T. Ohyama, Kahori Matsumoto, Haruka Goto, Akihiro Saito, K. Higuchi
Soybean plants can fix atmospheric N2 in the root nodule, a symbiotic organ with rhizobia. The primary forms of N transported from N2 fixation are ureides, allantoate, and allantoin, supplemented with asparagine. The nitrate absorbed in the roots is transported to the shoots in the forms of NO3− and asparagine with a little portion of ureides. The concentrations of N-metabolites were analyzed by capillary electrophoresis after supplying various concentrations of urea, precursors of ureides, and allopurinol, an inhibitor of xanthine dehydrogenase, to investigate the ureide synthesis pathway in the roots. When the non-nodulated soybean plants were treated with 0–5 mM of urea, the concentrations of asparagine and glutamine in the xylem sap and the roots increased remarkably. In addition, allantoate concentration increased with the urea concentrations becoming higher. Allopurinol inhibited the accumulation of allantoate but did not affect the asparagine and glutamine accumulation in roots, stems, leaves, and xylem sap, supporting that allantoate is synthesized by purine degradation in roots the same as in the nodules. When ureide precursors were supplied to the nodulated soybean plants, the concentrations of asparagine and glutamine in the xylem sap and roots increased, suggesting that the ureide precursors were absorbed and assimilated to amides in the roots.
{"title":"Nitrogen Metabolism in Non-Nodulated and Nodulated Soybean Plants Related to Ureide Synthesis","authors":"T. Ohyama, Kahori Matsumoto, Haruka Goto, Akihiro Saito, K. Higuchi","doi":"10.3390/nitrogen4020014","DOIUrl":"https://doi.org/10.3390/nitrogen4020014","url":null,"abstract":"Soybean plants can fix atmospheric N2 in the root nodule, a symbiotic organ with rhizobia. The primary forms of N transported from N2 fixation are ureides, allantoate, and allantoin, supplemented with asparagine. The nitrate absorbed in the roots is transported to the shoots in the forms of NO3− and asparagine with a little portion of ureides. The concentrations of N-metabolites were analyzed by capillary electrophoresis after supplying various concentrations of urea, precursors of ureides, and allopurinol, an inhibitor of xanthine dehydrogenase, to investigate the ureide synthesis pathway in the roots. When the non-nodulated soybean plants were treated with 0–5 mM of urea, the concentrations of asparagine and glutamine in the xylem sap and the roots increased remarkably. In addition, allantoate concentration increased with the urea concentrations becoming higher. Allopurinol inhibited the accumulation of allantoate but did not affect the asparagine and glutamine accumulation in roots, stems, leaves, and xylem sap, supporting that allantoate is synthesized by purine degradation in roots the same as in the nodules. When ureide precursors were supplied to the nodulated soybean plants, the concentrations of asparagine and glutamine in the xylem sap and roots increased, suggesting that the ureide precursors were absorbed and assimilated to amides in the roots.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84968233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought.
豆科植物混种草地比单种草地产量更高。此外，有些豆科植物甚至在干旱条件下也能维持生长。本研究的第一个目的是测量当考虑到共生固氮的N输入时，豆科植物的多物种草地是否也更多产。我们的第二个目标是确定在自然发生的干旱条件下，草-豆科植物混合物在干物质生产方面的效益。混合种草地，由单一栽培和可变混合(a)三叶草，(b)三叶草。(c)多年生黑麦草(Lolium perenne)和(d)耐旱禾草(GSWT为基础)的混合物，在对比的天气模式下评估了它们在两年内的干物质产量。豆科植物-禾草混合播种采用固定(180 kg N ha - 1)或适应性氮肥(0-180 kg N ha - 1)施用，后者考虑了豆科植物共生固氮的假设。在相对潮湿和干旱的年份，混合种草地的产量都比单一种草地高。多种草-豆科植物混合施用的效益在固定的氮肥制度下更为明显，但在适应的氮肥制度下仍可测量。物种多样性效应明显依赖于豆科植物共生固氮所带来的额外氮供应。豆科植物和耐旱禾本科植物在干旱条件下产量相同，但豆科植物在中度干旱和湿润条件下表现出主要优势。白三叶草和红三叶草虽然都是豆科植物，但在高氮条件下的持久性和低氮条件下的干物质产量差异显著，但对干旱的耐受性相同。
{"title":"The Influence of Nitrogen Applications and Low Rainfall Conditions on Yield of Mixed Grass-Legume Grassland for 2 Years","authors":"K. Weggler, M. Elsässer","doi":"10.3390/nitrogen4020013","DOIUrl":"https://doi.org/10.3390/nitrogen4020013","url":null,"abstract":"Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74372921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anthropogenic nitrogen (N) emissions can have considerable effects on terrestrial ecosystems, with chronic N deposition leading to changes in plant species composition. The Athabasca Oil Sands Region (AOSR) represents a large point source of N emissions, which has prompted concern for surrounding habitats. The objective of this study was to determine the relative importance of N deposition as a driver of plant species community composition against bioclimatic and soil chemical variables. Further, we sought to identify community thresholds in plant species composition across a N deposition gradient. This assessment was performed for 46 Jack pine (Pinus banksiana Lamb.)