Intensive Fertilizer Application Research Articles

Assessment of N-related microbial processes in the soil of the Polesie National Park and adjacent areas, including reclaimed land.

Soil microorganisms are essential for maintaining ecosystem functionality, particularly through their role in the nitrogen (N) biogeochemical cycle. Thus, they also contribute to greenhouse gas emissions from soils. Microorganisms are sensitive indicators of soil health, as they respond rapidly to disturbances caused by factors like unsustainable agricultural practices or industrial activities, such as mining. These bioindicators are also useful for monitoring the effectiveness of environmental remediation treatments, such as soil reclamation. The study aimed to assess microbial activity related to the N cycle in soils across various habitats (peatland, grassland, forest, and field) under conservation management within the Polesie National Park (PNP), as well as in comparable conventionally managed habitats. Additionally, the effectiveness of soil reclamation was assessed using waste from the mining industry, specifically gangue. Significant differences were observed in the assessed activities, both between habitats and their locations, i.e., within the PNP and outside of it. It was found that microbial activity was lower in soils from the PNP area. This was likely a result of more intensive fertilizer application on soils not subject to the restrictions imposed by park regulations. It should be noted that urease activity, which can contribute to the adverse phenomenon of nitrogen loss from soils when elevated, similarly to nitrous oxide (N2O) emission, was lower in the soils from the park than in those located outside of it. Therefore, designating an area as a national park protects the soil environment from human pressures associated with intensive agriculture, thereby helping to maintain its homeostasis. Reclamation using gangue proved ineffective in restoring microbial activity in degraded soil to the level of cultivated soil outside the park. The assessed activities in the reclaimed soil were lower than the target levels. The results provided valuable information useful for environmental management decisions in terms of soil and air protection, as well as the use of waste for reclamation.

Manganese losses induced by severe soil acidification in the extensive Lei bamboo (Phyllostachys violascens) plantation stands in Eastern China

Manganese (Mn) is a critical element in soils, essential to plant growth. Long-term and intensively managed Lei bamboo (Phyllostachys violascens) stands are usually subjected to severe soil acidification and Mn activation. However, Mn migration from topsoil to deep soil induced by severe soil acidification was poorly recognized and studied. The distribution and changes of the total and the operationally defined Mn forms in soil profiles and its potential stress and environmental effect were investigated in a chronosequence of Lei bamboo stands (0, 2, 6, 11, and 16 years of stand age). The results showed that the Mn amount was significantly decreased in topsoil and accumulated in subsoil with the long-term and intensive fertilizer application. Soil exchangeable Mn and superphosphate extractable Mn demonstrated large different variation to total Mn, whereas their sum was largely higher than and highly correlated with 8-hydroxyquinoline (HQN) extractable Mn. Soil organic carbon, pH value, exchangeable bases, and soil redox simultaneously controlled soil Mn depletion. In conclusion, long-term and intensive fertilizer application leads to soil acidification and accelerated soil Mn depletion in bamboo stand soil, promoting Mn accumulation in bamboo shoots.

How do biochar size fractions and organic fertilizers interactively influence nitrous oxide emission from a tropical vertisol?

AbstractBackgroundNitrous oxide (N2O) emission from agriculture is increasing alarmingly due to intensive application of inorganic and organic fertilizers. Recently, biochar has been identified as a promising additive to improve agriculture by enhancing soil function and mitigate greenhouse gas emission. However, it is unclear how biochar of different size fractions influences N2O emission from agricultural soil.AimsThe current experiment aims to understand how the size of biochar (BC) and organic fertilizers interactively influence N2O emission from a tropical vertisol.MethodsBC was prepared using pigeon pea (Cajanus cajan) stalks and further processed to obtain two size fractions (<0.25 mm or 0.25–2.00 mm). Organic fertilizers (vermicompost [VC], poultry manure [PM], or farmyard manure [FYM]) and BC were added to soil to evaluate N2O emission potential. BC was added to soil at 10% (w/w), whereas the organic fertilizers were added at 80 kg N ha–1. Emission of CO2 and the abundance of 16S rRNA and amoA gene copies were estimated after incubation period. The interactive effect of BC size fractions and organic fertilizers were statistically evaluated.ResultsBoth BC and organic fertilizers stimulated N2O emission in soil. BC of larger size stimulated N2O emission (µg N2O produced g–1 soil day–1) more than smaller size. Of the three organic fertilizers, PM resulted highest N2O (0.380) emission followed by FYM (0.240) and VC (0.210). BC (0.25 mm) + PM produced least N2O. Abundance of heterotrophic bacterial 16S rRNA gene copies and ammonia‐oxidizing bacterial (AOB) amoA gene copies were highest in PM + BC and lowest in control. Significant relation (p < 0.0001) existed among N2O emission, CO2 emission, and microbial abundance.ConclusionsBC of small size fraction along with organic fertilizers can be an effective strategy to mitigate N2O emission from tropical vertisol.

