Nitrogen Fixation Efficiency Research Articles

Inoculation with Rhizobium tropici can totally replace N-fertilization in the recently released BRSMG Uai bean cultivar

The BRSMG Uai common bean cultivar (Phaseolus vulgaris L.) unites traits required by producers, such as high yield and upright stands, the latter of which is considerably improved in relation to previously released cultivars such as BRSMG Madrepérola and Pérola. However, the potential of the cultivar to form symbiotic relationships with rhizobia to fix N2 has not yet been assessed. Here, field experiments were conducted to assess the efficiency of biological nitrogen fixation (BNF) in the cultivar, and to compare this to the efficiencies of other genetic materials widely grown throughout Brazil (BRSMG Madrepérola and Pérola). Experiments were conducted on two Oxisols in Minas Gerais State, Brazil (one during the dry season in the south, and the other during the winter season in the Alto-Paranaíba region), under a no-tillage system over maize stover. A randomized block experimental design was implemented in a 3 × 3 factorial arrangement with four replicates. Individual and combined Analysis of Variance were performed and the data were normalized. Homogeneity of the residual mean squares was observed. Significant effects of factors were identified by Scott-Knott tests and F tests. The BRSMG Uai cultivar responded to inoculation with the rhizobial strain CIAT 899, with yields similar to those achieved upon fertilization with 80 kg ha-1 of N-urea and to the yields of the BRSMG Madrepérola and Pérola cultivars inoculated with the same rhizobial strain. In terms of commercial use, this cultivar may be successful under either of the management practices adopted for N supply, and from the perspective of plant breeding, it has potential for inclusion in breeding programs directed toward improving BNF.

N-doping TiO2 hollow microspheres with abundant oxygen vacancies for highly photocatalytic nitrogen fixation

Photocatalytic fixation of nitrogen to ammonia (NH3) is a green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N2 and the band position of TiO2 are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO2 hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol gcat−1h−1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H2O2 treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol gcat−1h−1 after reducing oxygen vacancies by H2O2 treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol gcat−1h−1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.

Identification of the Important Genes of Bradyrhizobium diazoefficiens 113-2 Involved in Soybean Nodule Development and Senescence.

Legume nodule development and senescence directly affect nitrogen fixation efficiency and involve a programmed series of molecular events. These molecular events are carried out synchronously by legumes and rhizobia. The characteristics and molecular mechanisms of nitrogen fixation at soybean important developmental stages play critical roles in soybean cultivation and fertilizer application. Although the gene expression of soybean were analyzed in nodules at five important soybean developmental stages, information on the expression of rhizobial genes in these nodule samples is limited. In the present study, we investigated the expression of Bradyrhizobium diazoefficiens 113-2 genes in the nodule samples from five developmental stages of soybean (Branching stage, flowering stage, fruiting stage, pod stage and harvest stage). Similar gene expression patterns of B. diazoefficiens 113-2 were existed during optimal symbiotic functioning, while different expression patterns were found among early nodule development, nitrogen fixation progress and nodule senescence. Besides, we identified 164 important different expression genes (DEGs) associated with nodule development and senescence. These DEGs included those encoding nod, nif, fix proteins and T3SS secretion system-related proteins, as well as proteins involved in nitrogen metabolism, ABC transporters and two-component system pathways. Gene Ontology, KEGG pathway and homology analysis of the identified DEGs revealed that most of these DEGs are uncharacterized genes associated with nodule development and senescence, and they are not core genes among the rhizobia genomes. Our results provide new clues for the understanding of the genetic determinants of soil rhizobia in nodule development and senescence, and supply theoretical basis for the creation of high efficiency soybean cultivation technology.

