Effect of rate and time of nitrogen application on the performance of cowpea Vigna unguiculata (L) Walp in the northern guinea savannah zone of Nigeria

Abstract

Ffields trials were conducted (each on bi-location) at Maiduguri (Latitude 11°51') and longitude 13°15') during 1997 cropping season. The main objective was to determine the amount and time of application of nitrogen that would boost the  field performance of cowpea. The two experiments were laid in a spilt-plot design. In each of the two (2) experiments, three cowpea varieties (95K-596, 93K-597 and TVU2027) were assigned to the main plots, while the subplots were aAssigned to nitrogen (at 0, 10, 20, 30 and 40Kg/ha) in the first experiment and for the second experiment, nitrogen application at (0, 1, 2, 3 and 4) weeks after sowing were assigned to the subplots. It was observed that variety significantly (P≥0.05)(p≤0.05) affected striga infestation on cowpea. TVU 2027 (local) recorded the lowest striga population.Variety superiority to others. 93K-597 recorded the significantly highest (P≥0.05)(p≤0.05) dry matter yield (DMY) and nodulation. Nitrogen at 40Kg/ha significantly (P≥0.05)(p≤0.05) increased cowpeas’ DMY,  and nnodulation a, ond as well effected a significant (P≥0.05) a reduction in striga infestation. Time of application of nitrogen did not significantly (P≥0.05)(p≤0.05) increase DMY at the two locations. Nitrogen significantly (P≥0.05)(p≤0.05) affected striga count and nodulation at location 1 where application at 0, 3 and 4 weeks after sowing significantly reduced striga infestation. Similarly, at location 1 nitrogen application at 0, 1, 2 and 4 weeks after sowing, were significantly (P≥0.05)(p≤0.05) highest. Nitrogen however did not significantly increase nodulation at location 2. It was concluded that the results of the experiment amongst locations might have been influenced by variation in the environments. However, variety TVU 2027, is recommended for its resistance to striga while 95K-597 is recommended for high nodulation and high dry matter yieldDMY and basal application of 40N/Kg nitrogen at planting is recommended for improving the productivity/field performance of cowpea in this zone.