Intensity of CO2 emissions of sod-podzolic soil depending on fertilization and lime application

Topicality. With climate change, agricultural production accounts for about 15 % of green-house gas emissions. Disbalance of organic carbon decreases the environmental sustainability and productivity of agroecosystems and soil fertility. With soil management, the intensity of carbon monoxide emission from the soil can reduce to optimize its organic matter. Issues. There is a crucial need to study and analyze comprehensively the effects of different rates of chemical meliorants and mineral fertilizers for crops in the Western Polissia crop rotation on the volume of CO2 emissions from sod-podzolic soil. Aim. To study the characteristic features of carbon dioxide emissions from sod-podzolic soil during winter wheat and spring barley cultivation with different rates of meliorants and fertilizers. Materials and Methods. Field experiment, agrochemical and statistical methods. Results. On the background of mineral fertilization, land reclamation with limestone materials at 0.5 and 1.0 rates determined by the hydrolytic acidity of the soil generally decreases CO2 emissions into the air. During the growing season, depending on the development stage of spring barley, the level of carbon dioxide emission in the variant with N90P90K90 was 89.8–68.3–63.5 mg CO2/kg soil, and in combination with 1.0 rate of dolomite powder – 83.1–59.8–63.6 mg CO2/kg soil. It is noted that the intensity of CO2 accumulation in the surface layer depended on rates of ameliorant, soil moisture and temperature. Thus, the carbon dioxide emission in a winter wheat field was the highest when 1.5 rates of dolomite powder were applied on the background of N120P60K90 , and in the stem elongation stage at air temperature 13.2 ℃ was 77.7 mg CO2/kg of soil. When air temperature increased to 22.0 ℃ in the heading stage, this indicator increased by 1.2 times and at air temperature of 20.4 ℃ in the full maturity stage, it decreased by 1.3 times. When 1.0 rate of dolomite powder was applied, CO2 emission decreased to 18.2 mg CO2/kg of soil compared with 1.5 rates in the full maturity stage of wheat due to the intensity of redox processes in the soil when different rates of limestone materials was applied. Conclusions. In the short-term crop rotation, lime application had a positive effect on the for-mation of deficit-free balance of organic carbon in sod-podzolic soil with intensive application of mineral fertilizers for crops. When we applied 1.0 and 1.5 rates of dolomite powder on the background of N120P60K90 in winter wheat crops, the organic carbon balance was 0.35–0.28 t/ha, in spring barley crops on the background of N90P90K90 – 0.10–0.16 t/ha. Key words: winter wheat, spring barley, land reclamation, fertilizers, carbon dioxide, balance.

The Impact of Aqueous Extracts of Verbesina sphaerocephala and Verbesina fastigiata on Germination and Growth in Solanum lycopersicum and Cucumis sativus Seedlings

The use of extracts derived from different plants has gained popularity as an alternative option to manage weeds and support phenological development in plants. One of the main problems facing agricultural production is the intensive application of chemical fertilizers that harm the environment. This study investigated the biostimulant effects of the aqueous extracts of Verbesinasphaerocephala and Verbesinafastigiata on the germination and growth of tomato (Solanum lycopersicum) and American cucumber (Cucumis sativus) seedlings. The aqueous extracts of both species of Verbesina were tested at concentrations of 0.5 and 1%. Seed germination and seedling development under nursery conditions were evaluated. The seed germination percentage was reduced in all treatments with the extracts of both Verbesina species when compared to that of the control treatment, which was considered an allelopathic effect. However, seedling growth in pots showed different behavior, with the extracts beneficially affecting certain agronomic variables, such as root and leaf length. The results suggest potential uses for V. sphaerocephala and V. fastigiata extracts, although a greater range of action may be experienced through the effects of certain molecules on weed growth. Additional studies with chemical approaches are necessary to better direct the uses and applications of Verbesina biomolecules, as they also functioned as growth promoters.