Isolation and Characterization of Chickpea (Cicer arietinum L.) Nodulating Rhizobia Collected from South Wollo Zone, Ethiopia

This study aimed at screening rhizobial isolates of chickpea and evaluating their symbiotic nitrogen fixation efficiency and tolerance to abiotic stresses. A total of 107 (100%) isolates were collected of which 52 (48.6%) were confirmed as chickpea rhizobia using preliminary tests. Among 52 (48.6%) isolates, 46 (88.5%) have induced nodulation on chickpea under greenhouse and were screened under in vitro conditions and 6 (11.5%) of them were discarded due to fail to nodulate. The greenhouse data showed the highest nodule number (68.67 plant−1), nodule dry weight (0.17 g plant−1), and shoot dry weight (0.81 g plant−1) were scored by plants inoculated with isolates WUCR 17, WUCR 1, and WUCR 66, respectively. Among authenticated isolates, 73.9%, 21.7%, and 4.3% were highly effective, effective, and lowly effective, respectively. The physiological test showed 15% of isolates tolerated 13% salt concentration and 10.9% of isolates grew at pH 4–10 range. All isolates grew at 20–35°C and 13% grew at maximum temperature (50°C). The isolates showed better resistance to the tested antibiotics at low concentration (2.5 μg/ml) but the majorities were sensitive at high concentration (10 μg/ml). Among the isolates, 13% tolerated all tested heavy metals but 48% were sensitive to mercury. Regarding the carbohydrate utilization test, 52.2% catabolized all the tested 11 carbon sources but 6.5% of them utilized only 63.6% carbon sources. Amino acid utilization showed isolates (85%) utilized D-alanine except WUCR (14, 25, 31, 34, 39, 59, and 76) and 76% of the isolates utilized arginine and phenylalanine and 74% utilized leucine as a nitrogen source. Of the isolates, 43.5% of them utilized both D-alanine and arginine as a nitrogen source. In almost all tests conducted, isolates WUCR 1 and 5 performed top and were recommended as potential candidates for microbial inoculants.

On the promising performance of single Ta atom in efficient nitrogen fixation

The electrocatalytic nitrogen reduction reaction (NRR) with atomic Ta catalysts as supported by carbon materials is investigated using a combination of experiments and theoretical calculations. The Ta catalysts were prepared via photodeposition (Ta-GO) and impregnation (Ta-NC), respectively. Surprisingly, the Ta-GO catalyst exhibits excellent NRR efficiency with an ammonia yield rate of 19.97 μ g N H 3 h − 1 m g C a t . − 1 (14.26 m g N H 3 h − 1 m g T a − 1 ) and a Faraday efficiency (FE) of 8.52%. By contrast, the Ta-NC species exhibits lower atomic efficiency (y NH3 = 17.71 μ g N H 3 h − 1 m g C a t . − 1 [3.34 m g N H 3 h − 1 m g T a − 1 ]) but higher NRR selectivity (FE = 17.86%). The reaction mechanisms have been revealed by computation, based on which the electronic origins for the performances of atomic Ta at different coordination environments are discussed. This work demonstrates the potential of Ta to conduct an efficient NRR process, and the promising electronic structure for constructing highly efficient Ta catalysts is discussed. • The Ta catalysts were prepared via photodeposition (Ta-GO) and impregnation (Ta-NC). • The Ta-GO exhibits an ammonia yield of 19.97 μ g N H 3 h − 1 m g C a t . − 1 and an FE of 8.52%. • Ta has the potential as the active center to conduct an efficient NRR process. In the field of ammonia synthesis, the traditional Haber-Bosch process requires high temperature and high pressure, while the hydrogen comes from fossil fuels, thus consuming a large amount of energy and causing environmental pollution. Electrochemical nitrogen reduction reaction (NRR) has been considered as an eco-friendly strategy for an alternative to the Haber-Bosch process under ambient conditions with renewable electricity from solar or wind sources, which is of great significance to the sustainable development of the national economy. The atomic Ta catalysts at different coordination environments as prepared for the NRR process by photodeposition (Ta-GO) and impregnation (Ta-NC), and the electrocatalytic performance has been investigated, which demonstrates the potential of Ta to conduct an efficient NRR process.

Drastically Increase in Atomic Nitrogen Production Depending on the Dielectric Constant of Beads Filled in the Discharge Space.

