Chemical attributes of soil and growth of castor beans fertilized with drilling gravel from oil wells and castor pie.

The extraction of oil from onshore wells and the production of biodiesel from castor bean crops have grown in recent years, resulting in the production of large volumes of drill cuttings from these wells and castor pie, which can be harmful to the environment. The objective of this work was to evaluate the influence of a combination of different doses of drill cuttings and castor pie on the chemical attributes of a Planosol and on the dry mass production of the aerial part (DMAP) and dry mass of roots (DMR) of castor bean crops (Ricinus communis L.), cultivar BRS-149 Nordestina. The experimental design was a randomized block with a factorial 6 × 6, consisting of five castor pie doses (2, 4, 8, 16, and 32 Mg ha); five drill cuttings doses (5, 15, 30, 45, and 60 Mg ha) and an experimental control using only soil samples, with three repetitions. The soil used as the main substrate was collected at 0.0-0.2 m depth in a Planosol. The mixture of the topsoil layer with the experimental doses was performed using a mixer for 5 min, and the samples were distributed in 8 dm pots; each pot corresponded to an experimental unit. The mixture of cuttings from drill wells and castor pie with a 30: 16 Mg ha ratio, provided favorable chemical conditions for castor bean crop development; however, drill cuttings doses >30 Mg ha can cause soil salinization, and negatively affect the development of castor bean crops.