Use Of Fertilizers In Agriculture Research Articles

UNDERSTANDING THE BEHAVIOUR OF CONTAMINATION SPREAD IN NAGARJUNA SAGAR RESERVOIR USING TEMPORAL LANDSAT DATA

LANDSAT images are used to identify organic contaminants in water bodies, but, there is no enough evidence in present literature that LANDSAT is also good in identifying a mixture of organic and mineral contaminants such as agricultural waste. The focus of this paper is to evaluate the effectiveness of LANDSAT imagery to identify organic and mineral contamination (OMC) and to identify spread extent variations of pollution over the season/year in the Nagarjuna Sagar (NS) reservoir using only satellite images. A new band combination is proposed in order to detect OMC, because existing formulae based on band ratio proved to be inadequate in detecting the contamination in NS. Difference in reflectance values of Red and Green channel of an image helps clearly distinguish clear water from OMC water. This procedure was applied over LANDSAT data of the calendar years 2008, 2014 and 2015 to understand the contamination spread pattern through the reservoir. Results show that contamination is following a similar pattern over these calendar years. In January contamination starts at inlets and by May contamination spreads to almost 90% of the reservoir when the total area of water spread is also reduced by half. Contamination spread is low during the monsoonal period of June to September due to heavy inflow and heavy outflow of waters from NS reservoir. Post monsoon NS is contaminated again because of heavy inflow of runoffs from neighboring land use and limited water outflow. This contamination spread pattern matches the agricultural seasons and fertilizer application pattern in this region, indicating that agricultural use of fertilizers could be one of the primary causes of contamination for this waterbody.

UNDERSTANDING THE BEHAVIOUR OF CONTAMINATION SPREAD IN NAGARJUNA SAGAR RESERVOIR USING TEMPORAL LANDSAT DATA

Abstract. LANDSAT images are used to identify organic contaminants in water bodies, but, there is no enough evidence in present literature that LANDSAT is also good in identifying a mixture of organic and mineral contaminants such as agricultural waste. The focus of this paper is to evaluate the effectiveness of LANDSAT imagery to identify organic and mineral contamination (OMC) and to identify spread extent variations of pollution over the season/year in the Nagarjuna Sagar (NS) reservoir using only satellite images. A new band combination is proposed in order to detect OMC, because existing formulae based on band ratio proved to be inadequate in detecting the contamination in NS. Difference in reflectance values of Red and Green channel of an image helps clearly distinguish clear water from OMC water. This procedure was applied over LANDSAT data of the calendar years 2008, 2014 and 2015 to understand the contamination spread pattern through the reservoir. Results show that contamination is following a similar pattern over these calendar years. In January contamination starts at inlets and by May contamination spreads to almost 90% of the reservoir when the total area of water spread is also reduced by half. Contamination spread is low during the monsoonal period of June to September due to heavy inflow and heavy outflow of waters from NS reservoir. Post monsoon NS is contaminated again because of heavy inflow of runoffs from neighboring land use and limited water outflow. This contamination spread pattern matches the agricultural seasons and fertilizer application pattern in this region, indicating that agricultural use of fertilizers could be one of the primary causes of contamination for this waterbody.

Groundwater quality analysis using multivariate statistical techniques (case study: Fars province, Iran).

This research investigated the quality of groundwater of 298 wells during 10years, in Fars province, southern Iran, to survey spatial variation of groundwater quality and also major sources of hydro-chemical components for drinking and agricultural uses. To classify the sampling stations in each year, hierarchical cluster analysis, using the Euclidean distances and "Ward" method, was used. According to the results of cluster analysis, there were three quality groups in groundwater of the research area: first group of 170 wells with type of Ca-HCO3, second group of 98 wells with type of Ca-HCO3, and third group of 30 wells with type of Na-Cl. Hydro-chemical parameters were increased from the first to the third group, and on the basis of Schoeller and USSL diagrams, the water of wells of the third group was considered unsuitable for irrigation and drinking. Principal component (PC) analysis and factor analysis reduced the complex and voluminous data matrix into three main components, accounting for more than 80% of the total variance. The first PC contained TDS, EC, TH, Na(+), Cl(-), Mg(2+), SO4 (2-), Ca(2+), and SAR parameters. Therefore, the first dominant factor was salinity. In PC2, HCO3 and pH were the dominant parameters, which may indicate weathering of silicate minerals. The PC3 contained high loadings for NO2 (2-) and NO3 (-). This factor indicates anthropogenic contaminants that may be caused by improper disposal of domestic wastes or the use of chemical fertilizers in agriculture and leaching of them.