Nitrogen activation, especially dissociation (production of atomic nitrogen), is a key step for efficient nitrogen fixation, such as nitrogen reduction to produce ammonia. Nitrogen reduction reactions using water as a direct hydrogen source have been studied by many researchers as a green ammonia process. We studied the reaction mechanism and found that the nitrogen reduction could be significantly improved via efficient production of atomic nitrogen through electric discharge. In the present study, we focused on packed-bed dielectric barrier discharge (PbDBD) using dielectric beads as the packing material. The experimental results showed that more atomic nitrogen was produced in the nitrogen activation by the discharge in which the discharge space was filled with the dielectric beads than in the nitrogen activation by the discharge without using the dielectric beads. Then, it was clarified that the amount of atomic nitrogen increased as the dielectric constant of the beads to be filled increased, and the amount of atomic nitrogen produced increased up to 13.48 times. Based on the results, we attempted ammonia synthesis using water as a direct hydrogen source with the efficiently generated atomic nitrogen. When the atomic nitrogen gas generated by the PbDBD was sprayed onto the surface of the water phase and subsequently reacted as a plasma/liquid interfacial reaction, the nitrogen fixation rate increased by 7.26-fold compared to that when using the discharge without dielectric beads, and the ammonia production selectivity increased to 83.7%.

Optimal Water-Fertilizer Combinations for Efficient Nitrogen Fixation by Sugarcane at Different Stages of Growth

High fertilizer application and over-irrigation in sugarcane systems can cause considerable N2O emissions. Optimized water-fertilization management which reduces N2O emissions, while maintaining sugarcane biomass, is crucial, but may affect nitrogen fixation by sugarcane. This study evaluated the combined effect of water-fertilization on sugarcane biomass and nitrogen fixation in field trials in southern China. Treatments included drip and spray irrigation, with three levels (0% (low), 50% (medium), 100% (high)) of irrigation and of fertilizer. A rain-fed crop (no irrigation or fertilizer) was included as the control. The results showed that (1) spray irrigation with medium water and high fertilization increased biomass. The optimum combination in sugarcane elongation stage was drip irrigation with medium water and high fertilization, while drip irrigation with high water and high fertilization was the best choice for maturity stage. (2) For sugarcane nitrogen (δ15N) content, spray irrigation with medium water and high fertilization was the best combination in seedling and tillering stages. The optimum combination in the elongation stage was drip irrigation with medium water and high fertilization, and in maturity stage was drip irrigation with high water and high fertilization. (3) For soil (δ15N content), drip irrigation with high water and high fertilization proved optimal for seedling, tillering, and maturity stages. (4) In seedling stage, sugarcane (δ15N content) was found to be strongly correlated with leaf area index, soil water, soil temperature, and soil electrical conductivity. Soil (δ15N content) was correlated with photosynthesis and soil temperature. In conclusion, drip irrigation appears most suitable for field planting, while the best treatment in seedling and tillering stages is medium water-high fertilization, and that the best in elongation stage is high water-medium fertilization. The optimum water-fertilizer combinations identified here can provide a scientific basis for optimization and management of irrigation and fertilization in China and other regions with similar environments.

Master regulator NtrC controls the utilization of alternative nitrogen sources in Pseudomonas stutzeri A1501

Pseudomonas stutzeri A1501 is a model strain used to study associative nitrogen fixation, and it possesses the nitrogen regulatory NtrC protein in the core genome. Nitrogen sources represent one of the important factors affecting the efficiency of biological nitrogen fixation in the natural environment. However, the regulation of NtrC during nitrogen metabolism in P. stutzeri A1501 has not been clarified. In this work, a phenotypic analysis of the ntrC mutant characterized the roles of NtrC in nitrogen metabolism and the oxidative stress response of P. stutzeri A1501. To systematically identify NtrC-controlled gene expression, RNA-seq was performed to further analyse the gene expression differences between the wild-type strain and the ∆ntrC mutant under nitrogen fixation conditions. A total of 1431 genes were found to be significantly altered by ntrC deletion, among which 147 associative genes had NtrC-binding sites, and the pathways for nitrogen fixation regulation, nitrogenous compound acquisition and catabolism and nitrate assimilation were discussed. Furthermore, the oxidative stress-related gene (katB), which was upregulated by ntrC deletion, was suggested to be a potential target gene of NtrC, thus highlighting the importance of NtrC in nitrogenase protection against oxygen damage. Based on these findings, we propose that NtrC is a high-ranking element in the regulatory network of P. stutzeri A1501 that controls a variety of nitrogen metabolic and oxidative stress responsive traits required for adaptation to complex rhizosphere environments.

