In search for sustainable agricultural methods for medicinal plants, a field experiment was conducted on isabgol-lentil mono and row intercropping, along with irrigation interval regimes (4-, 7- and 14-days irrigation interval) at the agricultural experimental farm of Zabol University during 2009. The experiment design was split-plot randomized complete block design with four replicates. Main plot treatments were giving irrigation at 4-, 7- and 14-days interval, and subplot treatments consisted of (a) sole isabgol; (b) sole lentil; (c) 1:1 isabgol-lentil intercropping system; (d) 1:3 isabgol-lentil intercropping system; and (e) 3:1 isabgol-lentil intercropping system. The results of the experiment confirmed that drought induced by increasing irrigation interval significantly decreased the growth of both crops and total N concentration of isabgol plants. Results also showed that lentil suppressed biological and grain yield of intercropped isabgol, but the reduction in isabgol yield was compensated by lentil grain yield. Isabgol biological and grain yield was significantly different across cropping systems and the yields were as follows: sole isabgol (281), 1:3 isabgol-lentil (93), 1:1 isabgol-lentil (191), and 3:1 isabgol-lentil (230). Lentil biological and grain yields was also significantly different across the treatments and was sole lentil (1096), 1:3 isabgol-lentil (846), 1:1 isabgol-lentil (644), and 3:1 isabgol-lentil (318). Intercropping isabgol and lentil increased the productivity with LER of 1.10, 1.27 and 1.11 for 1:3 isabgol-lentil, 1:1 isabgol-lentil and 3:1 isabgol-lentil, respectively. In intercrops a significant reduction in LAI, CGR, and also significant increase in leaf and tiller numbers per plant, plant height, spike length, spike numbers per plant, grain numbers per spike and 1000-grain weight of isabgol was observed over sole isabgol. These changes were proportional with row number of isabgol in intercropping. Significant interaction effect of cropping system by irrigation regimes on many cases of measured parameters showed intercropping protects plants from drought. Total concentration of N in isabgol were increased by intercropping, however cropping system by irrigation regimes interaction on N concentration was not significant. These findings suggest that intercropping isabgol-lentil at combination of 1:1 with 7-days irrigation interval may be recommended for yield advantage, more efficient utilization of resources and N concentration on hot and dry regions of South-East Iran.
