Relative Yield Loss Research Articles

Estimating Actual Evapotranspiration over a Large and Complex Irrigation System of the Nile Delta in Egypt

In the Nile Delta region of Egypt, measurements of Actual Evapotranspiration (ETa) and Potential Evapotranspiration (ETp) are difficult, expensive and labor-intensive. The current paper aimed at finding the superior method for estimating the ETa and ETa/ETp in the Nile Delta governorates by comparing different methods. Three different methods were used for ETa estimates being; Remote Sensing approach by Moderate Resolution Imaging Spectroradiometer (MODIS) ETa-product (MOD16A2), FAO (33) method, and Irrigation Water Balance Calculation (IWBC) method. The three ETa methods were applied for five governorates in 2017, where the data for IWBC were available. However, only MOD16A2 was compared with FAO (33) for ETa/ETp ratio and the two selected methods were applied for all eight Nile Delta governorates for the period of 2008 -2017. The MOD16A2 product was derived from the MODIS satellite images using an improved evapotranspiration algorithm based on the Penman-Monteith equation. FAO (33) was based on the relationship between the relative yield loss of any crop to relative reduction of water consumption. The IWBC required estimation of both; the field application and conveyance water losses as the only unknown elements of irrigation water balance in Delta governorates. For comparison between applied methods, descriptive statistics, analysis of variance (ANOVA) for checking difference, and cluster analysis were applied. The results showed a significant difference values between MOD16A2 and FAO (33) for estimating ETa/ETp ratios. However, the difference for ETa estimation was insignificant between the three methods indicating a significant relationship, with a strong correlation between MOD16A2 and IWBC. It was observed that ETa values were impacted by the cropping pattern, since they were very close in governorates having the same dominant crops. In conclusion, both MOD16A2 and IWBC can be utilized for ETa estimation. Both MOD16A2 and FAO (33) are not confirmed for estimation of ETa/ETp ratio due to the significant difference between both results. FAO (33) cannot be utilized for both ETa and ETa/ETp ratio estimates. Further data collection and investigation on ETa and ETp estimates methods are recommended.

Large regional differences of soil water limitation effect on ozone induced yield loss for wheat and potato in Switzerland

The accumulated stomatal ozone (O3) uptake over a threshold (Phytotoxic Ozone Dose POD6), calculated by an ozone deposition model, has been shown to be the most appropriate metric to quantify negative effects of O3 on food crops. In this study we used data of 13 sites in different regions of Switzerland with multiple years of O3 measurements to quantify the stomatal O3 uptake and the related yield loss of wheat and potato. Flux patterns for different years were calculated with the DO3SE model to disentangle the influence of contrasting seasonal environmental conditions. Regional and inter-annual differences in meteorological conditions led to considerable variations in soil water conditions and the POD6 values for wheat. Potato stomatal uptake was much less influenced by soil water and showed a more even distribution of POD6 values across sites and years. The estimated nationally and temporally average yield loss was 3.2 ± 1.2% for wheat and 2.4 ± 0.8% for potato, calculated based on an area weighting.It was found that soil water deficit, observed frequently in the western part of Switzerland, had a large attenuation effect on stomatal O3 uptake by wheat and on corresponding yield losses. This highlights the importance of including soil moisture limitation in O3 uptake modelling even in moist climatic regions. The comparison of modelled evapotranspiration with water flux measurements over a wheat field showed a reasonable agreement concerning the temporal pattern and the magnitude. But it is also concluded that the DO3SE soil moisture module will need further testing and adaptation to improve accuracy of the model in dryer conditions.

Incidence of Root-Knot Nematode (Meloidogyne graminicola) and Resulting Crop Losses in Paddy Rice in Northern India.

