Indigenous Nitrogen Research Articles

Noble Gases, Carbon and Nitrogen Isotopes in Different Lithologies of Pesyanoe: Irradiation History and Impact Processes on the Aubrite Parent Body

Abstract We present the results of stepwise crushing and combustion analyses for noble gases, carbon and nitrogen in Pesyanoe aubrite pyroxene lithologies, composed of grey (Px-G) and light (Px-B) enstatites differing in the degree of impact processing and the number of inclusions. Our study identifies three main noble gas endmembers in Pesyanoe: a cosmogenic component, radiogenic 40Ar, and an endmember representing a mixture of solar wind and Q components in variable proportions. Based on petrographic and noble gas data we argue that these gases accumulated in the material during its regolith history and were later redistributed into gas inclusions/voids as the result of an impact event. During impact metamorphism, Px-G acquired its grey color and multiple gas inclusions were formed within it, more than in case of Px-B. Our study demonstrates for the first time: (1) The host phase of gases trapped during shock metamorphism are grains of rock-forming minerals, in particular Px-G, due to the formation of a large number of cracks in the direction of cleavage during brittle deformation, (2) The gas capture is associated not with the final stage of the formation of consolidated fragmental breccia, at which lithification of the fragments occurred, but with one of the intermediate impact events. High amounts of trapped and cosmogenic noble gases are released during the stepwise crushing—significantly higher than in case of any other studied aubrite. Some unusually high 36Ar/132Xe ratios (up to 54 780 versus 22 705 in the solar wind) were discovered during crushing of Px-G. Our preferable explanation of this phenomenon is a specific superposition of noble gas elemental fractionation processes related to the impact cratering of the Pesyanoe parent body. The carbon isotopic composition (δ13C = –21.2 ± 0.2‰, 1σ) is slightly heavier than that of the Bustee aubrite carbon. The combined use of different extraction methods made it possible to determine that the solar type and indigenous (δ15Nindig = –0.1 ± 3.2‰, 1σ) nitrogen components are located in the gas inclusions, whereas the extraneous nitrogen component (~+45‰) is chemically bound. The large cosmic ray exposure age variations (44 and 55 Ma in case of Px-G and Px-B, respectively) and the heterogeneous distribution of solar-type gases in Pesyanoe aubrite point to a diverse irradiation history of the material before breccia formation. Alternatively/additionally, cosmogenic gases (as well as solar and primordial) in Px-G may have became lost and/or partly redistributed into gas inclusions as a result of the impact event.

Biogenic calcium improved Cd2+ and Pb2+ immobilization in soil using the ureolytic bacteria Bacillus pasteurii

Bioremediation based on microbial-induced carbonate precipitation (MICP) was conducted in cadmium and lead contaminated soil to investigate the effects of MICP on Cd and Pb in soil. In this study, soil indigenous nitrogen was shown to induce MICP to stabilize heavy metals without inputting exogenous urea. The results showed that applying Bacillus pasteurii coupled with CaCl2 reduced Cd and Pb bioavailability, which could be clarified through the proportion of exchangeable Cd and Pb in soil decreasing by 23.65 % and 12.76 %, respectively. Moreover, B. pasteurii was combined separately with hydroxyapatite (HAP), eggshells (ES), and oyster shells (OS) to investigate their effects on soil heavy metals' chemical fractions, toxicity characteristic leaching procedure (TCLP)-extractable Cd and Pb as well as enzymatic activity. Results showed that applying B. pasteurii in soil significantly decreased the heavy metals in the exchangeable fraction and increased them in the carbonate phase fraction. When B. pasteurii was combined with ES and OS, the content of carbonate-bound Cd increased by 114.72 % and 118.81 %, respectively, significantly higher than when B. pasteurii was combined with HAP, wherein the fraction of carbonate-bound Cd increased by 86 %. The combination of B. pasteurii and biogenic calcium effectively reduced the leached contents of Cd and Pb in soil, and the TCLP-extractable Cd and Pb fractions decreased by 43.88 % and 30.66 %, respectively, in the BP + ES group and by 52.60 % and 41.77 %, respectively, in the BP + OS group. This proved that MICP reduced heavy metal bioavailability in the soil. Meanwhile, applying B. pasteurii and calcium materials significantly increased the soil urease enzyme activity. The microstructure and chemical composition of the soil samples were studied, and the results from scanning electron microscope, Fourier transform infra-red spectroscopy, and X-ray diffraction demonstrated the MICP process and identified the formation of CaCO3, Ca0.67Cd0.33CO3, and PbCO3 in heavy metal-contaminated soil.

