The effect of farmyard manure was studied on senescence, nitrogen and protein content of the
leaves and grains of cowpea. The experimental site for this study was situated at the International Institute of Tropical Agriculture (IITA), Kano Station, Nigeria. The cowpea varieties used in this experiment were Kanannado a local variety and IT89 KD – 288 an improved variety, two treatments were used for the experiment single manure treatment (manurexl), and double manure
treatment (manurex2) at the ratio of 5:1 soil to manure and the control (no manure added). Plastic pots of 250mm diameter and 17.5cm for both length and height were used in this study. The pots were arranged in completely randomize block design and labeled appropriately using white and green plastic tags according to the plant treatment applied. The rainy season trial was carried out
between August 2006 to November, 2006 while the dry season trial was carried out between October, 2007 to January, 2008 onset of senescence, days to 50% senescence, 90% senescence and days to total death of the plants occurred earlier in IT89KD – 288 than in Kanannado, while comparison between the treatments showed that senescence started earlier in plant treated with double manure treatment than those treated with single manure treatment. Between the two seasons, senescence started earlier rainy season than in dry season. On the other hand nitrogen and protein content of the leaves and grains were higher in IT89KD – 288 than in Kanannado, also between the treatment double manure treatment induced higher nitrogen protein content of leaves and grains. More nitrogen and protein, content of leaves and grains were obtained during the dry
season trial than in the rainy season trial.