Effect of irrigation intervals in different phonological stages on quantitative and qualitative characteristics and water productivity of sesame

Sesame is an oilseed plant that is resistant to drought. But it is sensitive to water stress at seedling stage and during flowering to seed filling. Irrigation and drought stresses increase and decreases the amount of oil, resprctively. Environmental stresses have reverse effects on the amount of oil and protein. In addition, high soil moisture causes root rot disease and low moisture causes phyllody disease. To increase the yield and oil, the enhancment of soil fertility, planting bred cultivar and adequate supply of moisture are necessary through irrigation. This study was conducted to evaluate the effect of irrigation intervals in different phonological stages on quantitative and qualitative characteristics and water productivity of sesame.

This research was conducted in randomized complete block design with four replications at Behbahan Agricultural Research Station for two years (2013-2014). Treatments included I0 (irrigation interval based on farmer 's custom, twice weeks interval), I1, I2 and I3 irrigation after 90, 130 and 170 evaporation from class A pan, respectively, I4 (130 mm to flowering and afterward 90 mm), I5 (170 mm to flowering and afterward 90 mm) and I6 (170 mm to flowering and afterward 130 mm). During experiment: branches number and capsules number per plant, 1000- seed weight, first capsule height, plant height at harvesting time, seed oil percentage, seed yield, seed oil yield, water productivity of sesame seed and seed oil, root rot and phyllody diseases were recorded. Varince analysis were done by MSTATC statistical software and meanes were compared using Duncan,s Multiple Range Test.

The highest number of branches per plant (10.31), number of capsules per plant (154.50), 1000- seed weight (3.78 g), seed yield (1381.50 kg ha-1), oil amount (55.11%), were recorded in I1 treatment, so that the highest seed oil yield (795.55 kg ha-1) belong to this treatment. The differences of oil yield among I1 treatment and I4 and I5 treatments were not significant. Maximum seed water productivity (0.233 kgm-3) and seed oil water productivity (0.125 kgm-3) were observed in I3 treatment. However the difference among this treatment and I0, I5 and I6 treatments was not significant. The lowest infection severity to root rot disease (7.22 %) was recorded fot I5 treatment. The highest infection severity to root rot disease (20.63 %) was observed in I1 treatment while the lowest infection severity to phyllody disease was recorded in I1, I2 and I6 treatments.

The highest seed yield, 1000- seed weight and seed oil percentage were obtained in I1, I4 and I5 treatments. The differences of these characters among I1, I4 and I5 and other treatments were not significant (except I0 treatment). The highest seed oil yield were recorded for I1 and I5 treatments. The most seed water productivity and seed oil water productivity and the lowest water consumption belong to I5 treatment. Irrigation frequencies in I5 treatment were lower than I1 and I4 treatments. According to the results, I5 treatment has the lowest water consumption and the effect of this treatment on seed yield and gross income of seasame was similar to I1 treatment. Therefore I5 treatment is recommended for proper irrigation of sesame in Behbahan region.