Quantifying the exploitable gap between average farmer yields and yield potential (
Y
P) is essential to prioritize research and formulate policies for food security at national and international ...levels. While irrigated maize accounts for 58% of total annual maize production in the Western U.S. Corn Belt, current yield gap in these systems has not been quantified. Our objectives were to quantify
Y
P, yield gaps, and the impact of agronomic practices on both parameters in irrigated maize systems of central Nebraska. The analysis was based on a 3-y database with field-specific values for yield, applied irrigation, and N fertilizer rate (
n
=
777).
Y
P was estimated using a maize simulation model in combination with actual and interpolated weather records and detailed data on crop management collected from a subset of fields (
n
=
123). Yield gaps were estimated as the difference between actual yields and simulated
Y
P for each field-year observation. Long-term simulation analysis was performed to evaluate the sensitivity of
Y
P to changes in selected management practices. Results showed that current irrigated maize systems are operating near the
Y
P ceiling. Average actual yield ranged from 12.5 to 13.6
Mg
ha
−1 across years. Mean N fertilizer efficiency (kg grain per kg applied N) was 23% greater than average efficiency in the USA. Rotation, tillage system, sowing date, and plant population density were the most sensitive factors affecting actual yields. Average yield gap was 11% of simulated
Y
P (14.9
Mg
ha
−1). Time trends in average farm yields from 1970 to 2008 show that yields have not increased during the past 8 years. Average yield during this period represented ∼80% of
Y
P ceiling estimated for this region based on current crop management practices. Simulation analysis showed that
Y
P can be increased by higher plant population densities and by hybrids with longer maturity. Adoption of these practices, however, may be constrained by other factors such as difficulty in planting and harvest operations due to wet weather and snow, additional seed and grain drying costs, and greater risk of frost and lodging. Two key points can be made: (i) irrigated maize producers in this region are operating close to the
Y
P ceiling and achieve high levels of N use efficiency and (ii) small increases in yield (<13%) can be achieved through fine tuning current management practices that require increased production costs and higher risk.
Yield development of agricultural crops over time is not merely the result of genetic and agronomic factors, but also the outcome of a complex interaction between climatic and site‐specific soil ...conditions. However, the influence of past climatic changes on yield trends remains unclear, particularly under consideration of different soil conditions. In this study, we determine the effects of single agrometeorological factors on the evolution of German winter wheat yields between 1958 and 2015 from 298 published nitrogen (N)‐fertilization experiments. For this purpose, we separate climatic from genetic and agronomic yield effects using linear mixed effect models and estimate the climatic influence based on a coefficient of determination for these models. We found earlier occurrence of wheat growth stages, and shortened development phases except for the phase of stem elongation. Agrometeorological factors are defined as climate covariates related to the growth of winter wheat. Our results indicate a general and strong effect of agroclimatic changes on yield development, in particular due to increasing mean temperatures and heat stress events during the grain‐filling period. Except for heat stress days with more than 31°C, yields at sites with higher yield potential were less prone to adverse weather effects than at sites with lower yield potential. Our data furthermore reveal that a potential yield levelling, as found for many West‐European countries, predominantly occurred at sites with relatively low yield potential and about one decade earlier (mid‐1980s) compared to averaged yield data for the whole of Germany. Interestingly, effects related to high precipitation events were less relevant than temperature‐related effects and became relevant particularly during the vegetative growth phase. Overall, this study emphasizes the sensitivity of yield productivity to past climatic conditions, under consideration of regional differences, and underlines the necessity of finding adaptation strategies for food production under ongoing and expected climate change.
Climatic changes influence the long‐term yield development of crops. This study, therefore, determines the influence of single agrometeorological factors on the winter wheat yield development in Germany between 1958 and 2015 at sites of lower and higher soil quality. Except for the number of heat stress days with more than 31°C, yields were in particular afflicted at sites with lower soil quality by increasing mean temperatures and heat stress events during the grain‐filling period. Sites with higher soil quality were less prone to adverse weather effects.
