Diazotrophs for Lowering Nitrogen Pollution Crises: Looking Deep Into the Roots

Abstract

During and after the green revolution in the last century, agrochemicals especially nitrogen (N) were extensively used. However, it resulted in a remarkable increase in crop yield but drastically reduced soil fertility; increased the production cost, food prices, and carbon footprints; and depleted the fossil reserves with huge penalties to the environment and ecological sustainability. The groundwater, rivers, and oceans are loaded with N excess which is an environmental catastrophe. Nitrogen emissions (e.g., ammonia, nitrogen oxide, nitrous oxide) play an important role in global climate change and contribute to particulate matter and acid rain causing respiratory problems, cancers, and damage to forests and buildings. Therefore, the nitrogen-polluted planet Earth needs concerted global efforts to avoid the disaster. Improved agricultural N management focuses on the synchronization of crop N demand and N supply along with improving the N-use efficiency of the crops. However, there is very little focus on the natural sources of N available for plants in the form of diazotrophic bacteria present inside or on the root surface and the rhizosphere. These diazotrophs are the mini-nitrogen factories that convert available (78%) atmospheric N2 to ammonia through a process known as “biological nitrogen fixation” which is then taken up by the plants for its metabolic functioning. Diazotrophs also stimulate root architecture by producing plant hormones and hence improve the plant’s overall ability to uptake nutrients and water. In recent years, nanotechnology has revolutionized the whole agri-industry by introducing nano-fertilizers and coated/slow-releasing fertilizers. With this in mind, we tried to explore the following questions: To what extent can the crop N requirements be met by diazotroph inoculation? Can N input to agriculture be managed in a way leading to environmental benefits and farmers saving money? Can nanotechnology help in technological advancement of diazotroph application? The review suggests that an integrated technology based on slow-releasing nano-fertilizer combined with diazotrophs should be adopted to decrease nitrogen inputs to the agricultural system. This integrated technology would minimize N pollution and N losses to much extent.

Genetic diversity of microsymbionts nodulating Trifolium pratense in subpolar and temperate climate regions

“…This process, called biological nitrogen fixation (BNF), is an ecological and low-cost alternative providing nitrogen to legume crops. BNF decreases the amounts of synthetic nitrogen fertilizers applied in agriculture, and thus limits its adverse impacts on natural ecosystems (e.g., it reduces greenhouse gas emissions and pollutions of surface and underground waters) 8 – 10 . This process yields about 122 million tons of fixed nitrogen per year into the environment, with 50–70 million tons of N 2- fixed biologically by agricultural crops 9 – 11 .…”

What Did We Learn From Current Progress in Heat Stress Tolerance in Plants? Can Microbes Be a Solution?

“…Many of PGPM activate structural changes in plants that impart tolerance to heat stress, a phenomenon known as induced systemic tolerance (Yang et al, 2009 ). Apart from inducing direct stress tolerance, several plant-beneficial traits exhibited by these bacteria support plant growth in a synergistic manner under stress (Etesami and Beattie, 2017 ; Imran et al, 2021 ). They benefit plants either directly, through the phytohormones production, nutrient mobilization, and nitrogen fixation or indirectly by triggering the signaling cascades in the host plant.…”

“…Burkholderia phytofirmans strain PsJN is a well-reported PGPR that enhances heat tolerance in tomatoes, cold tolerance in grapevine, water stress tolerance in wheat, salt, and freezing tolerance in Arabidopsis . The same bacterium also has the antifungal property that protects the plant from biotic stress (Issa et al, 2018 ) revealing that a single bacterium can induce multiple benefits in same or different hosts (Imran et al, 2021 ).…”

Tailored Bioactive Compost from Agri-Waste Improves the Growth and Yield of Chili Pepper and Tomato

“…The addition of plant growth-promoting bacteria (PGPB) to the compost makes it biologically active and effective for seed germination and plant growth, soil rehabilitation, and disease suppression ( Tahir et al, 2006 ; El-Akshar et al, 2016 ; Kaur et al, 2019 ). The phytohormone-producing PGPB mediate water and nutrient uptake due to increased root proliferation that ultimately improve plant growth and yield ( Imran et al, 2021 ). The effectiveness of bioactive compost, however, depends upon the survival and physiological efficiency of microbes ( Altaf et al, 2014 ) along with the organic contents and moisture-holding capacity of the compost ( Mahdi et al, 2010 ; Calabi–Floody et al, 2019 ).…”