Nitrogen management through soil and plant analysis development and leaf colour charts in different groups of rice (Oryza sativa) varieties grown on Vertisols of Deccan plateau Mahender Kumar R., Subbaiah S.V., Padmaja K., Singh S.P., Balasubramanian V.1 Division of Agronomy, Directorate of Rice Research, Rajendranagar, Hyderabad, Andhra Pradesh, 500030 1 Present address: International Rice Research Institute, Manila, Philippines
Abstract A field experiment was conducted during the rainy (kharif) and winter (rabi) seasons of 1997–98 at Rajendranagar, Hyderabad, to compare the N-use efficiency of SPAD-502 (soil and plant analysis development) chlorophyll meter-based N fertilizer management with recommended fixed schedule of N fertilizer splits applied at critical growth stages and to assess the relation of SPAD and leaf colour chart (LCC) readings recorded at critical crop-growth stages with grain of rice (Oryza sativa L.). In SPAD-based N management, the N was applied when SPAD value decreased below 35 of fixed value and the amount applied as per the stage of the crop. Hybrids recorded higher grain yield of 4.85 and 5.16 tonnes/ha during rainy and winter season respectively than scented and high-yielding varieties respectively. The SPAD-N application gave significantly higher grain yield than 135 kg N/ha during rainy season, while on par with that in winter. The agronomic efficiency (Δ kg grain/A kg N) and partial factor productivity (kg grain/unit N) was higher for SPAD-based N application than 135 and 90 kg N/ha. The SPAD and leaf colour chart values recorded at critical stages were significantly higher with application of N. These values showed positive correlation (0.78 to 0.85 in rainy season and 0.78 to 0.90 in winter season) in both seasons at all crop-growth stages, indicating use of LCC as a tool for N top-dressing. Thus increased N fertilizer efficiency at high yield levels is possible in hybrids and high-yielding varieties using a chlorophyll meter and LCC to monitor leaf N status and guide fertilize N timing in irrigated rice. These methods not only reduced N requirement but also improved congruence of N supply and crop demand than fixed timing of N application treatment. Top Keywords Nitrogen management, SPAD meter, LCC, Cultivars, Hydrids, Rice. Top |