Abstract
A field experiment was conducted during 2006 and 2007 (June- December) at New Delhi to assess the performance of three cotton hybrids of which two Bt (MRC 6304 & RCH 317) and one non-Bt cotton hybrid LHH 144 (North zone check) in response to nitrogen fertilization (0, 60, 120 and 180 kg ha-1). Based on pooled analysis, both Bt hybrids produced similar seed cotton yield (SCY). Bt hybrid have produced 7.1 bolls/plant (on an average) and bolls 0.48 g heavier than non Bt hybrid LHH 144 that lead to 1.07 t ha-1 higher SCY of Bt hybrids than non-Bt hybrid (1.93 t ha-1). Though the N uptake by cotton hybrids was statistically similar N harvest index (NHI) was higher in Bt hybrid (57.85) as compared to non-Bt hybrid (40.5). The agronomic N use efficiency (ANUE) was highest in MRC 6304 Bt (6.44) and least in LHH 144 non-Bt cotton (3.91). Cotton growth, yield attributes, SCY, and N uptake increased with each successive increase to the highest level of 180 kg ha-1 however, the N response of cotton was quadratic in nature with optimum dose of 173.0 kg ha-1. The NHI decreased with increase in N dose i.e. from the highest of 56.3 in control to the lowest of 48.8 with 180 kg ha-1 N fertilization. ANUE and physiological NUE that was highest with 60 (5.73) and 120 kg N fertilization (17.05), respectively and decreased with further increase in N dose. The cotton hybrid x N interaction effect revealed that Bt cottons have quadratic N response while non-Bt cotton has linear N response. From the economic point of view, Bt hybrids with 120 kg Nha-1 could be optimum dose for cotton cultivation. DOI: http://dx.doi.org/10.3329/sja.v11i1.18389 SAARC J. Agri., 11(1): 121-132 (2013)
Highlights
Cotton (Gossypium sp) is the most important commercial fibre crop of India since time immemorial
The trial was laid out in split plot design with 3 cotton hybrids viz., MRC 6304, RCH 134 (Bt cottons), and LHH 144 as main plots and 4 nitrogen (N) levels (0, 60, 120, and 180 kg ha-1) as sub-plot
The leaf area expressed as leaf area index (LAI) and dry matter production (DMP) was recorded at 30 days interval from sowing to harvest for two plants
Summary
Cotton (Gossypium sp) is the most important commercial fibre crop of India since time immemorial. The LAI values reached their highest values at 120 DAS and the LAI and DMP values were reported for this stage only The nitrogen concentration of economic produce and cotton sticks along with leaves retained on plant at harvest was determined by kjeldahl.s method (Jackson, 1973) and uptake was obtained as product of concentration and yield. The interaction effect of cotton hybrids and nitrogen fertilization on yield attributes was found non-significant.
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