Use of neemex neem urea guard as a nitrification inhibitor for transplanted rice

摘要

Urea is the most important source of 'N' widely used. But out of the total quantity of 'N' applied through urea only about 30 to 40 per cent is utilized by the rice and the major part of the added N is lost from the soil through leaching, volatilization, denitrification, run off etc. (Natarajan and Pushpavalli 1994). Various methods such as split application of urea at critical stages of rice, coating of urea with chemicals or other indigenous materials to slow down the nitrification rate. Use of coated fertilisers is controlled by physical barrier, and deep placement of N with urea super granules (Savant et al. 1983) have been adopted to increase the N use efficiency for rice. Since the synthetic products such as N serve, DCD (Dicyandiamide), CMP(1-Carboxamide, 3-(5)-Methylpyrazol) as nitrification inhibitors are expensive, the use of locally available neem cake as substitute for nitrification inhibitor has gained much importance. The past studies revealed that fertiliser N of 75 per cent soil test based recommendation can be given in the form of urea blended with gypsum and neem cake (5:4:1) in two splits (1/3 at active tillering and 2/3 at panicle initiation) for dry season (Kuruvai) rice crop in Cauvery delta (Stalin et al. 1995). Similarly, a neem based product Neemex-neem urea guard containing neem friterpenes in semi liquid form, as a coating agent has not yet been evaluated for its performance on rice in Cauvery delta region. Hence a study was undertaken to evaluate its bio-efficacy.