Application of organic manure combined with synthetic fertilizer can maintain crop yield and improve soil fertility, but the long-term effects of substituting different proportions of synthetic ...fertilizers with organic manure on N2O emission remain unclear. In this study, field experiments and DNDC model simulations were used to study the long-term effects of substituting synthetic fertilizers with organic manure on crop yield and N2O emission. The field experiment was conducted at Guanzhong Plain, northern China, under a wheat-maize cropping system. Six treatments were included: no fertilization (CK); synthetic nitrogen (N), phosphorus (P) and potassium (K) fertilizers (NPK); and 25%, 50%, 75% and 100% of the synthetic N substituted by dairy manure (25%M, 50%M, 75%M, and 100%M), respectively. The DNDC model was calibrated using the field data from the NPK treatment from 2014 to 2017 and was validated for the other treatments. The results showed that the DNDC model can successfully simulate the crop yield (e.g. nRMSE < 5%) and annual N2O emission (nRMSE < 20%). In addition, a 30-year simulation found that organic manure substitution treatments could maintain wheat yield well, and the yield variation between different years was small. However, relative to the NPK treatment, the maize yields for the first 6 and 7 years were lower under 50%M and 75%M, and under 100%M maize yields were reduced for the first 15 years. The long-term simulation showed that N2O emission of fertilized treatment had an increasing trend over time, especially the 75%M treatment where the N2O emission was higher than that of NPK treatment after 25 years of fertilization. The annual mean N2O emission under different treatments was, in decreasing order, NPK > 25%M > 50%M > 75%M > 100%M > CK. The yield-scale N2O emission and emission factor were highest for the NPK treatment. Considering crop yield, yield stability and N2O emission, substitution of 25% synthetic fertilizer by organic manure can simultaneously ensure crop productivity and environmental protection under the tested environment.
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•DNDC model can successfully simulate crop yield and N2O emission under wheat-maize.•Organic manure addition had lower N2O emission than using mineral fertilizers alone.•Organic manure replacing 25% mineral fertilizer gets good yield and low N2O emission.
Soil ammonia (NH3) volatilization and nitrous oxide (N2O) emission decrease nitrogen (N) utilization efficiency and cause some environmental problems. The N-cycling inhibitors are suggested to apply ...to enhance N utilization efficiency. Quantifying effects of N-cycling inhibitors on yield-scaled NH3 volatilization and N2O emission and functional genes could provide support for the optimal selection and application of N-cycling inhibitor. We conducted a meta-analysis to reveal the effects of N-cycling inhibitors on soil abiotic properties, functional genes and yield-scaled NH3 volatilization and N2O emission by extracting data from 166 published articles and linked their comprehensive relationships. The N-cycling inhibitors in this meta-analysis mainly includes nitrification inhibitors 3, 4-dimethyl pyrazole phosphate, dicyandiamide and 2-chloro-6-trichloromethylpyridine, urease inhibitor N-(n-butyl) thiophosphoric triamide and biological nitrification inhibitors methyl 4-hydroxybenzoate and 1, 9-decanediol. The N-cycling inhibitor applications significantly increased alkaline soil pH but significantly decreased acidic soil pH. The N-cycling inhibitors decreased soil AOB amoA gene abundances mostly under the condition of pH 4.5–6 (mean: 212%, 95% confidence intervals (CI): 249% and −176%) and significantly decreased nirS gene (mean: 39%; 95% CI: 72% and −6%). The yield-scaled NH3 volatilization was significantly decreased by the N-cycling inhibitors under the condition of soil pH = 7–8.5 (mean: 45%; 95% CI: 59% and −31%). The yield-scaled N2O emission was also significantly reduced by all N-cycling inhibitors and had negative correlations with the soil nirK and nirS gene abundances. The effects of N-cycling inhibitors on soil pH, ammonium-N, nitrate-N and nitrifying and denitrifying genes and yield-scaled NH3 volatilization and N2O emission were dominated by the inhibitor types, soil textures, crop species and environmental pH. Our study could provide technical support for the optimal selection and application of N-cycling inhibitor under different environmental conditions.
