Major Rainfall Research Articles

Rainfall driven and wild-bird mediated avian influenza virus outbreaks in Australian poultry

Globally, outbreaks of Avian Influenza Virus (AIV) in poultry continue to burden economies and endanger human, livestock and wildlife health. Wild waterbirds are often identified as possible sources for poultry infection. Therefore, it is important to understand the ecological and environmental factors that directly influence infection dynamics in wild birds, as these factors may thereby indirectly affect outbreaks in poultry. In Australia, where large parts of the country experience erratic rainfall patterns, intense rainfalls lead to wild waterfowl breeding events at temporary wetlands and increased proportions of immunologically naïve juvenile birds. It is hypothesized that after breeding, when the temporary wetlands dry, increasing densities of immunologically naïve waterbirds returning to permanent water bodies might strongly contribute to AIV prevalence in wild waterfowl in Australia. Since rainfall has been implicated as an important environmental driver in AIV dynamics in wild waterbirds in southeast Australia and wild waterbirds are identified globally to have a role in virus spillover into poultry, we hypothesise that rainfall events have an indirect effect on AIV outbreaks in poultry in southeast Australia. In this study we investigated this hypothesis by examining the correlation between the timing of AIV outbreaks in poultry in and near the Murray-Darling basin in relation to temporal patterns in regional rainfall since 1970. Our findings support our hypothesis and suggest that the risk of AIV outbreaks in poultry increases after a period of high rainfall, with peak AIV risk two years after the onset of the high-rainfall period. This is presumably triggered by increased rates of waterbird breeding and consequent higher proportions of immunologically naïve juvenile waterbirds entering the population directly after major rainfall events, which subsequently aggregate near permanent water bodies when the landscape dries out.

Rainfall shocks and household welfare: Evidence from northern Ghana

CONTEXTRainfall shocks pose a threat to farmers in rural West Africa especially in the wake of the recurrent climate variability and its impacts on agricultural production. Despite the harm they pose, limited empirical studies exist on the welfare implications of rainfall shocks on farmers' welfare in West Africa. In addition, the potential impacts of rainfall induced commodity and labor market failures have not been given much attention in the empirical literature. OBJECTIVEOur study aimed to analyze the impact of negative rainfall shocks and commodity and labor market failures on farm households' welfare in northern Ghana. Examining the impact of commodity and labor market failures amidst the experience of a negative rainfall shock helps to identify the possible entry points through which the adverse impacts of rainfall deficits may be reduced. METHODSThe study is based on a household survey data from the Africa Rising program, historical daily climate data from the CCAFS-Climate data portal and random rainfall distributions from Monte Carlo simulation. A total of 1168 households were considered in the analysis. We analyze the impact of rainfall shocks and the above-mentioned entitlement failures using a static optimization model that incorporates a crop yield response function. RESULTS AND CONCLUSIONWe found that an increase in the frequency of negative rainfall shocks under a dry future with and without entitlement failures would impact negatively on the total income and consumption levels of both the asset non-poor and asset poor households in the study area. The asset poor households would however bear the brunt of the impact, and the anticipated impact would mostly be yielded through changes in agricultural incomes and expenditure on food purchases. With increasing risk of dry rainfall conditions, total incomes of farmers could decrease by 7.3% to 45.5%. It was found that ignoring potential failures in commodity and labor markets lead to over/underestimation of the impacts of major rainfall deficits on the different types of farmers. The impact of rainfall shocks on the welfare of farmers is scenario and cluster dependent. SIGNIFICANCEThe results have significance for policy formulation and future research. The findings from this study indicate a need for targeting and acknowledgement of the differential impacts of climate shocks on the different farmer groups. Efforts made in future research to incorporate entitlement failures in climate impact studies could produce more informative guide for effective policy formulation.

Where Does Moisture Come From Over the Congo Basin?

