Castor seed yield at suboptimal soil moisture: Is it high enough?

Abstract

This study discusses how soil moisture influences the seed yield of two castor plant varieties in an arid zone in Mexico. An experiment was set up with two factors: soil moisture, with three levels (high = -0.05 MPa, medium = -0.31 MPa and low = -0.91 MPa), and castor variety (Krishna and Rincon). The combination resulted in a factorial 3 × 2 experimental design. The experiment was set up as a randomized block with four replications under a split-plot arrangement, where the whole plots were for soil moisture and the subplots were for the castor variety. The measured variables were plant height (PH), days to flowering of 50% of the plants (DF), leaf area (LA), dry weight (DW), source-sink relationship, harvest index (HI) and seed yield. Data were analyzed by ANOVA, mean tests (HSD at α = 0.05) and regression analysis. There were significant differences in PH, LA, DW, HI and yield among the treatments. The values of PH, LA and DW tended to be higher at higher soil moisture levels than at lower moisture levels. The source strength was generally lower than the sink strength in all the treatments. There were significant differences between the varieties for HI, and the interaction between soil moisture and variety was also significant. Significant differences were found in yield; the Krishna variety had a greater yield than the Rincon variety, but there was only a significant difference between the yield of the Krishna variety cultivated under low soil moisture (5200 kg ha-1) and that of the Rincon variety cultivated under high soil moisture (2570 kg ha-1). The results of this study indicate that castor plants can be cultivated in arid regions at suboptimal soil moisture levels with supplementary irrigation without compromising plant performance or yield.