Productivity and Economic Viability of Carrot Fertilized with Calotropis procera in Different Growing Seasons

The objective of this work was to evaluate the productivity and economic viability of the carrot as a function of different amounts and times of incorporation to the soil of the green manure roostertree (Calotropis procera) in two growing seasons, in the semiarid region of Pernambuco, Brazil. The study was conducted in an experimental field belonging to the Federal Rural University of Pernambuco (UFRPE), in the autumn–winter (March to July 2012) and spring–summer (September 2012 to January 2013) periods. The experimental design was in randomized blocks, with three replications. The treatments were arranged in a 4 x 4 factorial scheme, with the first factor consisting of four amounts of roostertree biomass (5.4, 8.8, 12.2 and 15.6 Mg ha-1 on a dry basis), and the second factor consisting of four incorporation times of this fertilizer into the soil (0, 10, 20 and 30 days before sowing the carrot). The commercial productivity of carrot roots and production costs were evaluated, in addition to the following economic indicators: gross return, net return, rate of return and profit margin. The cultivation of the carrot fertilized with roostertree was economically viable, regardless of the quantity of green manure, of the time of incorporation into the soil or the time of cultivation. In autumn–winter, the lowest amount of roostertree (5.4 Mg ha-1) associated with the incorporation time of 10 days before planting the carrot was considered ideal for the agro-economic viability of the crop. The carrot cultivation in spring–summer was most profitable when fertilized with 14.0 Mg ha-1 of roostertree on the same day of carrot planting.