Effect of intercropping on the growth and yield of cowpea and maize crops irrigated with brackish water

The aim of this study was to evaluate the effect of the salinity of irrigation water on the growth, productivity and land-use efficiency in mono- and intercropping systems, using maize and cowpea plants. The experiment was carried out in a randomized-block design in split plots. The plots consisted of the crop year (2012 and 2013), the irrigation water salinity treatments (0.9, 2.5 and 5.0 dS m-1) made up the sub-plots, and the sub-sub-plots included the cropping system tested (cowpea, maize, and maize intercropped with cowpea). The accumulation of salts in the soil increased in proportion to the electrical conductivity of the irrigation water, the highest values being observed in the maize, explained by the longer cycle and greater irrigation depth employed. The total rainfall recorded for the rainy seasons of 2013 and 2014 were sufficient to promote leaching of the excess salts below the root zone of the crops. The effect of salts on total plant biomass and productivity was highly significant in the monocropped systems, especially the cowpea. The microclimate conditions of the intercropping system may have contributed to the reduced effect of salinity on productivity, mainly in the cowpea, resulting in higher values for land-use efficiency.