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•Global meta-analyses of performances of N-cycling inhibitors (NI) were conducted.•Yield-scaled NH3 volatilization was reduced by the NI.•NI decrease yield-scaled N2O emission via altering soil abiotic and biotic properties.•The effects of NI on soil pH were depended on soil types.•Yield-scaled N2O emission had negative correlations with soil nirK and nirS genes.
This reprint focuses on quantitatively assessing the impact of climate change on agricultural production based on multi-source model simulation and reveals the role and mechanism of improved ...management measures in adapting to climate change. Modeling is a key tool for exploring the impacts of climate change on agriculture and proposing adaptation strategies. The insights derived from this reprint will be helpful for relevant decision makers in the areas of agricultural adaptation and food security.
This reprint focuses on quantitatively assessing the impact of climate change on agricultural production based on multi-source model simulation and reveals the role and mechanism of improved ...management measures in adapting to climate change. Modeling is a key tool for exploring the impacts of climate change on agriculture and proposing adaptation strategies. The insights derived from this reprint will be helpful for relevant decision makers in the areas of agricultural adaptation and food security.
Yield-scaled nitrous oxide (N2O) emission (YSNE) has been recognized as a means for developing appropriate nitrogen (N) management strategies to balance food security and mitigating N2O emissions. To ...better understand and use the concept of YSNE, it is essential to be assessed under various field conditions. The main objectives of this study were to assess the relationship between N inputs and YSNE with published results and identify response patterns of YSNE to N inputs. We assessed the relationship between N inputs and YSNE using published results encompassing 1800 observations (published from 1980 to 2020) from maize, rice, and wheat crops worldwide. Background yield-scaled N2O emission (BYSNE; a YSNE in the condition of zero N input) was significantly different by crop type. Rice (90.8 ± 12.9 g N2O−N Mg−1) had lower BYSNE compared to maize (174.2 ± 30.1 g N2O−N Mg−1) and wheat (325.4 ± 41.8 g N2O−N Mg−1). BYSNE was positively correlated with annual mean temperature in maize, rice, and wheat fields. BYSNE was negatively correlated with soil total nitrogen contents in rice fields. Over 60% data set showed a positive relationship between N inputs and YSNE in all three crops studied. A small proportion of the dataset had an optimum N rate that minimized YSNE. The results suggest that in general, lower N input rates result in lower YSNE in crop production. YSNE can be reduced in three ways: increasing yields (Type 1), reducing N2O emissions (Type 2), and both increasing yields and reducing N2O emissions (Type 3). To identify appropriate measures, we suggest a N2O emission-yield curve combining responses of yields and N2O emissions to N inputs. In type 1, 2, and 3 measures, an N2O emission-yield curve is shifted to the right, down, and both right and down, respectively. Through identifying direction and magnitude of the shifting, the effects of applied measures on yields and N2O emission in N input levels can be easily compared and recognized. This study provided insights into the nature of YSNE and how YSNE responds to N inputs. It also suggested an N2O emission-yield curve, which can be useful to identify how certain measures affect both N2O emissions and crop yields. The information can be useful for scientific community and policymakers developing appropriate N management strategies to balance food security and the mitigation of N2O emissions.
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•Background yield-scaled N2O emission (BYSNE) varied by crop type.•BYSNE was positively correlated with annual mean temperature.•Over 60% data sets showed consistently lower yield-scaled N2O emission as N input decreased.•N2O emissionyield curve showed the effects of mitigation measures on both yields and N2O emission.
The yield stress tensor Thompson, Roney L.; Sica, Luiz U.R.; de Souza Mendes, Paulo R.