AbstractThe Congo Basin hosts the world's second largest rainforest and is a major rainfall center. However, the primary sources of moisture needed to maintain this forest, either from evapotranspiration (ET) or advection from the ocean, remain unclear. We use satellite observations of the deuterium content of water vapor (), solar induced fluorescence (SIF), precipitation, and atmospheric reanalysis to examine the relative contribution of ET to moisture in the free troposphere. We find that SIF, an indicator of photosynthesis, covaries with in early rainy seasons, suggesting that ET is an important contributor to atmospheric moisture in both the spring and fall rainy seasons. However, the relative contribution of ET to the free tropospheric moisture varies between the two rainy seasons. Observed relative to a range of observationally constrained, isotopic mixing models representative of water vapor coming from land suggests that of the free tropospheric moisture come from ET in February, and in April, versus in August and in October. Reanalysis indicate that this difference between seasons is due to increased advection of ocean air during the fall season, thus reducing the relative contribution of ET to the Congo Basin in the fall. In addition, ET is the primary atmospheric moisture source in the winter and summer dry seasons, consistent with estimates reported in literature. Our results highlight the importance of ET from the Congo rainforest as an important source of moisture for initiating the rainy seasons.

Polycyclic Aromatic Hydrocarbons and Quinones in Urban and Rural Stormwater Runoff: Effects of Land Use and Storm Characteristics

Changes in streamwater concentrations in two creeks draining contrasting urbanized landscapes in southern Ontario, Canada, during a major summer rainfall event were used to assess how land use and ...

The Current Status of Opportunities for Rice Cultivation in Uganda

The purpose of this article is to explore the current status of opportunities in the Ugandan rice sector in order to form informed decisions for future investment and support for the farmers. The Government of Uganda has prioritised rice as a strategic commodity for the national economy. Uganda produces up to 350,000 metric ton (MT) of rice annually, and has set a target to produce 680,000 MT by 2020. A national rice development strategy and a robust rice stakeholder platform have been put in place in order to guide potential investors. Despite the already-existing economic opportunities for the smallholder farmers who participate in producing more than 90% of the rice output in Uganda, productivity still remains low. This is primarily due to the frequent use of low-yielding rice varieties, limited farmer access to the seed of improved varieties and other yield-enhancing inputs, the limited usage of time and labour-saving technologies, and limited knowledge of good agronomic practices. There are three major high rainfall areas in the Northern, Eastern, and Western parts of the country. The mean annual rainfall is estimated at 1,180 mm, and the mean annual temperature is within the range of 18 to 35oC. Nine major varieties of rice, including Namche, Komboka, Kaiso, Wita 9, Basmat 370, IR 64, Supa, Buyu, and NERICA are being cultivated in Uganda. The two Korean rice varieties, such as KAF- 172-67 and KAF-304-287 strains, which were developed through a Korea-Africa Food & Agriculture Cooperation Initiative (KAFACI) project, will also be registered. This will help to increase domestic rice production, stabilize domestic prices, and make rice more affordable for consumers.

Epiphytotics of chickpea Ascochyta blight in Turkey as influenced by climatic factors

Chickpea Ascochyta blight caused by Didymella rabiei is one of the most important fungal diseases affecting yield and seed quality negatively in Turkey. Breeding efforts against this devastating disease fail as the resistance/tolerance is broken in a short period of their commercial cultivation. This study was aimed to determine the status of Ascochyta blight epiphytotics and the effect of climatic factors on the disease incidence and severity in Turkey. Chickpea fields were surveyed for disease prevalence and severity in forty-five major chickpea-growing provinces in 9 climatic regions in the cropping season 2014, 2015, and 2016 in Turkey. The data on major weather parameters, i.e., rainfall (mm), air temperature (oC) and relative humidity (%), were procured from Ministry of Agriculture and Forestry, Turkey, and correlations among disease severity, altitude, weed density, nodule numbers, and climatic conditions were calculated. Principal component analysis was studied to determine the complex effects of all the variables on Ascochyta disease severity. It was observed that there was significant difference in percent incidence and severity of Ascochyta blight among the 45 provinces representing nine agro-climatic regions during the period under study. The highest disease incidence and severity (%) were recorded in Bosporus, Black Sea, Aegean and Mediterranean regions, while it was the lowest in Eastern Anatolia and Southeastern Anatolia. Negative correlation was recorded between disease severity and altitude and temperature, and that relative humidity (%) and rainfall (mm) showed statistically positive correlation with the disease severity. The disease severity was not effected by nodule numbers and weed density ratios.

