Journal of Agriculture Policy ISSN 2520-7458 (Online) Vol.2, Issue 1 No.3, pp 58 - 69, 2017 www.carijournals.org 57 INTERACTION EFFECTS BETWEEN WATER HARVESTING TECHNIQUES AND SPACING ON GRAIN YIELD AND ABOVE GROUND BIOMASS OF COWPEA Armara Macimiliam Galwab and Prof. Peter Kamau