Effect of Organic Manures and Fertilizers on Potassium Fractions in Coastal Saline Soil under Rice

Abstract

A field experiment was carried out with no manure, farmyard manure, Glyricidia sepium, Sesbania aculeata, Thespesia populnea, no fertilizers, the recommended dose of fertilizers, Konkan Annapurna briquettes, and urea-diammonium phosphate briquettes in coastal saline soils of Maharashtra during kharif season 2023 to examine how different nutrient management practices influence the availability of potassium with rice as test crop. Results indicated that the maximum (100.33 mg kg-1) water-soluble K+ was observed with treatment receiving recommended dose of fertilizers + 10 t Glyricidia ha-1 at tillering stage, however, the highest exchangeable K+ (579 mg kg-1) was recorded with the integration of Glyricidia and Konkan Annapurna briquettes @ 170 kg ha-1 at panicle initiation stage. The significantly highest non-exchangeable K+ (1056 mg kg-1) was observed at harvest stage with Urea-Diammonium Briquettes (UB-DAP) which was placed without manure. There was significantly higher lattice K+ (9117.00 mg kg-1) with UB-DAP @ 170 kg ha-1 along with Thespesia @10 t ha-1 during harvest stage. The data showed that the water-soluble and exchangeable K got declined from tillering stage to harvest stage and the available K was low during tillering and panicle initiation but increased at harvest of the crop. Non-exchangeable K increased from tillering to harvest stage, however, lattice K and total K were declined from tillering to harvest stage. The sequence of K+ fractions followed the order as: total K+ > lattice K+ > non-exchangeable K+ > exchangeable K+ > water-soluble K+. The combination of Gliricidia sepium and Sesbania aculeata with chemical fertilizers was effective in sustaining the elevated potassium levels and reducing the decline of reserve soil K, particularly in the early and mid-growth phases of rice crop in saline coastal soils.