Claudivan Feitosa de Lacerda, Flávio Batista da Silva, Antônia Leila Rocha Neves, Francisco Leandro Barbosa da Silva, Hans Raj Gheyi, Ricardo Luiz Lange Ness, Enéas Gomes-Filho
Salt stress can reduce canopy development in most plant species, and in such conditions, decreasing spacing between plants and consequently increasing planting density may result in higher yields and increase in water and radiation use efficiency. The objective of this study was to evaluate the interaction between water quality and plant spacing in a cowpea-maize cropping system. The use of saline water in irrigation reduced the radiation intercepted by apical leaves and consequently, increased the radiation intercepted by the basal leaves, increasing their photosynthetic rates. The increase in spacing between rows resulted in more vigorous plants, with greater dry biomass production, when plants were irrigated with low-salinity water. However, the use of high salinity water resulted in less growth and productivity in plants, with the greatest relative reductions observed in plants with greater spacing. For the minor spacing between rows (0.5 m) the irrigation with saline water caused a reduction of 17% in grain yield and water productivity, while for the larger spacing (0,9 m) this reduction reached almost 40%. On the other hand, the shorter planting distance and the residual effect of saline water used in irrigation of the previous crop had negative impacts on the growth and final yield of maize.
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