Arup Ghosh
CSIR-CSMCRI, India
Title: Increasing productivity of agricultural crops and improved abundance of soil bacteria upon application of Kappaphycus alvarezii seaweed extract under normal and drought stress conditions
Biography
Biography: Arup Ghosh
Abstract
Inorganic fertilizers have detrimental effect to the soil. The organic seaweed (macroalgae) based biostimulants offers great potential for enhancing crop productivity with low associated carbon footprint. However, besides evaluating their efficacy across varied agro-ecological conditions, their effect on soil microbial flora ought to be simultaneously studied which would be important from long term use perspective. Thus, an experiment was conducted with five treatments wherein maize plants were subjected to soil moisture stress once (V5) or thrice (V5,10,15) at its critical growth stages to study the effect of Kappaphycus alvarezii seaweed extract (KSWE) on drought alleviation as well as its effect on soil bacteria along with suitable controls. Methodology & Theoretical Orientation: Cultivation technologies for several macroalgae like Gracilaria, Kappaphycus, etc., have been developed at CSIR-CSMCRI, Bhavnagar in India. A process to obtain liquid seaweed fertilizers (LSF) was developed from red seaweed, Kapppahycus alvarezii (US Patent No. 6,893,479). To demonstrate and validate its efficacy as biostimulant, over 170 agronomic and large scale demonstration trials were carried out on cereals, pulses, oilseeds, sugar, fodder and vegetables in varied agro-ecological zones across 20 states in India. In maixe crop under controlled condition, high throughput sequencing through Illumina platform was employed for sequence analysis of V3 region of 16S rRNA gene amplified from soil metagenome obtained from the soil underneath the crop canopy in the root zone. Findings: From multi-locational trials, KSWE proved an effective bio-stimulant that enhanced crop yields by 13-37 percent over and above the recommended chemical fertilizers dosages (control) and in several cases their quality. Studies on soil microbiome indicated that the Steroidobacter, Anaerolinea, Bacillus, Paenibacillus, Ammoniphilus and Nitrospira were the predominant genera falling under the Phyla Proteobacteria, Chloroflexi, Firmicutes and Nitrospirae and they got significantly influenced due to the treatments at harvest of maize. The abundance of these genera was significantly decreased (49-80%) by subjecting soil moisture stress three times at V5, 10 and 15 stages when compared to that in normally irrigated soil, which got significantly improved by subsequent KSWE application at the respective stages under drought. Members of some taxa associated in plant growth promotion and nutrient cycling (Nitrosomonas, Nitrosvibrio, Rubrobacter, Flavobacterium) were found significantly enriched by application of KSWE thrice under severe drought. Higher number of species were identified in normally irrigated treatment and treatment where KSWE and drought were applied thrice. The treatments having enriched microbial abundance due to KSWE application under severe stress also recorded significantly higher cob yields suggesting their contribution in stress amelioration through plant growth promotion and better soil nutrient cycling.