Coating of essential oils onto prilled urea retards its nitrification in soil

ABSTRACTIncreased use of nitrogenous fertilizers in agriculture has led to the increased pollution of ground water and atmosphere. Certain plant products can be used as coating materials onto urea to reduce the N losses. We evaluated the effectiveness of citronella and palmarosa grass oils as nitrification inhibitors in a soil incubation study. The treatments (14) were combinations of 4 N sources (neem, citronella and palmarosa oil coated prilled ureas, and uncoated prilled urea), 2 coating thicknesses of oils (500 and 1000 mg kg−1) and 2 N levels (75 and 150 kg N ha−1), replicated thrice in a randomized block design. N levels at 75 and 150 kg ha−1 were equivalent to 34 and 68 mg N kg−1 soil, respectively. Results showed that N sources citronella (CCPU1000) and neem oil (NCPU1000) coated prilled ureas at 1000 mg kg−1 coating thickness with 75 kg ha−1 released similar amount of ammonical-N to uncoated prilled urea at 150 kg N ha−1, suggesting the beneficial effect of coated ureas. The highest nitrification inhibition (%) was recorded with NCPU1000, the reference nitrification inhibitor, which was significantly greater to all the other N sources at 7 days after incubation (DAI), and at par to CCPU1000 at 14 and 21 DAI.

Assessing the environmental impact of wastewater treatment plants by chemometric approach

This paper presents the results of principal factor analysis technique (PFA) developed for a 3-year study (2010–2012) on two urban wastewater treatment plants (WWTPs) situated in Murcia, Southeast of Spain. One of them receives wastewater for a medium-sized city (WWTP1), with an important industrial area, and the other one treats only domestic wastewater from a small-sized town (WWTP2), with slightly different treatment systems between them. Process performance and operation of WWTP are carried out to ensure their compliance with legislative requirements imposed by European Union. Because high amounts of variables are daily measured, a coherent and structured approach of such a system is required to understand its inherent behavior and performance efficiency. In this sense, PFA as a chemometric technique allowed us to investigate and propose a data reduction that allowed to group water-quality variables into selected factors with common features to describe the behavior of both plants, and their similarities and differences. Four main factors were extracted for WWTP1, associated with the presence of nutrients, the ionic component, the organic load to the plant, and the efficiency of the whole process, with an explaining variance of 62.12%. For WWTP2, also four main components were extracted, explaining 63.82% of the variance. These factors were pollution load to the plant, pollution output, marine intrusion, and, finally, the ionic component of water. The geochemical background composition of water in this zone and the important use of fertilizers in agriculture appeared to be two significant factors driving the results.

Experimental determination of nanofiltration models: application to nitrate removal

Nowadays, nitrate contamination of groundwater is a growing problem both in developed and developing countries. Such contamination comes mainly from the intensive use of nitrogen fertilizers in agriculture. Other possible sources of water contamination by nitrates are improper discharges of industrial effluents, the inadequate management of leachate from landfill of municipal solid waste and effluents from intensive farming. The maximum permissible concentration of nitrates in the water for public consumption in the EU countries is 50 mg/L, although the World Health Organization established a value of 25 mg/L to be considered a quality water. This problem of nitrate contamination, widespread in countries of the European Union, is very important in Spain, where there are some regions with a high presence of aquifers with nitrate concentrations significantly higher than the established limits. Among the possible treatments for nitrate removal from contaminated waters, nanofiltration (NF) is a technically proven process that eliminates nitrates without causing a significant imbalance in the rest of dissolved salts. In this work, the removal of nitrates from water using a commercial NF membrane is studied. Synthetic feeds with levels of nitrate concentration higher than the ones usually found in contaminated aquifers have been considered. On the other hand, the experimental results have been fitted to the solution-diffusion model, having found mathematical expressions that can be used to predict membrane performance for feed concentrations higher than 100 mg/L. The model considers the concentration on the surface of the membrane, estimated by the film theory model. It has been proved that concentration polarization cannot be neglected for this application. The tested membrane allows nitrate decontamination of water (concentration below the legal limit) in one pass for values of feed concentration up to 100 mg/L, with a transmembrane pressure of 5 bar.