-dominant forest sites surrounding the AOSR spanning Alberta and Saskatchewan. In total, 35 environmental variables were evaluated using redundancy analysis (RDA), followed by gradient forest analysis applied to plant species abundance data. Soil chemical variables accounted for just over 26% of the total explainable variation in the dataset, followed by bioclimatic variables (19%) and deposition variables (5%), but joint effects between variables also explained a significant portion of the total variation (p < 0.001). Total deposited nitrogen (TDN), and sulphur (TDS) along with bioclimatic and soil chemical variables, were identified as important variables in gradient forest analysis. A single, definitive threshold across TDN was identified at approximately 5.6 kg N ha−1 yr−1 (while a TDS threshold was found at 14.4 kg S ha−1 yr−1). The TDN threshold range was associated primarily with changepoints for several vascular species (Pyrola asarifolia, Pyrola chlorantha, Cornus canadensis, and Arctostaphylos uva-ursi) and bryophyte and lichen species (Pleurozium schreberi, Vulpicida pinastri, and Dicranum polysetum). These results suggest that across Jack pine-dominant forests surrounding the AOSR, the biodiversity-based empirical critical load of nutrient N is 5.6 kg N ha−1 yr−1.
人为氮(N)排放对陆地生态系统有相当大的影响，慢性氮沉降导致植物物种组成的变化。阿萨巴斯卡油砂区(AOSR)是一个巨大的氮排放点源，引起了人们对周围栖息地的关注。本研究的目的是确定氮沉降作为植物物种群落组成对生物气候和土壤化学变量的驱动因素的相对重要性。此外，我们试图确定跨N沉降梯度的植物物种组成的群落阈值。这项评估是对46个杰克松(Pinus banksiana Lamb.)进行的，它们是横跨阿尔伯塔省和萨斯喀彻温省的AOSR周围的主要森林遗址。利用冗余分析(RDA)对35个环境变量进行了评价，并对植物物种丰度数据进行了梯度森林分析。土壤化学变量占数据集中总可解释变异的26%以上，其次是生物气候变量(19%)和沉积变量(5%)，但变量之间的联合效应也解释了总变异的很大一部分(p < 0.001)。总沉积氮(TDN)和总沉积硫(TDS)以及生物气候和土壤化学变量是梯度森林分析的重要变量。TDN的单一确定阈值约为5.6 kg N ha−1 yr−1(而TDS阈值为14.4 kg S ha−1 yr−1)。TDN阈值范围主要与几种维管束植物(鹿蹄草、鹿蹄草、鹿蹄草和熊蹄草)以及苔藓植物和地衣植物(虎肋草、狐尾草和多毛草)的变化点有关。这些结果表明，在青松优势林周围，基于生物多样性的养分N经验临界负荷为5.6 kg N ha−1 yr−1。
{"title":"Biodiversity-Based Empirical Critical Loads of Nitrogen Deposition in the Athabasca Oil Sands Region","authors":"Nicole Vandinther, J. Aherne","doi":"10.3390/nitrogen4020012","DOIUrl":"https://doi.org/10.3390/nitrogen4020012","url":null,"abstract":"Anthropogenic nitrogen (N) emissions can have considerable effects on terrestrial ecosystems, with chronic N deposition leading to changes in plant species composition. The Athabasca Oil Sands Region (AOSR) represents a large point source of N emissions, which has prompted concern for surrounding habitats. The objective of this study was to determine the relative importance of N deposition as a driver of plant species community composition against bioclimatic and soil chemical variables. Further, we sought to identify community thresholds in plant species composition across a N deposition gradient. This assessment was performed for 46 Jack pine (Pinus banksiana Lamb.)-dominant forest sites surrounding the AOSR spanning Alberta and Saskatchewan. In total, 35 environmental variables were evaluated using redundancy analysis (RDA), followed by gradient forest analysis applied to plant species abundance data. Soil chemical variables accounted for just over 26% of the total explainable variation in the dataset, followed by bioclimatic variables (19%) and deposition variables (5%), but joint effects between variables also explained a significant portion of the total variation (p < 0.001). Total deposited nitrogen (TDN), and sulphur (TDS) along with bioclimatic and soil chemical variables, were identified as important variables in gradient forest analysis. A single, definitive threshold across TDN was identified at approximately 5.6 kg N ha−1 yr−1 (while a TDS threshold was found at 14.4 kg S ha−1 yr−1). The TDN threshold range was associated primarily with changepoints for several vascular species (Pyrola asarifolia, Pyrola chlorantha, Cornus canadensis, and Arctostaphylos uva-ursi) and bryophyte and lichen species (Pleurozium schreberi, Vulpicida pinastri, and Dicranum polysetum). These results suggest that across Jack pine-dominant forests surrounding the AOSR, the biodiversity-based empirical critical load of nutrient N is 5.6 kg N ha−1 yr−1.