Wheat response to irrigation cease at different growth stages and nitrogen levels under Ahvaz climatic conditions

Introduction Drought and nitrogen deficiency are major environmental factors limiting plant growth and selection of product types in many agricultural ecosystems limit. Drought stress and decreasing the nitrogen rate caused a significant decrease in the yield and yield components. According to some reports, the average wheat yield in the world is 30-60% of the yield, the main reason for which is the lack of water. Therefore, the purpose of this experiment was to investigate the response of wheat to different irrigation and nitrogen levels in Ahwaz climatic conditions. Materials and Methods In order to study Wheat response to different levels of nitrogen and irrigation regimes in Ahwaz condition, an experiment was conducted in 2014-2015 at Agricultural and Natural Resources Research Center of Khuzestan. The experimental design was split plot with randomized complete block design in three replications. Treatments were included: irrigation regimes (full irrigation, Cutting off Irrigation at stem elongation, anthesis and grain filling stages) as main plot and three nitrogen levels (0, 100 and 200 kg N ha-1) as sub plot. Results and Discussion The factors of grain yield, biological yield, harvest index, the number of ear per m2, the number of grain per ear, 1000-grain weight, grain nitrogen percentage and residues nitrogen percentage were measured in this research. The results indicated that grain yield, biological yield, grain and residues nitrogen percentage were significantly affected by interaction between irrigation regimes and nitrogen levels. The greatest amount of biomass, grain yield, and grain and residues nitrogen percentage was obtained from full irrigation and 200 N ha-1. The results of regression analysis revealed that with increasing nitrogen increased the traits grain yield, biological yield and grain and residues nitrogen percentage of all the regimes of irrigation. But the cutting off irrigation at grain filling stage on grain yield and don’t cutting off irrigation during the growing season on biological yield, grain and residues nitrogen content gain more benefit from other regime. Shoot nitrogen content increased with increasing nitrogen supply and at the level of 200 kg per hectare reached to the highest level. Slicing interaction indicated that the regime of irrigation at grain filling stage there is a significant difference between the different levels of nitrogen. In irrigation cut in stage stem elongation and flowering was not difference between different levels of nitrogen in terms of impact on the biological yield. In other words, the performance of these treatments did not react to use of different levels of irrigation and nitrogen. Meanwhile, according to the b factor regression analysis it was found that the increase in biomass per unit increase in the amount of nitrogen in the regime of irrigation during the growing season was more visible than other regime. 200 plants per m2 could more efficient use of environmental conditions such as light, water and food and the lowest density level, the non-application of nitrogen not able to make full use of environmental resources because the plant couldn't cover the ground completely. Conclusions In general, different irrigation and nitrogen levels have a significant effect on grain yield, biological yield and grain and residues nitrogen percentage. The highest performance of the treatment of don’t cutting off irrigation during the growing season and the application of 200 kg nitrogen per hectare. Levels of irrigation levels have responded differently to nitrogen. The results of regression analysis of the studied traits showed that with increasing nitrogen, the grain yield, biological yield and nitrogen content of the grain and the remnants of all levels of irrigation increased. Interaction cropping also showed that there was a significant difference in grain yield in irrigation cuttings at stem and seed filling stage between different levels of nitrogen, but the yield of full irrigation during plant growth period and cuttings of water in Flowering stage did not react to the application of different levels of irrigation and nitrogen. Key words: Moisture stress, grain nitrogen and residues, yield components.