Application of Multivariate Statistical Techniques for Determining of Affecting Factors in Water Use Efficiency of Maize (Zea mays L.) under Conditions of Simultaneous Application of Nitrogen and Ecofriendly Inputs

Water stress is one of the most important factors in reducing the yield of agricultural products worldwide. If the stress is intensive and continuous, plant growth and productivity are severely diminished. Water superabsorbent polymer can absorb and retain extremely large amounts of a liquid relative to its own mass. They have a wide range of applications because of their high water absorbing capacity, biodegradability and low cost.Humic acid is an organic compound that is derived from the decomposition of organic matter and contains carbon, hydrogen, oxygen and nitrogen. This acid plays a key role in increasing the fertility of the soil and feeding the plant when added to the plant, in helps to increase its growth through its effect to photosynthesis, respiration, increase the plants resistance to harsh environmental conditions and stimulates many of the vital interactions within the plant.Salicylic acid, a naturally occurring plant hormone, acts as an important signaling molecule and enhances tolerance of treated plants against biotic stresses. Salicylic acid also has a vital role in plant growth, ion uptake, and nutrient transport within the plant.Factor analysis is a technique that is used to reduce a large number of variables into fewer numbers of factors. This technique extracts maximum common variance from all variables and puts them into a common score.

In order to evaluate the effects of different irrigation levels and nutritional treatments and determining factors affecting water use efficiency of maize (Zea mays L.), a split plots experiment based on RCBD design with three replications was conducted during 2015-16 growing season, at Research Field of Ferdowsi University of Mashhad, Iran. Irrigation levels in two levels (50 and 100% of water requirement) and nutritional treatments in five levels (1- Nitrogen+Superabsorbent, 2- Superabsorbent+Humic acid+Salicylic acid, 3- Humic acid+Salicylic acid+Nitrogen, 4- Humic acid+ Salicylic acid+Nitrogen+Superabsorbent and 5- Control) assigned to main and sub plots, respectively.

The results showed that all of the nutritional treatments affected water use efficiency, but in both conditions of 50 and 100% of water requirement, the highest water use efficiency were obtained in treatment of Humic acid+Salicylic acid+Nitrogen+Superabsorbent. The highest seed yield (17542 kg.ha-1) observed in treatment of nitrogen+superabsorbent+humic acid+Salicylic acid and supply 100% of water requirement and the lowest seed yield (12515 kg.ha-1) obtained in treatment of control and supply 50% of water requirement. Factor analysis results showed that variables analyzed to two factors. First factor included 51% of variables variance, respectively. First factor included variables of seed yield, biological yield, plant height, leaf area index, crop growth rate and soil nitrogen, phosphorous and pH and variables of seed weight per plant, soil EC and water use efficiency were in second factor. In first factor, important variables such as soil nitrogen, phosphorous were included, so this factor describe soil conditions and second factor which had the highest impact on water use efficiency was called as water use efficiency factor. In a research reported that application of water superabsorbent increased seed yield of maize compared to control. In another research, the highest seed yield of maize obtained in treatment of simultaneous application of 120 kg.ha-1 water superabsorbent and 8 kg.ha-1 humic acid. Application of salicylic acid and humic acid enhanced seed yield of maize 24.5 and 24.2% compared to control, respectively.

In general, based on results of this research, it seems simultaneous application of nitrogen and ecological inputs can improve yield, growth characteristics and water use efficiency. Factor analysis and high correlation among 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.