The nitrogen challenge: building a blueprint for nitrogen use efficiency and food security

The Nitrogen Worlshop is a leading network on all issues related to Nitrogen, since 1982. From an European network, the Nitrogen workshop grew to an international network, integrating more and more countries and enlarging its focus to broader questions about NitrogenN/

Estimating the effect on nitrogen mineralization from organic residues applied to degraded soils

RAMIRAN International ConferenceNitrogen (N) is the nutrient most likely to be limiting for plant and animal production. Also, increasing world population, is giving rise to the need for more food production, in quantity and quality enough to supply man’s needs. It is therefore necessary to supply more and more nutrients to the soil in order to achieve the production levels required to reduce world hunger. Intensive and somewhat indiscriminate use of commercial fertilizers is not environmentally sustainable, and excessive application of N, as mineral fertilizers, may lead to many environmental problems such as nitrate pollution of water resources, amongst others. Simultaneously, intensification of agriculture, as well as the development of industry, has been leading to the increasing production of organic residues such as manure, municipal solid waste, crop and forest waste, food industry waste, among others (Sims, 1995). Their application to agricultural land is a good solution for recycling, can increase soil organic matter content, and to provide plant nutrients such as N, as a good alternative to commercial fertilizers (Cordovil, 2004). The application of organic residues to agricultural soils as a source of N needs a better understanding of the processes involving the mineralization of organic N compounds. A good prediction of the amounts of N mineralized from the residues is an interesting issue, and also a valuable tool for the sustainable and rational use of these sources of nutrients for plant growth, while reducing the environmental impact. More than 90% of the N in soils is in organic forms. Available N is considered to be a fraction of easily mineralizable organic N that can be estimated based on the mineral N released during incubation of soil at an appropriate temperature. However, incubation procedures are time consuming, and several chemical methods have been developed as substitutes for incubations by several authors. Thus, the development of a rapid, accurate and cost-effective method for the prediction of N supply both from soil organic matter and the application of organic waste materials is of great interes

Use of organic residues in the recovery of organic matter pools, after forest fires

RAMIRAN International ConferenceIn Portugal, as in other Mediterranean countries, fire events are common primarily due to climate and progressive rural abandon, and contribute largely to desertification. Top layers of soil are constituted mostly by organic residues and decomposed organic matter, and are the most sensitive layers to fire damages. Soil organic matter is an important factor on physical, chemical and biological properties of soil. Quantity and duration of heat transfer and soil thermal conductivity, which varies according to soil conditions (humidity, organic matter, texture, etc), are the main responsible factors for the more or less physical, chemical and biological changes in soil after fire (Neary et al,1999). A soil temperature of only forty degrees is enough to initiate biological changes that may begin with plant and roots death caused by dehydration, and protein degradation. Microbial populations have different thermal resistances and most are killed between 50 and 120 ºC. Organic matter (OM) losses may occur at low temperatures, through the volatilization of volatile compounds which may occur between 100º and 180 ºC or OM distillation at 200 to 315 ºC (DeBanno et al, 1998). Under 200 ºC, decomposition of resistant compounds as hemicelullose and lignin starts (Chandler et al, 1983, cit by González-Pérez et al, 2004). At 300 ºC, decarboxylation and loss of Oxigen-containing functional groups (as phenols) occur in the Humic (HA) and Fulvic acids (FA) (Knoepp, 2005). Humin content increases, due to formation of aromatic compounds, because the more soluble fraction, the FA fraction, is transformed into insoluble acids like HA, and this last ones suffer dehydratation and decarboxylation, becoming insoluble – Black Carbon – resembling the Humin fraction (González-Pérez et al, 2004, Tinoco et al, 2006, Hatten and Zabowski, 2009). Above 450 ºC, all OM is loss. The main purpose of this work was to evaluate the effect of soil heating in forest soils, using a natural burned (B) and an unburned (U) soils and thermally treated soils at different temperatures (65, 105 and 250ºC). Further, we examined the benefic effects of application of organic residues to soils that had been exposed to fire, we added digested pig slurry, municipal solid waste compost and a mixture of both, and evaluated organic matter composition after 2 months of incubation

Recovery of burned forest soil by organic residue application - substrate induced respiration in soil