One-step synthesis of N, P co-doped porous carbon electrocatalyst for highly efficient nitrogen fixation

One-step synthesis of N, P co-doped porous carbon electrocatalyst for highly efficient nitrogen fixation

Hydrogen-bond activation of N2 molecules and photocatalytic nitrogen fixation

In this issue of <i>Chem</i>, Wang and co-workers report an innovative strategy for activating inert N₂ molecules through hydrogen bonding for efficient photocatalytic nitrogen fixation. This preview carefully discusses the mechanism, presents the challenges associated with photocatalytic nitrogen fixation, and proposes methods for enhancing its performance in the future.

Enhancing the compatibility of abiotic and biological components for efficient nitrogen fixation

The realization of compatibility between the abiotic and biological components is critically important for building a successful hybrid biological/inorganic system. In this issue of Chem Catalysis , Lu et al. demonstrate a prototype hybrid system along with a unique methodology to enhance the communication between the abiotic and biological components for electrically converting N 2 /CO 2 into value-added chemicals.

Vacancy and N dopants facilitated Ti3+ sites activity in 3D Ti3-xC2Ty MXene for electrochemical nitrogen fixation

Identification of the intrinsic active sites and understanding of the kinetics processes on electrocatalysts is essential in the rational design of highly efficient electrochemical nitrogen fixation electrocatalysts. In this work, 3D N-doped-TiV-Ti3-xC2Ty-1.2 MXene was fabricated for ENRR. The intrinsic active-site, as well as the activated mechanism of 3D porous N-doped Ti3-xC2Ty MXene, were elucidated by in situ electrochemical Raman spectrum and DFT simulation. It was demonstrated that the Ti3+ species were the intrinsic active sites for electrocatalytic nitrogen reduction reaction (ENRR), and the electronic state of the active Ti3+ species in 3D porous N-doped Ti3-xC2Ty MXene can be adjusted by surface atomic engineerings, such as vacancy creation and heteroatom doping. The introduction of Ti vacancies can trap the electrons that inject into an antibonding orbital of adsorbed N2, which facilitates the activation of N2. Besides, the N-dopant species in the MXene can not only act as steady active sites for ENRR but also promote the desorption of NH3 by minimize the orbits overlap between Ti3+ and N2, which was confirmed by a bidirectional isotopic exchange labeling method and DFT simulation. This finding paves a valuable strategy for the surface engineering design of efficient catalysts in ENRR.

Highly Efficient CRISPR-Mediated Base Editing in Sinorhizobium meliloti.

Rhizobia are widespread gram-negative soil bacteria and indispensable symbiotic partners of leguminous plants that facilitate the most highly efficient biological nitrogen fixation in nature. Although genetic studies in Sinorhizobium meliloti have advanced our understanding of symbiotic nitrogen fixation (SNF), the current methods used for genetic manipulations in Sinorhizobium meliloti are time-consuming and labor-intensive. In this study, we report the development of a few precise gene modification tools that utilize the CRISPR/Cas9 system and various deaminases. By fusing the Cas9 nickase to an adenine deaminase, we developed an adenine base editor (ABE) system that facilitated adenine-to-guanine transitions at one-nucleotide resolution without forming double-strand breaks (DSB). We also engineered a cytidine base editor (CBE) and a guanine base editor (GBE) that catalyze cytidine-to-thymine substitutions and cytidine-to-guanine transversions, respectively, by replacing adenine deaminase with cytidine deaminase and other auxiliary enzymes. All of these base editors are amenable to the assembly of multiple synthetic guide RNA (sgRNA) cassettes using Golden Gate Assembly to simultaneously achieve multigene mutations or disruptions. These CRISPR-mediated base editing tools will accelerate the functional genomics study and genome manipulation of rhizobia.

Altering Hydrogenation Pathways in Photocatalytic Nitrogen Fixation by Tuning Local Electronic Structure of Oxygen Vacancy with Dopant.

