Rice Husk Ash as a Low Cost Soil Ameliorant for Abating Iron Toxicity in Lowland Rice

Background: The Fe toxicity is a perpetual problem of low lying poorly drained acid soils. It also affects the solubility and availability of most of the plant nutrients, by reducing toxic concentrations of iron, aluminum and manganese. To overcome these constraint, application of lime is inevitable but high cost of liming materials necessitate the use of low-cost, internally sourced, environmentally friendly and adoptable organic sources. In present study rice husk ash was used as a soil ameliorant in lieu of liming.Methods: A field experiment was conducted at Rice Research Station, Moncompu during 2017-2018 with nine treatments replicated thrice in RBD using rice variety Uma. A customized formulation with composition of K (8.9 %), Mg (3.2 %), Ca (3.7 %), Zn (2.1 %), Mn (0.23 %), B (3.5 %) and Cu (0.96 %) was developed based on the available nutrient status of the region and crop requirement and used for supplementary foliar nutrition.Result: It was found that treatment comprising of Soil test based RDF + Rice husk ash @ lime (based on pH) + foliar spray of 0.5 % solution of customized formulation @ 5 kg ha-1 as foliar application of 0.5 % solution in two splits at maximum tillering and panicle initiation stage was the best treatment in increasing yield by 23 % compared to recommended dose of lime and fertilizer application and B:C ratio increased from 1.53 to 1.91. Effect of rice husk ash in ameliorating soil acidity was found to be on par with application of lime based on pH in acid sulphate soils of Kuttanad zone.