Mobilization and transport of pesticides with runoff and suspended sediment during flooding events in an agricultural catchment of Southern Brazil

Brazil is one of the largest consumers of pesticides in the world, and these chemicals present a high contamination risk for the country's water bodies. The mechanisms of mobilization and transport of pesticides from cropland to river systems are controlled by runoff and erosion processes occurring at the catchment scale. In addition to the excessive use of pesticides, the transport processes of these substances are also accelerated by inadequate soil management and the absence of soil conservation measures at the catchment scale. The current research relied on hydrological monitoring to investigate the transport and persistence of pesticides in response to hydrological dynamics. The study was conducted in the Conceição River watershed where runoff and suspended sediment fluxes are continuously monitored at the outlet. This study area is representative of the grain production system in southern Brazil including the application of large amounts of pesticides combined with extensive runoff and erosion problems. Sample collection in the river for pesticide analysis included the analysis of both water and suspended sediment. The sediment deposit analysis was performed in a single location at 4 depths. Results demonstrate the occurrence of pesticides including simazine, 2,4-D, carbendazim, imidacloprid, tebuconazole, propiconazole, tetraconazole, and trifloxystrobin in water, while glyphosate and AMPA were detected in suspended sediments, and AMPA and carbendazim were found in sediment deposits. The study demonstrated the strong dependence of the mechanisms of pesticide mobilization and transport in the catchment with the intra- and interevent variability of hydro-sedimentary processes. Pesticide detections can be related to several factors, including the magnitude of the rainfall event, the period of pesticide application, or the transport of suspended sediment. All these factors are correlated, and the mechanisms of transportation play an important role in the connections between sink and sources. The results suggest that pesticide monitoring should take into account the runoff and erosion pathways in each particular catchment, and it should especially include the monitoring of major rainfall events for identifying and quantifying the occurrence of pesticides in the environment. The transport of pesticides indicates to be potentiated by intensive pesticide use, the magnitude of rainfall-runoff events, and the absence of runoff control measures (e.g., terracing). These results demonstrate that water and soil conservation techniques should be planned and coordinated at the watershed scale to reduce the connectivity of water and sediment flows from agricultural areas to river systems with the implementation of effective runoff control practices. This will control the mobilization agents (runoff), as well as limit the connection between the sources and the water bodies.

Repeated high flows drive morphological change in rivers in recently deglaciated catchments

AbstractClimate change is decreasing glacier cover and increasing the frequency and magnitude of precipitation‐driven high flows and floods in many regions of the world. Precipitation may become the dominant water source for river systems in recently deglaciated catchments, with major rainfall events driving significant changes in river channel morphology. Few studies, however, have examined river channel response to repeated precipitation‐driven high flows. In this study, we measured the geomorphological condition of four low‐order rivers in recently deglaciated catchments (70–210 years ice free) before and after a series of repeated precipitation‐driven high flows during summer 2014. High flows drove substantial initial morphological change, with up to 75% change in baseflow channel planform position and active channel form change from pre‐ to post‐high flow. Post‐high flow years were associated with increased instream wood and geomorphological complexity at all but the youngest river. Channel changes were part of an active relaxation stage at all rivers, where channels continued to migrate, and complexity varied through time. Overall, these measurements permit us to propose a conceptual model of the role of geomorphologically effective high flows in the context of paraglacial adjustment theory. Specifically, we suggest that older rivers in recently deglaciated catchments can undergo a short‐term (<10 years) increase in the rate of geomorphological development as a result of the recruitment of instream wood and channel migration during and following repeated precipitation‐driven high flows. Enhancing our knowledge of these geomorphological and paraglacial processes in response to high flows is important for the effective management of riverine water and ecosystem resources in rapidly changing environments.

