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1.
Genetically modified crops are superior in their nitrogen use efficiency-A meta-analysis of three major cereals.
Li, M, Xu, J, Gao, Z, Tian, H, Gao, Y, Kariman, K
Scientific reports. 2020;(1):8568
Abstract
It is currently uncertain to what extent genetic transformations of strategic crops (targeting diverse traits) have improved their N use efficiency (NUE), and what the key factors affecting their NUE are. Based on data collected from 130 publications, the effect sizes of genetic transformations and the key factors influencing NUE for three major cereal crops (rice, maize, and wheat), were investigated using a meta-analysis approach. Genetic transformations increased yield, shoot biomass, N uptake efficiency (NUpE), and partial factor productivity of N (PFPN) in the crops, but decreased shoot NUE (SNUE) and grain NUE (GNUE). Transporter genes improved yield and NUE parameters more efficiently, than did the other gene types. The effect sizes for some NUE parameters varied according to crop species and experimental conditions but did not differ between the overexpression and ectopic expression methods. Most effect sizes did not correlate with gene overexpression levels. These results indicate a promising potential of genetic transformations approaches for improving certain NUE parameters.
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2.
Application of controlled release urea improved grain yield and nitrogen use efficiency: A meta-analysis.
Zhu, S, Liu, L, Xu, Y, Yang, Y, Shi, R
PloS one. 2020;(10):e0241481
Abstract
The application of controlled release urea (CRU) has been proposed as a crucial method to reduce the adverse environmental effects induced by conventional urea (CU). Yet, a systematic and quantitative analysis on how CRU affects staple crop production including wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) is lacking. Here, a meta-analysis was conducted to determine how CRU influences soil chemical properties, total nitrogen (TN) uptake, grain yield, and nitrogen use efficiency (NUE) of staple crop in China. The results indicated that CRU application significantly increased soil organic carbon (SOC), TN, and available nitrogen (AN) by 5.93%, 3.89% and 13.98% respectively overall, while soil pH showed no significant changes. Compared to the application of CU, applying CRU significantly increased grain yield by 7.23%, which was mainly owing to the higher TN uptake (9.13%) across all the studies. In addition, the application of CRU significantly increased NUE, nitrogen agronomy efficiency (NAE), utilization rate of nitrogen fertilizer (NUR), and nitrogen physiological efficiency (NPE) by an average of 23.4%, 34.65%, 25.83% and 15.8% respectively which could be attributed to the slow nitrogen (N) release characteristics of CRU. The positive effect of CRU on grain yield and NUE of staple crop was greatest when the content of SOC and TN were extremely low, indicating that it was most effective to improve grain production of infertile soil by applying CRU. The finding of this study indicated that the application of CRU should be promoted for grain production, especially for infertile soil.
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3.
A meta-analysis of crop response patterns to nitrogen limitation for improved model representation.
Seufert, V, Granath, G, Müller, C
PloS one. 2019;(10):e0223508
Abstract
The representation of carbon-nitrogen (N) interactions in global models of the natural or managed land surface remains an important knowledge gap. To improve global process-based models we require a better understanding of how N limitation affects photosynthesis and plant growth. Here we present the findings of a meta-analysis to quantitatively assess the impact of N limitation on source (photosynthate production) versus sink (photosynthate use) activity, based on 77 highly controlled experimental N availability studies on 11 crop species. Using meta-regressions, we find that it can be insufficient to represent N limitation in models merely as inhibiting carbon assimilation, because in crops complete N limitation more strongly influences leaf area expansion (-50%) than photosynthesis (-34%), while leaf starch is accumulating (+83%). Our analysis thus offers support for the hypothesis of sink limitation of photosynthesis and encourages the exploration of more sink-driven crop modelling approaches. We also show that leaf N concentration changes with N availability and that the allocation of N to Rubisco is reduced more strongly compared to other photosynthetic proteins at low N availability. Furthermore, our results suggest that different crop species show generally similar response patterns to N limitation, with the exception of leguminous crops, which respond differently. Our meta-analysis offers lessons for the improved depiction of N limitation in global terrestrial ecosystem models, as well as highlights knowledge gaps that need to be filled by future experimental studies on crop N limitation response.
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4.
Nitrogen - essential macronutrient and signal controlling flowering time.
Weber, K, Burow, M
Physiologia plantarum. 2018;(2):251-260
Abstract
Nitrogen, as limiting nutrient for plant growth and crop yield, is a main component of fertilizers and heavily used in modern agriculture. Early reports from over-application of fertilizers in crop production have shown to repress the transition from vegetative to reproductive phase. For the model plant Arabidopsis thaliana, there is evidence that low nitrogen conditions promote early flowering, while high nitrogen as well as nitrogen starvation conditions display the opposite effect. To gain a better understanding of how nitrogen affects the onset of flowering, we reviewed the existing literature for A. thaliana and carried out a meta-analysis on available transcriptomics data, seeking for potential genes and pathways involved in both nitrogen responses and flowering time control. With this strategy, we aimed at identifying potential gateways for integration of nitrogen signaling and potential regulators that might link the regulatory networks controlling nitrogen and flowering in A. thaliana. We found that photoperiodic pathway genes have high potential to be involved in nitrogen-dependent flowering.
