Application of Dairy Manure Amended with Mineral Fertilizer on Stubble-Covered Soil: Effects on Ammonia Emissions

Presented at the 1st International Electronic Conference on Agronomy, 3–17 May 2021The reduction in the manure application rates through enrichment with mineral fertilizer has the potential to reduce costs, decrease environmental pollution, and extend the manure benefits to greater acreage. A pot experiment was carried out to assess ammonia emissions from dairy manure amended with mineral fertilizers applied on wheat stubble. The treatments were: control (no fertilization), urea (U), calcium ammonium nitrate (AN), dairy manure (MAN), urea + dairy manure (UMAN), and calcium ammonium nitrate + dairy manure (ANMAN). A dynamic chamber system was used to measure NH3 emissions during seven days after soil application. UMAN and ANMAN treatments led to higher NH3 emissions than each isolated component. This might be motivated by the manure pH. Thus, the enrichment of dairy manure with U or AN for application on stubble-covered soil should not be recommended. Nevertheless, some manure pre-treatments, such as acidification, or the use of other mineral fertilizers might improve such solutioninfo:eu-repo/semantics/publishedVersio

Slurry Acidification as a Solution to Minimize Ammonia Emissions from the Combined Application of Animal Manure and Synthetic Fertilizer in No-Tillage

The combined application of manure/slurry and synthetic fertilizer (SF) might be a solution to decrease transport and application costs involving those by-products as well as enable access to them in regions where availability is low. Moreover, their joint application can potentially reduce environmental pollution, enlarge the manure benefits to more areas, and enhance the SF efficiency. However, such a strategy might result in increased ammonia emissions when applied to crop residues. Two experiments were implemented to assess ammonia emissions from stubble-covered soil fertilized with manure amended with SF. In Experiment 1 (E1), urea (U) and calcium ammonium nitrate (AN) were applied combined with dairy manure (MAN). In Experiment 2 (E2), urea was combined with acidified pig slurry (APS) and applied just after sowing (T0) or eight days later (T8). The combinations U + MAN and AN + MAN increased the ammonia emissions, while APS decreased the emissions from U, in APS + U combination, by more than 75%. Therefore, manure combined with SF applied on stubble-covered soil should not be recommended. T8 reduced ammonia emissions from U. APS enhanced the efficiency of U, being then an interesting strategy to mitigate ammonia emissions when applied on stubble-covered soil, as in no-tillageinfo:eu-repo/semantics/publishedVersio

Soil Microbial Biomass And Activity In A Cork Oak Savanna

Cork oak savannas are composed by a sparse tree canopy (30-70 trees/ha) and a grassland understory predominantly composed of C3 annuals that survive the hot and dry Mediterranean summers as seeds in the soil. Microbial communities can be more or less efficient at converting organic substrates into microbial biomass carbon depending on the quantity and quality of organic matter inputs. The cork oak savannas have two distinct types of plant litter that can affect soil microbial biomass and activity differently: herbaceous litter and the more recalcitrant woody plant litter resulting from the trees. Spatial variability of soil microbial biomass and activity due to the tree-grassland component of cork oak savannas were evaluated in order to better understand the soil carbon dynamics of these systems.

To quantify changes in soil microbial biomass and activity, measurements were performed in a Cork oak savanna in Southern Portugal. At this site 8 plots were randomly established under mature cork oak trees and paired with 8 open grassland plots. During one year soil cores (0-10 cm) were monthly collected at each site for measuring soil microbial biomass C and other eco-physiology parameters.


Results/Conclusion

Soil microbial biomass carbon (Cmic) and nitrogen (Nmic) were always higher under the tree canopy than in the open grasslands. Organic carbon (Corg) was also higher under the tree canopies. The Cmic/Corg ratio relates to the microbial activity and its potential to mineralize organic substances. The Cmic/Corg ratio was lower under the tree canopies than in the open grasslands. Less microbial biomass was supported per unit of Corg. Basal activity was always higher under the canopy than in the open grassland.