To avoid the energy-consuming step of direct N≡N bond cleavage, photocatalytic N2 fixation undergoing the associative pathways has been developed for mild-condition operation. However, it is a fundamental yet challenging task to gain comprehensive understanding on how the associative pathways (i.e., alternating vs. distal) are influenced and altered by the fine structure of catalysts, which eventually holds the key to significantly promote the practical implementation. Herein, we introduce Fe dopants into TiO2 nanofibers to stabilize oxygen vacancies and simultaneously tune their local electronic structure. The combination of in situ characterizations with first-principles simulations reveals that the modulation of local electronic structure by Fe dopants turns the hydrogenation of N2 from associative alternating pathway to associative distal pathway. This work provides fresh hints for rationally controlling the reaction pathways toward efficient photocatalytic nitrogen fixation.

Altering Hydrogenation Pathways in Photocatalytic Nitrogen Fixation by Tuning Local Electronic Structure of Oxygen Vacancy with Dopant

AbstractTo avoid the energy‐consuming step of direct N≡N bond cleavage, photocatalytic N2 fixation undergoing the associative pathways has been developed for mild‐condition operation. However, it is a fundamental yet challenging task to gain comprehensive understanding on how the associative pathways (i.e., alternating vs. distal) are influenced and altered by the fine structure of catalysts, which eventually holds the key to significantly promote the practical implementation. Herein, we introduce Fe dopants into TiO2 nanofibers to stabilize oxygen vacancies and simultaneously tune their local electronic structure. The combination of in situ characterizations with first‐principles simulations reveals that the modulation of local electronic structure by Fe dopants turns the hydrogenation of N2 from associative alternating pathway to associative distal pathway. This work provides fresh hints for rationally controlling the reaction pathways toward efficient photocatalytic nitrogen fixation.

Isolation and nitrogen fixing efficiency of Gluconacetobacter diazotrophicus associated with sugarcane: A review

The present review was focused on the isolation and nitrogen-fixing efficiency of Gluconacetobacter diazotrophicus associated with sugarcane crop. Gluconacetobacter diazotrophicus has a long-standing partnership with the bacterium Escherichia coli as an entophyte, which can efficiently fix atmospheric nitrogen. It plays a significant role and occurs in most sugarcane growing countries. It has been found to reside in the sugar cane root, stem, buds and leaves. Biological nitrogen fixation based farming systems would enhance agricultural production in the long term in both economically viable and socially acceptable way. This process not only replaces the most expensive fertilizer but also reduces considerably groundwater pollution with nitrates because biological nitrogen fixation was self-regulated. Convincing evidence has pointed out that biological nitrogen fixation requiring a relatively simple and low-cost technology, easy to execute and largely renewable sources of energy has a tremendous role to play in the immediate further of agriculture, especially in the developing and underdeveloped countries.

Atomically Dispersed Iron Metal Site in a Porphyrin-Based Metal-Organic Framework for Photocatalytic Nitrogen Fixation.

The rational design of photocatalysts for efficient nitrogen (N2) fixation at ambient conditions is important for revolutionizing ammonia production and quite challenging because the great difficulty lies in the adsorption and activation of the inert N2. Inspired by a biological molecule, chlorophyll, featuring a porphyrin structure as the photosensitizer and enzyme nitrogenase featuring an iron (Fe) atom as a favorable binding site for N2via π-backbonding, here we developed a porphyrin-based metal-organic framework (PMOF) with Fe as the active center as an artificial photocatalyst for N2 reduction reaction (NRR) under ambient conditions. The PMOF features aluminum (Al) as metal node imparting high stability and Fe incorporated and atomically dispersed by residing at each porphyrin ring promoting the adsorption and the activation of N2, termed Al-PMOF(Fe). Compared with the pristine Al-PMOF, Al-PMOF(Fe) exhibits a substantial enhancement in NH3 yield (635 μg g-1cat.) and production rate (127 μg h-1 g-1cat.) of 82% and 50%, respectively, on par with the best-performing MOF-based NRR catalysts. Three cycles of photocatalytic NRR experimental results corroborate a stable photocatalytic activity of Al-PMOF(Fe). The combined experimental and theoretical results reveal that the Fe-N site in Al-PMOF(Fe) is the active photocatalytic center that can mitigate the difficulty of the rate-determining step in photocatalytic NRR. The possible reaction pathways of NRR on Al-PMOF(Fe) were established. Our study of porphyrin-based MOF for the photocatalytic NRR will provide insight into the rational design of catalysts for artificial photosynthesis.

