Factor analysis of water use efficiency and some quantitative characteristics and yield in sesame (Sesamum indicum L.) affected by application of nitrogen and ecological inputs in conditions of drought stress

Insufficient access to water in arid and semi-arid areas has considered water use efficiency as one of the main pillars of sustainable agriculture in these areas. Therefore, in recent years, many efforts have been done to increase water use efficiency, in this regard, the use of superabsorbents and spraying of ecological inputs such as humic acid and salicylic acid are considered as fundamental solutions for saving and optimizing water usage, therefore, this research was conducted with the aim of using factor analysis to determine the affecting factors on water use efficiency of sesame in the conditions of simultaneous application of nitrogen and ecofriendly inputs.

In order to evaluate the effects of different irrigation levels and nutritional treatments and determining factors affecting water use efficiencis of common bean (Phaseolus vulgaris L.), sesame (Sesamum indicum L.) and maize (Zea mays L.) a split plots experiment based on RCBD design with three replications was conducted during 2015-16 growing season, at Research Farm of Ferdowsi University of Mashhad, Iran. Irrigation levels (50 and 100% of water requirement) and nutritional treatments (1- 75 kg.ha-1 Nitrogen+80 kg.ha-1 Superabsorbent, 2- 80 kg.ha-1 Superabsorbent+6 kg.ha-1 Humic acid+1 Mm Salicylic acid, 3- 6 kg.ha-1 Humic acid+1 Mm Salicylic acid+75 kg.ha-1 Nitrogen, 4- 6 kg.ha-1 Humic acid+1 Mm Salicylic acid+75 kg.ha-1 Nitrogen+80 kg.ha-1 Superabsorbent and 5- Control) assigned to main and sub plots, respectively.

The results showed that the highest seed yield (1672 kg.ha-1) obtained in 100% of water requirement and application of nitrogen+superabsorbent+humic acid+salicylic acid. The role of humic acid and salicylic acid in improving most of the studied traits was significant, so that seed yield, leaf area index, crop growth rate and water use efficiency were 22, 31, 30 and 21% more than treatments without the two inputs, respectively. Factor analysis results showed that variables analyzed to two factors. First factor 59 of variables variance, respectively. First factor included variables of seed yield, seed weight per ,plant, crop growth rate, soil nitrogen and phosphorous and water use efficiency and variables of dry matter yield, plant height, leaf erea index and soil pH were assigned in second factor.

In general, the results of this research showed that treatments of nitrogen+superabsorbent, superabsorbent+humic acid+salicylic acid, nitrogen+humic acid+salicylic acid and nitrogen+superabsorbent+humic acid+salicylic acid increased water use efficiency 15, 27, 32 and 40% compared to control, respectively. According to the results of factor analysis and variables belonging to each factor, it seems that the first factor is the index of yield and the second factor reflects the inherent characteristics of the spatial arrangement of the plant (high load of plant height and leaf area index on this factor). In general, it seems simultaneous application of nitrogen and ecological inputs can improve yield, growth characteristics and water use efficiency. Factor analysis and high correlation between variables in same group showed that with change of variables that are in same group of water use efficiency, can increased water use efficiency and decreased damages of drought stress.