Trees scattered in the savanna function as islands inducing larger soil microbial communities and higher basal activity under the canopies. Lower Cmic/Corg ratio under the tree canopies suggests a more recalcitrant nature of the litter and a decrease in relative availability of organic matter under the trees.
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Evaluation of a Tomato Waste Biofilter for the Retention of Gaseous Losses from Pig Slurry Hygienization by pH Modification

The use of pig slurry as organic fertilizer in intensive horticulture could be possible after hygienization to avoid contamination of products. This research aimed to evaluate a mixture of a tomato waste and rice husk as biofilter media to reduce NH3, N2O, CO2, and CH4 losses from a simple and low-cost solution for slurry hygienization by pH modification. The experiment was made in a system of laboratory scale biofilters connected to jars filled with raw slurry as control and three treatment methods: acidified slurry, alkalinized slurry, and neutralized slurry. The gas concentrations were measured for 35 days, and the composition of slurries and biofilters were determined. The results of this study showed that the mixture of biofiltering media, composed of tomato waste and rice husk, has the potential to retain NH3 and greenhouse gases (GHG) from a simple and low-cost solution for slurry hygienization by pH modification. Compared to the treatment raw slurry biofilter, the treatment neutralized slurry biofilter, subjected to a combined treatment by alkalinization/neutralization, retained 19% NH3, 4% CO2, and 83% CH4 losses and had no impact on N2O and global warming potential. Thus, the use of tomato waste biofilter during alkalinization did not increase the loss of NH3 and reduced GHG compared to raw slurry, avoiding the subsequent neutralization of slurry for environmental reasons, and could be used as an organic fertilizer in horticulture. However, using the combined alkalinization/neutralization treatment will improve the fertilizer value of the slurry by adjusting the pH from 9.5 to 7.5info:eu-repo/semantics/publishedVersio

Bio-acidification and enhanced crusting as an alternative to sulphuric acid addition to slurry to mitigate ammonia and greenhouse gases emissions during short term storage

Several solutions are today proposed to farmers to minimize ammonia (NH3) emissions during storage. In the present study, special attention was given to slurry acidification and slurry crust enhancement and our objective was to assess the effect of slurry bio-acidification using sugar and cheese whey as an alternative to sulphuric acid, and the potential of rice bran as crust enhancer on NH3 and greenhouse gases emissions during storage. Both the cheese whey and the rice bran are materials, available in large amounts, with low commercial value in some EU regions as Portugal and its use, at farm scale, will be a win-win situation. Sugar is also a good alternative to acid attending its relatively low value. A laboratory experiment was performed for 2 months with five treatments: non-treated cattle slurry (CTRL), slurry treated with sulphuric acid (ACID), slurry treated with sugar (SUGAR), slurry treated with cheese whey (WHEY) and rice bran applied on the slurry surface (RICE). The SUGAR treatment led to a reduction of NH3 emissions by 45% relative to CTRL while WHEY and RICE resulted in a reduction of 68% and 25%, respectively. Nevertheless, this effect of SUGAR and WHEY was shorter than in ACID, since NH3 emissions started to be observed in those 2 treatments after 31 and 35 days of storage, respectively. Nitrous oxide emissions remained close to zero in ACID and SUGAR. RICE led to the highest emissions of carbon dioxide (CO2) releasing almost 5% of carbon present in the initial mixture (slurry þ rice bran) and presented the highest methane emissions. The ACID and SUGAR led to a significant decrease of the total greenhouse gas (GHG) emissions. Our results indicate that bio-acidification using a source of sugar could be a good alternative to H2SO4 to reduce simultaneously NH3 and GHG emissions during storageinfo:eu-repo/semantics/publishedVersio

Nitric oxide and nitrous oxide emissions from cattle-slurry and mineral fertiliser treated with nitrification inhibitor to an agricultural soil: a laboratory approach

