Studies on performance of some open-pollinated maize cultivars in the Guinea savanna. III. Nitrogenuse efficiencies of four cultivars

Abstract

Nitrogen use efficiency (NUE), defined as grain produced per unit of fertilizer nitrogen (N) applied, is a highly desirable agronomic character of non-leguminous crop varieties. This study was conducted to compare the NUEs of one local maize (Zea mays L.) variety and three improved composites released in Ghana since 1972, and determine the effects of breeding for improved agronomic performance on the NUEs of the improved cultivars. The four late-maturing maize cultivars (local, Composite 4,Dobidi, and Okomasa) were evaluated at 0, 80, and 160 kg N ha-1 and under three plant densities at Nyankpala and Damongo in 1992 and 1993. Across environment analysis for grain yield showed environment, plant density, nitrogen, and cultivar effects were significant (P<0.05). The environment W cultivar, environment W nitrogen, density W nitrogen, and nitrogen W cultivar interactions were also significant. Mean grain yields for the improved cultivars were 3.5, 4.7, and 5.3 t ha-1 at 0, 80, and 160 kg N ha-1, respectively. Yields for the local variety were lower by 40.0, 42.2, and 51.4 per cent at 0, 80, and 160 kg N ha-1, respectively. NUEs for the local variety, Composite 4, Dobidi, and Okomasa were 9.8, 16.4, 15.7, and 15.1 at 80 kg N ha-1, and 6.4,11.0, 11.3, and 11.4 at 160 kg N ha-1, respectively. The NUEs over the two N levels were 8.1, 13.7, 13.5, and 13.1 for the four cultivars, respectively. NUE increased linearly at 0.15 yr-1 in improved cultivars over the local variety at both N levels. It was concluded that improved maize cultivars were more efficient in using fertilizer N than the local variety, NUEs did not differ among the improved cultivars, and that breeding resulted in 1.8 per cent yr-1 improvement in NUE over the local variety.


Ghana Jnl.agric. Sci Vol.32(1), 1999: 19-26