Surveys of major rice growing districts in the state of Uttar Pradesh in Northern India were conducted for 3 consecutive years during 2013 to 2015 under a government-funded major research project to determine the frequency of occurrence and disease incidence of the rice root-knot nematode, Meloidogyne graminicola, in rice paddy fields. More than 800 paddy fields from 88 Tehsils (divisions within a district) in 18 major rice growing districts in Uttar Pradesh were surveyed, where M. graminicola was associated with root-knot disease in rice paddy fields based on morphological and molecular characterization of juveniles and adults. The highest frequency of disease in rice fields was observed in Aligarh (44.6%), followed by Muzaffarnagar, Shahjahanpur, and Kheri Lakhimpur (29.3, 28.0, and 27.4%, respectively). Maximum disease incidence was also recorded in Aligarh (44.6%), followed by Sultanpur, Mainpuri, and Muzaffarnagar (5.7, 5.2, and 4.5, respectively). Gall index and egg mass index values (on a 0 to 10 scale) were highest in Aligarh (3.5 and 2.1, respectively), followed by Muzaffarnagar (2.6 and 2.0) and Mainpuri (2.3 and 1.8). The average soil population of M. graminicola was highest in Aligarh (3,851 ± 297 second-stage juveniles [J2]/kg of soil), followed by Muzaffarnagar (2,855 ± 602 J2/kg of soil), whereas the lowest population was recorded in Barabanki (695 ± 400 J2/kg of soil) at the time of harvesting. Relative yield losses were also determined, and the highest yield loss attributed to M. graminicola infestation was recorded in Aligarh (47%). The yield loss was linearly correlated with the soil population density of M. graminicola and disease incidence.

Verification of Fungicide and Its Application Frequency for Management of Frog eye Leaf Spot (Cercospora capcisi) on Hot Pepper Under Rain Fed Condition at Bako

Cercospora leaf spot is caused by Cercospora capcisi is an important disease which reduces the productivity of hot pepper (Capsicum spp.). Field experiment was conducted to evaluate different fungicides and its application frequencies against Cercospora leaf spot in order to select an important fungicides and its application frequency at Bako Agricultural Research Center. The experiment was laid out in randomized complete block design with three replication. Two different fungicides (Mancozeb 80WP and Trust-Cymocop 439.5WP) and four application frequencies (two, three, four and five) times with untreated control were used. Data on disease severity, area under disease progress curve, marketable yield and unmarketable yield of hot pepper were recorded. The result revealed that, both fungicides sprayed control Cercospora leaf spot which is significantly different from untreated check in disease severity, area under disease progress curve (AUDPC) and marketable yield. However, application frequencies of fungicides were not significantly different on disease severity, AUDPC and marketable yield of the plant. Application of Trust Cymocop 439.5WP reduces 26.67% relative yield loss of hot pepper over control check. An economic analysis was done for fungicides and shows feasibility of fungicide application for management of Cercospora leaf spot. Fungicide which has the highest Marginal Rate of Return was used for recommendation. Two times application of Trust-Cymocop 439.5WP was recommended to reduce disease severity and yield loss of the plant. Keywords: Cercospora leaf spot, frequency, hot pepper, and trust-Cymocop 439.5WP DOI : 10.7176/JBAH/9-20-01 Publication date :October 31 st 2019

Cropland acidification increases risk of yield losses and food insecurity in China

Distinct cropland acidification has been reported in China due to nitrogen (N) fertilizer overuse. However, the impacts on food production and thereby on food security are largely unknown. Yield losses in the period 1980–2050 were therefore assessed by simulating soil pH changes combined with derived pH-yield relationships for wheat, maize and rice. If the N fertilizer input continues to increase at 1% annually, the predicted average soil pH decline is about one unit and relative yield losses are expected to increase from approximately 4%–24% during 2010–2050. If the N fertilizer increase stops in 2020 (N2020), the expected losses are approximately 16% in 2050, which is comparable to a scenario of 100% crop residue return (100%RR). However, if 30% of the N fertilizer is replaced by manure N (30%MR), the losses reduce to near 5% in 2050. Soil acidification was predicted to reverse and expected losses are only 2.5% in 2050 in a combined scenario of N2020, 100%RR and 30%MR. Our results illustrate the potential food insecurity induced by cropland acidification and address the necessity of mitigation.

