Farm yard manure reduces the virulence of Alectra vogelii (Benth) on cowpea (Vigna unguiculata)

Abstract

The average productivity of cowpea in arid and semi-arid regions of Kenya is low due to a complex of biotic and abiotic stresses. Among the major biotic factors is the parasitic weed Alectra vogelii. Six cowpea varieties were evaluated in 2010 to determine the effect of farm yard manure on A. vogelii on six cowpea genotypes. Treatments consist of three tolerant (Kib-18, Kir/Nya-005 and Sia/Cia-004) and three susceptible genotypes (K80, M66 and Tra/Kir-001). Three levels of manure (0, 5 and 10 ton/ha) were applied. The experiment was conducted at Kiboko research sub-centre (37°43’N and 2°13’ E). Most of the yield and yield determining attributes recorded significant (P < 0.05) at 5 and 10 ton/ha. M66 and K80 recorded the highest A. vogelii count at 6, 8, 10 and 12 weeks after planting (WAP) in all treatments. Average grain yield ranged between 365 to 2276 kg/ha at 0 ton/ha, 1693 to 4042 kg/ha at 5 ton/ha and 476 to 6797 kg/ha at 10 ton/ha. Sia/cia-004 (local cultivar) recorded the highest yield of 2276 kg/ha at 0 ton/ha. On the other hand, M66 (commercial variety) recorded the lowest yields of 365 kg/ha at 0 ton/ha. Application of a handful of (5 and 10 ton/ha) farm yard manure reduced A. vogelii density by >50% at 6, 8, 10 and 12 WAP with increase in mean number of pods per plant and yield. Therefore, farm yard manure application is advantageous in reducing the effect of Alectra parasitism on cowpea.