Research ArticleThe application of organic and mineral fertilisers to soil can result in increased gaseous emissions to the atmosphere such as nitric oxide (NO) and nitrous oxide (N2O) gases. The aim of this study was to evaluate under laboratory conditions the effects on mineral N dynamics and NO and N2O emissions of application to soil of cattle slurry derived liquid fraction (LF) obtained by screw press and mineral fertiliser (MF), both treated with or without the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP). An aerobic laboratory incubation was performed over 93 days with a Dystric Cambisol amended with mechanically separated LF or mineral fertiliser ammonium sulphate only or combined with DMPP. Two additional treatments were included: soil only and soil amended with DMPP. Nitrogen immobilisation was the dominant process with MF amendment, whereas N mineralisation has been observed with LF. The application of LF reduced significantly NO emissions by 80% relative to mineral but no differences were observed with N2O emissions. The addition of DMPP to MF induced a decrease of 18 and 29% in NO and N2O emissions whereas DMPP combined with LF reduced (numerically but not statistically) these emissions in 20 and 10%, respectively. Results obtained in our study suggest that N (NO + N2O) losses can be mitigated by adding DMPP to mineral fertilisers or replacing mineral fertiliser by LFinfo:eu-repo/semantics/publishedVersio

Remote Sensing (NDVI) and Apparent Soil Electrical Conductivity (ECap) to Delineate Different Zones in a Vineyard

Presented at the 1st International Electronic Conference on Agronomy, 3–17 May 2021The intensification of agriculture has greatly enhanced crop productivity, but also its potential environmental impact. Nutrient recycling and an increase in resource use efficiency are the key points to keep production at high levels with minimum impact. The present work’s goal was to provide new insight on the spatial variability of soil chemical properties in a vineyard. For this, three different zones were identified in a 6.77 ha parcel, according to the remote sensing of apparent soil electrical conductivity (ECap) and the normalized difference vegetation index (NDVI). Soil samples from specific locations were then collected and chemically described, and the resulting data were statistically analyzed. ECap and NDVI appeared to be efficient tools to define different zones within the vineyard, with most of the soil chemical properties varying at the highest significance level (p < 0.001) according to the F test, except for extractable phosphorus (Égner-Rhiem) and organic carbon (TOC method). Overall, our results revealed potential for the implementation of site-specific soil fertilization and soil quality managementinfo:eu-repo/semantics/publishedVersio

