Nitrogen use efficiencies using leaf colour chart in rice (Oryza sativa)-wheat (Triticum aestivum) cropping system

Abstract

A field experiment was conducted at Project Directorate for Cropping Systems Research, Modipuram, Meerut during 2001-02 and 200243 to determine the threshold leaf colour chart values for N application in rice (Oryza sariva L.) and wheat (Triricum aestivum L. emend. Fiori & Paol.) for increasing fertilizer N use efficiency, reducing nitrate-N leaching and work out economics of leaf colour chart-based N management in rice-wheat cropping system. Combinations of 3 rice-wheat cultivars ('Basmati 370' followed by 'PBW 343', 'Saket 4' followed by 'HD 2687' and 'Hybrid 61 1 IIPHB- 71' followed by PBW 226) were grown in main plot and 6 N management practices under a split-plot design with 3 replications. Leaf colour chart threshold values of 3 for 'Basmati 370', 4 for 'Saket 4' and 5 for 'Hybrid 61 111 PHB-71' gave higher grain yield (14.7, 15.6 and 12.4 % respectively) with greater N use efficiencies (AE,, 3554% and RE,, 22- 38%) than recommended N use, i e 120 kg Nha in 3 splits. In wheat, leaf colour chart threshold value < 4 gave higher grain yield (0.45 to 0.70 tonnesha), N uptake and N use efficiency than with 120 kg Nha applied in 3 fixed time splits. A significant positive effect of N management through leaf coIour chart on different yield attributing parameters, viz panicled m2, fertile grains/panicle and grain weightlpanicle of rice and wheat was noticed. In addition, results showed that nitrate N content in lower layer (beyond 60 cm depth) was less under leaf colour chart based N management vis-a-vis recommended N split. The net returns in leaf colour chart-based N management were 16-338 higher than recommended N application.