Electromagnetic induction as a basis for soil salinity monitoring within a Mediterranean irrigation district

28 Pag., 4 Tabl., 9 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/00221694Soil salinity encroachment is an increasing concern in many irrigated lands, because of the undesirable effects of soluble salts on agricultural production and on water quality. From this point of view, the design and management of irrigation districts can be evaluated by monitoring the soil salinity. There are few cases in the world where comparisons can be undertaken from ‘historic’ data sets for extents other than individual plots. We demonstrate a monitoring procedure using electromagnetic induction (EMI) survey in an irrigated district in Spain. This district is the only one having an established soil salinity baseline. The EMI data acquired at the same plots were converted to soil electrical conductivity by calibrating with augered soil samples. The presented calibrations improve the baseline for future comparisons and for the treatment and understanding of new acquisitions of field data in next surveys. A shortcoming inherent to destructive soil sampling is its potential for biasing effects on long-term monitoring of soil salinity by means of GPS or other means of accurate localization and relocalization of soil sampling, the herein called “localization paradox”, rarely treated in scientific papers. The localization paradox is relevant for any variable soil property requiring repeated sampling. This issue is discussed, and a way for its overcoming by using EMI readings displaced from the augering is presented. EMI needs calibration with a reduced number of soil samples analyzed in the lab. The adoption of our data treatment procedures will facilitate soil salinity monitoring.This article was completed thanks to the funds of the Spanish projects GALC-006-2008, PIE-CSIC 200840I246, and AGL2009-08931/AGR.Peer reviewe

Electromagnetic induction as a basis for soil salinity monitoring within a Mediterranean irrigation district

28 Pag., 4 Tabl., 9 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/00221694Soil salinity encroachment is an increasing concern in many irrigated lands, because of the undesirable effects of soluble salts on agricultural production and on water quality. From this point of view, the design and management of irrigation districts can be evaluated by monitoring the soil salinity. There are few cases in the world where comparisons can be undertaken from ‘historic’ data sets for extents other than individual plots. We demonstrate a monitoring procedure using electromagnetic induction (EMI) survey in an irrigated district in Spain. This district is the only one having an established soil salinity baseline. The EMI data acquired at the same plots were converted to soil electrical conductivity by calibrating with augered soil samples. The presented calibrations improve the baseline for future comparisons and for the treatment and understanding of new acquisitions of field data in next surveys. A shortcoming inherent to destructive soil sampling is its potential for biasing effects on long-term monitoring of soil salinity by means of GPS or other means of accurate localization and relocalization of soil sampling, the herein called “localization paradox”, rarely treated in scientific papers. The localization paradox is relevant for any variable soil property requiring repeated sampling. This issue is discussed, and a way for its overcoming by using EMI readings displaced from the augering is presented. EMI needs calibration with a reduced number of soil samples analyzed in the lab. The adoption of our data treatment procedures will facilitate soil salinity monitoring.This article was completed thanks to the funds of the Spanish projects GALC-006-2008, PIE-CSIC 200840I246, and AGL2009-08931/AGR.Peer reviewe

Effects of Cropping Systems on Soil Physicochemical Properties and Abundances and Spatial Distributions of Nitrogen-Cycling Bacteria

Soil nitrogen (N) is a common limiting factor where soil N-cycling is a key component of agroecosystems. Soil N transformation processes are largely mediated by microbes, and understanding bacteria involvement in soil N-cycling in agricultural systems has both agronomic and environmental importance. This 2 yr field-scale study examined the abundances and spatial distributions of the total bacterial community (16S rRNA), bacteria involved in nitrification (amoA) and denitrification (narG, nirK, and nosZ), and soil physicochemical properties of winter wheat (Triticum aestivum L.)–soybean (Glycine max L.) double-crop with 2–3 weeks of spring grazing (WGS) and without grazing (WS) and tall fescue (Festuca arundinacea (L.) Schreb.) pasture (TF) managed to near-natural conditions with similar grazing. The TF soil had a significantly higher abundance of 16S rRNA, amoA, narG, nirK, and nosZ genes than the WS and WGS soils, which had similar levels between themselves. Soil organic matter (OM) and soil pH had stronger effects on the N-cycling bacteria gene abundance. All bacterial gene concentrations and soil pH showed nonrandom distribution patterns with a 141–186 m range autocorrelation. These results indicate that biological N transformation processes are more important in natural agricultural systems and the abundance of N-cycling bacteria can be manipulated by field-scale management strategies

Persistence of antibiotic resistance genes in beef cattle backgrounding environment over two years after cessation of operation.

Confined animal feeding operations can facilitate the spread of genes associated with antibiotic resistance. It is not known how cattle removal from beef cattle backgrounding operation affects the persistence of antibiotic resistance genes (ARGs) in the environment. We investigated the effect of cessation of beef cattle backgrounding operation on the persistence and distribution of ARGs in the beef cattle backgrounding environment. The study was conducted at a pasture-feedlot type beef cattle backgrounding operation which consisted of feeding and grazing areas that were separated by a fence with an access gate. Backgrounding occurred for seven years before cattle were removed from the facility. Soil samples (n = 78) from 26 georeferenced locations were collected at the baseline before cattle were removed, and then one year and two years after cattle were removed. Metagenomic DNA was extracted from the soil samples and total bacterial population (16S rRNA), total Enterococcus species and class 1 integrons (intI1), and erythromycin (ermB and ermF), sulfonamide (sul1 and sul2) and tetracycline (tetO, tetW and tetQ) resistance genes were quantified. Concentrations of total bacteria, Enterococcus spp., class 1 integrons, and ARGs were higher in the feeding area and its immediate vicinity (around the fence and the gate) followed by a gradient decline along the grazing area. Although the concentrations of total bacteria, Enterococcus spp., class 1 integrons and ARGs in the feeding area significantly decreased two years after cattle removal, their concentrations were still higher than that observed in the grazing area. Higher concentrations over two years in the feeding area when compared to the grazing area suggest a lasting effect of confined beef cattle production system on the persistence of bacteria and ARGs in the soil

Effect of solution properties, competing ligands, and complexing metal on sorption of tetracyclines on Al-based drinking water treatment residuals

In the current batch study, we investigated the effect of solution properties, competing ligands (phosphate (P(V)) and sulfate), and complexing metal (calcium (Ca2+)) on tetracycline (TTC) and oxytetracycline (OTC) sorption by Al-based drinking water treatment residuals (Al-WTR). The sorption behavior for both TTC and OTC on Al-WTR was pH dependent. The sorption in absence of competing ligands and complexing metal increased with increasing pH up to circum-neutral pH and then decreased at higher pH. The presence of P(V) when added simultaneously had a significant negative effect (p \u3c 0.001) on the sorption of TTC and OTC adsorbed by Al-WTR at higher TTC/OTC:P ratios. However, when P(V) was added after the equilibration of TTC and OTC by Al-WTR, the effect was minimal and insignificant (p \u3e 0.1). The presence of sulfate had a minimal/negligible effect on the sorption of TCs by Al-WTR. A significant negative effect (p \u3c 0.001) on the adsorption of TCs by Al-WTR was observed in the pH range below 5 and at higher TCs:Ca2+ ratios, probably due to TCs-Ca2+ complex formation. Fourier transform infrared (FTIR) analysis indicated the possibility of inner-sphere-type bonding by the functional groups of OTC/TTC on Al-WTR surface. Results from the batch sorption study indicate high affinity of Al-WTR for TCs in the pH range 4–8 (majorly encountered pH in the environment) in the presence of competing ligands and complexing metal