Impacts of current ozone pollution on wheat yield in China as estimated with observed ozone, meteorology and day of flowering

Wheat yield loss due to ambient ozone (O3) and the associated economic losses in China were evaluated for years 2015 and 2016 using for the first time measured O3 concentration ([O3]) and meteorological data as well as phenological observations. Relative yield losses (RYL) were estimated using response functions based on both O3 exposure and flux metrics: AOT40 (the accumulated hourly [O3] over a threshold of 40 ppb) and POD12 (Phytotoxic Ozone Dose over a threshold of 12 nmol O3 m−2 s−1). Both metrics showed consistent spatial patterns being highest in the North China Plain, the largest wheat-producing area in China, followed by some provinces in Yangtze River region. The higher stomatal conductance in areas with high [O3] in year 2015 contributed to higher POD12 values than in 2016. The RYLs for the whole China estimated with AOT40 were 17.1% and 18.1% for years 2015 and 2016, respectively, whereas those with POD12 were lower, 10.6% and 10.2%, respectively. Wheat production losses as translated to annual economic losses were 10 304 and 10 745 million USD (AOT40) or 5912 and 5554 million USD (POD12), for 2015 and 2016, respectively. The O3 impact estimated with monitoring data suggests its overestimation by some of the previous studies based on model estimates of surface [O3]. The overestimation could be attributed to the uncertainties in estimating meteorological variables and [O3], particularly the omission of the correction for the vertical gradient of [O3] near crop canopy in some studies.

Effects of ozone on the growth and yield of rice (Oryza sativa L.) under different nitrogen fertilization regimes.

To examine whether the sensitivity of growth and yield of rice (Oryza sativa L.) to ozone (O3) varies under different nitrogen (N) fertilization conditions, rice cultivar 'Koshihikari' was exposed to O3 under either standard N (SN) fertilization or no N (NN) fertilization. The rice plants were subjected to three gas treatments (charcoal-filtered air (CF) and O3 at 1.0 (1.0×O3) and 1.5 (1.5×O3) times the ambient concentration) in combination with two conditions of N fertilization. At five time points throughout the growth period, plant samples were collected to measure the leaf area and dry mass of each plant organ. At the final harvest, yield, yield components, and harvest index were measured. There was a significant interactive effect of O3 and N on leaf, stem, root, and whole-plant dry mass at the final harvest. The dry mass of each plant organ and the whole-plant dry mass of rice plants grown in 1.5×O3 were significantly lower than those in the plants grown in CF and 1.0×O3 under SN, whereas there were no significant differences in the dry mass among the three gas treatments under NN. Brown rice yield was significantly reduced by the exposure to O3 under SN, but not under NN. Relative yield loss rate based on the AOT40 (accumulated exposure over a threshold of 40nmolmol-1) was pronounced under SN, whereas relative yield was almost unchanged at different AOT40 levels under NN. We concluded that the sensitivity of growth and yield of rice to O3 is dependent on N levels in the soil; the exposure to ambient levels of O3 has a negative effect on rice under SN, but not under NN.

Response of chickpea varieties and sowing dates for the management of chickpea ascochyta blight (Ascochyta rabiei (Pass.) Disease at West Belesa District, Ethiopia

A two year experiment was conducted at Ascochyta rabiei sick plot infested West Belesa District to evaluate potential chickpea varieties and sowing date for the management of Ascochyta blight. Five varieties namely, Dhera, Habru, Ejeri, Chefe, Teje; and three sowing dates at 10-day intervals (15th July (early), 25th July (optimum) and 5th August (late) were used as treatments. Treatments were arranged in split plot design with three replications. Varieties were assigned on main plot and sowing date to sub-plot. Results indicated that the maximum incidence and severity of 44.65 and 30.06% respectively were recorded from Teje variety in early sowing while the minimum incidence and severity of 28.1 and 15.45%, respectively were recorded from Dhera variety in optimum sowing. The maximum grain yield of 33.49 q/ha and insignificance yield loss were recorded from Dhera variety in optimum sowing while the minimum grain yield and maximum yield loss of 18.41 q/ha and 44.97% respectively were recorded from Teje variety in early sowing. Based on mean value of two years experiment result suggested that Dhera variety applied at optimum sowing caused significant reduction in ascochyta blight incidence leading to a corresponding increase in grain yield of chickpea. Key words: Chickpea, ascochyta blight, didymellarabiei, disease incidence, percentage severity index, area under disease progress curve, relative yield loss.