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84463855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Biological N2 fixation, a major pathway for new nitrogen (N) input to terrestrial ecosystems, largely determines the dynamics of ecosystem structure and functions under global change. Nevertheless, the responses of N2 fixation to multiple global change factors remain poorly understood. Here, saplings of two N2-fixing plant species, Alnus cremastogyne and Cajanus cajan, were grown at rural and urban sites, respectively, with the latter representing an environment with changes in multiple factors occurring simultaneously. Symbiotic N2 fixation per unit of nodule was significantly higher at the urban site than the rural site for A. cremastogyne, but the rates were comparable between the two sites for C. cajan. The nodule investments were significantly lower at the urban site relative to the rural site for both species. Symbiotic N2 fixation per plant increased by 31.2 times for A. cremastogyne, while that decreased by 88.2% for C. cajan at the urban site compared to the rural site. Asymbiotic N2 fixation rate in soil decreased by 46.2% at the urban site relative to the rural site. The decrease in symbiotic N2 fixation per plant for C. cajan and asymbiotic N2 fixation in soil was probably attributed to higher N deposition under the urban conditions, while the increase in symbiotic N2 fixation per plant for A. cremastogyne was probably related to the higher levels of temperature, atmospheric CO2, and phosphorus deposition at the urban site. The responses of N2 fixation to multiple global change factors and the underlying mechanisms may be divergent either between symbiotic and asymbiotic forms or among N2-fixing plant species. While causative evidence is urgently needed, we argue that these differences should be considered in Earth system models to improve the prediction of N2 fixation under global change.
{"title":"Effects of Multiple Global Change Factors on Symbiotic and Asymbiotic N2 Fixation: Results Based on a Pot Experiment","authors":"Zhenchuan Wang, Xibin Sun, Hao Chen, Dejun Li","doi":"10.3390/nitrogen4010011","DOIUrl":"https://doi.org/10.3390/nitrogen4010011","url":null,"abstract":"Biological N2 fixation, a major pathway for new nitrogen (N) input to terrestrial ecosystems, largely determines the dynamics of ecosystem structure and functions under global change. Nevertheless, the responses of N2 fixation to multiple global change factors remain poorly understood. Here, saplings of two N2-fixing plant species, Alnus cremastogyne and Cajanus cajan, were grown at rural and urban sites, respectively, with the latter representing an environment with changes in multiple factors occurring simultaneously. Symbiotic N2 fixation per unit of nodule was significantly higher at the urban site than the rural site for A. cremastogyne, but the rates were comparable between the two sites for C. cajan. The nodule investments were significantly lower at the urban site relative to the rural site for both species. Symbiotic N2 fixation per plant increased by 31.2 times for A. cremastogyne, while that decreased by 88.2% for C. cajan at the urban site compared to the rural site. Asymbiotic N2 fixation rate in soil decreased by 46.2% at the urban site relative to the rural site. The decrease in symbiotic N2 fixation per plant for C. cajan and asymbiotic N2 fixation in soil was probably attributed to higher N deposition under the urban conditions, while the increase in symbiotic N2 fixation per plant for A. cremastogyne was probably related to the higher levels of temperature, atmospheric CO2, and phosphorus deposition at the urban site. The responses of N2 fixation to multiple global change factors and the underlying mechanisms may be divergent either between symbiotic and asymbiotic forms or among N2-fixing plant species. While causative evidence is urgently needed, we argue that these differences should be considered in Earth system models to improve the prediction of N2 fixation under global change.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90461295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Paula Bellés-Sancho, C. Beukes, E. James, G. Pessi
A century after the discovery of rhizobia, the first Beta-proteobacteria species (beta-rhizobia) were isolated from legume nodules in South Africa and South America. Since then, numerous species belonging to the Burkholderiaceae family have been isolated. The presence of a highly branching lineage of nodulation genes in beta-rhizobia suggests a long symbiotic history. In this review, we focus on the beta-rhizobial genus Paraburkholderia, which includes two main groups: the South American mimosoid-nodulating Paraburkholderia and the South African predominantly papilionoid-nodulating Paraburkholderia. Here, we discuss the latest knowledge on Paraburkholderia nitrogen-fixing symbionts in each step of the symbiosis, from their survival in the soil, through the first contact with the legumes until the formation of an efficient nitrogen-fixing symbiosis in root nodules. Special attention is given to the strain P. phymatum STM815T that exhibits extraordinary features, such as the ability to: (i) enter into symbiosis with more than 50 legume species, including the agriculturally important common bean, (ii) outcompete other rhizobial species for nodulation of several legumes, and (iii) endure stressful soil conditions (e.g., high salt concentration and low pH) and high temperatures.