Differential effects of salinity and osmotic stress on the plant growth-promoting bacterium Gluconacetobacter diazotrophicus PAL5

Plant growth-promoting bacteria (PGPB) represent a promising alternative to the massive use of industrial fertilizers in agriculture. Gluconacetobacter diazotrophicus is a PGPB that colonizes several plant species. Although this bacterium is able to grow at high sucrose concentrations, its response to environmental stresses is poorly understood. The present study evaluated G. diazotrophicus PAL5 response to stresses caused by sucrose, PEG 400, NaCl, KCl, Na2SO4 and K2SO4. Morphological, ultrastructural and cell growth analysis revealed that G. diazotrophicus PAL5 is more sensitive to salt than osmotic stress. Growth inhibition and strong morphological changes were caused by salinity, in consequence of Cl ion-specific toxic effect. Interestingly, low osmotic stress levels were beneficial for bacterial multiplication, which was able to tolerate high sucrose concentrations, Na2SO4 and K2SO4. Our data show that G. diazotrophicus PAL5 has differential response to osmotic and salinity stress, which may influence its use as inoculant in saline environments.

Sustainable sanitation: fertiliser from human waste

The global use of inorganic fertilisers in agriculture is rising, resulting in an increase in nitrous oxide emissions and heavy metals entering watercourses and groundwater. This paper outlines the potential for human waste to be reused as a fertiliser. It highlights techniques and work being undertaken in Haiti, where simple technology is being used to harness the nutrient content in human waste through a thermophilic composting process while providing necessary sanitation to communities and emergency camps. Ecological sanitation toilets are also being used to separate urine and faeces at source, providing a more sustainable alternative to traditional wastewater treatment processes adopted by the majority of the developed world.

The Need for a Coupled Human and Natural Systems Understanding of Agricultural Nitrogen Loss

Reactive nitrogen loss from agricultural fertilizer use remains a crucial environmental problem in the United States, contributing to ecosystem degradation and global climate change. This intractable problem requires a coupled human and natural systems approach that combines biophysical, sociological, and economic knowledge into an integrative analysis. Much is known about the biogeochemistry of nitrogen and agricultural nitrogen loss; however, much is not known about how soil variability and climate change will affect farmer decisionmaking. Although it is widely understood that personal values and beliefs, social norms, economics, and policies influence farmer decisionmaking, very little is known about decisionmaking specific to fertilizer management. In addition, little is known about the socioeconomic influences on decisionmaking across scales and how ecological change is perceived and responded to. Combining sociological, economic, and biophysical knowledge can provide key insights regarding how these factors interact and can support more effective strategies to address this persistent problem.

Integrated assessment of the impact of climate and land use changes on groundwater quantity and quality in the Mancha Oriental system (Spain)

