EFFECT OF NITROGEN MANAGEMENT THROUGH DECISION SUPPORT TOOLS ON GROWTH, YIELD AND ECONOMICS IN DIRECT SEEDED RICE (ORYZA SATIVA L.) UNDER TUNGABHADRA PROJECT (TBP) COMMAND AREA OF KARNATAKA

A field experiment was conducted during Kharif 2017 to study the “Nitrogen management through different decision support tools in Direct Seeded Rice (Oryza sativa L.) under Tungabhadra Project (TBP) command area of Karnataka” at Agricultural Research Station, Gangavathi. The soil type in the experimental site was medium black soil with soil pH and EC of 7.90 and 0.43 respectively. The initial soil available nitrogen, phosphorus and potassium was 213.2, 31.05 and 374.8 kg ha-1, respectively which is in the range of low in nitrogen, medium in phosphorous and high in potassium content. The experiment consists of 12 treatments laid out in randomized block design with three replications. The results revealed that application of nitrogen through LCC ≤ 6.0 threshold recorded significantly higher grain yield, straw yield, Panicle length, ten panicle weight and number of grains per panicle (6230 kg ha-1, 6323 kg ha-1, 21.0 cm, 43.3 g and 262.0, respectively) compare to RDF (4410kgha-1, 4853 kg ha-1, 17.8 cm, 30.0 g and 219.7, respectively) and farmer practice (5086 kgha-1, 5330 kg ha-1, 18.2 cm, 35.8 g and 247.3, respectively)which was on par with application of N through LCC ≤ 5.0, SPAD ≤ 40, SPAD ≤ 50 and Green Seeker ≤ 0.8. Similar trend was also observed in growth parameters viz., plant height, leaf area, total dry matter production plant-1 and Number of tillers m-2. However, gross returns, net returns and B:C ratio was significantly higher with application of nitrogen through LCC ≤ 6.0 threshold (102847,59332Rs. ha-1 and 2.36, respectively), which was on par with LCC ≤ 5.0 threshold, SPAD ≤ 40, SPAD ≤ 50 and Green Seeker ≤ 0.8as compared to RDF (82422, 39682Rs. ha-1and 1.92, respectively) and farmers practice (87341,43020Rs. ha-1and 1.97, respectively). Hence, precision nitrogen management in DSR can be done through LCC ≤ 5.0 or SPAD ≤ 50 and green seeker ≤ 0.8 threshold for obtaining higher growth, yield and economics