Proteomic Analysis Dissects Molecular Mechanisms Underlying Plant Responses to Phosphorus Deficiency.

Phosphorus (P) is an essential nutrient for plant growth. In recent decades, the application of phosphate (Pi) fertilizers has contributed to significant increases in crop yields all over the world. However, low efficiency of P utilization in crops leads to intensive application of Pi fertilizers, which consequently stimulates environmental pollution and exhaustion of P mineral resources. Therefore, in order to strengthen the sustainable development of agriculture, understandings of molecular mechanisms underlying P efficiency in plants are required to develop cultivars with high P utilization efficiency. Recently, a plant Pi-signaling network was established through forward and reverse genetic analysis, with the aid of the application of genomics, transcriptomics, proteomics, metabolomics, and ionomics. Among these, proteomics provides a powerful tool to investigate mechanisms underlying plant responses to Pi availability at the protein level. In this review, we summarize the recent progress of proteomic analysis in the identification of differential proteins that play roles in Pi acquisition, translocation, assimilation, and reutilization in plants. These findings could provide insights into molecular mechanisms underlying Pi acquisition and utilization efficiency, and offer new strategies in genetically engineering cultivars with high P utilization efficiency.

Review of Large-Scale Biochar Field-Trials for Soil Amendment and the Observed Influences on Crop Yield Variations

Increasing pressure on farming systems due to rapid urbanization and population growth has severely affected soil health and fertility. The need to meet the growing food demands has also led to unsustainable farming practices with the intensive application of chemical fertilizers and pesticides, resulting in significant greenhouse gas emissions. Biochar, a multifunctional carbon material, is being actively explored globally for simultaneously addressing the concerns related to improving soil fertility and mitigating climate change. Reviews on biochar, however, mainly confined to lab-scale studies analyze biochar production and its characteristics, its effects on soil fertility, and carbon sequestration. The present review addresses this gap by focusing on biochar field trials to enhance the current understanding of its actual impact on the field, w.r.t. agriculture and climate change. The review presents an overview of the effects of biochar application as observed in field studies on soil health (soil’s physical, chemical, and biological properties), crop productivity, and its potential role in carbon sequestration. General trends from this review indicate that biochar application provides higher benefits in soil properties and crop yield in degraded tropical soils vis-a-vis the temperate regions. The results also reveal diverse observations in soil health properties and crop yields with biochar amendment as different studies consider different crops, biochar feedstocks, and local climatic and soil conditions. Furthermore, it has been observed that the effects of biochar application in lab-scale studies with controlled environments are not always distinctly witnessed in corresponding field-based studies and the effects are not always synchronous across different regions. Hence, there is a need for more data, especially from well-designed long-term field trials, to converge and validate the results on the effectiveness of biochar on diverse soil types and agro-climatic zones to improve crop productivity and mitigate climate change.

Cadmium pollution of soil-rice ecosystems in rice cultivation dominated regions in China: A review.

Cd accumulation in paddy soils and its subsequent transfer to the food chain are widespread environmental issues, which has been extensively investigated in China. However, most studies focused on regional scales and these results may not be applicable to present the Cd contamination status in soil-rice ecosystems at a national scale. Therefore, based on collected data from China's rice cultivation dominated regions, this study provides the Cd pollution level of paddy soils and rice grains in China. Results indicates that the Yangtze River basin, especially Hunan, required more attention due to the elevated Cd concentrations in soil-rice ecosystems. Moreover, this review summarizes the significant natural and anthropogenic sources, transport and accumulation mechanism as well as the influencing factors of Cd in soil-rice ecosystems. The wide occurrence of Cd contamination in paddy soils derived primarily from mining activities, intensive application of phosphates fertilizers and e-waste. Physicochemical characteristics of soil, soil microorganisms, temperature as well as the physiological features of rice plants all contribute to Cd accumulation in rice grains, which can be controlled to mitigate Cd accumulation in rice grains. This review will provide a scientific reference for Cd pollution control and management with respect to paddy field ecosystems in China and other countries.