Soybean yield, nutrient uptake and stoichiometry under different climate regions of northeast China

Climate and soil fertility influence seed yield, nutrient uptake, and nutrient stoichiometry in the plant. We collected soybean [Glycine max (L.) Merr.] data were collected from field experiments in northeast China (warm and cold regions) to study the effect of temperature variations during the crop growing season on seed yield, nutrient uptake and stoichiometry from 2001 to 2017. Soybean seed yield has been increased in the cold region but not in the warm region, where average seed yield was higher. The indigenous nitrogen (N) supply followed the same trend as yield, greater in warmer environments but also increasing over time. The internal efficiency (IE) of N and potassium (K) performed similarly in both climate regions, but phosphorus (P) IE was 30% greater in the warm region than the cold region. For soybean nutrient uptake ratio, the N/K ratio was similar between both regions; however, the N/P ratio was greater in the warmer region relative to the colder region. Overall, the higher temperature experienced in the warm region increased soybean seed yield relative to the cold region, and high soil P accumulation caused soybean P luxury uptake in the cold region of northeast China.

In-situ preservation of nitrogen-bearing organics in Noachian Martian carbonates

Understanding the origin of organic material on Mars is a major issue in modern planetary science. Recent robotic exploration of Martian sedimentary rocks and laboratory analyses of Martian meteorites have both reported plausible indigenous organic components. However, little is known about their origin, evolution, and preservation. Here we report that 4-billion-year-old (Ga) carbonates in Martian meteorite, Allan Hills 84001, preserve indigenous nitrogen(N)-bearing organics by developing a new technique for high-spatial resolution in situ N-chemical speciation. The organic materials were synthesized locally and/or delivered meteoritically on Mars during Noachian age. The carbonates, alteration minerals from the Martian near-surface aqueous fluid, trapped and kept the organic materials intact over long geological times. This presence of N-bearing compounds requires abiotic or possibly biotic N-fixation and ammonia storage, suggesting that early Mars had a less oxidizing environment than today.

Simultaneous nitrification and denitrification (SND) bioaugmentation with Pseudomonas sp. HJ3 inoculated for enhancing phenol and nitrogen removal in coal gasification wastewater.

A simultaneous nitrification and denitrification (SND) bioaugmention system with Pseudomonas sp. HJ3 inoculated was established to explore the potential of simultaneous phenol and nitrogen removal in coal gasification wastewater (CGW). When the concentration of influent chemical oxygen demand (COD) and total phenols (TPh) was 1,765.94 ± 27.43 mg/L and 289.55 ± 10.32 mg/L, the average removal efficiency of COD and TPh at the stable operating stage reached 64.07% ± 0.76% and 74.91% ± 0.33%, respectively. Meanwhile, the average removal efficiency of NH4 +-N and total nitrogen (TN) reached 67.96% ± 0.17% and 57.95% ± 0.12%, respectively. The maximum SND efficiency reached 83.51%. Furthermore, SND bioaugmentation performed with good nitrification tolerance of phenol shock load and significantly reduced toxic inhibition of organisms. Additionally, the microbial community analysis indicated that Pseudomonas sp. HJ3 was the predominant bacterium in the SND bioaugmentation system. Moreover, the indigenous nitrogen removal bacteria such as Thauera, Acidovorax and Stenotrophomonas were enriched, which further enhanced the nitrogen removal in the SND bioaugmentation system. The results demonstrated the promising application of SND bioaugmentation for enhancing simultaneous phenol and nitrogen removal in CGW treatment.