Abstract. Climate and land use change (global change) impacts on groundwater systems cannot be studied in isolation. Land use and land cover (LULC) changes have a great impact on the water cycle and contaminant production and transport. Groundwater flow and storage are changing in response not only to climatic changes but also to human impacts on land uses and demands, which will alter the hydrologic cycle and subsequently impact the quantity and quality of regional water systems. Predicting groundwater recharge and discharge conditions under future climate and land use changes is essential for integrated water management and adaptation. In the Mancha Oriental system (MOS), one of the largest groundwater bodies in Spain, the transformation from dry to irrigated lands during the last decades has led to a significant drop of the groundwater table, with the consequent effect on stream–aquifer interaction in the connected Jucar River. Understanding the spatial and temporal distribution of water quantity and water quality is essential for a proper management of the system. On the one hand, streamflow depletion is compromising the dependent ecosystems and the supply to the downstream demands, provoking a complex management issue. On the other hand, the intense use of fertilizer in agriculture is leading to locally high groundwater nitrate concentrations. In this paper we analyze the potential impacts of climate and land use change in the system by using an integrated modeling framework that consists in sequentially coupling a watershed agriculturally based hydrological model (Soil and Water Assessment Tool, SWAT) with a groundwater flow model developed in MODFLOW, and with a nitrate mass-transport model in MT3DMS. SWAT model outputs (mainly groundwater recharge and pumping, considering new irrigation needs under changing evapotranspiration (ET) and precipitation) are used as MODFLOW inputs to simulate changes in groundwater flow and storage and impacts on stream–aquifer interaction. SWAT and MODFLOW outputs (nitrate loads from SWAT, groundwater velocity field from MODFLOW) are used as MT3DMS inputs for assessing the fate and transport of nitrate leached from the topsoil. Three climate change scenarios have been considered, corresponding to three different general circulation models (GCMs) for emission scenario A1B that covers the control period, and short-, medium- and long-term future periods. A multi-temporal analysis of LULC change was carried out, helped by the study of historical trends (from remote-sensing images) and key driving forces to explain LULC transitions. Markov chains and European scenarios and projections were used to quantify trends in the future. The cellular automata technique was applied for stochastic modeling future LULC maps. Simulated values of river discharge, crop yields, groundwater levels and nitrate concentrations fit well to the observed ones. The results show the response of groundwater quantity and quality (nitrate pollution) to climate and land use changes, with decreasing groundwater recharge and an increase in nitrate concentrations. The sequential modeling chain has been proven to be a valuable assessment tool for supporting the development of sustainable management strategies.

Assessing the impact of RDP agri-environment measures on the use of nitrogen-based mineral fertilizers through spatial econometrics: The case study of Emilia-Romagna (Italy)

Agriculture is the main source of nitrogen loading (EEA, 2012) and is the sector with the largest residual emission reduction potential (Sutton et al., 2011). Moreover, surpluses of nitrogen are forecast to grow in the next decade (FAO, 2012). The objective of this study is to evaluate the determinants of the use of N-based mineral fertilizers in agriculture and the effectiveness of Agri-Environmental Schemes (AES) implemented in Emilia-Romagna, Italy, in preventing nitrate pollution.The indicator N mineral fertilizer application rate in agriculture was first estimated at the municipality level for the years 2000 and 2010. Thereafter, we performed a Moran's statistics and a LISA (Local Indicators of Spatial Association; Anselin, 1995) analysis to test the data for local spatial autocorrelations. Finally, in order to provide a quantitative evaluation of the impact of the agri-environmental measures on the application rate of N fertilizers, we constructed an aspatial model (Ordinary Least Square model) and two spatial models (spatial lag and error models). All of the models are able to explain more than 70% of the change in the N mineral fertilizer application rate between the years 2000 and 2010 (the dependent variable).The results indicate that the observed decrease in the application rate of N mineral fertilizers in the considered decade was positively influenced by both the uptake of specific AES and the location in Nitrate Vulnerable Zones (NVZ). Among the policy variables, the participation in AES is less important than the location in a NVZ for explaining the reduction in the N mineral fertilizer application rate in the municipalities of Emilia-Romagna. Other significant variables are farm size, population density and share of certified organic surface in the utilized agricultural area (UAA). The availability of finer scale data for the estimation of changes in nitrogen inputs would improve the robustness of the models.

Hydrochemical processes regulating groundwater quality in the coastal plain of Al Musanaah, Sultanate of Oman

The Al Batinah coastal aquifer is the principal source of water in northwestern Oman. The rainfall in the Jabal Al Akhdar mountain region recharges the plain with freshwater that allowed agricultural and industrial activities to develop. The over-exploitation of this aquifer since the 1970s for municipal, agricultural and industrial purposes, excessive use of fertilizers in agriculture and leakage from septic tanks led to the deterioration of groundwater quality. The objective of this study was to investigate the hydrochemical processes regulating the groundwater quality in the southwestern section of Al Batinah. From available data collected during the spring of 2010 from 58 wells located in Al Musanaah wilayat, it was determined that the groundwater salinity increased in the direction from the south to the north following the regional flow direction. In addition to salinisation, the groundwater in the upstream and intermediate regions was contaminated with nitrate, while groundwater in the downstream region was affected by fluoride. Calculations of ionic ratios and seawater fraction indicated that seawater intrusion was not dominant in the study area. The primary factors controlling the groundwater chemistry in Al Musanaah appear to be halite dissolution, reverse ion exchange with clay material and anthropogenic pollutants.