Journal of non-Newtonian fluid mechanics,
11/2018, Volume:
261
Journal Article
Peer reviewed
Yield stress materials are known to possess a certain threshold property, a strength, that must be overcome in order for flow to occur. This strength is commonly conceived as a scalar representation ...of the stress tensor at the yielding point, here called the yield stress tensor. The recognition of the importance of elastic, thixotropic, and other effects not predicted by ideal viscoplastic models is becoming more and more present in the study of yield stress materials. Nevertheless, the paradigm built by the theoretical analysis of inelastic viscoplastic models has a strong influence in the literature. For example, the common denomination of the shear component of the stress tensor at the yielding point as the yield stress of the material. This nomenclature is so spread in the literature that is explicitly employed even in articles where elastic effects are investigated. Viscometric rheometry is the most widely imposed kinematics used to probe the material, and the flow curve is considered the most useful single information about the material related to flow. However, even for this fixed kinematics, the conditions at the yielding point are not uniquely determined by the shear stress component. Although the existence of normal stress differences are known to be present in a variety of yield stress materials, and virtually all yielding criteria are dependent on the invariants of the deviatoric stress tensor at the yield point, the components of the yield stress tensor other than the yield shear stress are ignored altogether. In the present work, we measure not only the shear stress component of the yield stress tensor, but also the normal stress differences at the yielding point for eight yield stress materials, in order to determine the full deviatoric yield stress tensor in viscometric flow. To this end, besides creep tests performed to find the yield shear stress, cone-plate as well as plate-plate geometries are employed to determine, respectively, the first normal stress difference, N1, and the difference of normal stress differences, N1 − N2. A low-slope shear stress ramp is imposed and the normal stress differences are plotted as a function of the shear stress, in order to determine their values at the yield shear stress. In most of the cases, it is found that the normal stresses of the deviatoric yield stress tensor are significant when compared to the yield shear stress component. Therefore, in general all the yield stress tensor components can contribute significantly to the composition of a yield criterion. This fact imposes the need for reliable measurements to determine the full yield stress tensor of the material.
Soybean, belonging to legumes, has a specific ability to biological nitrogen fixation, which can be reinforced by seeds inoculation. However, support with a starter dose of mineral nitrogen ...fertilizer may be necessary to achieve high seed yields. A four-year field experiment was conducted to determine the effect of mineral N fertilization (0, 30, 60 kg ha
), seed inoculation with two commercial inoculants and combinations of these treatments on yield components and yielding of soybean in conditions of south-western part of Poland. The synergistic effect of mineral fertilization at dose 30 kg ha
and inoculation on soybean productivity was the most beneficial. Similar effects were observed when 60 kg N ha
was applied both separately and with inoculation. However, due to the environmental impact of mineral fertilizers and to promote plants to biological nitrogen fixation (BNF), it is advisable to use lower doses of N fertilizer (at 30 kg ha
) and inoculate soybean seeds in agro- climatic conditions of south-western Poland. Therefore, based on this study we recommend to apply starter dose of N and inoculation.
This paper proposes a simple coupling of quadratic and non-quadratic yield functions with a non-associated flow rule to describe the evolution of yield surface (or anisotropic hardening). The ...non-quadratic part is an isotropic function and is supposed to control curvature of the whole model. The quadratic part takes a role to describe anisotropic hardening throughout a deformation history by employing the hardening functions of different loading conditions. The new yield model just multiplies a quadratic and non-quadratic parts, and it does need neither any interpolation nor optimization at a discrete level of equivalent plastic strain. The new model is compared with several material models with four different material data in order to validate advantages of the new model in capturing anisotropic hardening and controlling its curvature of yield surface. In addition, artificial material cases are applied to the new model to study sensitivity of the model.
•This paper proposes a simple coupling of quadratic and non-quadratic yield functions with a non-associated flow rule.•The non-quadratic part controls curvature of the whole model. The quadratic part describes anisotropic hardening.•The new yield model does need neither any interpolation nor optimization at a discrete level of equivalent plastic strain.•The new model is verified with several material models with four different material data.
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