{"title":"Nitrogen-Fixing Symbiotic Paraburkholderia Species: Current Knowledge and Future Perspectives","authors":"Paula Bellés-Sancho, C. Beukes, E. James, G. Pessi","doi":"10.3390/nitrogen4010010","DOIUrl":"https://doi.org/10.3390/nitrogen4010010","url":null,"abstract":"A century after the discovery of rhizobia, the first Beta-proteobacteria species (beta-rhizobia) were isolated from legume nodules in South Africa and South America. Since then, numerous species belonging to the Burkholderiaceae family have been isolated. The presence of a highly branching lineage of nodulation genes in beta-rhizobia suggests a long symbiotic history. In this review, we focus on the beta-rhizobial genus Paraburkholderia, which includes two main groups: the South American mimosoid-nodulating Paraburkholderia and the South African predominantly papilionoid-nodulating Paraburkholderia. Here, we discuss the latest knowledge on Paraburkholderia nitrogen-fixing symbionts in each step of the symbiosis, from their survival in the soil, through the first contact with the legumes until the formation of an efficient nitrogen-fixing symbiosis in root nodules. Special attention is given to the strain P. phymatum STM815T that exhibits extraordinary features, such as the ability to: (i) enter into symbiosis with more than 50 legume species, including the agriculturally important common bean, (ii) outcompete other rhizobial species for nodulation of several legumes, and (iii) endure stressful soil conditions (e.g., high salt concentration and low pH) and high temperatures.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84240692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Auges Gatabazi, M. Botha, Mireille Asanzi Mvondo-She
Lucerne is regarded as the best legume crop for forage to be cultivated in South Africa. It is commonly used to produce good quality hay. It also plays an important role in soil conservation, regeneration, and crop rotation systems as it supplies substantial amounts of nitrogen to succeeding crops through symbiotic N2 fixation, which makes it the preferable choice for intensive forage production systems. Fertilizer in liquid inoculant formulations has demonstrated to contribute growth and yield increase for leguminous crops. Therefore, the aim of this paper was to determine the effects of Sinorhizobium meliloti liquid formulation inoculation on the growth, yield, and nitrogen content in lucerne. The strain RF14 (Sinorhizobium meliloti) was collected from the Agricultural Research Council at Roodeplaat (Plant Health and Protection located (East), Pretoria (South Africa). The liquid inoculant contained 6.5 × 109 viable cells mL−1. According to the Kooen–Gieger climatic classification, the experiments were conducted on two different climatic zones. The first site was in Bronkhorspruit (Blesbokfontein farm) in the Gauteng province and the second was in Hartbeesfontein (Rietfontein Farm) in the Northwest province. The results showed that lucerne inoculation with liquid inoculant formulation of Sinorhizobium meliloti significantly increased nodule number, size, growth, and yield in both bioclimatic zones. The significantly increased were compared to the negative control. The Sinorhizobium meliloti inoculant increased nitrogen accumulation in all inoculated treatments compared to the control. The finding of this research provides important information on the impact of rhizobium microbial inoculant application in the improvement of soil fertility through nodule formation. In addition, seed vigor improvement was translated in overall growth and yield increase in lucerne plants.