Assessing Hydrus-2D Model to Investigate the Effects of Different On-Farm Irrigation Strategies on Potato Crop under Subsurface Drip Irrigation

The objective of this paper was to assess the performance of Hydrus-2D model to simulate the effects of different on-farm irrigation strategies applied on potato crop. The ability of the model to simulate the stress coefficient (Ks), obtained as the ratio between actual and maximum transpiration, and to define the productive function of potato crop under the semi-arid conditions of central Tunisia were also evaluated. Experiments were carried out on potato crop under full (FI) and deficit irrigation (DI) and two different water qualities supplied by means of a subsurface drip irrigation system. Results evidenced that the model, despite some discrepancies locally observed, can fairly accurately predict soil water contents and electrical conductivity around buried emitters. Furthermore, under water and salt stress conditions, “measured” Ks, based on crop water stress index (CWSI) obtained on thermal images, resulted in a good correlation with the corresponding estimated by the model (R2 = 0.8). The database collected during the three growth seasons also allowed the definition of the crop productive function represented by a linear relationship between the relative yield loss and Ks. This function represents a useful guidelines for the sustainable use of irrigation water in countries characterized by a semi-arid climate and a limited availability of water for irrigation.

Effect of weed species on drought tolerant rice genotypes at Sundarbazar, Lamjung, Nepal

Abstract Weeds compete with rice for water, nutrients, space and light. The effect of weeds on productivity of rice genotypes were studied at research field of Institute of Agriculture and Animal Science, Lamjung Campus, Lamjung, Nepal in 2016. Eight rice genotypes (IR-87684- 18-1-2-3, IR-83388-3-3-140-4, IR-8839-39-1-6-4, IR-87759-7- 1-2-3, IR-88966-22-1-1-1, IR-88839-3-1-2-2, IR-88869-2-2-2-2, and Sukhadhan-3) and two weed management practices (Weeded condition and non weeded condition) were studied in randomized complete block design (RCBD) with three replications. Results showed that weeding operation significantly increased the growth traits and final yield of rice genotypes. Non-significant results among tested genotypes were obtained for grain yield and straw yield however the maximum grain yield (3.68 t ha-1) and straw yield (5.99 t ha-1) were found in IR-88839- 39-1-6-4 which might be due to highest test grain weight (30.64 g), tallest plant height (105.7m) and lower sterility percentage (21.84%). Similarly, the relative grain yield loss due to weed infestation was 41.8%. The highest grain yield (3.99 t ha-1) and straw yield (6.90 t ha-1) was found in weeded plots compared to non-weeded plots (2.321 t ha-1 and 6.43 t ha-1, respectively). Among weed species, Rotala indica was found most dominant (1091 m-2) and proportion 18%) followed by Eriocaulon cinereum (245.83 m-2 and 12%). Interaction effect between variety and weed population showed non-significant results for all growth and yield attributes. The plots having highest number of weed population showed greater loss of rice yield. Thus this study suggests that weeding should be carried out to achieve higher rice production.