Spatiotemporal Rainfall Distribution of Soan River Basin, Pothwar Region, Pakistan

This study evaluates the spatiotemporal rainfall variability over the semimountainous Soan River Basin (SRB) of sub-Himalayan Pothwar region, Pakistan. The temporal rainfall trend analysis of sixteen rain gauges was performed on annual basis with long-term (1981–2016) data. The results depicted that there is substantial year-to-year and season-to-season variability in rainfall patterns, and rainfall patterns are generally erratic in nature. The results highlight that most of the highland rainfall stations showed decreasing trends on annual basis. The central and lowland stations of the study area recorded an increasing trend of rainfall except for Talagang station. The average annual rainfall of the study area ranges between 492 mm and 1710 mm in lowland and high-altitude areas, respectively. Of the whole year’s rainfall, about 70 to 75% fall during the monsoon season. The rainfall spatial distribution maps obtained using the inverse distance weighting (IDW) method, through the GIS software, revealed the major rainfall range within the study area. There is a lack of water during postmonsoon months (November–February) and great differences in rainfall amounts between the mountainous areas and the lowlands. There is a need for the rational management of mountainous areas using mini and check dams to increase water production and stream regulation for lowland areas water availability. The spatiotemporal rainfall variability is crucial for better water resource management schemes in the study area of Pothwar region, Pakistan.

Plot test in a 50-year abandoned mine tailings dam

Knowing the evolution of water content in a tailings dam is essential when analysing its stability. The case study is a small tailings dam abandoned more than 50 years ago, located in the Andes region of San Juan province, Argentina, where the climate is arid. This paper presents the results obtained in a plot test to study the interaction of tailings with the atmosphere, and to explain the reasons that generate internal zones in the dams with surprisingly high degrees of saturation, despite the strong water deficit of the site. The plot was hydraulically isolated on the four lateral faces where ten capacitive sensors were installed at different depths (volumetric moisture, matrix suction and temperature). At the beginning of the test, a major rainfall event was simulated with a sprinkler irrigation system. The plot was then allowed to interact freely with the atmosphere for an additional period of one and a half years. The records obtained suggest that the stratigraphy of the hydraulically deposited tailings has a preponderant influence on the interaction with the atmosphere. Heterogeneous flow phenomena and multiple capillary barriers during the infiltration and evaporation processes, respectively, appear to control the long-term moisture state of the tailings dam.

Analysis of Major Rainfall Factors Affecting Inundation Based on Observed Rainfall and Random Forest

It is important to analyze urban floods according to uncertain rainfall patterns. This study was carried out to determine key statistical characteristics of rainfall affecting the occurrences of flooding by using observed rainfall, one- and two-dimensional hydraulic analysis models, and random forests. The target area selected was the Centum City area of Busan, where flooding occurs frequently with heavy rainfall. For analysis, the rainfall data from the Automatic Weather System (AWS) and radar observatory in the entire city of Busan were collected. Using the results from the one- and two-dimensional numerical models, the occurrence of flooding was determined according to the observed rainfall events. The random forest was used to classify the presence or absence of flooding according to the statistical characteristics of rainfall, and the importance evaluation function was applied to determine the impact of each statistical factor. The three main statistical factors of rainfall with the greatest impact on the occurrence of flooding were analyzed as the 1-hr maximum rainfall, the average rainfall, and the skewness. On the other hand, the three main factors affecting the maximum flood depth were the 3-hrs maximum rainfall, the 1-hr maximum rainfall, and the total rainfall. It is judged that the results of this study will be useful in suggesting quantitative urban flood forecasting standards when rainfall is examined in real-time by using various observation equipment.

Seasonal Rainfall Variability and Arable Farming within the Dry Equatorial: Evidence from the Effutu Municipality

Over the past three decades, one of the major problems that confront developing economies in Africa is the impact of climate variability on agricultural development. In the face of seasonal rainfall variation and the rain-fed nature of farming, agriculture, which is the main source of livelihood for most communities in Ghana, is threatened. The study sought to ascertain the impact of seasonal rainfall variation on arable farming within the Dry Equatorial climate of Ghana, focusing on evidence from the Effutu Municipality. Using coefficient of variation (CV) and the Precipitation Concentration Index (PCI) models, rainfall data spanning for twenty-three years obtained from the Ghana Meteorological Authority were analysed for interseasonal and interannual patterns and variability. The Pearson moment correlation coefficient was used to induce a statistical index to establish the relationship between rainfall distribution and crop yield, particularly for rice production. The findings of the study revealed a high coefficient of variation for both the major and minor rainfall seasons for the past two decades with a corresponding relatively high PCI for the period. This suggests high variability in rainfall patterns in the two seasons over the past twenty years with detection of a general decline in rainfall amounts. A moderate positive P-value for rainfall and crop yield indicates that rice production output is dependent on rainfall patterns within the Effutu Municipality. High rainfall amounts were associated with more rice outputs and vice versa. The study recommends on-farm adaptive practices such as mulching, use of drought-resistant varieties, and government-supported irrigated farming.