卢塞恩被认为是南非最好的豆科作物。它通常用于生产优质干草。它还在土壤保持、更新和作物轮作系统中发挥重要作用，因为它通过共生固氮为后续作物提供大量氮，这使其成为集约化饲料生产系统的首选。液体孕育剂配方的肥料已被证明有助于豆科作物的生长和产量的增加。因此，本文旨在研究接种墨氏中华根瘤菌液体制剂对苜蓿生长、产量和含氮量的影响。菌株RF14 (Sinorhizobium meliloti)来自南非比勒陀利亚(Pretoria) (East) Roodeplaat (Plant Health and Protection)的农业研究理事会。液体接种剂含活细胞6.5 × 109 mL−1。根据Kooen-Gieger气候分类，实验在两个不同的气候带进行。第一个地点在豪登省的Bronkhorspruit (Blesbokfontein农场)，第二个地点在西北省的Hartbeesfontein (Rietfontein农场)。结果表明，在两种生物气候带，用墨氏中华根瘤菌液体接种剂接种苜蓿苜蓿均能显著提高根瘤数量、大小、生长和产量。与阴性对照相比显著增加。在所有接种处理中，与对照相比，墨氏中华根瘤菌接种剂增加了氮素积累。本研究结果为应用根瘤菌接种剂通过结瘤提高土壤肥力提供了重要信息。此外，种子活力的提高还转化为苜蓿植株的整体生长和产量的提高。
{"title":"Assessing Liquid Inoculant Formulation of Biofertilizer (Sinorhizobium meliloti) on Growth, Yield, and Nitrogen Uptake of Lucerne (Medicago sativa)","authors":"Auges Gatabazi, M. Botha, Mireille Asanzi Mvondo-She","doi":"10.3390/nitrogen4010009","DOIUrl":"https://doi.org/10.3390/nitrogen4010009","url":null,"abstract":"Lucerne is regarded as the best legume crop for forage to be cultivated in South Africa. It is commonly used to produce good quality hay. It also plays an important role in soil conservation, regeneration, and crop rotation systems as it supplies substantial amounts of nitrogen to succeeding crops through symbiotic N2 fixation, which makes it the preferable choice for intensive forage production systems. Fertilizer in liquid inoculant formulations has demonstrated to contribute growth and yield increase for leguminous crops. Therefore, the aim of this paper was to determine the effects of Sinorhizobium meliloti liquid formulation inoculation on the growth, yield, and nitrogen content in lucerne. The strain RF14 (Sinorhizobium meliloti) was collected from the Agricultural Research Council at Roodeplaat (Plant Health and Protection located (East), Pretoria (South Africa). The liquid inoculant contained 6.5 × 109 viable cells mL−1. According to the Kooen–Gieger climatic classification, the experiments were conducted on two different climatic zones. The first site was in Bronkhorspruit (Blesbokfontein farm) in the Gauteng province and the second was in Hartbeesfontein (Rietfontein Farm) in the Northwest province. The results showed that lucerne inoculation with liquid inoculant formulation of Sinorhizobium meliloti significantly increased nodule number, size, growth, and yield in both bioclimatic zones. The significantly increased were compared to the negative control. The Sinorhizobium meliloti inoculant increased nitrogen accumulation in all inoculated treatments compared to the control. The finding of this research provides important information on the impact of rhizobium microbial inoculant application in the improvement of soil fertility through nodule formation. In addition, seed vigor improvement was translated in overall growth and yield increase in lucerne plants.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82273725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chronic elevated nitrogen (N) deposition can have adverse effects on terrestrial ecosystems. For large areas of northern Canada distant from emissions sources, long-range atmospheric transport of N may impact plant species diversity, even at low deposition levels. The objective of this study was to establish plant species community thresholds for N deposition under multiple environmental gradients using gradient forest analysis. Plant species abundance data for 297 Jack pine (Pinus banksiana Lamb.)-dominant forest plots across Alberta and Saskatchewan, Canada, were evaluated against 43 bioclimatic and deposition variables. Bioclimatic variables were overwhelmingly the most important drivers of community thresholds. Nonetheless, dry N oxide (DNO) and dry N dioxide deposition inferred a total deposited N (TDN) community threshold of 1.4–2.1 kg N ha−1 yr−1. This range was predominantly associated with changes in several lichen species, including Cladina mitis, Vulpicida pinastri, Evernia mesomorpha and Lecanora circumborealis, some of which are known bioindicators of N deposition. A secondary DNO threshold appeared to be driving changes in several vascular species and was equivalent to 2.45–3.15 kg N ha−1 yr−1 on the TDN gradient. These results suggest that in low deposition ‘background’ regions a biodiversity-based empirical critical load of 1.4–3.15 kg N ha−1 yr−1 will protect lichen communities and other N-sensitive species in Jack pine forests across Northwestern Canada. Nitrogen deposition above the critical load may lead to adverse effects on plant species biodiversity within these forests.
