Effect of Time of Introducing Sesame and Nitrogen, Phosphorus, Potassium (15:15:15) Fertilizer on Sesame/Soybean Intercropping in the Southeastern Rain Forest Belt of Nigeria

Field experiments were conducted during the cropping seasons of 2004 and 2005 at Obubra, Nigeria, to ascertain the most suitable time to introduce sesame or soybean and the effect of nitrogen:phosphorus:potassium (N:P:K; 15:15:15) fertilizer on sesame/soybean intercropping. Treatments comprised five times of introduction as follows: sesame + soybean sown same day, sesame sown two weeks before soybean, sesame sown four weeks before soybean, sesame sown two weeks after soybean, and sesame sown four weeks after soybean. Four levels of NPK (15:15:15) fertilizer (0, 50, 100, and 150 kg/ha) were factorially combined with the above treatments and arranged into a randomized complete block design with three replications. The parameters measured were; plant height, number of branches/plant, number of leaves/plant, shoot dry matter/plant, number of capsules/plant, number of seeds/capsule and seed yield. The number of leaves, branches and capsules per plant, shoot dry matter and seed yield of sesame as well as soybean shoot dry matter, number of pods per plant and seed yield increased significantly when either component was sown earlier than the other. Incremental application of NPK fertilizer up to 150 kg/ha significantly increased, on average, sesame seed yield as well as soybean plant height, shoot dry matter and seed yield. The yield advantages associated with sowing soybean four and two weeks before, same day with and two and four weeks after sesame were 0, 25, 44, 72, and 53%, respectively, over sole cropping. The yield advantages accrued to intercropping at 0, 50, 100 and 150 kg/ha NPK fertilizer were 109, 27, 8, and 11%, respectively. Simultaneous or same day sowing produced more satisfactory yields of the component crops relative to other sowing schedules while fertilizer use was enhanced by NPK application at 150 kg/ha.