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5.
Modulation of intestinal microbiota, control of nitrogen products and inflammation by pre/probiotics in chronic kidney disease: a systematic review.
Lopes, RCSO, Balbino, KP, Jorge, MP, Ribeiro, AQ, Martino, HSD, Alfenas, RCG
Nutricion hospitalaria. 2018;(3):722-730
Abstract
Dysbiosis may favor the occurrence of inflammation and oxidative stress in chronic kidney disease (CKD). It has been suggested that the intake of pre/probiotics may control the progression of chronic kidney disease. Thus, the objective of this study was to systematically review the literature on the effects of pre/probiotic intake on the intestinal microbiota, control of nitrogen products, oxidative stress, and inflammation in CKD patients.The literature search was conducted on MEDLINE, LILACS, Cochrane Library of Clinical Trials, and Science Direct. After careful evaluation by the reviewers, ten potentially relevant articles were selected for this study. Based on previous studies, intake of prebiotics appears to have the following effects: increased bifidobacteria and lactobacillus counts; reduced formation of uremic toxin, p-cresol, and its serum concentrations; improved lipid profiles; reduced systemic inflammatory state and concentrations of oxidative stress markers. Similarly, consumption of probiotics can reduce blood urea and serum phosphate concentrations. Furthermore, an increase in fecal volume and intestinal Bifidobacteriumand a reduction in p-cresol serum and blood urea concentrations were observed in response to symbiotic intake. These results suggest that consumption of pre/probiotics may modulate the intestinal microbiota, and promote the growth and metabolism of anaerobic bacteria by decreasing the production of uremic solutes, further causing oxidative stress and systemic inflammation in CKD patients.
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6.
Nutrient-limited conditions determine the responses of foliar nitrogen and phosphorus stoichiometry to nitrogen addition: A global meta-analysis.
You, C, Wu, F, Yang, W, Xu, Z, Tan, B, Yue, K, Ni, X
Environmental pollution (Barking, Essex : 1987). 2018;:740-749
Abstract
To test the hypothesis that nutrient-limited conditions can determine the responses of nitrogen (N) and phosphorus (P) stoichiometry to N addition, a meta-analysis was conducted to identify the different responses of foliar N and P concentrations and N-to-P ratios to N addition under N limitation, N and P co-limitation and P limitation. N addition increased the foliar N-to-P ratios and N concentrations by 46.2% and 30.2%, respectively, under N limitation, by 18.7% and 19.7% under N and P co-limitation, and by 4.7% and 12.9% under P limitation. However, different responses of foliar P concentrations to N addition were observed under different nutrient limitations, and negative, positive, and neutral effects on P concentrations were observed under N limitation, P limitation and N and P co-limitation, respectively. Generally, the effects of N addition on N-to-P ratios and N concentrations in herbaceous plants were dramatically larger than those in woody plants (with the exception of the N-to-P ratio under N limitation), but the opposite situation was true for P concentrations. The changes in N-to-P ratios were closely correlated with the changes in N and P concentrations, indicating that the changes in both N and P concentrations due to N addition can drive N and P stoichiometry, but the relative sizes of the contributions of N and P varied greatly with different nutrient limitations. Specifically, the changes in N-to-P ratios may indicate a minimum threshold, which is consistent with the homeostatic mechanism. In brief, increasing N deposition may aggravate P limitation under N-limited conditions but improve P limitation under P-limited conditions. The findings highlight the importance of nutrient-limited conditions in the stoichiometric response to N addition, thereby advancing our ability to predict global plant growth with increasing N deposition in the future.
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7.
Integrative Multivariate Logistic Regression Analysis of Risk Factors for Kashin-Beck disease.
Yu, FF, Liu, H, Guo, X
Biological trace element research. 2016;(2):274-279
Abstract
To determine the current evidence on risk factors for Kashin-Beck disease (KBD) using an integrative meta-analysis. We searched five English and three Chinese databases from inception to September 2015, to identify case-control studies that examined risk factors for KBD using multivariate logistic analysis. DerSimonian and Laird effective models are applied in processing data using pooled odds ratios (ORs) and 95 % confidence intervals (CI). Seven studies were identified with 3087 cases and 6402 controls. The main risk factors found to be significantly associated with the onset of KBD were age (OR 1.19, 95 % CI 1.10-1.28), parents prevalence (OR 5.16, 2.51-7.80), family hygiene (OR 1.68, 1.42-1.93), food source (OR 3.29, 2.38-4.19), wheat (OR 1.12, 1.08-1.16), wheat germ necrosis rate (OR 6.03, 1.87-12.92), total volatile basic nitrogen (OR 6.85, 1.01-28.67), low selenium in hair (OR 2.29, 1.08-3.50) were found to be significant risks factors. The pooled ORs (95 % CI) of protein intake and rice were 0.79 (0.66-0.93) and 0.90 (0.86-0.95), respectively, indicating that the two factors may be protective for KBD. We found that the combination of low protein intake, polluted grain, and selenium deficiency may contribute to be onset of KBD together.
