Real time nitrogen management for higher N-use efficiency in transplanted rice (Oryza sativa) under temperate Kashmir conditions

Abstract

A field experiment was conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar Campus, Srinagar during 2004 and 2005 to study the leaf colour chart (LCC)-based nitrogen management for increasing N-use efficiency and reducing nitrate N leaching in transplanted rice under temperate conditions of Kashmir. The experiment comprised 8 N management practices; control, use of threshold values of LCC < 3 and LCC < 5 and use of recommended N rates [120 kg/ha applied in 3 splits (50% as basal, 25% at active tillering and 25% at panicle initiation)] were conducted in randomized block design with 3 replications. LCC < 5 (180 kg N/ha applied in 6 splits) recorded significantly higher grain yields (6.61 and 6.70 tonnes/ha, respectively in 2004 and 2005) but remained at par with application each of 20 kg N/ha at same LCC level (5.96 and 6.03 tonnes/ha, respectively in 2004 and 2005) without basal dose of nitrogen application (total of 100 kg N/ha), as compared to recommended dose of 120 kg N (4.86 and 4.81 tonnes/ha) and LCC < 3 (60 and 90 kg N/ha). The LCC < 3 (60 and 90 kg N/ha applied in 2 and 3 splits, respectively) was statistically at par with recommended dose of 120 kg N/ha in respect of yield and yield attributes. The nitrogen-use efficiency and apparent recovery were significantly higher with LCC-based N management than the recommended N management. Further higher agronomic efficiency (29.4 and 32.7 kg grain/kg N applied), apparent N recovery (52 and 57% respectively in 2004 and 2005) and returns/rupee investment in account of applied N (19.2 and 19.3/Re in the respective years) were recorded with LCC < 5, where 20 kg N/ha was applied in 5 equal splits without basal application. Thus LCC threshed value < 5 (100 kg N/ha) helped avoid over application of N to rice.