RAMIRAN International ConferenceThe Mediterranean is one of the most vulnerable regions to climatic changes. One of the impacts of these changes is a substantial increase in the meteorological risk of fire. The forest fire regime instantaneously responds to climatic changes and may become the dominant factor of alteration in forest communities (Santos & Miranda, 2006). Therefore, understanding the impact of fire on natural ecosystems may be important in the recovery of post-fire ecosystems, hence allowing a better forest restoration. A fire impacted soil can recover, namely through soil organic matter (OM) correction by the application of organic residues. Applying agricultural (e.g. pig slurry) and municipal solid wastes as organic matter sources to soil may represent a good way to recycle these wastes. Fire leads to important changes in the physical, chemical and biological properties of soils, which are relevant for the future productivity and sustainability of ecosystems (Neary et al., 2005). The extent and duration of these effects on soil properties depend on the intensity and residence time, ergo fire severity (Certini, 2005). Soil microorganisms perform an important and essential role in soil biological processes. Biological properties however, are extremely sensitive to soil warming, where lethal temperature thresholds for most organisms are below 100 oC. Biological diversity represents a sensitive means to determine soil quality. This is related to functional diversity, which comprises the ability of organisms to use a vast range of carbon substrates and be able to perform several biochemical reactions. Soil health and quality can be assessed by microbial community level physiological profiles (CLPP), using different carbon substrates. MicroRespTM can be applied to a vast range of soils and has good sensibility to detect changes in microbial communities, offering a rapid and sensitive method to determine CLPP (Chapman et al., 2007). Soil (Litosol) was collected in Sintra Mountain (Portugal), on a Pinus Pinaster forest, 11 days after a forest fire. The impact on recovery of burned soil by organic residue application and its influence on soil microorganisms was studied using the MicroRespTM method, concerning fire effects on soil microorganisms and the need to recycle wastes

Development of a groundwater contamination index based on the agricultural hazard and aquifer vulnerability: Application to Portugal

Reducing nitrate leachingmay not result in a significant improvement of groundwater quality. The amount of nitrate reaching groundwater depends not only on the hazard related to agricultural activities but also on-site specific groundwater vulnerability. Using national databases and other compiled datasets, the agricultural hazard was calculated as the ratio of (i) the nitrate leached estimated from the N surplus, and (ii) the water surplus, a proxy of the percolatingwater belowthe root zone. By combining the hazardwith a multi-parameter groundwater vulnerability, a spatially explicit groundwater contamination risk, developed for mainland Portugal,was computed for 1999 and 2009. Results showan increase from8,800 to 82,679 ha of the territory ratedwith a very high contamination risk. The priority areas were successfully screened by the Index, coinciding with the current Vulnerable Zones, although additional hotspots were detected in southern Portugal. Percolation, including both irrigation activity and precipitation, was found to be a key driver for the groundwater contamination risk due to its opposite effects in the hazard and in the vulnerability. Reducing nitrogen leaching may be insufficient to reduce the risk of nitrate contamination if there is a relatively larger reduction in precipitation. This index is particularly useful when applied to contrasting situations of vulnerability and hazard,which require distinct mitigation measures to mitigate groundwater contaminationinfo:eu-repo/semantics/publishedVersio

Shifts in the structure of a mine contaminated soil (Pb, Cu, As) following different organic and inorganic treatments

RAMIRAN International ConferenceSoil microbial community structure is increasingly being marketed as ecologically-relevant endpoint and it can realistically be incorporated for assessing the potential risks associated with anthropogenic disturbances and soil amendment strategies on sustainability of soil ecosystems. In Portugal, additional research is needed if technologies based on the combined action of plants and the microbial communities they support within the rhizosphere are to be adopted in large-scale remediation actions (Nabais et al., 2008). The information about this fact in mine soils is scarce and had focused on soil biochemical properties, producing no clear results. Furthermore, the effects of phytoremediation as soil remediation technique and metal contamination on microbial community structural would be achieved by PLFA studies. By phospholipid fatty acid analysis it is possible to examine broad scale patterns in microbial community structure (Bååth et al. 2005) and generally, after the application of multivariate statistical analyses, whole community fatty acids profiles indicate which communities are similar or different. Determination both microbial community composition and biomass size by this direct method gives results that very closely represent the in situ soil conditions and is currently used for soil monitoring purposes (Nielsen and Winding, 2002). The present investigation studies the medium-term response in the soil microbial community structure after the application of different remediation technologies including several organic and inorganic treatments

Spatial distribution and uncertainties of nitrogen budgets for agriculture in the Tagus river basin in Portugal - implications for effectiveness of mitigation measures