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8.
No-tillage effects on grain yield, N use efficiency, and nutrient runoff losses in paddy fields.
Liang, X, Zhang, H, He, M, Yuan, J, Xu, L, Tian, G
Environmental science and pollution research international. 2016;(21):21451-21459
Abstract
The effect of no-tillage (NT) on rice yield and nitrogen (N) behavior often varies considerably from individual studies. A meta-analysis was performed to assess quantitatively the effect of NT on rice yield and N uptake by rice, N use efficiency (NUE, i.e., fertilizer N recovery efficiency), and nutrient runoff losses. We obtained data from 74 rice-field experiments reported during the last three decades (1983-2013). Results showed the NT system brought a reduction of 3.8 % in the rice yield compared with conventional tillage (CT). Soil pH of 6.5-7.5 was favorable for the improvement of rice yield with the NT system, while a significant negative NT effect on rice yield was observed in sandy soils (p < 0.05). N rate, ranging from 120 to 180 kg N ha-1, for at least 3 years was necessary for NT to enable rice yield comparable with that of CT. Furthermore, the observations indicated NT reduced N uptake and NUE of the rice by 5.4 and 16.9 %, while increased the N and P exports via runoff by 15.4 and 40.1 % compared with CT, respectively. Seedling cast transplantation, N rate within the range 120-180 kg N ha-1, and employing NT for longer than 3 years should be encouraged to compromise between productivity and environmental effects of NT implementation in rice fields.
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9.
Down-regulation of tissue N:P ratios in terrestrial plants by elevated CO2.
Deng, Q, Hui, D, Luo, Y, Elser, J, Wang, YP, Loladze, I, Zhang, Q, Dennis, S
Ecology. 2015;(12):3354-62
Abstract
Increasing atmospheric CO2 concentrations generally alter element stoichiometry in plants. However, a comprehensive evaluation of the elevated CO2 impact on plant nitrogen: phosphorus (N:P) ratios and the underlying mechanism has not been conducted. We synthesized the results from 112 previously published studies using meta-analysis to evaluate the effects of elevated CO2 on the N:P ratio of terrestrial plants and to explore the underlying mechanism based on plant growth and soil P dynamics. Our results show that terrestrial plants grown under elevated CO2 had lower N:P ratios in both above- and belowground biomass across different ecosystem types. The response ratio for plant N:P was negatively correlated with the response ratio for plant growth in croplands and grasslands, and showed a stronger relationship for P than for N. In addition, the CO2-induced down-regulation of plant N:P was accompanied by 19.3% and 4.2% increases in soil phosphatase activity and labile P, respectively, and a 10.1% decrease in total soil P. Our results show that down-regulation of plant N:P under elevated CO2 corresponds with accelerated soil P cycling. These findings should be useful for better understanding of terrestrial plant stoichiometry in response to elevated CO2 and of the underlying mechanisms affecting nutrient dynamics under climate change.
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10.
Soil mulching significantly enhances yields and water and nitrogen use efficiencies of maize and wheat: a meta-analysis.
Qin, W, Hu, C, Oenema, O
Scientific reports. 2015;:16210
Abstract
Global crop yields are limited by water and nutrient availability. Soil mulching (with plastic or straw) reduces evaporation, modifies soil temperature and thereby affects crop yields. Reported effects of mulching are sometimes contradictory, likely due to differences in climatic conditions, soil characteristics, crop species, and also water and nitrogen (N) input levels. Here we report on a meta-analysis of the effects of mulching on wheat and maize, using 1310 yield observations from 74 studies conducted in 19 countries. Our results indicate that mulching significantly increased yields, WUE (yield per unit water) and NUE (yield per unit N) by up to 60%, compared with no-mulching. Effects were larger for maize than wheat, and larger for plastic mulching than straw mulching. Interestingly, plastic mulching performed better at relatively low temperature while straw mulching showed the opposite trend. Effects of mulching also tended to decrease with increasing water input. Mulching effects were not related to soil organic matter content. In conclusion, soil mulching can significantly increase maize and wheat yields, WUE and NUE, and thereby may contribute to closing the yield gap between attainable and actual yields, especially in dryland and low nutrient input agriculture. The management of soil mulching requires site-specific knowledge.