Authors:R. Nandakumar, A. Saravanan, P. Singaram, and B. Chandrasekaran
Field experiments were conducted with rice (ADT-39) during the wet Kharif season (July- October 2001) at two locations, the Tamil Nadu Rice Research Institute (TRRI) farm, Aduthurai (Vertisol) and the Agricultural Research Station (ARS) farm, Pattukkottai (Alfisol), representing the old and new delta areas of the Cauvery, respectively. The same set of treatments was followed in both soils. The treatments consisted of the recommended NPK fertilizer application at 75% and 100% alone, and 10 or 20 kg ha-1 humic acid (HA) in combination with NPK fertilizers as soil application, besides an integrated method involving soil application, root dipping and foliar spraying with humic acid and NPK fertilizers. initial soil samples from the experimental fields were analysed for physical, physico-chemical and chemical properties. Surface soil samples were collected at critical growth stages and analysed for various available nutrients. The results of the field experiments revealed that the application of humic acid along with inorganic fertilizers led to higher soil nutrient availability at all the growth stages of rice. Similar results were obtained in both Vertisol and Alfisol. The present investigation concluded that the best treatment for soil nutrient availability was 10 kg ha-1 HA (soil application) + 0.1% HA foliar spray (twice) + 0.3% HA root dipping + 100% NPK, which was on par with the treatment involving 20 kg ha-1 HA (soil application) + 100% NPK compared to the other treatments.