Soil microbiomes associated with two dominant Costa Rican tree species, and implications for remediation: A case study from a Costa Rican conservation area

It is now widely accepted that the majority of tropical landscapes are in transition from disturbance to recovery. Remediation efforts are occurring in Central and South America, attempting to recuperate the soils, often using indigenous nitrogen (N)-fixing tree species. Tree species-generated soil microbial heterogeneity might be important in facilitating regeneration of forest vegetation growth and, although some work has identified these efforts may enhance the soil carbon (C), there have been few studies conducted on how these trees are affecting the below-ground soil biological dynamics in these regions. Here, we explored how and to what extent individual plant effects of a native N-fixing and non-N-fixing plant has affected the below-ground soil C and N metrics and soil bacterial and fungal community composition. To begin to address this, we examined if there were differences in various soil abiotic factors (ToC, TN, C:N ratio, Cmic, NH4+, NO3−, pH, and % moisture) and in the soil bacterial and fungal community composition associated with soil of a native non-N-fixer, Dipteryx panamensis and a native N-fixer, Pentaclethra macroloba, and in comparison to the primary forest bulk-soil in which these tree species occur. We found that primary forest-soils had the greatest amounts of soil NH4+ and Cmic, followed by Pentaclethra-soils. Dipteryx-soils had the least amount of soil Cmic and NH4+, but the greatest amounts of soil NO3−. The PERMANOVA results indicated that the Bray-Curtis soil bacterial and fungal community compositions were significantly different between N-fixing and non-N-fixing tree-soils, and also to that of the primary forest-soils. Our results also demonstrated that soil NH4+ best explained the variation observed in the soil Cmic patterns (39.2%), and, both the soil bacterial (22.8%) and fungal community composition (18.1%). Furthermore, we provide evidence that the N-fixer Pentaclethra-soils stimulates the production of more soil Cmic than the non-N-fixer Dipteryx-soils. It is clear that these tree species are important in creating changes in the soil microbial community composition, and that NH4+ may be associated with a shift in a functional response that may have implications for CUE and remediation in this region.

Is soybean yield limited by nitrogen supply?

As soybean yield continues to increase, it seems critical to know if there is a yield level at which potential contribution of indigenous nitrogen (N) sources (N fixation and soil mineralization) becomes insufficient to meet crop N requirements for high yields, while still maintaining or increasing protein and oil concentration. We have hypothesized that, in absence of other limiting factors, degree of N limitation increases with increasing yield potential (Yp) of the production environment. To test this hypothesis, we developed a novel protocol to ensure an ample N supply during the entire crop season (full-N treatment). That protocol was applied to field-grown irrigated soybean in Balcarce (Argentina) and Nebraska (USA), where measured full-N seed yields were ±15% of their simulated Yp in 92% of the cases. The combination of locations, years, sowing dates, and N treatments resulted in a wide range of seed yields, from 2.5 to 6.5Mgha−1. Overall, full-N seed yield averaged 11% higher than seed yield without N addition (zero-N). However, magnitude of yield difference between full-N and zero-N depended upon Yp, ranging from no detectable yield difference in low-Yp (ca. 2.5Mgha−1) to up to 900kgha−1 in high-Yp environments (ca. 6Mgha−1). Seed yield differences were associated with higher aboveground dry matter, seed number, and seed weight in the full-N versus zero-N treatments. Seed protein (but not oil) concentration was higher in the full-N treatment, and both protein and oil yields were higher in the full-N versus zero-N treatments. Findings from this study indicate that (i) N limits soybean seed yield (as well as protein yield, and oil yield) in environments with high Yp, where indigenous N sources seem insufficient to fully satisfy crop N requirements, and (ii) yield response to N fertilizer can occur above a 2.5Mgha−1 Yp threshold and has an upper limit of 250kg seed per Mg increase in Yp.

A poly (ethylene oxide), poly (vinylidene fluoride) and polycapro lactone polymer blend doped with an indigenous nitrogen–sulfur based organic compound as a novel electrolyte system for dye-sensitized solar cell applications

The present study reports, for the first time, the strategy of blending three different polymers followed by the doping of an organic nitrogenous compound to develop a solvent-free novel doped multi-polymer blend electrolyte system for dye-sensitized solar cell (DSSC) applications. Precisely, this novel electrolyte consists of poly (ethylene oxide) (PEO) blended with poly (vinylidene fluoride) (PVdF) and poly (capro lactone) (PCL) that is incorporated into the synthesized 2,6-bis (2-thio pyridyl) pyridine (BTPP) along with KI and I2. The current–voltage (I–V) characteristics of the nanocrystalline DSSC fabricated using the present electrolyte generates a photocurrent of 15.5mA/cm2, a photo-voltage of 905mV, a fill factor of 0.53 and yields an overall energy conversion efficiency of 9.3% under a simulated sunlight radiation of 80mW/cm2. The impressive photoelectric performance of the fabricated solar cell is mainly attributed to the synergic effects of the electrolyte composed of the unique blending of three polymers and the electron donicity of BTPP that leads to strongly influence the interaction between the nanocrystalline TiO2 electrode and I−/I3− electrolyte, thereby leading to high conversion efficiency.