Yield loss of ginger (Zingiber officinale) due to bacterial wilt (Ralstonia solanacearum) in different wilt management systems in Ethiopia

BackgroundGinger bacterial wilt is the most destructive disease that causes qualitative and quantitative rhizome yield losses in Ethiopia. Field studies were conducted to assess yield loss caused by bacterial wilt of ginger in different wilt management systems at Teppi and Jimma, Ethiopia, during 2017. Management systems were host resistance (Boziab and Local) and cultural practices (lemon grass, potassium fertilizer and soil solarization), which were applied as sole and in different levels of integrations. The experiments were factorial arranged in a randomized complete block design with three replications. Disease, growth, yield and yield-related data were collected from central rows of each experimental plot. Data were subjected to analysis of variance using linear general model (GLM) procedure of SAS version 9.3. Mean separation was made using least significant difference test. Correlation among parameters and linear regression of rhizome yield versus final wilt incidence were computed using Minitab 14 statistical package.ResultsAnalysis of variance indicated that variety, cultural practices and variety × cultural practice interaction effects significantly reduced wilt incidence and increased rhizome yield and its components. Variety Boziab recorded relatively more yield and yield components than the Local variety. Rhizome yield gains of about 51.4% in Local and 51.9% in Boziab at Teppi and 39.4% in Local and 49.1% in Boziab at Jimma were obtained due to integrated application of lemon grass with soil solarization and soil fertilization. The mean relative yield loss calculated for control plots due to bacterial wilt ranged from 51.4 to 51.9% at Teppi and 39.4 to 49.1% at Jimma. The lowest relative yield loss was computed from plots treated with either lemon grass with soil fertilization and solarization or lemon grass with soil fertilization. Final wilt incidence was inversely and highly significantly (P ≤ 0.001) correlated (r = − 0.90** and − 0.88**) with rhizome yield of Boziab and Local, respectively, at Teppi. The slope of the regression line also estimated that for each unit increase in percent of final mean wilt incidence, there was a rhizome yield reduction of 0.18 t ha−1 for Boziab and 0.19 t ha−1 for Local variety at Teppi. Similar trends were observed at Jimma. Moreover, the most integrated treatment provided higher net benefit with optimum marginal rate of return than others.ConclusionThe overall results indicated that integration of host resistance with cultural practices reduces yield loss, improves ginger productivity and significantly reduces bacterial wilt epidemics, and thus, it is recommended in the study areas and other related agroecologies.

Revisiting the crop yield loss in India attributable to ozone

Crop Yield Loss (CYL) due to surface ozone substantially affects the Indian economy and the food availability for a billion residents. Nevertheless, the incurring losses over India remain uncertain due to limited measurements and significant uncertainties in the surface O3 simulated by chemistry-transport models, amongst other causes. Here, we revisit the ozone-attributable CYL using WRF-Chem model, with a set up previously shown to better reproduce the observed ozone variations over the contrasting chemical environments across the Indian region. WRF-Chem simulated ozone fields are converted to Accumulated Ozone above a Threshold of 40 ppbv (AOT40) for two primary crop growing seasons in India, i.e. Kharif (mid-June to mid-September), and Rabi (December to February). Relative Yield Losses (RYL) for wheat are found to be higher (∼21–26%) than those in a recent study based on observations (∼15%), as the model accounts for the rural chemistry which can be different from urban/suburban/high altitude environments where measurements are largely conducted. Additionally, RYL for rice estimated here (∼6%) is 3 times greater than a previous study using this model at a relatively coarser resolution to derive average surface ozone with a set of simulations with varying emission inventories, not evaluated in detail before deriving crop losses. The economic losses due to CYL estimated in this study (∼5 billion USD for wheat and 1.5 billion USD for rice) are on the higher side, when estimations from various studies are inter-compared (0.6–4.3 billion USD for wheat, and 0.5–1.5 billion USD for rice), for which increasing crop prices is also a contributing factor. Our study highlights an urgent need to conduct strategic ozone observations especially over agricultural fields, and the development of yearly regional-emission database to support policy making in India.

