Effect of seaweed extract on rice (Oryza sativa var. ADT53) productivity and soil fertility in Cauvery delta zone of Tamil Nadu, India

The monocropping of rice in the Deltaic zone deteriorates soil health and crop productivity. Seaweeds are marine resources easily available at negligible cost and also rich in bioactive compounds. A field experiment was conducted at Cauvery Delta zone of Tamil Nadu during summer season2021 to evaluate the bio-efficacy of Seaweed extract on growth, yield, and soil properties of rice, Oryza sativa var. ADT53. The experiment was framed in RBD comprising of 12 treatments viz., soil application of Seaweed extract(SWE) @ 12.5kg/ha,25kg/ha, 37.5kg/ha , foliar spraying of SWE gel & liquid @ 0.5% twice at tillering and panicle initiation stages, a combination of soil application and foliar spray and fertilizer alone. Experimental findings revealed that the soil application of SWE  @ 12.5kg/ha along with a foliar spray of seaweed liquid recorded higher plant height (121.1cm),dry matter production (11390kg/ha),yield attributes viz., number of grains per panicle (166), panicle length (21.8 cm), thousand grain weight (14.7g), number of productive tillers per m2 (275), grain yield (5612 kg/ha)and straw yield (7829 kg/ha). However, The soil application of SWE @ 25kg/ha recorded higher soil available nutrients viz.,N(260 kg/ha);P(42kg/ha); K(170kg/ha);Ca(27.7meq/100g); Mg(5.5meq/100g);S(18.2mg/kg);Zn (1.17ppm); Fe (33.82ppm); Cu(1.61ppm);Mn(18.97ppm).The study will help sustain rice productivity and soil fertility in the deltaic zone of Tamil Nadu. The soil application of seaweed extract @ 12.5kg/ha along with foliar spraying (0.5% twice) could be a promising option in the rice ecosystem.