Indigenous nitrogen in the Moon: Constraints from coupled nitrogen–noble gas analyses of mare basalts

Nitrogen and noble gas (Ne–Ar) abundances and isotope ratios, determined by step-wise CO2 laser-extraction, static-mass spectrometry analysis, are reported for bulk fragments and mineral separates of ten lunar mare basalts (10020, 10057, 12008, 14053, 15555, 70255, 71557, 71576, 74255, 74275), one highland breccia (14321), and one ferroan anorthosite (15414). The mare basalt sub-samples 10057,183 and 71576,12 contain a large amount of solar noble gases, whereas neon and argon in all other samples are purely cosmogenic, as shown by their 21Ne/22Ne ratios of ≈0.85 and 36Ar/38Ar ratios of ≈0.65. The solar-gas-free basalts contain a two-component mixture of cosmogenic 15N and indigenous nitrogen (<0.5 ppm). Mare basalt 74255 and the olivine fraction of 15555,876 record the smallest proportion of 15Ncosm; therefore, their δ15N values of −0.2 to +26.7‰ (observed at the low-temperature steps) are thought to well represent the isotopic composition of indigenous lunar nitrogen. However, δ15N values ≤−30‰ are found in several basalts, overlapping with the isotopic signature of Earth's primordial mantle or an enstatite chondrite-like impactor. While the lowest δ15N values allow for nitrogen trapped in the Moon's interior to be inherited from the proto-Earth and/or the impactor, the more 15N-enriched compositions require that carbonaceous chondrites provided nitrogen to the lunar magma ocean prior to the solidification of the crust. Since nitrogen can efficiently be incorporated into mafic minerals (olivine, pyroxene) under oxygen fugacities close to or below the iron-wustite buffer (Li et al., 2013), the mare basalt source region is likely characterized by a high nitrogen storage capacity. In contrast, anorthosite 15414 shows no traces of indigenous nitrogen, suggesting that nitrogen was not efficiently incorporated into the lunar crust during magma ocean differentiation.

Evaluation of nitrogen requirement and efficiency of rice in the region of Yangtze River Valley based on large-scale field experiments

Overestimation of nitrogen (N) uptake requirement is one of the driving forces of the overuse of N fertilization and the low efficiency of N use in China. In this study, we collected data from 1 844 site-years of rice (Oryza sativa L.) under various rotation cropping systems across the Yangtze River Valley. Selected treatments included without (N0 treatment) and with N application (N treatment) which were recommended by local technicians, with a wide grain range of 1.5–11.9 t ha−1. Across the 1 844 site-years, over 96% of the sites showed yield increase (relative yield>105%) with N fertilization, and the increase rates decreased from 78.9 to 16.2% within the lowest range <4.0 to the highest >6.5 t ha−1. To produce one ton of grain, the rice absorbed approximately 17.8 kg N in the N0 treatment and 20.4 kg N in the N treatment. The value of partial factor productivity by N (PFPN) reached a range of 35.2–51.4 kg grain kg−1 with N application under the current recommended N rate. Averaged recovery rate of N (REN) was above 36.0% in yields below 6.0 t ha−1 and lower than 31.7% in those above 6.0 t ha−1. Soil properties only affected yield increments within low rice yield levels (<5.5 t ha−1). There is a poor relationship between N application rates and indigenous nitrogen supply (INS). From these observations and considering the local INS, we concluded there was a great potential for improvement in regional grain yield and N efficiency.

