ABSTRACT

The field experiment was conducted during kharif 2021 to study the “Nitrogen substitution through different organic manures in colour cotton under rainfed ecosystem” at ARS, Hebballi farm, Dharwad, Karnataka. The experiment was laid out in split plot design with seven sources of nutrients as main plots and three levels of nitrogen equivalents as sub plots along with three controls viz., C1: Recommended package of practices, C2: 100% NPK only (RDF: 60:30:30 kg NPK ha-1) and C3: Absolute control replicated thrice. The main plot treatments were different sources of nutrients viz., M1: Farmyard manure (FYM), M2: Vermicompost (VC), M3: Poultry manure (PM) and their combinations. Sub plots were levels of nitrogen equivalents viz., N1 - 75% Recommended dose of nitrogen (RDN), N2 - 100% RDN and N3 - 125% RDN.
Among the different N equivalent organic sources and controls, C1: RPP (RDF + FYM 10 t ha-1) recorded significantly higher seed cotton yield per hectare (2,086 kg ha-1) as compared to any other treatments. However, it was on par with C2: RDF 60:30:30 kg NPK ha-1 (1,862 kg ha-1) and M2N3: VC equivalent to 125% RDN (1,763 kg ha-1). Significantly higher net returns (Rs. 1,75,646 ha-1) were recorded with C1: RPP (RDF + FYM 10 t ha-1) as compared to other treatments. However, M2N3: VC equivalent to 125% RDN (Rs. 1,49,460 ha-1) and M2N2: VC equivalent to 100% RDN (Rs. 1,47,303 ha-1 ) were found on par with C1: RPP (RDF + FYM 10 t ha-1). Studies of the different organic nitrogen equivalents indicated that 100% to 125% N equivalents of Vermicompost is the best alternative manorial practice for production of higher seed cotton yield and net returns per hectare which is equivalent to present recommended practice of RPP (RDF + FYM 10 t ha-1) or RDF alone.