Productivity and economic analysis of sunflower/maize crop rotation under different levels of salinity and nitrogen

This study aimed to assess the effect of salinity of irrigation water and nitrogen fertilization on yield and oil production of sunflower, cv. BRS 324, and yield of maize hybrid AG1051, as well as economic analysis of crop rotation (sunflower/maize). The experimental was laid out in a randomized complete block design in split plot with five replications, the plots were formed by five levels of electrical conductivity of the irrigation water (0.8, 2.2, 3.6, 5.0 and 6.4 dS m-1) and the subplots by four rates of nitrogen (0, 25, 50 and 75 kg ha-1), in sunflower crop. For maize crop the same design was used, studying on the same plots the residual effects of salts and four nitrogen rates (0, 108.5, 217 and 325.5 kg ha-1). Sunflower was grown in dry seasons (2011 and 2012), while maize was grown in the rainy seasons (2012 and 2013). For the sunflower crop, the productivity and potential oil production showed the highest values when the plants were not salt-stressed and subjected to the maximum dose of nitrogen. But yield was decreased with increasing salinity, even with increasing the rate of nitrogen. For the maize crop, productivity was strongly influenced by increasing the rate of nitrogen; the leaching of salts, caused by rainfall, virtually eliminated any residual effect of the salts on this crop. A soil management system employing sunflower-maize crop rotation was found to be economically viable, being more attractive when using low saline water and the highest application rate of nitrogen. Key words: Helianthus annuus L., Zea mays L., salt stress, nitrogen fertilization, economic viability.