Extreme rainfall events and cooling of sea turtle clutches: Implications in the face of climate warming.

Understanding how climate change impacts species and ecosystems is integral to conservation. When studying impacts of climate change, warming temperatures are a research focus, with much less attention given to extreme weather events and their impacts. Here, we show how localized, extreme rainfall events can have a major impact on a species that is endangered in many parts of its range. We report incubation temperatures from the world's largest green sea turtle rookery, during a breeding season when two extreme rainfall events occurred. Rainfall caused nest temperatures to drop suddenly and the maximum drop in temperature for each rain‐induced cooling averaged 3.6°C (n = 79 nests, min = 1.0°C, max = 7.4°C). Since green sea turtles have temperature‐dependent sex determination, with low incubation temperatures producing males, such major rainfall events may have a masculinization effect on primary sex ratios. Therefore, in some cases, extreme rainfall events may provide a “get‐out‐of‐jail‐free card” to avoid complete feminization of turtle populations as climate warming continues.

Prevalence and seasonal trends of malaria at general hospital, Palanpur Banaskantha, Western part of India

Aim: Malaria is one of the known endemic disease in India. Malaria is transmitted by infected female anopheles mosquito vector transmitting mainly two Plasmodial species named P. falciparum and P. vivax. Prevalence of malaria is affected by atmospheric and socioeconomic condition of geographical area. Aim of the study is to know the prevalence of malaria and the seasonal trend of malaria at general hospital Palanpur, Banaskantha in western part of India. Material and Methods: This study was carried out at Central Laboratory, General Hospital, Palanpur, Banaskantha over period of July 2014 to June 2018. 41660 samples from fever patients were collected. We used Microscopic examination for the diagnosis of malaria by preparing thick and thin smears from these 41660 samples and stained using field stain. Results: We had collected total 41660 samples of fever patients. Out of 41660 samples, 688 samples were detected positive for malaria. So prevalence of malaria in our hospital was 1.65%. Prevalence of P. Vivax, P. Falciparum and mixed (infection of P. Falciparum and P. Vivax at a same time) were found 77.90%, 21.80% and 0.30% respectively. Malaria was seen relatively higher in males and affecting 15-30 years of age group more. Most cases of malaria were found in months of September and October near the end of monsoon and post monsoon season. Conclusion: From our study we concluded that there was high prevalence of P. vivax than P. Falciparum infection. Maximum numbers of cases were after major rainfall, reported in month of September and October. Morbidity and mortality of malaria must be reduced by strengthening Malaria Surveillance, risk factor assessment during pre and postmonsoon period. Premonsoon preventive actions need strengthening and strict monitoring of all these actions are needed. Keywords: Prevalence, Plasmodium vivax, Plasmodium falciparum, Malaria, Thin and Thick smear, Seasonal trends.

Evaluating the estrogenicity of an effluent-dominated river in California, USA: Comparisons of in vitro and in vivo bioassays