Degradation of kerosene hydrocarbon by indigenous diazotropic bacteria isolated from crude oil contaminated soil

Hydrocarbon contamination significantly increases supply of carbon, but the availability of nitrogen and phosphorus generally become the growth limiting factors for indigenous oil degraders. This nitrogen imbalance selectively favors the development of the soil asymbiotic dinitrogen fixing microorganisms. The present study was undertaken to isolate such diazotrophic bacteria capable of degrading petroleum hydrocarbons. Two bacterial strains were isolated, and identified by using their 16SrDNA as Achromobacter sp. and Arthrobacter sp . Both the isolates could degrade almost all major components of kerosene hydrocarbon within 60 days. Hydrocarbon degradation by the isolates was studied under Gas chromatography-Mass spectroscopy (GC-MS) and the nitrogenase activity of the isolates was measured by Acetylene Reduction Assay. Results of the present investigation revealed the potentiality of free living indigenous nitrogen fixing bacteria to degrade petroleum hydrocarbon and thereby contribute to bioremediation and bio-fertilization of crude oil contaminated soil.

Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars

The Sample Analysis at Mars (SAM) investigation on the Mars Science Laboratory (MSL) Curiosity rover has detected oxidized nitrogen-bearing compounds during pyrolysis of scooped aeolian sediments and drilled sedimentary deposits within Gale crater. Total N concentrations ranged from 20 to 250 nmol N per sample. After subtraction of known N sources in SAM, our results support the equivalent of 110-300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70-260 and 330-1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively. Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history. The detection of nitrate in both wind-drifted fines (RN) and in mudstone (JK, CB) is likely a result of N2 fixation to nitrate generated by thermal shock from impact or volcanic plume lightning on ancient Mars. Fixed nitrogen could have facilitated the development of a primitive nitrogen cycle on the surface of ancient Mars, potentially providing a biochemically accessible source of nitrogen.

Indigenous Nitrogen Supply of Rice Is Predicted by Soil Organic Carbon

Indigenous Nitrogen Supply of Rice Is Predicted by Soil Organic Carbon

Role of Legumes in Sustainable Agriculture and Food Security: An Indian Perspective

Because most animal food products are too expensive for the rural poor, a significant proportion of the Indian population suffers from both protein energy malnutrition and chronic energy deficiency. Statistics on food demand and fertilizer requirements highlight the dependence on foreign imports of fertilizer for food crop production. However, legume crops have a potentially important role to play in increasing indigenous nitrogen production, besides meeting human demands for protein and energy. Some legumes have the ability to solubilize otherwise unavailable phosphate by excreting organic acids from their roots, in addition to improving soil fertility. Legumes also help to restore soil organic matter and reduce pest and disease problems when used in rotation with non-leguminous crops. In the north-eastern Indian Himalaya, indigenous legumes such as rice bean, jack bean and tree bean are more nutritious than other legumes and offer major scope to restore soil fertility. This paper describes the importance of promoting legumes in the context of national food security.

Evaluating regional mean optimal nitrogen rates in combination with indigenous nitrogen supply for rice production

Nitrogen (N) is an essential nutrient that requires careful management in intensive rice systems, since insufficient amounts might result in yield losses, and excessive application might harm the environment. However, farmers often tend to apply a large excess of N fertilizer to ensure high rice yields, primarily because of the absence of reliable methods to estimate optimal N application rates. Therefore, a large-scale study comprising 514 field experiments for rice was conducted in seven rice regions (totaling 1.253millionha) in Hubei province, Central China. We (i) evaluated yield responses to different N application levels, (ii) established indigenous soil N supply (INS) classification systems for different rice regions by identifying and using the preferable predictor of INS, and (iii) determined the optimal N application rates for each region based on regional mean optimal N rates (RMONR) in combination with INS. In all of the rice regions, rice yields were significantly higher in plots receiving N than in plots without N (termed no-N plots). The highest yields were obtained in plots receiving medium nitrogen (MN) treatment, where the average partial factor productivity (PFPN) and agronomic efficiency (AEN) were 50.4kggrainkg−1N and 12.5kggrainkg−1N, respectively. Yield responses of rice to N fertilizer were different among different rice regions because of regional variations in climatic conditions and soil fertility. A significant positive relationship between grain yield with and without N fertilizer also proved an important effect of INS on yield response to N fertilizer. On the basis of regression models, relative yields of 90%, 80%, 70%, 60%, and 50% were used as the critical values to obtain INS classifications, which were estimated by the yield of the no-N treatment but not by alkaline hydrolyzable-N. An obvious increasing trend of economic optimum N rate (EONR) with decreasing INS (from Class 1 to Class 6) was found for each rice region. Averaged across all rice regions of Hubei province, EONR was 150kgha−1, which was lower than the N application rate for the MN treatment of 171kgha−1. The results indicated that the N application rate recommended by local rice technicians could be cut by 12% (1–18% in different rice regions) without any loss of yield. In conclusion, the recommended N fertilizer application, based on RMONR in combination with INS, is feasible for regional rice production in China and other countries that have large numbers of small farmland areas and where agricultural testing equipment is absent or less modern.