English

This paper presents the effect of recharge, irrigation and soil nature on the variation of nitrate in the groundwater of Wadi Nil (Jijel – North-East Algeria) where the intensive use of fertilizers and the recycling of irrigation water have resulted in an alarming increase in nitrate concentrations. In this plain, the groundwater is increasingly polluted by excessive use of fertilizers in agriculture. Indeed, in several areas cultured with irrigated vegetable crops, water contains nitrate levels which exceed the allowed standards for human consumption. The present study consists of a spatio-temporal monitoring of nitrate in groundwater in relation to the dilution caused by charging during the rainy season, on the one hand, and to the leaching caused by irrigation water during the dry season, on the other hand. The results obtained show an increase in the contamination of groundwater by nitrates and their seasonal variations under the effects of recharge, irrigation and soil nature.   Key words: Agricultural pollution, nitrates, recharge, irrigation, groundwater, soil nature.

Effects of biochar and chicken litter ash on selected soil chemical properties and nutrients uptake by Oryza sativa L. var. MR 219

Environmental pollution caused by chemical fertilizers and public awareness of healthy food has created an interest in the use of organic fertilizers in agriculture. Biochar should be considered as an alternative of chemical fertilizers in agriculture because biochar applications can improve soil properties and plant productivity. The objective of this greenhouse study was to determine the effects of biochar and chicken litter ash on selected soil chemical properties and nutrients uptake of rice plants (Oryza sativa L. var. MR 219). Treatments evaluated were: soil only, normal fertilization, 7, 6, 5, 4, 3, and 2 tons ha-1 of biochar. The biochar treatments were supplemented with chicken litter ash at a rate of 5 tons ha-1. Biochar amended with chicken litter ash showed positive effect on soil pH, EC, TOC, exchangeable acidity, and exchangeable Al. The different rates of amended biochar increased K uptake regardless of plant parts. However, the chemical fertilization increased N, P, Ca, and Mg uptake. Although the chemical fertilization increased most nutrients uptake, organic amendment treatments could be a better alternative in the long term because the amended biochar requires a time to decompose to release nutrients for plant uptake whereas chemical fertilizer is rapidly soluble in soil. Moreover, chemical fertilizers provide short term results however, in the long run, it will damage the soil, groundwater, and human health. Therefore, further investigation is essential to understand the influence of biochar in field trial in the long term (2 or 3 cycle) and the complete cycle of rice cultivation.

Growth, Physiological, Yield and Quality Response in Chilli (Capsicum annuum L.) Under Wastewater Irrigation and Different Levels of Phosphorus