氮沉降长期升高会对陆地生态系统产生不利影响。对于远离排放源的加拿大北部大片地区，即使在低沉降水平下，氮的远距离大气输送也可能影响植物物种多样性。本研究旨在利用梯度森林分析方法，建立不同环境梯度下植物群落氮沉降阈值。对加拿大阿尔伯塔省和萨斯喀彻温省的297个短叶松(Pinus banksiana Lamb.)优势林样地的植物物种丰度数据进行了43个生物气候和沉积变量的评价。生物气候变量绝对是群落阈值的最重要驱动因素。尽管如此，干N氧化物(DNO)和干N二氧化氮沉积推断出总沉积N (TDN)群落阈值为1.4-2.1 kg N ha−1 yr−1。这一变化范围主要与几种地衣物种的变化有关，其中包括Cladina mitis、Vulpicida pinastri、mesomorphia Evernia和Lecanora circumborealis，其中一些是已知的氮沉降生物指标。次生DNO阈值似乎驱动了几种血管物种的变化，在TDN梯度上相当于2.45-3.15 kg N ha−1 yr−1。这些结果表明，在低沉积“背景”区域，基于生物多样性的1.4-3.15 kg N ha−1 yr−1的经验临界负荷将保护加拿大西北部短叶松林中的地衣群落和其他N敏感物种。超过临界负荷的氮沉降可能会对这些森林内的植物物种多样性产生不利影响。
{"title":"Ecological Risks from Atmospheric Deposition of Nitrogen and Sulphur in Jack Pine forests of Northwestern Canada","authors":"Nicole Vandinther, J. Aherne","doi":"10.3390/nitrogen4010008","DOIUrl":"https://doi.org/10.3390/nitrogen4010008","url":null,"abstract":"Chronic elevated nitrogen (N) deposition can have adverse effects on terrestrial ecosystems. For large areas of northern Canada distant from emissions sources, long-range atmospheric transport of N may impact plant species diversity, even at low deposition levels. The objective of this study was to establish plant species community thresholds for N deposition under multiple environmental gradients using gradient forest analysis. Plant species abundance data for 297 Jack pine (Pinus banksiana Lamb.)-dominant forest plots across Alberta and Saskatchewan, Canada, were evaluated against 43 bioclimatic and deposition variables. Bioclimatic variables were overwhelmingly the most important drivers of community thresholds. Nonetheless, dry N oxide (DNO) and dry N dioxide deposition inferred a total deposited N (TDN) community threshold of 1.4–2.1 kg N ha−1 yr−1. This range was predominantly associated with changes in several lichen species, including Cladina mitis, Vulpicida pinastri, Evernia mesomorpha and Lecanora circumborealis, some of which are known bioindicators of N deposition. A secondary DNO threshold appeared to be driving changes in several vascular species and was equivalent to 2.45–3.15 kg N ha−1 yr−1 on the TDN gradient. These results suggest that in low deposition ‘background’ regions a biodiversity-based empirical critical load of 1.4–3.15 kg N ha−1 yr−1 will protect lichen communities and other N-sensitive species in Jack pine forests across Northwestern Canada. Nitrogen deposition above the critical load may lead to adverse effects on plant species biodiversity within these forests.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86390119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. B. Braos, Roberta Souto Carlos, A. C. T. Bettiol, Marina Ali Mere Bergamasco, Maira Caroline Terçariol, Manoel Evaristo Ferreira, Mara Cristina Pessôa da Cruz
Cover crops and N fertilization strongly impact the forms of soil organic C and N and their availability, which change the responses of plants to N fertilization and soil organic C accumulation. Our study objectives were to evaluate the effects of cover crops and N doses on soil total and soluble C and N contents, N fractions, and potentially available N in a long-term no-till experiment. The experiment was conducted in a randomized block design with split plots and four replicates. The main treatments were cover crops species, jack bean, lablab bean, millet, velvet bean, and fallow cultivated prior to maize. Secondary treatments included two doses of mineral N (0 and 120 kg ha−1). Soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–40 cm, which were analyzed for total and water-soluble C and N contents, N fractions (acid hydrolysis method), and potentially available N (hot KCl solution and direct steam distillation methods). Cover crop velvet bean resulted in the highest soil organic carbon levels, and cover crop millet plus fertilization resulted in the highest levels of soil total N. The amino sugar was the largest N fraction, which decreased by 8% with N fertilization. The soluble C and N content strongly correlated with total and available N content. The changes in soil N were influenced by cover crop species and fertilization and the interactions of both, so the combination of fertilization regime and cover crops must be chosen with care. Additionally, legumes are a good source of plant and soil N in systems with low input of N via fertilizer; however, the combination of N fertilizer with legumes can reduce soil N reserves, leading to its long-term depletion.