Efficient Nitrogen Fixation to Ammonia through Integration of Plasma Oxidation with Electrocatalytic Reduction

AbstractPresent one‐step N2 fixation is impeded by tough activation of the N≡N bond and low selectivity to NH3. Here we report fixation of N2‐to‐NH3 can be decoupled to a two‐step process with one problem effectively solved in each step, including: 1) facile activation of N2 to NOx− by a non‐thermal plasma technique, and 2) highly selective conversion of NOx− to NH3 by electrocatalytic reduction. Importantly, this process uses air and water as low‐cost raw materials for scalable ammonia production under ambient conditions. For NOx− reduction to NH3, we present a surface boron‐rich core–shell nickel boride electrocatalyst. The surface boron‐rich feature is the key to boosting activity, selectivity, and stability via enhanced NOx− adsorption, and suppression of hydrogen evolution and surface Ni oxidation. A significant ammonia production of 198.3 μmol cm−2 h−1 was achieved, together with nearly 100 % Faradaic efficiency.

Efficient Nitrogen Fixation to Ammonia through Integration of Plasma Oxidation with Electrocatalytic Reduction.

Present one-step N2 fixation is impeded by tough activation of the N≡N bond and low selectivity to NH3 . Here we report fixation of N2 -to-NH3 can be decoupled to a two-step process with one problem effectively solved in each step, including: 1) facile activation of N2 to NOx - by a non-thermal plasma technique, and 2) highly selective conversion of NOx - to NH3 by electrocatalytic reduction. Importantly, this process uses air and water as low-cost raw materials for scalable ammonia production under ambient conditions. For NOx - reduction to NH3 , we present a surface boron-rich core-shell nickel boride electrocatalyst. The surface boron-rich feature is the key to boosting activity, selectivity, and stability via enhanced NOx - adsorption, and suppression of hydrogen evolution and surface Ni oxidation. A significant ammonia production of 198.3 μmol cm-2 h-1 was achieved, together with nearly 100 % Faradaic efficiency.

Differential Response of Cylindrospermum musicola, Calothrix javanica and Westiellopsis prolifica to Endotaf (Endosulfan, 35%), an Organochlorine Pesticide

The effect of Endotaf (Endosulfan, 35%) pesticide was studied on nitrogen fixation efficiency of Cylindrospermum musicola, Calothrix javanica and Westiellopsis prolifica at different concentrations of pesticide in the nitrogen free BG-11 medium. Total nitrogen fixed by blue-green algal species was estimated by conventional Micro- kjeldahl method in the laboratory cultures at each concentration of Endotaf pesticide. The results obtained during the present investigation indicated a progressive decrease in the total nitrogen content of the tested blue-green algae with increasing concentrations of the Endotaf pesticide. However, nitrogen fixation of most of the blue-green algae was also increased at the lower doses of pesticide. The consequences of the results revealed that Calothrix javanica was emerged as most compatible and tolerant to the increasing Endotaf pesticide doses than the other tested blue-green algal species. On the other hand, Cylindrospermum musicola was found to be highly susceptible as even at 2.5 ppm of Endotaf. Calothrix species was capable to tolerate upto 10 ppm of Endotaf while in Westiellopsis prolifica and Cylindrospermum musicola, the pesticide tolerance range was found to be upto 5 ppm and 2.5 ppm with Endotaf, respectively. Further increase in pesticides concentrations a gradual decline in the total nitrogen content occurred in all the tested blue-green algal strains. It is concluded that indiscriminate use of these pesticides may cause adverse effects on the nitrogen fixing blue-green algae of various crop fields, which has a direct influence on total productivity. Since it is essential to screen efficient blue-green algal strains those are capable of growing and fixing nitrogen at higher rate even in presence of recommended doses of the agrochemicals including pesticides, before their inoculation into the field.