Aims: India is one of the most densely populated, developing and industrially fast growing country of the earth that not only facing the problem of water scarcity, but also the mismanagement of tremendous amount of wastewater (WW) produced every day. Therefore a study was conducted in the Aligarh city of India on chilli (Capsicum annuum L.) cv. Pusa Sadabahar to observe the suitability of wastewater for irrigation along with different levels of phosphorus and how minimize the use of chemical fertilizers in agriculture by supplementing mineral nutrients through wastewater. Study Design: Factorial randomized block design Place and Duration of Study: The pot experiment was conducted during 2011-2012 in the net house of the Plant Physiology, Department of Botany, Aligarh Muslim University, Aligarh. Methodology: Three levels of water, 50% wastewater, 100% wastewater and groundwater (GW) were used along with four basal doses of phosphorus at the rates of 0, 20, 40 and 60kgPha with a uniform basal dose of nitrogen and potassium with the rates of 60kgNha and 50kgKha Original Research Article Iqbal et al.; AJEA, 5(1): 70-81, 2015; Article no. AJEA.2015.009 71 respectively. Fertilizers were applied one day before sowing. Both the waters and soil were analyzed for various physico-chemical characteristics. Results: All the growth, physiological, yields as well as quality parameters were recorded at 60 days after sowing. Results revealed that wastewater irrigation significantly increases the growth, photosynthesis, yield and quality of the chilli. Lower dose of phosphorus fertilizer at the rate of 40kg ha together with wastewater proved optimum and gave greater shoot and root length, shoot fresh and dry mass, leaf area, photosynthetic rate, chlorophyll content, nitrate raductase, carbonic anhydrase, ascorbic acid and leaf nitrogen content than control and even to higher nitrogen doses along with groundwater. Conclusion: The wastewater proved an effective source of essential nutrients and even it could not be supplemented the whole nutrient requirement of the chilli but it can reduced the quantity of fertilizers because wastewater also a source of nutrients.

Groundwater movement, recharge, and perchlorate occurrence in a faulted alluvial aquifer in California (USA)

Perchlorate from military, industrial, and legacy agricultural sources is present within an alluvial aquifer in the Rialto-Colton groundwater subbasin, 80 km east of Los Angeles, California (USA). The area is extensively faulted, with water-level differences exceeding 60 m across parts of the Rialto-Colton Fault separating the Rialto-Colton and Chino groundwater subbasins. Coupled well-bore flow and depth-dependent water-quality data show decreases in well yield and changes in water chemistry and isotopic composition, reflecting changing aquifer properties and groundwater recharge sources with depth. Perchlorate movement through some wells under unpumped conditions from shallower to deeper layers underlying mapped plumes was as high as 13 kg/year. Water-level maps suggest potential groundwater movement across the Rialto-Colton Fault through an overlying perched aquifer. Upward flow through a well in the Chino subbasin near the Rialto-Colton Fault suggests potential groundwater movement across the fault through permeable layers within partly consolidated deposits at depth. Although potentially important locally, movement of groundwater from the Rialto-Colton subbasin has not resulted in widespread occurrence of perchlorate within the Chino subbasin. Nitrate and perchlorate concentrations at the water table, associated with legacy agricultural fertilizer use, may be underestimated by data from long-screened wells that mix water from different depths within the aquifer.

Transport of nitrate and ammonium ions in a sandy loam soil treated with potassium zeolite – Evaluating equilibrium and non-equilibrium equations

The increased use of nitrogen fertilizers in agriculture would cause migration of nitrogen to surface and groundwater; accordingly, would lead to water resources contamination. The objective of this study is to investigate the effect of potassium zeolite on nitrate and ammonium ions sorption and retention in a saturated sandy loam soil in a laboratory condition. The study was conducted as a completely randomized block design with four treatments of 0, 2, 4 and 8 g zeolite per kilogram soil and three replications. Ammonium nitrate fertilizer with concentration of 10 g l−1 was added to soil columns and then leaching was performed. The results show that increasing potassium zeolite to soil causes reduction to the mobility of both nitrate and ammonium and enhancement of the retention of ions in soil. Ions leaching were simulated with convection–dispersion-equation (CDE) and mobile–immobile model (MIM) using HYDRUS-1D code. The results indicate that ammonium ion sorption by soil followed the Freundlich isotherm model. Absorption isotherms and dispersion (De) coefficient were determined through the inverse modeling for both ions. Based on the results, optimized values of Freundlich isotherm were much less than the observed amounts. This shows that the HYDRUS-1D model underestimated the adsorption parameters to predict the ammonium ion mobility in soil macropores. Since soil has been disturbed, the prediction of CDE model was equal to MIM model approximately. Both models showed that as the amount of applied zeolite increases, the dispersion (De) coefficient of nitrate and ammonium ions in the soil increases.