English

Intensive application of nitrogen and phosphorus fertilizers can lead to negative consequences, such as a decrease in Zn content, as well as an increase of Cd in plants. In a long-term field experiment, we studied the influence of the increasing doses of phosphorus fertilizers on the concentration of Zn and Cd in the soil and corn plants (stem and leaves). The obtained results show that the application of the increasing doses of phosphorus significantly decreased the pH reaction of the soil, but did not affect the amount of total and potentially available Zn in the soil. Zinc was accumulated in the corn stem to a higher extent on the unfertilized treatment with respect to corn stem exposed to other fertilizing treatments. Bearing in mind the fact that phosphorus fertilizers contain a different concentration of Cd, results have shown that the long-term application of the increasing doses of phosphorus has led to higher amounts of Cd in the soil and in corn as well, in the plots fertilized with 100 and 150 kg P2O5/ha. However, those values are far below the maximum permissible recommendation.

USE OF AQUATIC PLANTS PISTIA STRATIOTES, EICHHORNIA CRASSIPES AND SALVINIA MOLESTA AS ORGANIC FERTILIZER IN SUSTAINABLE AGRICULTURE – REVIEW

The intensive application of pesticides and chemical fertilizers, in the context of the continuous development of agriculture, has led to a high level of environmental pollution and a serious deterioration in soil fertility. In an attempt to reduce all these negative effects, classical agriculture is moving towards sustainable agriculture. An ecological alternative to the use of chemicals is the application of organic fertilizers. One of the ecological sources is aquatic plants. Often considered invasive due to their rapid development, aquatic plants have a real potential in sustainable agriculture. This review presents the use of aquatic plants pistia stratiotes, eichhornia crassipes and salvinia molesta as organic fertilizer in sustainable agriculture.

Greater Contribution From Agricultural Sources to Future Reactive Nitrogen Deposition in the United States

AbstractMany sensitive ecosystems in areas protected for biodiversity conservation in the United States suffer from exposure to excess reactive nitrogen (Nr) released by fossil fuel combustion and agricultural practices and deposited onto the land surface and water bodies. The Community Multiscale Air Quality (CMAQ) model was applied over the contiguous United States to link emissions and climate change to reactive nitrogen deposition by simulating both present‐day and future speciated Nr deposition to protected areas. Future conditions included examining the Representative Concentration Pathway 8.5 climate and the Shared Socio‐Economic Pathway 5 emission scenarios. We further identify protected areas that would benefit most from better Nr management strategies by comparing the simulated deposition with multiple critical loads (CLs) for both biodiversity and acidification in terrestrial and aquatic ecosystems. Achieved by further NOx emission reductions from the mobile and power generation sectors, future Nr deposition is expected to decrease. However, in regions with intensive fertilizer application or hosting concentrated animal feeding operations, the reduction may be offset by rising agricultural NH3 emissions. The protected areas having CL exceedances in 2050 are expected to increase by 5.5% for empirical lichen‐based CL, and by 11% and 22% for surface water and forest soil acidity, respectively, because of the agricultural NH3 emission increase. By linking the deposition simulations with a water quality model, we identified that atmospheric deposition is the dominant source of nitrogen for several remote watersheds, including several lakes in National Parks and National Wilderness areas in Colorado, Montana, and Minnesota.

Efisiensi Pupuk dan Peningkatan Hasil Padi Gogo dengan Aplikasi Pupuk Hayati dan Arang Tempurung Kelapa

The intensive application of inorganic fertilizers has a negative impact on soil health. Furthermore, the price of inorganic fertilizers has increased hence the production costs will also increase. Efforts to improve fertilizer efficiency and encourage environmentally friendly crops can be done by application of biofertilizers and organic ameliorants. The field experiment has been carried out to study the effect of biofertilizers application and coconut shell charcoal to increase inorganic fertilizers efficiency and yield of upland rice at Rancakalong, Sumedang, West Java. The experiment used factorial randomized block design consisted two factors. The first factor were biofertilizers and coconut shell charcoal and the second factors were inorganic fertilizers doses. Biofertilizers with consortia of Azotobacter chroococum, Azospirillum sp., Pseudomonas mallei, Burkolderia sp., Aspergillus niger, and Penicillium sp. and organic ameliorant was coconut shell charcoal. NPK fertilizers were applied in 25%, 50%, 75% and 100% of recommended doses. The results revealed that biofertilizers and coconut shell charcoal increased growth and yield of upland rice. This finding concludes that applica

The Availability and Accumulation of Heavy Metals in Greenhouse Soils Associated with Intensive Fertilizer Application.

