tillers contribution on wheat yield in rainfed and saline soil in different row spacing and plant density

according to the contradictory reports of researchers, tillers may have positive or negative effect on wheat yield. thus, this study was conducted to investigate the role of tillers on wheat yield under two row spacing of 12.5 and 25 cm and four plant densities of 125, 250, 375 and 500 plants per m2, at gorgan university of agricultural sciences and natural resources farm in anbare-ololum reign in rainfed and saline conditions during 2008-09. the results showed that increasing of row spacing had no effect on fertilized tillers number per m2, but increased total dry mater, total grain yield and main stems grain yield (about 200 kg) per ha-1. the plant density increasing, increased number of fertilized spikes per m2, total dry mater and grain yield per ha-1. also main stems grain yield in 375 plant density per m2 was about 120% higher than 125 plants per m2 and more plant density increasing had no significant effect on it. on the contrary, plant density increasing reduced tillers grain yield and main stems harvest index. the interaction between row spacing and plant density on tillers number per m2, fertilized tillers percentage, tillers and main stems dry mater contribution showed that there was highest difference between two row spacing on 250 plant density per m2 and the deference between two row spacing reduced with more plant density per m2. but the difference of tillers harvest index between to row spacing was higher in 125 plant density per m2. in generally, the results showed, in this study, tillers had negative effect on wheat grain yield, therefore, in this condition, relying on tillers production that results to not optimum using form valuable resources, specially moisture, is wrong. consequently, for preventing of these wastes of resources, increasing plant density up to 375 plants m-2 and using of row spacing of 25 cm, will reduced tillers dry mater contribution and will result to less moisture wastes form tillers, on other hand, more moisture will remain for main stems and will result in maximum resource use efficiency and grain yield.