Influence of potash levels on growth, yield, nutrient uptake and economics in irrigated summer rice of Assam

A field experiment was conducted during the dry season of 2005–06 and 2006–07 at Nagaon, Assam to study the effect of potassium levels (25, 37.5 and 50 Kg K ha⁻¹) and timing of potassium application (full basal, ½ as basal + ½ at maximum tillering stage, ⅓ as basal + ⅓ at maximum tillering + 1/3 at panicle initiation stage and ⅓ at maximum tillering + ½ at panicle initiation stage) on growth, yield, K uptake and economics of summer rice (var. Joymati) grown under irrigated condition. The results indicated that application of 37.5 Kg K ha⁻¹ recorded significantly higher growth, yield attributes, yield and nutrient uptake as compared to lower levels of Potash. Further application of potassium in 3 equal split (⅓ as basal + ⅓ at maximum tillering + ⅓ at panicle initiation stage) resulted in higher plant growth, yield attributes, yield, K uptake by summer rice, net return, and benefit: cost ratio and significantly superior to K application schedule of full basal and Y₂ as basal + ½ at maximum tillering stage. Application of K in 3 splits resulted in 5.5 to 13.2% increase in grain yield over the other application timings. Agronomic efficiency and apparent K recovery % were the highest at 37.5 Kg ha⁻¹ application.