Manoj Kaushal

Plant-growth-promoting rhizobacteria: drought stress alleviators to ameliorate crop production in drylands

Drylands are known for being a drought stressed environment, which is an alarming constraint to crop productivity. To rescue plant growth in such stressful conditions, plant-growth-promoting rhizobacteria (PGPR) are a bulwark against drought stress and imperilled sustainability of agriculture in drylands. PGPR mitigates the impact of drought stress on plants through a process called rhizobacterial-induced drought endurance and resilience (RIDER), which includes physiological and biochemical changes. Various RIDER mechanisms include modification in phytohormonal levels, antioxidant defense, bacterial exopolysaccharides (EPS), and those associated with metabolic adjustments encompass accumulation of several compatible organic solutes like sugars, amino acids and polyamines. Production of heat-shock proteins (HSPs), dehydrins and volatile organic compounds (VOCs) also plays significant role in the acquisition of drought tolerance. Selection, screening and application of drought-stress-tolerant PGPRs to crops can help to overcome productivity limits in drylands.

Evaluation of Ageratum conyzoides in field scale constructed wetlands (CWs) for domestic wastewater treatment

Ageratum conyzoides were evaluated in field scale subsurface flow constructed wetlands (CWs) to quantify its nitrogen (N) and phosphorus (P) uptake and compare with wetland plants (Pistia stratiotes, Typha latifolia and Canna indica). The two-field scale subsurface flow CWs, located in the International Crops Research Institute for Semi-Arid Tropics, received wastewater from an urban colony. The CW1 and CW2 had the same dimensions (length:10 m, width:3 m, total depth:1.5 m and sand and gravel:1 m), similar flow rates (3 m3/d), hydraulic loading rates (HLRs-10 cm/d) and hydraulic retention time (HRT-5 days) from July 2014-August 2015. The vegetation in both CWs consisted of Pistia stratiotes, Typha latifolia, Canna indica, and Ageratum conyzoides, respectively. The CW1 (% reduction with respect to concentrations) reduced total suspended solids (TSS) (68%), NH4-N (26%), NO3-N (30%), soluble reactive P (SRP) (20%), chemical oxygen demand (COD) (45%) and fecal coliforms (71%), while the CW2 (%-reduction with respect to concentrations) reduced TSS (63%), NH4-N (32%), NO3-N (26%), SRP (35%), COD (39%) and fecal coliforms (70%). Ageratum conyzoides can be used in combination with Pistia stratiotes, Typha latifolia and Canna indica to enhance removal of excessive N, P and fecal coliforms from domestic wastewater.

Integrated Nutrient Management for Improved Cauliflower Yield and Soil Health

ABSTRACT Nutrient management in Cauliflower (Brassica oleracea var. botrytis L.) cultivation is in part dependent on the microbial population in the rhizosphere. Fertilizer must be applied to support plant growth and development. Whether fertilizer usage in cauliflower can be reduced needs to be determined. Rhizospheric isolates of cauliflower, obtained from soil around the roots and from their roots, in the low and mid-hills agro-ecological zones of India were tested for their efficacy to support cauliflower productivity. The plant growth–promoting rhizobacteria SB5, SB8, SB10, and SB11 exhibited the best plant growth–promoting traits with antagonism against soilborne pathogens compared to the reference strain Bacillus pumilus (JN559852). Application of SB11 (Bacillus spp.) exhibited the most plant growth–promoting attributes in field trials at 75% N and P and increased yield by 33% over the uninoculated control at 100% N and P. The isolate SB11 exhibited P solubilization, siderophore production, indole acetic acid production, hydrocyanic acid (HCN) production, and antifungal activity that may be developed as a plant growth–promoting rhizobacteria (PGPR) to enhance crop productivity and sustain soil health while saving 25% usage of chemical fertilizers.

Nanosensors: Frontiers in Precision Agriculture

In the last decennium, nanotechnology has earned strength in and become the influential gizmo in current agriculture. Nanotechnology can boost agricultural production by improving nutrient use efficiency with nanoformulations of fertilizers; agrochemicals for crop enhancement, detection and treatment of diseases, host-parasite interactions at the molecular level using nanosensors, plant disease diagnostics, contaminants removal from soil and water, postharvest management of vegetables and flowers, and reclamation of salt-affected soils; etc. Nanobiosensors can be also employed for sensing a wide variety of pathogens, fertilizers, moisture and soil pH aiming to remove plant protection product applications, reduce loss of nutrients, and enhance crop yields through good nutrient management. Here we review nanotechnology applications for agriculture production, metal oxide-based nanosensors for protection of crops from diseases caused by bacteria and counter microbial attacks.

Efficacy of Biological Soil Amendments and Biocontrol Agents for Sustainable Rice and Maize Production

Exploiting the agroecosystem services of soil microbes appears as a promising effective approach to alleviate the negative impacts on soil systems and crop production. Lack of soil organic matter (SOM) is a prevalent feature of degraded soils. Different biological soil amendments, such as organic manure, compost, vermicompost, indigenous microbes, and crop residues, are widely used in reclamation of degraded soils. The biological soil amendments also furnish a valuable source of fertilizer for growing rice and maize and also boost physicochemical and biological parameters of soil such as water holding capacity, moisture content, electrical conductivity, organic carbon content, and population of beneficial microbes which directly correlates to soil health and fertility. However, efficiency of amendments applied based on variety of factors including the composition and characteristics, soil microflora, and environmental conditions can accelerate initial reclamation and lead to self-sustaining primary productivity of crops. On the other hand, high cost of chemical fertilizers, pesticides, and other agricultural inputs and their harmful environmental legacy have encouraged researchers to explore the use of microbial-mediated amendments to play a central role in raising productivity and inhibition/suppression of pathogenic population below levels at which they cause economic and other effects to the crops as well as the environment. Biological control can be achieved through one or more mechanisms, viz., antibiosis, competition for nutrients and/space, induced resistance, plant growth promotion, and rhizosphere colonization ability. Potent biocontrol agents such as Bacillus sp., Pseudomonas sp., and Tricoderma sp. prove to be very promising in controlling soilborne diseases of rice and maize crops employing both antibiosis and induction of host resistance. Determination of the modes of action of biocontrol agents is obligatory to provide higher level of protection to crop under a particular environmental condition that exists in divergent agroecosystems. This chapter reviews an insight of mechanisms of biological soil amendments and biocontrol agents and their emphasis on soil amelioration with the goal of a sustainable agricultural system.