In China, greenhouse agriculture, which provides abundant vegetable products for human consumption, has been rapidly developed in recent decades. Heavy metal accumulation in greenhouse soil and products obtained have received increasing attention. Therefore, the availability and accumulation of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) and their association with soil pH, soil organic matter (SOM), inorganic nitrogen (IN), total nitrogen (TN), available phosphorus (AP), and planting year (PY) in greenhouse soils were analyzed. The results showed that the mean concentrations of available Cd, Cu, Ni, Pb, and Zn were 17.25 μg/kg, 2.89, 0.18, 0.36, and 5.33 mg/kg, respectively, while their suggested levels in China are 0.6, 100, 100, 120, and 250 mg/kg. Cd, Cu, and Zn might be mainly originated from fertilizer application. A lower soil pH significantly increased the available Cu, Ni, and Zn concentrations and reduced Cd, Cu, Ni, and Zn accumulation. A higher AP significantly increased the proportions of available Cu, Ni, and Zn and elevated Cd, Cu, and Zn accumulation. There was a strong positive correlation between Cd, Pb, and Zn availability and TN, while IN was negatively related to the availability and accumulation of Cu and Zn. It was concluded that chemical fertilizer application increased the availability of Cu, Ni, Pb, and Zn and the accumulation of Cd, Cu, and Zn. Manure application clearly elevated the accumulation and availability of Cd and Zn in greenhouse soil.

Ameliorative Effects of PGPB on Yield, Physiological Parameters, and Nutrient Transporter Genes Expression in Barattiere (Cucumis melo L.)

The intensive application of chemical fertilizers to overcome deficiency of nutrients and achieve maximum agricultural productivity has led to environmental impacts. A significant strategy for sustainable management, by decreasing the use of chemical fertilizers, can consist in the technology based on suitable levels of fertilization in combination with plant growth-promoting bacteria (PGPB) inoculation. This work aimed to test in vivo a consortium of three PGPB, previously isolated and characterized in vitro, on Barattiere plants (Cucumis melo L.). Plants were grown in a soilless system at the commercial dose of mineral fertilizer and at half dose, in order to evaluate the effects of these microorganisms on plant physiology, yield, and the transcriptional expression of four genes involved in NH4+ (AMT2), Fe (FRO, IRT1), and Pi (PHT1) transport and uptake by plant. Our results indicate that even in a soilless pot experiment, where a mineral nutrition solution is used, the bacterial consortium of PGPB improves fruit yield and early maturity, some physiological parameters, and upregulates the expression of some key genes related to N, Fe, and Pi plant nutrition, remarking the environmental and economic gains deriving from the use of half dose of mineral fertilizer.

Watershed Scale Nitrate-N Abatement of Instream Wetlands: An Appraisal Using the Soil and Water Assessment Tool

HighlightsSWAT used to address watershed scale nitrate-N abatement of instream wetlands (ISWs).Experimental ISW results were incorporated into the watershed modeling framework.SWAT successfully captured and reproduced ISW impact on nitrate-N at sub-basin level.Scenarios of ISWs implementation were simulated, effects on nitrate-N export were evaluated.Results show ISWs can be used as conservation structures aimed at enhancing water quality.Abstract. In watersheds under high agricultural production, nitrate nitrogen (nitrate-N) pollution often originates from intensive application of fertilizers and animal manure to croplands. Surface runoff and nitrate-N export from farmlands contributes to the pollution of nearby reaches which flow into the watershed stream network. Experimental studies reported significant nitrate removal capacities of constructed instream wetlands (ISWs). However, cases of large-scale implementations of ISWs are uncommon, probably due to a paucity of watershed-scale studies which highlight the influence of ISWs on riverine water quality. To elucidate the ISWs nitrate-N abatement potential at the watershed scale, the Soil and Water Assessment Tool (SWAT) was used to model nitrate-N export in a highly agricultural watershed located in the Coastal Plain of North Carolina. SWAT was first calibrated and validated for streamflow and for nitrate-N export using data collected from the inlet and outlet of an experimental instream wetland. The validated SWAT model was used to simulate a decade of nitrate-N export under two scenarios: 1) watershed with ISWs implemented; and 2) watershed without ISWs. The results of the case study indicated that a watershed-wide implementation of ISWs is likely to curtail annual nitrate-N export by 49%. The study also evaluated cases where ISWs are implemented in selected percentage of sub-basins across the watershed. The outcomes show higher increments of nitrate-N curtailment when ISWs are implemented in the first top agricultural sub-basins. Hence, implementation of ISWs on selected sub-basins can mitigate nitrate-N from non-point sources and enhance water quality in the watershed’s stream network. Keywords: Runoff, Croplands, Instream wetland, Nitrate-N export, Denitrification, SWAT model, Watershed.

