Effect of different irrigation regimes on yield and yield components of wheat (Triticum aestivum L.) cultivars in Ramin climate

Wheat (Triticum aestivum L.) is the most important cereal used as staple food in Iran. Despite higher yield wheat potential in Iran, average grain yield of wheat in Iran is much less than most of the wheat growing countries of the world (FAO., 2013). Nowadays increase of population and need for food and limitation of water for food and limitation of water resources have, increase yield in the volum e of water have a crucial inpact. Limitation of water resources in order to increasing tolerant Cultivars to severe conditions with high water use productivity. Earlier research showed that irrigation consistently increased wheat yield (Rahim et al., 2007). Wajid et al. (2002) reported that wheat yield by applying irrigation at all definable growth stages. Jamal et al. (1996) concluded that grain yield of different wheat cultivars were significantly reduced by water stress at all critical growth stages and greatest reduction was at anthesis stage. The present study was therefore undertaken to examine the yield response of wheat cultivars to different water irrigation in Ramin climate conditions.
In order to a field study pertaining to the effect of irrigation intervals on yield and yield components of wheat cultivars was conducted during 2011-2012 growing season at Agronomic Research Field of Ramin Agriculture and Natural Resources University of Khouzestan. Khouzestan Province is south-western Iran, its covers and area 63633/6 km2 between lattitudes 29o-33o N and longitudes 47o 40`- 50o 33` E. The climate of the province is affected by weather systems from the Mediterranean and the Persian Gulf so that the weather is typically that of a semi-arid/temperate climate. The experiment was laid out using RCBD with split plot arrangement. Treatment were three cultivars wheat (Chamran, Aflak and Verinak) which were kept in main plot and five irrigation intervals I1 (irrigation after two leaf stage), I2 (irrigation after two leaf stage tillering stage), I3 (irrigation after two leaf stage Tillering stage booting stage), I4 (irrigation after two leaf stage Tillering stage booting stage anthesis stage) and I5 (irrigation after two leaf stage Tillering stage bootingstage anthesisstage milking stage) that were placed in sub plots. Experiment was replicated thrice having plot size of 1.5m × 6m with six rows per plot. Half does of nitrogen and full does of phosphorus was applied during seed bed preparation while remaining half does of nitrogen was applied with first irrigation post emergency. Data on plant height, number of fertile tillers, number of spikelets per spike, number of fertile tillers, number of spikelets per spike, number of grains per spike, 1000-grain weight, grain yield, straw yield and harvest index were recorded by using standard procedures. Data were analyzed statistically by using SAS analysis of variance technique and treatment means were compared by using least significant difference (LSD( test at 5% probability level (Steel and Torrie., 1984).
Chamran cultivar recorded highest grain yield (4822.5 kg ha-1), number of tillers (335m-2) and harvest index (45/33) which were significantly higher than the other two cultivars. Highest grain yield in Chamran cultivar might be due to the increase in number of tillers m-2 (Sharif et al., 1999) and with higher 1000-grain weight (Wajid et al., 2002). Howover minimum plant height (73cm) and number of spikelets spike-1 (17) recorded at Chamran cultivar. Wheat crop supplied with five irrigations at irrigation after two leaf Tillering booting anthesis milking recorded the highest grain yield (5670.4 kg ha-1) which was significantly higher than all the other intervals irrigation. Interaction between cultivars and irrigation levels was significant for grain yield. At I5, cultivars Chamran and Aflak increased yields (52.68% and 57.07%) over I1 which were statistically at par with each other.
Finally, the results revealed that soil moisture stress causes low grain yield, by inducing low 1000-grain weight, number of tillers m-2. Thus, wheat, a staple food, appears to be suffering yield losses due to deficiency of irrigation water at any critical stage. Therefore, wheat grower must be careful about water stress on critical stage which can cause tremendous yield losses. It is also clear that there is a considerable span to exploit the yield potential of wheat cultivars in irrigation area of Iran.