Stability of Cotton Yield Influenced by Nitrogen Fertilization and Irradiation with Gamma-Rays

Cotton and Durum Wheat Research Institute, BG-6200 Chirpan, Bulgaria


PANAYOTOVA, G. and N. VALKOVA, 2003. Stability of cotton yield influenced by nitrogen fertilization and irradiation with Gamma-rays. Bulg. J. Agric. Sci., 9: 17–22

The investigation was carried out during 1996–1999 on the Cotton and Durum Wheat Research Institute, Chirpan under conditions of pellic vertisol without irrigation. Seeds of Beli Izvor cotton variety were irradiated with gamma-rays in doses of 150, 200 and 250 Gy and then were sown at fertilizer levels of 0, 6, 12 and 18 kg.da–1N. Block design with four replications was used.
The aim of the study was (i) to estimate stability of cotton yield under different meteorological conditions, using traditional and new methods of estimation and (ii) to define the nitrogen rates and gamma-rays doses that lead to high and stable yield parameters. For this purpose a computer program STABLE was used and were determined the parameter of stability: variance (σi2) by Shukla, ecovalence (Wi ) by Wricke and Kang's parameter (YSi ) for simultaneous evaluation of yield and stability.
The results showed that the cotton yield was the greatest influenced by gamma-rays, less by years and much less by nitrogen rates. As regards to interaction between nitrogen and gamma-rays it was observed that the productivity increased to N12 and 150 Gy, but the parameters of stability presented as most valuable of referring to yield and stability a N rate 6 kg.da–1 regardless of gamma rays doses, irrespective of year conditions. The fertilization with N6–12 increased the total cotton yield with 13.1–20.2% in comparison with unfertilized. The differences among years affected the yield, which ranged from 130.3–180.6 kg.da–1.

Key words: cotton, nitrogen, gamma-rays, yield, stability