Spatial variability in regional scale drought index insurance viability across Australia’s wheat growing regions

Wheat is key global food crop that is heavily influenced by climatic variability. There has been extensive research on improving forecasts and management practices to minimise climate related yield losses, but less on how to handle yield losses caused by climate variability. We investigated whether index insurance could be used to manage climate related losses, specifically from winter rainfall drought for wheat crops in Australia. We utilised 31 years of yield data from 15 of Australia’s key wheat producing regions. The winter rainfall index was developed and tested using generalised additive regression models, allowing for non-linear effects. Models with the winter rainfall index explained significant variation in wheat yields in each of the regions assessed. Wheat yield models had cross-validated R2 values > 0.5 for two-thirds of the 15 regions modelled and best explained wheat yields in the Mallee, Western Australia (cross-validated R2 of 0.70). Calculated fair premiums ranged from $8.62 to $77.1 AUD/ha, while maximum liability was $59.25 to $212.12 AUD/ha. Throughout the eastern most wheat growing regions the winter rainfall index was consistently inefficient (i.e. not beneficial). In contrast, the winter rainfall index was financially efficient (i.e. beneficial) in the western wheat regions of eastern Australia and parts of Western Australia, with benefits of up to $97 AUD/ha and loss reductions of $9 AUD/ha. The spatial variability in insurance efficiency was explained by rainfall variance. As rainfall variance increased the efficiency of the winter rainfall index insurance for wheat decreased. Our findings have two important policy implications; (1) in areas where climate change is anticipated to increase rainfall variability risk-transfer options, such as index insurance, may become less viable and as such policies that support the development of index insurance without acknowledging or adjusting for variability in its benefit could lead to inefficient outcomes for both government and agricultural producers; and (2) where index rainfall insurance is not efficient then greater emphasise may need to be placed on developing alternate types of index insurance (e.g. using satellites) and/or on risk-management and climate adaptation strategies that minimise losses.

Influence of a Cereal Rye Cover Crop and Conservation Tillage on the Critical Period for Weed Control in Cotton

AbstractCover crops are being increasingly recommended as an integrated approach to controlling glyphosate-resistant Palmer amaranth and other troublesome weeds. Thus, a field experiment was conducted in 2010 through 2012 to evaluate the critical period for weed control (CPWC) in cotton as affected by a cereal rye cover crop and tillage. The management systems evaluated included conventional tillage following winter fallow, conservation tillage (CT) following winter fallow, and CT following a cereal rye cover crop managed for maximum biomass. Throughout most of the growing season, weed biomass in cereal rye cover crop plots was less than the CT winter-fallow system in both years and less than both CT winter fallow and conventional tillage in 2012. The CPWC was shortest in 2010 following conventional tillage; however, in 2012, production system influences on CPWC were less. The presence of the rye cover crop delayed the critical timing for weed removal (CTWR) approximately 8 d compared with fallow treatment both years, while conventional tillage delayed CTWR about 2 wk compared with winter fallow. Relative yield losses in both years did not reach the 5% threshold limit until about 2 wk after planting (WAP) for CT following winter fallow, 3 WAP for CT following a cover crop, and 3.5 WAP following conventional tillage. Thus, CT following winter fallow should be avoided to minimize cotton yield loss.

Effects of drought stress on growth, grain filling duration, yield and quality attributes of barley (Hordeum vulgare L.)

A pot experiment was conducted to investigate the effect of drought stress at start of anthesis (applied by adjusting the field capacities at 100, 50 and 30%) on barley growth, grain filling duration, grain shape, yield and quality attributes. The effect of drought stress was more prominent on plant fresh biomass accumulation, grain yield and grain filling duration. However, it produced non-significant effect on total number of tillers and grain protein contents. With the increasing intensity of drought stress, barley growth and yield traits significantly diminished. Water stress gradually shortened the plant height and biomass accumulation but the difference was more prominent in fresh biomass accumulation (– 45%) over dry biomass accumulation. The field capacity of 30% caused 29 - 41% reduction in leaf chlorophyll content and 10 - 27% in grain quality traits. Root fresh and dry biomass accumulation decreased by drought stress while root length increased. Drought stress produced uneven grain size that resulted in lower grain yield (42%) specially at 30% field capacity. This reduction in yield was also due to the decreased grain filling duration (38 d) at 30% field capacity as compared to 100% field capacity. So, it may be concluded that drought stress affected barley yield through impaired grain development and grain filling duration. The results of present study are satisfactory and needed further exploration about the physiological mechanism and management strategies to overcome drought stress related yield losses in barley crop.