覆盖作物和施氮对土壤有机碳和氮的形态及其有效性产生强烈影响，从而改变植物对施氮和土壤有机碳积累的响应。本研究的目的是评价覆盖作物和施氮量对长期免耕试验土壤总碳和可溶性碳、氮含量、氮组分和潜在有效氮的影响。试验采用随机区组设计，分图4个重复。主要处理为覆盖作物、豆角、小豆、谷子、绒豆和玉米前休耕。二次处理包括两个剂量的无机氮(0和120 kg ha - 1)。在0-5、5-10、10-20和20-40 cm深度采集土壤样品，分析总碳和水溶性碳、氮含量、N组分(酸水解法)和潜在有效氮(热氯化钾溶液和直接蒸汽蒸馏法)。覆盖作物蚕豆导致土壤有机碳含量最高，覆盖作物谷子加施氮肥导致土壤全氮含量最高，氨基糖是最大的氮组分，施氮后降低了8%。可溶性C和N含量与全氮和速效氮含量呈显著正相关。土壤氮的变化受覆盖作物种类和施肥及其相互作用的影响，因此应谨慎选择施肥制度和覆盖作物的组合。此外，在低氮肥输入系统中，豆科植物是植物和土壤氮的良好来源;而豆科作物配施氮肥会使土壤氮储量减少，导致土壤氮储量长期耗竭。
{"title":"Soil Carbon and Nitrogen Forms and Their Relationship with Nitrogen Availability Affected by Cover Crop Species and Nitrogen Fertilizer Doses","authors":"L. B. Braos, Roberta Souto Carlos, A. C. T. Bettiol, Marina Ali Mere Bergamasco, Maira Caroline Terçariol, Manoel Evaristo Ferreira, Mara Cristina Pessôa da Cruz","doi":"10.3390/nitrogen4010007","DOIUrl":"https://doi.org/10.3390/nitrogen4010007","url":null,"abstract":"Cover crops and N fertilization strongly impact the forms of soil organic C and N and their availability, which change the responses of plants to N fertilization and soil organic C accumulation. Our study objectives were to evaluate the effects of cover crops and N doses on soil total and soluble C and N contents, N fractions, and potentially available N in a long-term no-till experiment. The experiment was conducted in a randomized block design with split plots and four replicates. The main treatments were cover crops species, jack bean, lablab bean, millet, velvet bean, and fallow cultivated prior to maize. Secondary treatments included two doses of mineral N (0 and 120 kg ha−1). Soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–40 cm, which were analyzed for total and water-soluble C and N contents, N fractions (acid hydrolysis method), and potentially available N (hot KCl solution and direct steam distillation methods). Cover crop velvet bean resulted in the highest soil organic carbon levels, and cover crop millet plus fertilization resulted in the highest levels of soil total N. The amino sugar was the largest N fraction, which decreased by 8% with N fertilization. The soluble C and N content strongly correlated with total and available N content. The changes in soil N were influenced by cover crop species and fertilization and the interactions of both, so the combination of fertilization regime and cover crops must be chosen with care. Additionally, legumes are a good source of plant and soil N in systems with low input of N via fertilizer; however, the combination of N fertilizer with legumes can reduce soil N reserves, leading to its long-term depletion.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"115 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85910655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nitrogen availability is among the major limiting factors for the production of organic crops. A central goal of organic farming, according to certification standards, is to rely on ecological and biological principles to build and maintain soil health. Nitrogen is among the most complex nutrient elements with respect to its different chemical forms and its flow within the environment at the soil, microbial, plant, aquatic, and atmospheric levels. Because, from an ecological perspective, all production variables on the farm are interrelated, a challenge for scientists and practitioners is to better understand nutrient cycles on the farm with respect to how particular production practices may improve N availability during particular stages of crop growth while minimizing potential environmental losses that may lead to contamination of the groundwater and aquatic habitats or to undesirable greenhouse gas emissions. Here, based on a selected review of the literature, we evaluate N cycles at the farm level and present key ecologically-based management strategies that may be adopted to improve internal N cycles. Given the location-specific nature of most ecosystem interactions, a participatory agroecology approach is proposed that incorporates the knowledge of indigenous and traditional cultures to better understand and design resilient and socially-equitable organic systems.