Estrogenically active compounds (EACs) in surface waters can disrupt the endocrine system of biota, raising concern for aquatic species. Concentrations of EACs are generally higher in effluent-dominated aquatic systems, such as California's Santa Ana River (SAR). Addressing estrogenicity of effluent-dominated waters is increasingly important due to both increasing urbanization and climate change. To this end, water samples were collected from multiple sites downstream of wastewater treatment plants (WWTPs) and intermittent points along the SAR during 2018–2019 and cell-based bioassays were used to determine estrogen receptor activity. During baseflow conditions, the highest estradiol equivalencies (EEQs) from all SAR water between summer (August and September) and fall (November) sampling events in 2018 were from Yorba Linda (EEQ = 1.36 ± 0.38 ng/L) and Prado (1.14 ± 0.13 ng/L), respectively. Water extracts in January 2019 following a major rainfall generally had higher EEQs with the highest EEQ of 10.0 ± 0.69 ng/L observed at Yorba Linda. During low flow conditions in November 2018, male Japanese medaka (Oryzias latipes) fish were exposed to SAR water to compare to cell bioassay responses and targeted analytical chemistry for 5 steroidal estrogens. Chemical-based EEQ correlations with in vitro EEQs were statistically significant. However, vitellogenin (vtg) mRNA expression in the livers of medaka exposed to SAR water was not significantly different compared to controls. These results indicate that seasonal variation and surface water runoff events influence estrogenic activity in the SAR and may induce estrogenic effects to native fish populations in wastewater-dominated streams in general.

Automated Mapping of Water Table for Cranberry Subirrigation Management: Comparison of Three Spatial Interpolation Methods

In this paper we first compare three different methods of spatial interpolation, i.e., inverse distance weighting (IDW), thin plate splines (TPS), and kriging on weekly water table depth (WTD) measurements from 80 observation wells in two cranberry farms (Farm A and Farm B) located in Québec, Canada. We use the leave-one-out cross-validation approach to assess the performance of the methods. Second, we evaluate the influence of the density of measurement points over the interpolation error for the cited methods. Third, we assess the performance of drainage systems and their impacts on crop productivity as a result of cumulative rainfall. Results along with practical considerations show that TPS is the best interpolator for WTD and this superiority is maintained and further demonstrated through a sensitivity analysis of the methods to spatial sampling density, i.e., partitioning the data into subsets of 25, 50, and 75% of the dataset. However, the random approach for selecting these subsets shows an unexpected result; that is, the interpolation methods exhibit a higher performance in terms of the Pearson correlation (r) for the 25% data subset at Farm B. Meanwhile, the cumulative precipitation over a three-day period, the maximum time required to return the soil matric potential to the optimal value after a major rainfall event, had a steady influence on WTD and thus crop productivity in the studied farms. This influence is more apparent for Farm A, but a rather random effect is noted for Farm B. This study presents a water-management-based strategy that mitigates the supplementary cost and effort for sensor deployment in water table monitoring for cranberry production. It is therefore of practical interest to cranberry growers and decision-makers who aim to maximize yields through water-management-oriented strategies.

Object-Based Comparison of Data-Driven and Physics-Driven Satellite Estimates of Extreme Rainfall.

The Global Precipitation Measurement (GPM) constellation of spaceborne sensors provides a variety of direct and indirect measurements of precipitation processes. Such observations can be employed to derive spatially and temporally consistent gridded precipitation estimates either via data-driven retrieval algorithms or by assimilation into physically based numerical weather models. We compare the data-driven Integrated Multisatellite Retrievals for GPM (IMERG) and the assimilation-enabled NASA-Unified Weather Research and Forecasting (NU-WRF) model against Stage IV reference precipitation for four major extreme rainfall events in the southeastern United States using an object-based analysis framework that decomposes gridded precipitation fields into storm objects. As an alternative to conventional "grid-by-grid analysis," the object-based approach provides a promising way to diagnose spatial properties of storms, trace them through space and time, and connect their accuracy to storm types and input data sources. The evolution of two tropical cyclones are generally captured by IMERG and NU-WRF, while the less organized spatial patterns of two mesoscale convective systems pose challenges for both. NU-WRF rain rates are generally more accurate, while IMERG better captures storm location and shape. Both show higher skill in detecting large, intense storms compared to smaller, weaker storms. IMERG's accuracy depends on the input microwave and infrared data sources; NU-WRF does not appear to exhibit this dependence. Findings highlight that an object-oriented view can provide deeper insights into satellite precipitation performance and that the satellite precipitation community should further explore the potential for "hybrid" data-driven and physics-driven estimates in order to make optimal usage of satellite observations.

