Phenology and yield of sunflower (Helianthus annuus L.) hybrids as affected by varying plant spacing and nitrogen levels under semi arid conditions of Sargodha, Punjab

The field experiment was conducted to study the effect of different plant spacing and nitrogen rates on phenology, and yield of sunflower hybrids at research area of University College of Agriculture, Sargodha, during spring season, 2010. The treatments include two hybrids (Hysun-33 and S-278) at three plant spacing (20, 25 and 30 cm) with three levels of nitrogen (100, 125 and 150 kg N per ha). The trial was conducted in split plot design and the data collected were statistically analyzed by employing the Fisher's analysis of variance technique and treatments means were compared using least significant difference (LSD) test at 0.05 level of probability. The obtained results revealed that there was a significant difference for days taken to flowering (DF), achene's formation (DAF) & physiological maturity (DPM) and yield in both of the hybrids except, number of days to germination (DG.). The hybrid S-278 started reproductive stages and matured earlier and gave higher achene's yield (3.34 t per ha) than hybrid Hysun-33 (2.73 t per ha). Increasing plant density decreased the days taken to flowering (DF), achene's formation (DAF) and physiological maturity (DPM) while increases the achene, yield (AY) in sunflower. By contrast, with increasing nitrogen application phonological duration and achene's yield was increased. There was an interaction between hybrids and planting densities (HxD), hybrids and nitrogen (HxN) for days taken to flowering, achene's formation, physiological maturity, achene's yield per ha while no interaction for number of days to germination. The highest achene's yield (3.75 t per ha) was produced by sunflower hybrid S-278 sown with 20 cm plant spacing (H2D1). Similarly Hybrid S-278 gave highest achene yield (3.57 t per ha) with the application of 125 kg N per ha (H2N2). In the interaction of density and nitrogen, highest achene's yield (3.72 t per ha) was in D1N3 treatment which was statistically similar with D1N2 treatment and was followed by D2N2 and D2N3 treatment.