DEVELOPMENT AND INITIAL GROWTH OF CASTOR BEAN (Ricinus communis) CROP SUBMITTED TO DIFFERENT SOIL WATER TENSIONS

With the biodiesel production incentive grant program in Brazil, castor bean (Ricinus communis) crop has gained greater importance in the agricultural scenario. Therefore, the objective of this study was to evaluate the castor bean response to different levels of soil water tension. A greenhouse study was carried out with castor bean plants, cv. Al Guarany 2002, cultivated in pots, and a tensiometer was installed at 0.15 m deep to monitor soil water tension. The experimental design was completely randomized with three treatments (T) and four replicates: T1, water tension maintained at 0.01 MPa; T2, when soil water tension reached 0.03 MPa, water was added to restore it to 0.01 MPa; T3, when soil water tension reached 0.06 MPa, water was added to restore it to 0.01 MPa. Between 30 and 105 d after plant emergence, the leaf area, plant height, stem diameter and transpiration rates were measured every two weeks. The time of initial flowering and height of insertion of the first raceme were also determined. Results show that the castor bean is sensitive to the increase in water soil tension, and higher stress conditions lead to decreased growth, and lower transpiration rates and vegetative period.