Photochemical production of ozone and emissions of NOx and CH4 in the San Joaquin Valley

Abstract. Midday summertime flight data collected in the atmospheric boundary layer (ABL) of California's San Joaquin Valley (SJV) are used to investigate the scalar budgets of NOx, O3, and CH4, in order to quantify the individual processes that control near-surface concentrations, yet are difficult to constrain from surface measurements alone: these include, most importantly, horizontal advection and entrainment mixing from above. The setting is a large mountain–valley system with a small aspect ratio, where topography and persistent temperature inversions impose strong restraints on ABL ventilation. In conjunction with the observed time rates of change this airborne budgeting technique enables us to deduce net photochemical ozone production rates and emission fluxes of NOx and CH4. Estimated NOx emissions from our principal flight domain averaged 216 (±33) t d−1 over six flights in July and August, which is nearly double the California government's NOx inventory for the surrounding three-county region. We consider several possibilities for this discrepancy, including the influence of wildfires, the temporal bias of the airborne sampling, instrumental interferences, and the recent hypothesis presented by Almaraz et al. (2018) of localized high soil NO emissions from intensive agricultural application of nitrogen fertilizers in the region and find the latter to be the most likely explanation. The methane emission average was 438 Gg yr−1 (±143), which also exceeds the emissions inventory for the region by almost a factor of 2. Measured ABL ozone during the six afternoon flights averaged 74 ppb (σ=9.8 ppb). The average midafternoon ozone rise of 2.8 ppb h−1 was found to be comprised of −0.8 ppb h−1 due to horizontal advection of lower O3 levels upwind, −2.5 ppb h−1 from dry deposition loss, −0.5 ppb h−1 from dilution by entrainment mixing, and 6.9 ppb h−1 net in situ photochemical production. The O3 production rates exhibited a dependence on NO2 concentrations (r2=0.35) and no discernible dependence on methane concentrations (r2∼0.02), which are correlated with many of the dominant volatile organic compounds in the region, suggesting that the ozone chemistry was predominantly NOx-limited on the flight days. Additionally, in order to determine the heterogeneity of the different scalars, autocorrelation lengths were calculated for potential temperature (18 km), water vapor (18 km), ozone (30 km), methane (27 km), and NOx (28 km). The spatially diffuse patterns of CH4 and NOx seem to imply a preponderance of broad areal sources rather than localized emissions from cities and/or highway traffic within the SJV.

ASSESSMENT OF GRAY FOREST SOIL ENZYMATIC ACTIVITY IN AGRICULTURAL SYSTEMS

On the grey forest medium-loamy soil of Vladimir Opolye region we have studied the impact of various methods of basic cultivation and fertilizer systems on the activity of redox and hydrolytic enzymes: ure-ase (nitrogen cycle), invertase (carbon cycle), phosphatase (phosphorus cycle), and catalase, involved in the cycle of carbon in the soil. The second humus horizon with capacity of 19-24cm was found at the depth of 20 - 21 cm on the experimental field. We have studied three modes of basic soil cultivation: an-nual shallow flat plowing (6-8 cm), annual deep flat plowing (20-22 cm), and annual moldboard plowing (20-22 cm) with normal and intensive application of fertilizers. The most enzymatically active layer is 0-20 cm. No relevant difference has been found in the level of enzymes activity between variants of basic soil treatment. Activity of enzymes increases with application of fertilizers on the intensive background. In agrogenic soils, soil enzymatic activity is lower on average by 16-22% compared to the soil of the res-ervoir. The biggest negative transformation of activity has been observed at the urease enzyme (up to 50%). With annual moldboard plowing on the intensive backgroung, enzyme activity has been close to the natural level – 98.4%. Catalise and invertase activity in this case were found to be higher (105 and 116% respectively) than that of natural analogues. Activity of enzymes increases with intensive application of fertilizers as compared with normal background. This is particularly evident with 6-8cm deep beardless plowing and 20-22cm deep moldboard plowing. In general, the obtained biochemical indicators charac-terize the highest environmental sustainability of this variation within our research.

