Sustainable agro-technology for enhancement of rice production in the red and lateritic soils using seaweed based biostimulants

Abstract

A field trial was conducted to evaluate the efficacy of Kappaphycus and Gracilaria based seaweed extracts (SWEs) to enhance the yield of rice in red and lateritic soils and also simultaneously assess the sustainability of the use of SWEs through life cycle assessment. A total of thirteen treatments involving combinations of recommended rate of fertilizers (RRF) 80: 40: 40 N: P2O5: K2O kg ha−1 and SWEs applied at concentrations (2.5, 5, 7.5, 10 and 15%) were tested along with a suitable control (water spray + RRF) in a randomized block design. The efficacy of SWEs at 7.5% was also tested with lower dose of RRF (50% RRF). The SWEs were foliar applied 25, 50, and 70 d after transplanting of rice. Life cycle impact assessment (LCIA) for the production of fertilizers and SWEs required for 1ha of rice cultivation was carried out using ReCiPe Midpoint method and were expressed as impacts t−1 of rice production. Combined analysis of data of the experiment revealed that SWEs from Kappaphycus (KSWE) and Gracilaria (GSWE) when applied at 15% concentration significantly increased the grain yield of rice by 29% and 28%, respectively, over control; however, SWEs at 10% gave more net benefit per unit investment compared to the control. Notably, the grain yield in the treatments involving combination of SWEs with 50% RRF was statistically at par with control. LCIA revealed that in comparison to the control, maximum reductions of 11.4% and 14.8% in climate change (CC) impact category t−1 of rice were obtained in treatments involving combination of RRF with 15% KSWE and 10% GSWE, respectively. Interestingly, treatments involving 50% RRF + SWEs brought about at least 43% reduction in CC impact t−1 of rice, which amounts to savings of about 35 kg CO2-equivalents t−1 of rice. Similarly, reductions were also observed for other impact categories. SWEs offer great promise in global perspective towards mitigating climate change as well as other environmental impacts and sustainably increasing rice yield.