Investigation of yield and yield components of different cereal mixtures subject to water stress in hot and dry ecological conditions

According to the 2030 Document (FAO, 2016), agriculture is facing more challenges today than ever before. More people need food, water shortages, declining land productivity, and declining agricultural labor are increasing the need for sustainable agriculture around the world.Therefore,the aim of this study is to diversify the grain crop system using a mixture of winter cereals,wheat,barley and triticale and their response to end-of-season water stress in hot and dry ecological conditions.

In order to investigate the yield response and yield components of mixed culture of different cereal cultivars to water stress in hot and dry ecological conditions,an experimental split plot design in the form of a randomized complete block design with three replications in the 2017-2018 crop year in the research farm of the Faculty of Agriculture and Darab Natural Resources-Shiraz University.In this experiment,the first factor of irrigation regime in two levels of normal irrigation and water stress and the second factor including ten levels of genotypes(tall barley line EB-95-97,dwarf barley line EB-95-97 dwarf bread wheat line S-92-19,tall bread wheat cultivar Khalil and a cultivar of Triticale called Juanilo) which were grown as a series of alternatives to double and pure row mixture. Double mixed crops as one in a row, including:dwarf barley,tall barley(one row of dwarf barley+one row of tall barley),dwarf barley-triticale (one row of dwarf barley+one row of triticale),tall barley-triticale (one row tall barley+one row of triticale),dwarf wheat-triticale (one row of dwarf wheat+one row of triticale) and tall wheat-triticale (one row of tall wheat+one row of triticale) with a 50:50 planting ratio and pure cultivation including:barley Dwarf, tall barley, triticale, tall wheat and dwarf wheat had a planting ratio of 100:0. According to plant density(400 plants per square meter for barley,450 plants per square meter for wheat and triticale(seeds per plot) and exactly each planting line (before planting according to the weight of one thousand seeds calculated and measured Were placed in separate bags and planted on each stack(including two planting lines) when planting. The final harvest of the crop was done manually after removing the rows. Traits such as 1000-seed weight, biological yield,harvest index, number of spikes per spike, number of spikes per plant, spike length,plant height and grain yield were measured.

The results of this experiment showed that the highest grain yield was obtained in tall wheat-triticale mixed culture with9472kg ha-1 under normal irrigation and the lowest grain yield was achieved in pure dwarf barley with 3934 kg ha-1 under water stress conditions.The results of correlation coefficients under normal irrigation conditions showed that there was the highest positive and significant correlation between grain yield and biological yield under normal irrigation conditions (r=0.847**) and water stress (r=0.792**).

The tall-Triticale mixed wheat cultivation system under normal irrigation conditions showed a 16% increase in yield compared to the tall wheat pure cultivation system,while it did not show a significant difference with the Triticale pure cultivation system. Existence of more vegetation, less weeds, lower shading temperature and consequently higher photosynthesis under water stress and higher yield components in intercropping systems than pure cereals, which together increase the yield.Seeds in mixed cropping systems were different from pure cereals.The decrease in yield in pure crop compared to mixed crop is due to water stress in the grain filling stage.Therefore, mixed cultivation under water stress conditions shows better yields than pure cultivation,which is probably due to the reduction of exogenous competition in mixed cultivation of cultivars.