Métodos de fraccionamento de metais vestigiais em águas e sedimentos estuarinos

Doutoramento em QuímicaOs metais vestigiais têm um papel importante em sistemas bifásicos água / sedimento tais como a “Ria de Aveiro”. Por outro lado, alguns destes metais podem ser tóxicos para o homem, sendo, por esse motivo, importante estimar a sua mobilidade no ambiente assim como a sua capacidade de migrar na cadeia alimentar. O objectivo principal deste trabalho foi desenvolver e optimizar métodos de fraccionamento de metais vestigiais (Cu, Cd e Pb) em águas e sedimentos estuarinos. Adicionalmente, foi também estudado o carácter operacional da fracção de metal lábil determinada nos estudos de fraccionamento de metais vestigiais em águas naturais. O fraccionamento do cobre, do cádmio e do chumbo em sedimentos foi realizado seguindo a cinética da extracção pelo EDTA destes metais vestigiais. Para tal, foram inicialmente optimizados vários parâmetros experimentais e compararam-se dois protocolos de extracção. As curvas de extracção pelo EDTA em função do tempo, obtidas para os 3 metais estudados, foram depois ajustadas com duas equações cinéticas e dois modelos cinéticos. Provou-se que o modelo de duas reacções de primeira ordem é o mais eficiente para ajustar as curvas de extracção permitindo dividir os metais em três fracções diferentes, a fracção "rapidamente extraível", a fracção "lentamente extraível" e a fracção "inerte". Este método de fraccionamento, em conjunto com este modelo, foram finalmente aplicados a vários sedimentos da Ria de Aveiro e mostrou-se que a composição do sedimento tem influência sobre o fraccionamento do cobre e do chumbo pelo EDTA. O fraccionamento dos metais vestigiais em águas foi realizado com dois métodos diferentes: a voltametria, nomeadamente a voltametria de redissolução anódica (ASV) e a voltametria de redissolução catódica com acumulação adsortiva (AdCSV), e a extracção em fase sólida (SPE) com as resinas Chelex 100 e Amberlite CG-50. Com ambos os métodos, foram optimizados vários parâmetros experimentais antes da sua aplicação à amostras de águas provenientes da Ria de Aveiro. De modo a comparar a fracção lábil de metal determinada com cada método, as várias técnicas de fraccionamento de metais em águas naturais usadas neste trabalho foram, finalmente, aplicadas a uma mesma amostra. Mostrou-se, assim, que a fracção de metal lábil determinada por AdCSV e por SPE com a Chelex 100 é muito semelhante apesar do tempo de análise em cada técnica ser muito diferente. No caso da SPE, estudou-se, ainda, o carácter operacional da fracção de metal lábil determinada com esta técnica e mostrou-se que a extensão da dissociação dos complexos metálicos depende da natureza do metal, dos ligandos e da própria resina utilizada. A SPE foi, ainda, usada para o estudo da labilidade dos complexos metálicos com húmicos.Trace metals are usually present in significant quantities in water/sediment systems such as "Ria de Aveiro" lagoon (Portugal). However, some of this trace metals may be toxic for humans and it becomes of prime importance to be able to assess their mobility, i.e., their ability to migrate to fishes and plants. The aim of this work was to develop and optimise methods of fractionation of trace metals in water and in sediments. The operational character of the labile fraction obtained with methods used to study trace metal fractionation was also evaluated. The fractionation of copper, cadmium and lead in sediments was performed following the kinetic extraction with EDTA. Initially, several experimental parameters were optimised and two extraction protocols have been compared. The curves of extraction by EDTA as a function of time for the three studied metals were adjusted with two kinetic equations and two kinetic models. It has been showed that the two first order reactions model was the most efficient to fit extraction curves and allowed to separate those metals into three fractions: “quickly extractable", "slowly extractable" and an inert fraction. Then, the optimised fractionation method has been applied to several sediment samples from “Ria de Aveiro” (Portugal) and it has been concluded that the composition of sediment influences the copper and lead fractionation by EDTA. The fractionation of trace metals in waters were performed using two methods: voltammetry, namely Anodic Stripping Voltammetry (ASV) and Cathodic Stripping Voltammetry with adsorptive accumulation (AdCSV) and Solid Phase Extraction (SPE) with two resins, Chelex 100 and Amberlite CG-50. Relevant experimental parameters were optimised for both methods and they were, then, applied to water samples from “Ria de Aveiro” lagoon. In order to compare the labile fraction of metal obtained with voltammetric techniques and with SPE, these methods were applied to a same water sample. It was showed that labile fractions obtained with AdCSV and SPE with Chelex 100 were similar even though the analysis time of each technique is very different. SPE was also used to study the operational character of the labile fraction obtained with this technique. It has been shown that the extension of the dissociation of complexed metal depends on the nature of the metal, the ligands and the resin considered. SPE was, also, used to study the lability of humic complexes.Parmi les polluants associés à l’industrialisation et au développement urbain, les éléments traces métalliques font partie des plus préoccupants. En effet, ce sont des contaminants terrestres et aquatiques dont le caractère toxique est rendu insidieux par leur accumulation dans les organismes et par leur bioaccumulation le long des chaînes alimentaires, ce qui les rend dangereux même présents à l’état de traces. Ce sont de plus, des contaminants persistants qui ne sont jamais éliminés mais seulement transférés d’un compartiment naturel à un autre, l’eau étant leur principal vecteur de transport dans leurs cycles biogéochimique. Un effort important est donc fourni afin d’estimer le danger potentiel représenté par ces éléments dans l’environnement. Il est désormais admis que le risque posé par la présence de métaux dans l’environnement ne dépend pas tant de leur concentration totale mais surtout de leur aptitude à migrer de la phase solide vers les eaux interstitielles puis à se fixer sur différents organismes le long de la chaîne alimentaire. Afin d’estimer cette mobilité, il est d’usage de recourir à des études de fractionnements des métaux. Le principal objectif de ce travail repose sur le développement et l’optimisation de méthodes de fractionnement d’éléments traces métalliques dans les eaux et les sédiments d’un système lagunaire. Ainsi, ce travail de décompose en deux parties principales: une première consacrée au fractionnement d’éléments traces métalliques dans les sédiments et une seconde consacrée au fractionnement des éléments traces métalliques dans les eaux. Les métaux considérés sont le cuivre, le cadmium et le plomb. Dans les systèmes aquatiques naturels, les sédiments jouent un rôle clef dans le contrôle des métaux en solution. Par leur capacité d’accumulation, ils reflètent la qualité des eaux en témoignant des pollutions. Mais ils vont aussi, en les accumulant, constituer des réservoirs de polluants susceptibles d’être remobilisés. Ils représentent donc un risque potentiel de pollution des systèmes aquatiques naturels. Les schémas d’extraction séquentielle, qui consistent en l’utilisation successive de différents réactifs afin d’extraire spécifiquement les métaux fixés aux différentes phases du sédiment (matière organique, oxydes de fer, manganèse ou aluminium, carbonates, sulfures…), sont la méthode la plus utilisé pour déterminer le fractionnement d’éléments traces métalliques dans les sédiments. Cependant, de nombreuses critiques ont été élevées contre cette méthode dénonçant, notamment, le manque de sélectivité des réactifs utilisés ou encore la possible ré-adsorption des métaux. Dans ce travail, une approche cinétique du fractionnement a été préférée à ces schémas d’extraction séquentielle. Le fractionnement cinétique consiste en l’évaluation des flux de métaux extraits par un réactif qui est, dans notre cas, l’EDTA. Il s’agit donc d’étudier la cinétique d’extraction d’un métal lié au sédiment. Cette approche à l’avantage d’indiquer, en plus des classiques équilibres de distributions, la labilité relative des complexes formés entre les métaux et les différentes phases du sédiment

