Effect of cropping systems induced shading on the physiology of cowpea varieties intercropped with sorghum based systems in the savannah ecology of Nigeria

Six cowpea varieties (IT98K-131-1, IT04K-227-4, IT89KD-288, IT93K-452-1, IT97K-499-35 and IT99K-573-1-1) were intercropped with a local sorghum (Kaura) using four row arrangements (1C:1S, 2C:2S, Mixed crop and sole) in fields experiment conducted at Minjibir and research farm of the Faculty of Agriculture Bayero University Kano located in the Sudan Savannah ecological zone of Nigeria during the 2015 and 2016 rainy seasons. In the field, the experiment was laid in a randomized complete block design (RCBD), Analysis of variance (ANOVA) showed significant difference on cowpea cropping systems and variety on the physiology of cowpea. At BUK in both years and the combined, cowpea had higher non significant percent light interception at sole, at both sampling period’s varieties IT98K-131-1 and IT93K-452-1 intercepted higher percent light compared with the other varieties similarly chlorophyll content was higher at sole, varieties IT97K-499-35, IT04K-227-4 and IT98K-131-1 had significantly higher chlorophyll content. At Minjibir in both years and the combined, sole row arrangement had the higher non significant percent light interception while variety IT89KD-288 had no significant higher light interception. In both trials, higher percent light interception was recorded in variety IT98K-131-1 and varieties IT04K-227-4 and IT97K-499- 35 had a significant combined effect on chlorophyll content. Keywords: Cropping systems, Cowpea varieties, Shading and physiology