Cultivo da mamoneira sob irrigação com águas salinas e doses de nitrogênio.

Abstract

Considering that the availability of water in nature is decreasing both in terms of quantity and quality and the increasing need for expansion of agricultural áreas, makes the use of saline waters as an altemative to consider these issues. Thus, this research was conducted to evaluate the cultivation of castor bean cv. BRS Energia, when subjected to irrigation water of different salinity leveis associated with nitrogen doses. A completely randomized block design in a 5x4 factorial scheme, whose treatments were combinations of five leveis of eléctrica! conductivity of irrigation water - ECw (0.3, 1.2, 2.1, 3.0 and 3, 9 dS m"1) and four doses of nitrogen (70, 100, 130 and 160% of the indicated dose) and three replications. The use of saline water with ECw starting at 0.3 dS m"1 negatively affected the emergence rate index and the percentage of emergence, and growth of components and production as measured by the number of leaves, plant height, stem diameter, leaf area, number of fruits and seeds and seed mass of cluster primary and secondary. The salinity of irrigation water delayed the emission of primary and secondary cluster. The highest rate of absolute and relative growth for plant height were observed in treatment with ECw of 1.9 and 2.1 dS m"1, respectively, between 30 to 40 and 22 to 30 days after sowing (DAS). ECw leveis up to 3.3 dS m"1 provides oil content in the seeds of primary cluster more than 48%. Irrigation with saline water íncreased the leveis of sodium and chlorine in ali parts of the plant, the highest leveis of potassium in roots and leaves were achieved respectively, with ECw 0.3, 2.2 dS m"1. The N fertilization provided an increase in leaf area and stem diameter, and the best results were obtained with doses of 160% N at 60 and 120 DAS respectively, besides the number of fruits in primary cluster, emission time for the secondary cluster and foliar chlorine content. however, decreased the leveis of phosphorus and potassium. The salinity of irrigation water when combined with nitrogen fertilization caused significant changes in leaf area at 120 DAS, the effective length of primary and secondary cluster, the oil content of the seeds of the subsequent production and the Na+/K+ in stems and leavês.