Effect of water stress on growth, productivity and water expense efficiency of summer rice

A field study was carried out during 1997 and 1998 cropping seasons on a fine loamy (Typic Ustochrept) soil type. to assess the performance of 'IET 4786' summer rice (Oryza saliva L.) under stressed (intermittent pending) and non-stressed (continuous pending) situations. In case of intermittent pending, irrigation was given when soil-moisture tension at 20 cm depth attained the suction value of 0-02 M Pa, Entire irrigation period was divided into 3 stages, ie early [11 to 30 days after transplanting (DAT), middle (31 to 60 DAT) and late (61 to 80 DAT) stages. Intermittent pending was imposed at single, ie in early (I-2). middle (I-3) and late (I-4) stage or at two stges, ie early plus middle (Is), early and late (I-6) and middle plus late (I-7) stages. Besides, there were 2 more irrigation regimes. ie continuous pending was maintained throughout the entire irrigation period (I-1) and intermittent pending was maintained during the entire irrigation period (I-g). The highest grain yield (6.79 Mg ha) was attained under II, followed by yield of 6.71 Mg ha under I-2. Grain yeild markedly decreased under I-3, I-5, I-7 regimes and it attained lowest value (5.37 Mg ha) under I-g. Water expense efficiency (W-ee) value attained the lowest level (5.26 kg/ha/mm) under I-7 regime. While it was highest (5.99 kg/ha/mm) under I-2 regime and this W-ee value was 8.7% higher over I-1. Though grain yield attained lowest value under Is but minimum level of water expense value (910.4 mm) responsible towards greater W-ee value (5.71 kg/ha/mm) under this treatment.