A diversity of learning configurations in work situations to reduce the use of agricultural fertilizers and pesticides

« Developper une agriculture plus ecologique », injonction pregnante des politiques territoriales actuelles, invite a s’interroger sur les conditions d’apprentissage des agriculteurs en situation de travail. Notre methodologie, a l’interface entre didactique professionnelle et agronomie, s’appuie sur des entretiens aupres de vingt cerealiers francais, qui ont reduit l’usage des pesticides et engrais au cours de leur carriere professionnelle. Pour analyser la configuration de conditions d’apprentissage accompagnant chaque changement de pratiques vers la reduction d’intrants, nous avons concu un cadre d’analyse distinguant trois phases successives (la mise en alerte, l’experience, et l’evaluation), en nous inspirant de la theorie de l’enquete de Dewey (1993). Chaque phase du processus d’apprentissage a ete caracterisee par un ensemble de variables elles-memes declinees en un ensemble de modalites. Une classification ascendante hierarchique a permis d’identifier dix types de configurations de conditions d’apprentissage. Chaque agriculteur mobilise, au fil de sa carriere, plusieurs configurations-types combinant des formes d’experience et des personnes ressources variees. Si en tendance les agriculteurs ont modifie leurs pratiques dans la proximite avec autrui, certaines configurations-types se deroulent en autonomie complete (20 % des cas) ce qui revele a la fois un isolement de certains agriculteurs, et une capacite d’autres agriculteurs a combiner apprentissages en groupe et apprentissages en autonomie. L’identification que nous avons faite de configurations de conditions d’apprentissage constitue une approche originale pour traiter des apprentissages en situation de travail et offre des outils pour structurer un travail d’accompagnement des agriculteurs vers des systemes de culture innovants.

Hydrogeochemical assessment of the Upper Cheliff groundwater (North West Algeria)

The quality of the Upper Cheliff groundwater, located in North West Algeria, has in recent years undergone serious deterioration due to uncontrolled discharge of urban wastewaters, intensive use of chemical fertilizers in agriculture as well as to overexploitation. This study aims at analyzing the flow pattern of the Upper Cheliff groundwater, determining its current hydrochemical status and understanding the mineralization processes involved in its chemical quality. Two piezometric and sampling campaigns were carried out in 2008 in high water (April) and low water (October) periods. The major chemical ions (Ca2+, Mg2+, Na+, K+, Cl−, HCO3 −, NO3 −, SO4 2−) were analyzed in all samples. The piezometric data were mapped and allowed to analyze the groundwater flow conditions, in particular at the boundaries of the aquifer. The interpretation of hydrochemical data was made using various methods (Piper diagram, Stabler classification, base exchanges index, bi-elements scatter diagrams, saturation indices, mapping and multivariate principal component analysis). The results provide a better understanding of this aquifer hydrogeology and hydrochemistry. Several hydrochemical types (chloride-calcium, chloride-sodium and bicarbonate-calcium) characterize the groundwater. Mineralization processes and the origin of salinity are determined by the lithology of the aquifer (dissolution, base exchanges), and by climatic (evaporation) and anthropogenic factors (agricultural and urban wastes). The groundwater in the Upper Cheliff is currently of poor quality. This status is worrying, as this groundwater is an important natural resource for the socio-economic development of this region. Urgent measures must be taken to preserve this resource.

A study on N2O measurement characteristics using photoacoustic spectroscopy (PAS).

N2O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N2O measurement methods for these emission sources may be divided into chromatography, optical, and electrical current measurements. Chromatography has been widely utilized for analyzing N2O. However, up until now, few studies have been conducted on N2O using photoacoustic spectroscopy. Therefore, this study aimed to evaluate performance of photoacoustic spectroscopy in this regard based on laboratory and field test results. The repeatability of photoacoustic spectroscopy was measured at 1.12%, which is lower than the repeatability of 3.0% suggested by the ISO 1564 standard, so, it has shown an excellent repeatability. The detection limit was determined to be 0.025 ppm, and the response time was confirmed to be 3 min and 26 s. The results of comparison between these measurements and GC show that the latter has superior accuracy, but mobility and convenience are superior for PAS. On the contrary, GC has a continuous measurement limitation, but PAS makes it possible to conduct continuous measurements. Therefore, PAS can be extremely useful to confirm the characteristics of N2O emissions and to quantify their amount.