Impacts of O3 on premature mortality and crop yield loss across China

Exposure to ambient ozone (O3) is a risk factor for public health and causes damage to vegetation, including agricultural crops. In this study, we performed a comprehensive estimate of the spatial distribution of premature deaths and main crop yield losses attributed to ambient O3, across China in 2014, by applying the Global Burden of Diseases approach and AOT40 metric (i.e., above a threshold of O3 concentration of 40 ppb). Our results show that China's total premature deaths in 2014 due to COPD attributed to O3 exposure were 89,391 (CI95: 32,225–141,649) with spatial variation across provinces. O3 induced production losses from all crops were 78.4 million metric tons, and the relative yield losses ranged from 8.5 to 14.0% for winter wheat, 3.9–15.0% for rice, and 2.2–5.5% for maize. The top four Chinese provinces (Sichuan, Shandong, Henan and Hunan) for premature deaths attributed to O3 pollution also suffered severe losses in yields of winter wheat and rice. Our results provide quantitative evidence of O3 induced impacts on both the public health and crop yields across Chinese provinces, which have important policy implications for the government to alleviate O3 pollution in addition to PM2.5 pollution that is currently being addressed.

Assessment of yield and economic losses for wheat and rice due to ground-level O3 exposure in the Yangtze River Delta, China

In recent years, ground-level O3 and its potential risks on agricultural crops have attracted worldwide attention from both society and academic community. According to the hourly O3 concentration data in 24 cities of the Yangtze River Delta during wheat (16 March to 29 May 2015) and rice (20 July to 20 October 2015) growing seasons, we estimated the yield and economic losses of wheat and rice resulted by O3 exposure using O3 exposure-response functions based on AOT40 (accumulated hourly O3 concentration above 40 ppb, this exposure index is the current standard for vegetation protection against O3). The results showed that the O3 mean concentration during wheat and rice growing seasons ranged from 28.2 to 44.3 ppb and 27.6–44.2 ppb, respectively. The AOT40 values during wheat and rice growing seasons ranged from 4.33 to 15.82 ppm h and 7.64–25.15 ppm h, respectively. Relative yield loss ranged from 9.86 to 36.05% for wheat and 7.25–23.87% for rice. The total crop production loss for wheat and rice amounted to 552.55 × 104 tons and 535.06 × 104 tons, respectively. The total economic loss amounted to 209.31 × 107 US$ for wheat and 237.03 × 107 US$ for rice. Our study revealed the potential regional risk of ground-level O3 exposure to crops in the Yangtze River Delta. Therefore, some effective measures should be taken urgently to reduce the negative effects of O3 on crop productivity.

Variability in defence mechanism operating in three wheat cultivars having different levels of sensitivity against elevated ozone

Wheat cultivars namely HD 2987 [ozone (O3) sensitive], PBW 502 (intermediately sensitive to O3) and Kharchiya 65 (O3 tolerant) were chosen on the basis of earlier study to investigate the effect of elevated O3 (ambient + 30 ppb) on histochemical localisation assay, native-PAGE analysis, metabolites and enzymes of antioxidative and phenylpropanoid pathway as well as on reproductive structures and related yield losses. In the histochemical study, highly distinguished and intensified stains were found in leaf tissues of sensitive cultivar due to the formation of reactive oxygen species (ROS). Greatest induction in activities of enzymes i.e. superoxide dismutase (SOD), peroxidase (POX), glutathione reductase (GR) and guaiacol peroxidase (GPX) was found in sensitive cultivar HD 2987 compared to other two cultivars. Jasmonic acid was constitutively more in Kharchiya 65 while salicylic acid was maximally induced in HD 2987 indicating its higher susceptibility towards O3 stress. Modern cultivar HD 2987 suffered maximum oxidative stress and tried to overcome it by greatly enhancing antioxidative enzymes and also enzymes of the phenylpropanoid pathway (phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase and 4-coumarate CoA ligase) with subsequent induction of flavonoids and total phenolics; but ultimately suffered greatest decline in reproductive structures development and final yield. While in PBW 502 both enzymatic and non-enzymatic antioxidants played important role in combating O3 stress. Earlier released tolerant cultivar Kharchiya 65 manifested maximum increase in non-enzymatic antioxidants such as ascorbic acid, flavonoids, reduced glutathione along with jasmonic acid which offered resistance and probably rendered it most efficient in combating O3 stress. Further Kharchiya 65 showed high free radical scavenging activities compared to other cultivars. These findings will be useful for crop breeders to select O3 tolerant wheat cultivars for breeding purposes while developing cultivars for areas experiencing higher concentrations of O3.

