whether amending the soil with natural zeolite may induce a considerable impact on the water balance. Three control parcels were cultivated and irrigated according to the traditional way; two parcels were amended with coarse-grained natural zeolite at different zeolite/soil ratio (5 and 15 kg/m2) and two parcels were amended with fine-grained zeolite (7 and 10 kg/m2). Soil electrical conductivity, temperature and volumetric water content were continuously monitored via TDR probes at different depths. Climatic variables for water balance calculation were obtained by a meteorological station installed on-site. Continuous monitoring highlighted an increase of soil water availability in the amended parcels with respect to the control ones. The parcel amended with 10 kg/m2 of fine-grained natural zeolite showed an average water content always higher than the control ones, in the upper soil horizon. In addition, after intense rainfall, this parcel showed an increased field capacity and a reduced percolation towards the deeper soil horizon. Finally, the residual water content was improved by 1.2 ± 0.4 % throughout the summer droughts. © 2016, Springer International Publishing Switzerland