English

Soil degradation is among the serious environmental hazards of this generation. It is threatening agricultural production and leads to food insecurity. The objective of this study is to assess current soil degradation status and soil fertility enhancement technologies practiced by the land owners. Data were obtained through questionnaires administered to 156 respondents selected randomly from all watershed classification schemes (upstream, mid-land, and downstream). Field observations, interviews and discussions with village elders, farmers groups, and village scholars were conducted using a check list of topics focusing on soil degradation, and attempts were made to combat the problem. The result revealed that 70% of farmers experienced soil degradation on their farm land and also crop productivity decreased from time to time.  Productivity cannot be boosted without intensive fertilizer application. Most farmers (>64%) mentioned steep slope, high rainfall, deforestation and poor soil cover as the major causes to soil degradation. Soil fertility amelioration measures like application of compost, construction of terraces, farmyard manure, fallowing, the protection of regenerating natural vegetation, and tree planting were practiced but adoption level of technologies from farmer to farmer is entirely dependent on their awareness level. Simple soil conservation technologies which are easily adopted by farmers should be available. Above all, education infrastructure focusing on soil conservation should be available for land owners. Key words: Soil degradation, soil fertility, soil fertility amelioration. &nbsp

Evaluation of groundwater vulnerability to pollution using a GIS-based multi-criteria decision analysis

Abstract The groundwater contamination is due to different factors such as rapid urbanization, intensive fertilizer application , and wastewater disposal systems associated with human settlements and industries activities. Vulnerability mapping is considered as a fundamental aspect of sustainable groundwater management especially in overexploited and threatens aquifers by various sources of pollution. In the present study vulnerability and risk pollution maps were produced using a GIS based-multi-criteria decision analysis in an appropriate case study in Agareb area (southern Tunisia),and the results were validated using nitrate concentration. Eight appreciation criteria such as: aquifer type , hydraulic conductivity and depth to water table, slope, and proximity to concentrated land use, proximity to rivers, proximity to residential areas and proximity to main roads were selected. These factors were rated in one common interval from 0 to 10 using the fuzzy membership functions. Analytic Hierarchy Process (AHP) is adopted to weight factor assessment. The final groundwater vulnerability maps were created by weighted linear combination (WLC). The results reveal that about 1% area is covered under very high vulnerable zone, 6% area under moderately high vulnerable zone, 18% area under moderately vulnerable zone, 25% area under moderately low vulnerable zone, and 50% area under low vulnerable zone. The results were validated using nitrate concentration in groundwater. Observed nitrate concentrations in boreholes are in accordance with the vulnerability map. The GIS-based multi-criteria decision analysis was observed to be more conclusive in groundwater vulnerability assessment in overexploited areas.

Comparative approach of three popular intrinsic vulnerability methods: case of the Beni Amir groundwater (Morocco)

The study of the intrinsic vulnerability of groundwater resources to pollution is an effective tool to control their quality degradation and contribute to their protection. It is used to delimit the vulnerable zones which do not withstand a large flow of pollutants introduced from the soil surface. Three methods of assessing the intrinsic vulnerability of groundwater: DRASTIC (Depth to water table, Recharge, Aquifer, Soil type, Topography, Impact of zone vadose, Hydraulic conductivity), DRSTI, and GOD (Groundwater occurrence, Overall aquifer class and Depth of water table) coupled with a geographic information system (GIS) are applied to the groundwater of Beni Amir, and they are compared in order to adopt the method which better characterizes the vulnerability of the aquifer to pollution. The validation of this application was made by measurements of the nitrate levels in the aquifer. Because the pollution of groundwater, in this plain, is a direct consequence of agricultural activities characterized by an intensive fertilizer application. The results clearly show that the rate of the coincidence, between the measured nitrate concentrations and the different classes of vulnerability of three methods, is 81.81, 54.54, 72.72, and 27.27%, respectively, for methods DRASTIC (classification of Engel et al. (Int Assoc Hydrol Sci Publi 235:521–526, 1996)), DRASTIC (classifications of Aller et al. (1987)), DRSTI, and GOD. Of this rate of coincidences, the DRASTIC method, with the classification of Engel et al. (Int Assoc Hydrol Sci Publi 235:521–526, 1996), allows a finer assessment and turns out the most representative of the study area.