Seaweed extract as organic bio-stimulant improves productivity and quality of rice in eastern Himalayas

Enhancing productivity through integrated nutrient management is pertinent to sustainable intensification of agricultural ecosystems. Field experiments were conducted during 2012 and 2013 in Eastern Himalayas with extracts from Kappaphycus alvarezii (K sap) and Gracilaria edulis (G sap) to assess growth, productivity and quality enhancement of rice (Oryza sativa). A Petri dish experiment was also conducted to assess the efficacy of saps in improving germination percentage and seedling vigour of rice seedlings. Field experiment included foliar spray of K and G saps (2.5, 5, 10 and 15% concentrations) with 100% recommended dose of fertilizers (RDF) along with water spray + 100% RDF (control). The rice seeds soaked with lower concentrations (2.5 and 5%) of K and G saps recorded higher germination percentage, root and shoot length and seedling vigour index as compared to water soaking. Whilst soaking in higher concentrations (7.5% and above) reduced the germination percentage and seedling vigour index. Foliar spray of K or G sap at 5% and above concentrations + 100% RDF significantly increased plant height, dry matter accumulation, chlorophyll index, crop growth rate, yield attributes and yield of rice (5.4 to 18.4% higher) as compared to control. Application of K or G sap at 10% concentrations + 100% RDF also increased micro-nutrient (Fe, Cu, Zn and Mn) and protein concentration in rice grains. Thus, foliar application of 10% K or G sap along with 100% RDF is a recommendable option for improving yield and quality of rice and sustaining soil fertility in eastern Himalayas and similar agroecosystems elsewhere.