Quantifying spatial variability of indigenous nitrogen supply for precision nitrogen management in small scale farming

Understanding spatial variability of indigenous nitrogen (N) supply (INS) is important to the implementation of precision N management (PNM) strategies in small scale agricultural fields of the North China Plain (NCP). This study was conducted to determine: (1) field-to-field and within-field variability in INS; (2) the potential savings in N fertilizers using PNM technologies; and (3) winter wheat (Triticum aestivum L.) N status variability at the Feekes 6 stage and the potential of using a chlorophyll meter (CM) and a GreenSeeker active crop canopy sensor for estimating in-season N requirements. Seven farmer’s fields in Quzhou County of Hebei Province were selected for this study, but no fertilizers were applied to these fields. The results indicated that INS varied significantly both within individual fields and across different fields, ranging from 33.4 to 268.4 kg ha−1, with an average of 142.6 kg ha−1 and a CV of 34%. The spatial dependence of INS, however, was not strong. Site-specific optimum N rates varied from 0 to 355 kg ha−1 across the seven fields, with an average of 173 kg ha−1 and a CV of 46%. Field-specific N management could save an average of 128 kg N ha−1 compared to typical farmer practices. Both CM and GreenSeeker sensor readings were significantly related to crop N status and demand across different farmer’s fields, showing a good potential for in-season site-specific N management in small scale farming systems. More studies are needed to further evaluate these sensing technology-based PNM strategies in additional farmer fields in the NCP.

On-farm estimation of indigenous nitrogen supply for site-specific nitrogen management in the North China plain

Estimating indigenous nitrogen supply (INS) by measurement of crop N uptake in N omission plots for site-specific N management is not feasible on a routine basis because it involves destructive plant sampling and plant tissue analysis, which is time-consuming and expensive. The objective of this study was to determine the amount of INS and develop a method to estimate it using soil testing in the North China plain (NCP). On-farm experiments at 229 sites were conducted from 2003 to 2005 in seven key winter wheat (Triticum aestivum L.)/summer maize (Zea mays L.) production regions of the NCP. The mean INS during the wheat-growing season was129 kg N ha−1 with a range from 62 to 212 kg N ha−1, and it varied from 69 to 202 kg N ha−1 with a mean of 142 kg N ha−1 during the maize-growing season. Considering all sites, the variability of INS was not simulated by initial soil N min or apparent N mineralization (N organic) alone, while together they could explain about 38% and 60% of INS during the wheat and maize-growing seasons, respectively. During the wheat-growing season, mean N organic was 63 kg N ha−1, and 59% and 33% of its variation could be explained by SOM in high-yielding regions (mean yield, 7.6 t ha−1) and low-yielding regions (mean yield, 5.3 t ha−1), respectively. Mean N organic during the maize-growing season was 109 kg N ha−1, 22% of which could be explained by SOM across all sites. An average of 40% and 42% of INS variation could be explained by both SOM and initial soil N min content during the wheat and maize-growing seasons, respectively. We conclude that the accuracy of estimating crop N requirement for site-specific N management will be increased by using initial soil N min and SOM.

Legume Effect for Enhancing Productivity and Nutrient Use-Efficiency in Major Cropping Systems–An Indian Perspective: A Review

