Forage potentials of two cowpea (Vigna unguiculata L. Walp) varieties as influenced by varying irrigation frequencies and phosphorus application rates in Zaria

In Nigeria, the dietary energy and protein obtained from forages, particularly in the dry season, are generally too low to meet the nutrient requirements of ruminant livestock. Therefore, there is a clear need for alternative means of supplementing the year-round forage shortfall for livestock to improve productivity. A field experiment was conducted to evaluate the effects of irrigation frequencies and phosphorus application rates on forage quality of two cowpea varieties during dry season. The experiment was laid out in a 2×3×3 factorial arrangement in a split plot design with three replications. Treatments consisted of two cowpea varieties (SAMPEA 14 and 15), three irrigation frequencies (5, 10 and 15-days) and three phosphorus (P) rates (0, 20 and 40kg/ha), respectively. Chemical and mineral compositions were recorded. Results indicated that forage quality of the two cowpea varieties were affected (P<0.05) by some of the treatments during the two-year trial and the mean. Crude protein (CP) and crude fibre (CF) of forages were higher (P<0.05) in treatment with 20 kgP/ha and 40 kgP/ha compared to the control. SAMPEA 14 forage resulted in significantly higher (P<0.05) mean CP of 16.91% compared to SAMPEA 15 with 15.74%. The CP of SAMPEA 14 forage increased by 6.91% compared to SAMPEA 15 forage. Mean P increased by 11% with SAMPEA 14 comapred to SAMPEA 15. Calcium and potassium were higher (P<0.05) in treatment with 5 days irrigation frequencies compared to 15 days irrigation interval. Phosphorus application rates showed an increasing trend (P<0.05) in P determined with 40 kgP/ha application level in 2018 dry season. It is therefore, concluded that, farmers should irrigate SAMPEA 14 using the 5-day irrigation frequency in combination with 20 kgP/ha of phosphorus application rate for optimum fodder quality.