Understanding the dynamic of rice farming systems in southern Mozambique to improve production and benefits to smallholders

Rice farming systems (RFSs) in southern Mozambique are very heterogeneous and diversified, which has implications for smallholders’ adoption of each RFS, as well as on rice production and productivity in the region. In this regard, it is important to understand: (i) which RFS typologies can be leveraged to improve rice production and productivity; (ii) the drivers for smallholder farmers’ decisions to adopt an RFS; and (iii) which policies/incentives could enhance existing RFSs. The present study was based on surveys of 341 smallholder rice farmers in the Chókwè Irrigation Scheme (CIS), southern Mozambique. Data on the productivity of rice, size of the herd, and total other crop types were used to frame the RFS typologies. A multinomial logit model (MLM) and multiple linear regression (MLR) were applied to determine the driver for each RFS, and predict the constraints for production and yield. Based on cluster analysis, four typologies of RFSs were identified: the subsistence farming system (FS), specialised rice FS, mixed crops FS, and rice–livestock FS. Farms with longer experience reported applying more fertiliser and seedlings per unit hectare. The availability of labour increased the likelihood of adopting the mixed crops FS and rice–livestock FS. Older households were more likely to adopt the subsistence FS, and live closer to the farming fields. Yield of rice was positively associated with inputs such as fertilisers, pesticides, and seedlings, as well as years of experience of the household. Our results suggest that smallholder farmers need more assistance and technical support to identify and adopt more productive and less costly RFSs in this regioninfo:eu-repo/semantics/publishedVersio