{"title":"Ecological Management of the Nitrogen Cycle in Organic Farms","authors":"H. Valenzuela","doi":"10.3390/nitrogen4010006","DOIUrl":"https://doi.org/10.3390/nitrogen4010006","url":null,"abstract":"Nitrogen availability is among the major limiting factors for the production of organic crops. A central goal of organic farming, according to certification standards, is to rely on ecological and biological principles to build and maintain soil health. Nitrogen is among the most complex nutrient elements with respect to its different chemical forms and its flow within the environment at the soil, microbial, plant, aquatic, and atmospheric levels. Because, from an ecological perspective, all production variables on the farm are interrelated, a challenge for scientists and practitioners is to better understand nutrient cycles on the farm with respect to how particular production practices may improve N availability during particular stages of crop growth while minimizing potential environmental losses that may lead to contamination of the groundwater and aquatic habitats or to undesirable greenhouse gas emissions. Here, based on a selected review of the literature, we evaluate N cycles at the farm level and present key ecologically-based management strategies that may be adopted to improve internal N cycles. Given the location-specific nature of most ecosystem interactions, a participatory agroecology approach is proposed that incorporates the knowledge of indigenous and traditional cultures to better understand and design resilient and socially-equitable organic systems.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84405471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sachina Sunuwar, Arthur Siller, Samantha Glaze-Corcoran, M. Hashemi
Cover cropping is vital for soil health. Timing and method of termination are major factors influencing the agroecological benefits of cover crops. Delay in the termination of cover crops results in greater biomass production. Likewise, incorporation of cover crops during termination often speeds residue mineralization compared to no-till systems. We used four termination strategies for a late-terminated winter rye–legume mix (in tilled and no-till systems) and four N application rates in the succeeding sweet corn crop to examine how cover crop termination affected N response in sweet corn as well as the independent effects of N application rate and cover crop termination method. The experiment was conducted using a randomized complete block design with four replications. Increasing N fertilization up to 144 kg N ha–1 promoted yield and quality in sweet corn as well as summer weed growth. The cover crop termination method did not affect sweet corn response to N fertilizer. This suggests that when rye is terminated late in the spring before planting cash crops, the incorporation of its residues may not greatly affect the soil N dynamics. This indicates that decisions to incorporate rye residues may be taken by farmers with an eye mainly towards management issues such as weed control, environmental impacts, and soil health.
覆盖种植对土壤健康至关重要。终止的时机和方式是影响覆盖作物农业生态效益的主要因素。延迟终止覆盖作物导致更大的生物量生产。同样，与免耕系统相比，在终止期间纳入覆盖作物通常会加速残留物的矿化。为了研究覆盖作物终止对甜玉米氮素响应的影响，以及施氮量和覆盖作物终止方式对甜玉米氮素响应的独立影响，我们采用了四种终止策略(耕作和免耕)和后续甜玉米作物的四种施氮量。试验采用随机完全区组设计，共4个重复。施氮量增加至144 kg N hm - 1可促进甜玉米产量、品质和夏季杂草生长。封种终止方式对甜玉米对氮肥的响应没有影响。这表明，在种植经济作物前的晚春终止黑麦，其残茬的加入可能不会对土壤氮动态产生太大影响。这表明，农民在决定纳入黑麦残留物时，可能主要考虑到杂草控制、环境影响和土壤健康等管理问题。
{"title":"Cover Crop Termination Method and N Fertilization Effects on Sweet Corn Yield, Quality, N Uptake, and Weed Pressure","authors":"Sachina Sunuwar, Arthur Siller, Samantha Glaze-Corcoran, M. Hashemi","doi":"10.3390/nitrogen4010005","DOIUrl":"https://doi.org/10.3390/nitrogen4010005","url":null,"abstract":"Cover cropping is vital for soil health. Timing and method of termination are major factors influencing the agroecological benefits of cover crops. Delay in the termination of cover crops results in greater biomass production. Likewise, incorporation of cover crops during termination often speeds residue mineralization compared to no-till systems. We used four termination strategies for a late-terminated winter rye–legume mix (in tilled and no-till systems) and four N application rates in the succeeding sweet corn crop to examine how cover crop termination affected N response in sweet corn as well as the independent effects of N application rate and cover crop termination method. The experiment was conducted using a randomized complete block design with four replications. Increasing N fertilization up to 144 kg N ha–1 promoted yield and quality in sweet corn as well as summer weed growth. The cover crop termination method did not affect sweet corn response to N fertilizer. This suggests that when rye is terminated late in the spring before planting cash crops, the incorporation of its residues may not greatly affect the soil N dynamics. This indicates that decisions to incorporate rye residues may be taken by farmers with an eye mainly towards management issues such as weed control, environmental impacts, and soil health.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73928563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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