ABSTRACT Inclusion of legumes in the cropping system has been known since times immemorial. Legume is a natural mini-nitrogen manufacturing factory in the field and the farmers by growing these crops can play a vital role in increasing indigenous nitrogen production. Legume help in solubilizing insoluble P in soil, improving the soil physical environment, increasing soil microbial activity, and restoring organic matter, and also has smothering effect on weed. The carryover of N derived from legume grown, either in crop sequence or in intercropping system for succeeding crops, is also important. In a country like India, where the average consumption of plant nutrients from chemical fertilizers on national basis is very low, the scope for exploiting direct and residual fertility due to legumes has obviously a great potential. This article deals with the beneficial effect of important legumes on increasing productivity and nutrient use-efficiency in various systems. Sorghum, pearl millet, maize, and castor are mainstay in dry lands and marginal and sub-marginal lands. Sorghum yield increased when sown after cowpea, green gram, and groundnut. Grain legumes like groundnut or cowpea provide an equivalent to 60 kg N ha on the subsequent crop of pearl millet. Various studies have shown that among legume/cereal intercropping system, the combination of maize/pigeon pea is considered to be highly suitable with a minimum competition for nutrients, while legume/legume intercropping system, pigeon pea/groundnut system is the most efficient one in terms of resource use-efficiency. In alley cropping system, Leucaena leucocephala (Subabul) prunings provide N to the extent of 75 kg, which benefits the intercrop castor and sorghum. Nitrogen economy through intercropped legume is still a researchable issue because the key point for leguminous crop grown in intercropping system is the problem of nodulation. Incorporation of whole plant of summer green gram/black gram into soil (after picking pods) before transplanting rice resulted in the economizing (40–60 kg N ha−1, 30 kg P2O5, and 15 kg K2O per ha) of rice in rice-wheat system. Similarly, 6–8 weeks old green manure crop of sunhemp or dhaincha accumulates about 3–4 t ha−1 dry matter and 100–120 kg N ha−1 which, when incorporated in situ, supplements up to 50% of the total N requirement of rice. Legumes with indeterminate growth are more efficient in N2 fixation than determinate types. Fodder legumes in general are more potent in increasing the productivity of succeeding cereals. The carryover of N for succeeding crops may be 60–120 kg in berseem, 75 kg in Indian clover, 75 kg in cluster bean, 35–60 kg in fodder cowpea, 68 kg in chickpea, 55 kg in black gram, 54–58 kg in groundnut, 50–51 kg in soybean, 50 kg in Lathyrus, and 36–42 kg per ha in pigeon pea. Direct and residual effect of partially acidulated material and mixture of rock phosphate + single superphosphate were observed to be better when these were applied to green gram in winter season than to rice in rainy season simply because of legume effect.

Evolutionary trends in volatiles of the nakhlite source region of Mars

We report new data on isotopic systematics in nitrogen, Ar, and Xe of nakhlite NWA998 and discuss the implications of nakhlite signatures on the sources, evolution, and closed system properties of the nakhlite magma in the Martian mantle. The isotopic signatures of xenon in nakhlites are consistent and reveal a source region with the Chass‐S xenon signature, but which had assimilated fission gas starting with the initial early differentiation of Mars to the time of magma eruption 1.3 Gyr ago. We note a trend of correlated enrichments of the fission gas and of trace elements (REE) in the source. Nakhlite NWA817, which contains abundant mesostasis and a hydrous phase, shows a distinct nitrogen component as well as a fission gas excess in low‐temperature steps. Radiogenic 129Xe in nakhlites is associated with neither the fission gas nor the indigenous components and indicates a later incorporation, possibly during magma ascent. Indigenous nitrogen isotopic signatures of δ15N = 13‰ as observed in nakhlites (except NWA817) attest to very limited exchanges of modern atmospheric gases with the solid planet. This nakhlite nitrogen signature corresponds to the heavier of two indigenous signatures in Chassigny and supports other evidence for an origin in similar source regions.

Nitrogen in chondritic metal

We report new nitrogen isotopic data in metals of H-, L- and one LL -chondrites, with N abundances in the range of ∼0.3 to 3.3 ppm and half of these <1 ppm. Nitrogen isotopic signatures in metals with low indigenous N concentrations are modified by cosmic ray spallation components; corrections are required to determine the indigenous N signatures. The metals of type 4 and 5 show uniform indigenous nitrogen (δ 15N = −6.8 ± 0.5 ‰) and confirm a reported possible genetic association of chondritic metal with metal in IIE and IVA iron meteorites. Distinct isotopic signatures are observed in two metal samples of the Portales Valley (H6) meteorite which both are inconsistent with signatures in H4 and H5 chondrites, but possibly reveal a record of impact-induced melting and metamorphism on the parent asteroid. Anomalous nitrogen signatures in metals of type 3 chondrites, on the other hand, may reflect residues of surviving presolar isotopic signatures.