Evaluation and uncertainty estimation of the impact of air quality modelling on crop yields and premature deaths using a multi-model ensemble

This study promotes the critical use of air pollution modelling results for health and agriculture impacts, with the primary goal of providing more reliable estimates to decision makers. To date, the accuracy of air quality (AQ) models and the effects of model-to-model result variability (which we will refer to as model uncertainty) on impact assessment studies have been often ignored, thus undermining the robustness of the information used in the decision making process and the confidence in the results obtained.A suite of twelve PM2.5 and ozone concentration fields produced by regional-scale chemistry transport Air Quality (AQ) models during the third phase of the Air Quality Model Evaluation International Initiative (AQMEII) has been used to calculate the impact of air pollution on premature deaths and crop yields. An innovative technique is applied to bias-adjust the models to available observations.The model results for ozone and PM2.5 are combined in a multi-model (MM) ensemble, which is used to estimate the damage and economic cost to human health and crop yields, as well as the associated uncertainties. The MM ensemble quantifies directly the uncertainty introduced by AQ models into the air pollution impact assessment chain, while the indirect use of experimental information through a bias adjustment, reduces the uncertainty in the ozone and PM2.5 fields and subsequently the uncertainty of the final impact assessment and cost valuation.The analysis over the European countries analysed in this study shows a mean number of premature deaths due to exposure to PM2.5 and ozone of approximately 370,000 (inter-quantile range between 260,000 and 415,000) and a relative yield loss of approximately 7% to 9% (depending on the exposure metrics used, for wheat and maize together). Furthermore, the results indicate that a reduction in the uncertainty of the modelled ozone by 61% and by 80% (depending on the aggregation metric used) and by 46% for PM2.5, produces a reduction in the uncertainty in premature mortality and crop loss of >60%, and of an equivalent percentage in the final uncertainty of cost valuation, providing decision makers with more accurate estimations for more targeted interventions.

Yield loss of faba bean (Vicia faba L.) due to chocolate spot (Botrytis fabae Sard.) in Sinana, Southeastern Oromia

Field experiment was conducted at Sinana Agricultural Research Center in the 2014 main cropping season with the objective to assess yield losses caused by chocolate spot ( Botrytis fabae ) of faba bean varieties. The highest number of days to physiological maturity was recorded on the variety Shalo (141.6 days) and lowest in the variety Mosisa (138.5 days). The maximum biomass on hectare basis (6.6t/ha) was obtained from plot sprayed at weekly interval. The maximum relative grain yield loss were recorded from the varieties of Mosisa and local, 47.8% and 46.7% on unsprayed plots, respectively. Losses in hundred seed weight greater on the variety local than others, this variety had maximum hundreds seed weight loss of 16% when it was protected against the diseases. The local variety shows the maximum biomass loss compared to other varieties under unsprayed plots. This variety has a biomass loss of 33% under unsprayed plots. The highest marginal benefit (32022.9 ETB/ha) was obtained from variety Mosisa sprayed at weekly intervals and highest (233.7 ETB) marginal rate of return was obtained also from this variety when treated at weekly intervals.