Roles of the Tibetan Plateau vortices in the record Meiyu rainfall in 2020

AbstractMeiyu rainfall in June–July of 2020 hit the Yangtze‐Huaihe River basin, and the precipitation at lots of observational stations broke the records, inducing severe disasters there. Tibetan Plateau vortices (TPVs) generated over the Tibetan Plateau are local major rainfall triggers. In previous knowledge, TPVs can affect the rainfall in eastern China, only after emigrating from the Tibetan Plateau. In this work, roles of TPVs in the record Meiyu are revealed, implying that the effects of TPVs may be underestimated previously. Firstly, TPVs dying out over the Tibetan Plateau may be transformed into troughs and continue to move eastward, influencing the rainfall in Yangtze‐Huaihe River basin. Secondly, southwest vortices, the important rainfall producers in China, tend to be generated and maintained when TPVs are located over eastern plateau. The results give extended knowledge on the effects of TPVs, which are beneficial for the rainfall prediction in eastern China.

Nitrous oxide emissions and nitrogen use efficiency in wheat: Nitrogen fertilization timing and formulation, soil nitrogen, and weather effects

AbstractImproving N fertilization in croplands could minimize soil emissions of nitrous oxide (N2O) and mitigate climate change. This study investigated the effects of spring vs. fall N applications of conventional vs. enhanced‐efficiency N fertilizers (EENFs) on N2O emissions and N use efficiency in spring wheat (Triticum aestivum L.) over 2.5 yr in Alberta, Canada. Fertilizers were anhydrous ammonia and urea and the EENF formulations included urease and nitrification inhibitors and a polymer coating. We measured a fertilizer N2O emission factor of 0.31 ± 0.04%. Irrespective of N fertilizer and timing options peak N2O emissions were evident following soil thawing and major rainfalls. Because most of the annual N2O emissions were associated with soil thawing, spring‐applied N emitted half the N2O of the fall‐applied N during the second study year (P < .001). Conversely, the opposite was observed for the first study year when overall N2O emissions were 36% larger for spring‐ than fall‐applied N (P = .031) as major rainfalls occurred shortly after the spring N fertilization. Nevertheless, within this first study year, EENFs significantly reduced N2O emissions (by 26% on average; P = .019), with a tendency for 11% higher grain yield across springtime EENFs than for conventional fertilizers. Concomitantly, spring‐applied N doubled the fertilizer N recovery efficiency in the same year (P = .023). The soil at the study site inherently had high N availability (NH4 and NO3) and this probably moderated the beneficial effects of EENFs on N2O emissions and grain yields. Results suggest that spring EENFs can mitigate the risk for N2O emissions while sustaining high yields even under scenarios with high availability of native soil N.

Impacts of wildfire and post‐fire land management on hydrological and sediment processes in a humid Mediterranean headwater catchment

AbstractThe extensive afforestation of the Mediterranean rim of Europe in recent decades has increased the number of wildfire disturbances on hydrological and sediment processes, but the impacts on headwater catchments is still poorly understood, especially when compared with the previous agricultural landscape. This work monitored an agroforestry catchment in the north‐western Iberian Peninsula, with plantation forests mixed with traditional agriculture using soil conservation practices, for one year before the fire and for three years afterwards, during which period the burnt area was ploughed and reforested. During this period, continuous data was collected for meteorology, streamflow and sediment concentration at the outlet, erosion features were mapped and measured after major rainfall events, and channel sediment dynamics were monitored downstream from the agricultural and the burnt forest area. Data from 202 rainfall events with over 10 mm was analysed in detail. Results show that the fire led to a notable impact on sediment processes during the first two post‐fire years, but not on streamflow processes; this despite the small size of the burnt area (10% of the catchment) and the occurrence of a severe drought in the first year after the fire. During this period, soil loss at the burnt forest slopes was much larger than that at most traditionally managed fields, and, ultimately, led to sediment exhaustion. At the catchment scale, storm characteristics were the dominant factor behind streamflow and sediment yield both before and after the fire. However, the data indicated a shift from detachment‐limited sediment yield before the fire, to transport‐limited sediment yield afterwards, with important increases in streamflow sediment concentration. This indicates that even small fires can temporarily change sediment processes in agroforestry catchments, with potential negative consequences for downstream water quality.