The present study describes a methodology to quantify the gross soil nitrogen balance (SNB) for agricultural land use in the Tagus Nitrate Vulnerable Zone (TVZ) between 1989 and 2016, including effects of implementation of the EC Nitrates Directive (ND, 91/676/EEC) since 2004. The study uses decadal information from National Agricultural Census at parish level and is supported by a Geographical Information System (GIS). The average SNB of the TVZ decreased significantly (p < 0.001) from 125 kg ha−1 in 1989 to 63 kg ha−1 in 2016 (on average 1.8 kg ha−1 yr−1). The N input via irrigation water was particularly high in seven municipalities where it represents up to 35% of the total inputs. Using a Monte Carlo approach, the average uncertainty of the SNB was calculated at 12%. The most important sources of uncertainty were mineral fertilization, nitrate concentration in groundwater used for irrigation and the percentage of farmers complying with ND measures. GIS analysis shows that, at the scale of municipalities, the SNB has decreased since the ND implementation in regions dominated by irrigated intensive crop production, while the SNB has stabilized in municipalities in the south of TVZ with intensive livestock production (75% of area). We conclude that the implementation of ND and national measures to reduce the SNB was not equally effective across the TVZ. Our results indicate that the most effective measures to reduce the SNB in the future are increasing compliance of farmers with the ND related measures and measures increasing the nitrogen use efficiency of livestock manuresinfo:eu-repo/semantics/publishedVersio

Translating the agricultural N surplus hazard into groundwater pollution risk: Implications for effectiveness of mitigation measures in nitrate vulnerable zones

In the Nitrate Vulnerable Zones farmers are required to implement measures to reduce the nitrogen (N) surplus. Nevertheless, in some cases the status of the water bodies show that the effect of these measures remains insufficient despite the global decrease in N surpluses. The present work aims to contribute with a method that produces an appropriate indicator for the N mitigation measures effectiveness for reducing groundwater nitrate pollution. The Global Risk Index (GRI) results from overlaying the agricultural N surplus hazard and aquifer vulnerability. It includes both irrigation activity and precipitation contribution to water recharge calculated at the municipality level. It integrates a range of regional datasets combined with monitored nitrate (NO3 ) concentrations in groundwater under a GIS framework. Results show that the pollution status of the Tagus Vulnerable Zone (TVZ) aquifers has been aggravating in spite of the overall reduction in the N surpluses that resulted from the implementation of the Nitrates Directive measures. Twelve years after the TVZ designation, the GRI indicates high and moderate NO3- pollution risk, respectively in 33 % and 66 % of the territory. Scenario analysis indicates the potential of targeted measures for ending high risk areas and reducing moderate risk areas to 13 %. This supports that N mitigation measures must be reformulated and spatially targeted according to site specific hazards and vulnerabilitiesinfo:eu-repo/semantics/publishedVersio

Atrazine bound residues formation and dissipation in subtropical soil under swine wastewater application

The effects of swine wastewater on atrazine dissipation and formation of bound residues in subtropical clay soil were investigated in this study. The experiment was carried out in laboratory, under room conditions, where samples of Rhodic Hapludox soil received 168.61 mg kg-1 of atrazine and were incubated for 60 days in the following treatments: T1 (sterilized soil + swine wastewater), T2 (sterilized soil + distilled water), T3 (Non sterilized soil + swine wastewater) and T4 (Non sterilized soil + distilled water). The extractable residues and bound residues of atrazine were extracted and analyzed by high performance liquid chromatography. The results showed no effect of swine wastewater on atrazine dissipation. However, the addition of swine wastewater favored the increase of bound residues, which can increase the persistence of atrazine in the environment and reduce its bioavailabilityinfo:eu-repo/semantics/publishedVersio

A comparison between the quality of eggs from indigenous chicken breeds and that from commercial layers

There is an increased interest in animal products from more sustainable farming practices, which may include using local breeds. In addition, maintaining biodiversity is important, and naturally, indigenous breeds of chickens are well adapted to the local environmental conditions. In the current study, 286 eggs from 4 Portuguese breeds of chickens (Branca, Amarela, Pedr^es Portuguesa, and Preta Lusit^anica) and from a commercial hybrid laying hen were used. Chemical and physical characteristics of the eggs and the egg components such as weights, Haugh units, yolk color, albumen protein content, yolk fatty acid content, and mineral content in the albumen and yolk were analyzed. The Branca breed produced eggs with a lighter brown shell color and lower Haugh unit values than the remaining native breeds (P,0.05). The commercial hens produced eggs that were found to be more rounded shape than the ideal and with a darker colored shell and yolk than eggs from the 4 local breeds. In addition, the commercial hens also produced heavier eggs but with lower Haugh units than the Amarela, Pedr^es Portuguesa, and Preta Lusit^anica breeds (P , 0.05). The range of saturated fatty acids, monounsaturated fatty acids, and total polyunsaturated fatty acids between eggs from the 4 breeds was small and not significantly different. No differences were found in the percentage of albumen protein between breeds. Albumen and yolk ash content was not different between breeds. The overall analysis indicated that eggs from these native genotypes match the quality of a commercial product in many characteristics. In markets where eggs from local breeds are available, consumers are purchasing a high-quality product while aiding in the expansion of local genetic resources and investing in local farmersinfo:eu-repo/semantics/publishedVersio